Včasno se z nami je optimirat vstavljeni v delovit'u, kako vse zelo vse zelo, in prijeznaj spetanje. Kaj je inštak več, Fulio Paleari, kaj da smo priježivati, vzelo, z delovit'u, nekaj ne zelo vse vstavljeni, je nekaj nezelo, dar ne zelo, nesel vse vzelo na vrste poslutje. Daj, Fulio. Čekaj, David. Nelaj za dne občasno me glasbi. Tukaj, da jim ko se naprej tudi povdeli, idem koristim VL-om, ki kmorto šepega, in ovo je, ki se jim ovo izredali. Staj na pridem, je to je ovalo, zelo zelo, ki so domo se dovaj po povrbu zelo, z puknem jeva, si je, ki je to, ko je ovalo, je to, ki je to, t längite, vzalej. A početno, when we study neutral excitation, for example, light absorption by the electronic structure of the material, sometimes in semiconductor, the light absorption, is actually, happens with an energy that is lower than the band gap. And this is because of the electron-hole interaction between the excitered electron and the holder remains in the conduction band. Basically, this picture. In particula, it can be imagined that ljite in pinge in materijal. Makroskopik polarizacija, rapid oscillating in time is generated. And the absorption spectrum is just the Fourier transform of this polarization, so the frequencies that are encoded in this polarization end up as peaks in the absorption spectrum. This is also the path that you will take for giving a sketch for the derivation of the beta-salpeta equation, which describes electron interactions. Just to... Sorry, I should point it here probably. Well, okay. Nobody's connected to my laptop, so I think... Ah, no, now it's working, okay. So this is basically the outline. I will give you a brief introduction why we need to go beyond the independent particles picture to describe a response function like the one for optical absorption. Then we will sketch this derivation starting from the question of motion of the response function in real time. We arrive at the beta-salpeta equation and we will give you some examples of possible application of the BSE beyond optical absorption spectra, okay? So why do we need this? Well, okay, we can imagine we know more or less about DFT if we know the band structure of the system, we can also compute the absorption spectrum. So it's just a matter of knowing the wave functions of knowing the energies of the bands and then we can compute the spectrum. And this is given basically by the Fermi-Golden Rule that you can find in every book. We have the transition matrix element describing the coupling of the Konshamoi function with light, and then the possible transitions because of energy conservation happen at the transition energy between valence and conduction. However, if we apply this formula, let's say to a material like lithium fluoride, so let's say we do DFT, we also do GW correction, why not? We obtain basically the red curve for the absorption spectrum while the experiment shows this very sharp peak which even lies below this red curve. So actually there is something deeply wrong in this formula and the corrected formula let's say that allows us to describe this case as this shape. As you can see, it is a linear combination of the transition matrix elements across all possible electron-all transitions created by these weights. We will obviously explain these later on and the energy of the transition is not anymore the valence to conduction transition energy, but this new exciton energy. So these red quantities that I am outlining here come out of the solution of the beta-salpeter equation. And you see that if we apply this new expression then in this case of lithium fluoride we get a pretty good description of the optical absorption spectrum. There are even more lithium fluoride, it is pretty striking, but the best application of the BSc probably is in layered and 2D systems. I look for example here at monolayer-exagonal boron nitride again I do DFT plus JW compute the absorption, the absorption starts at the quasi-particle bandgap and it is like this potato-shaped curve but then I try to solve the beta-salpeter equation and check the difference in the independent particles and excitonic absorption spectra you see it is like completely different. All the oscillator strength is sucked at lower energies in really well-defined peaks that are ok, now you can see, basically almost like discrete states and so this is a very striking case the difference between a quasi-particle bandgap and the main peak for example is the binding energy of this exciton state which is almost 2 electron volts so this happens in such striking fashion into this system because of course as was explained by Alberto yesterday the screening of the interaction between electron and hole is pretty weak into these systems and therefore the binding energies are quite high. Ok, so now that we understood the need to go beyond the independent particles picture we can try to think about how to do this, there are several ways to get the beta-salpeter equation for example here there are kind of three, one uses the edins equations which you have already seen for GW yesterday, this is totally doable strategy but since we have already seen it yesterday we will not do it today again then there is like the schringer approach which employs functional derivatives with respect to the external potentials and we will see a version of this approach but basically starting from the equation of motion of the response function so this is an approach that can be easily extended to treat out of equilibrium systems while approach that are based on a frequency space cannot be extended out of equilibrium so this can be interesting also for applications beyond optical absorption Ok, so as always we start from the electronic Hamiltonian so kinetic term, electron-nucleos interaction and then the electronic interaction here you have the hearty term which depends on the ground state charge density and then here I just put the fork term so this is just hearty fork, ok and I do this because doing this with the DFT exchange correlation functionals makes the equation a bit more clunky but it's totally doable in these lights it's like this just for simplicity let's say and then of course from this electronic Hamiltonian of non-interacting single particle energies we can get the eigenvalues and the block functions and from the block functions we can also get the charge density at equilibrium we already more or less saw these the other days but the quantity that we are interested in is the response of the system when an external field external time-dependent field is added to this Hamiltonian and then the situation becomes like this we have our equilibrium Hamiltonian we have the external field but then we also need to account for a change in the electron-electron interaction because now the Hamiltonian gets an induced sorry the density gets an induced component which is time-dependent because it is induced by the time-dependent field and so the functions of the density must also change a little bit so before we have to add these pieces here which adjust the difference between the equilibrium electron-electron interaction and the time-dependent ones ok now of course we can get the density matrix of the system this time time-dependent not anymore necessarily at equilibrium you can get it for example as a time-equal limit of the single particle Green's function and then we can finally get to the quantity that we are really interested in in this presentation and today the response function which is here the variation of the density with respect to the external field so we would like to find an equation of motion for this response function which includes electron-hole interactions sorry of course the response functions just as the charge density can be expressed from the position basis to the single particle basis which would be the constant basis if you did the DFT calculation and then actually we will mostly work in these basis where N1 and N2 and N3 and N4 are single particle indices ok so now well the equation of motion for the density matrix is pretty simple no it's just the Eisenberg equation of motion so it's the commutator of our operator of choice this time the density in the fullamentonian of the system but then we can think about a way to transform this into an equation for the response function we just take the functional derivative of both sides with respect to the external field by doing this so this side becomes an equation of motion for the response function but then we have to kind of compute the functional derivative of these commutators and the let's say the most difficult part of this is computing the functional derivative with respect to the electron-electron interaction parts of the Hamiltonian for example let's consider the time dependent heart term we can actually immediately rewrite it just as a functional identity making the functional derivative with respect to the external field appear here we did nothing basically not just an identity but now we can apply the chain rule here to transform here this in a derivative with respect to the density so we applied the chain rule but now this additional term is just the definition of the response function so we basically transform this variation into some kernel let's say which is then a tensor product with the quantity that we want to find the response function we can do the same things also for the other part of the electron-electron interaction in this case the fork part the sum of the two will have this shape basically kind of two particle kernel it's two particle since it depends on four single particle indices now we will see better what this means later and then this is much easier to calculate as we will see in a moment in fact for example this is the hearty term so basically we have a density loop and the coulomb interaction here we can just replace here the single particle basis expression for the density so this goes out of the integral and we just get basically the density matrix product with the matrix element of the coulomb interaction keep in mind that because of momentum conservation this term will be only evaluated at zero momentum or the momentum of the incoming field at the end of the calculation we can do so in the end we arrive at this expression it's the same as before and then the functional derivative is pretty easy in this form this is a time dependent hearty we just get the coulomb matrix element basically we can do the same for the exchange part of the self energy this is just a fork term so here I wrote rho to maintain consistency we can also call it the Green's function at equal times of the system and this is still the coulomb interaction but here we have a problem in our treatment because if we just keep going so we do exactly as we did for the hearty term so we rewrite these in the single particle basis now we have a problem because this bear coulomb interaction is bare, it's not screened and therefore it will give wrong excitons so we have to actually replace this with a screened version of the interaction in order to avoid the over binding of the excitons and also to be consistent with what we learned yesterday the GW case in fact we just replaced V with the statically screened electronic interaction and the screening, the static screening is in the RPA approximation so this is exactly the GW approach now this is transformed it's not anymore pure exchange it's not anymore the fork term but it's the screened exchange approximation for the electronic interaction that is commonly used to compute excitons is the so called hearty sex so hearty screened exchange approximation now we can continue after overcoming this obstacle now we can write the screened exchange part also in this way notice the different sign with respect to the hearty part we can compute again the functional derivative that we need to get to the equation of motion neglecting the functional derivative of the W itself now W in principle depends implicitly on raw because of the screening but this is an higher order term we don't consider it and then we get this simple expression so to bring everything together now for our question of motion of the response function we get basically the commutator with the non interacting Hamiltonian then the commutator with the external field ok and then we get this part that we just computed which contains this W minus 2V which is the electron kernel now we can actually in practice like what does this mean for example the first term is pretty easy just this commutator we can apply H0 on the left and on the right and we just get the differences of the single particle energies in this case in the case of the field so remember that we are in linear response so we are at first order in this field therefore for the raw we can use the ground state value the equilibrium density and then we apply this also in this fashion to the left and to the right of the states and we get the equilibrium occupation of our system instead of here is the difference of the energies here is the difference of the occupations and then the last complicated term actually is stated in exactly the same way so is basically the same steps after we do this we finally have a simpler expression for the response function the equation of motion for the response function now consider that since we now are explicitly the equilibrium so we have used the equilibrium quantities in the evaluation of the commutator now actually turns out that the chi is just dependent on the differences of the two times and then here we have finally this k which is what we computed before just put it together in a single variable w minus 2v now the difference in sign plays an important role because the w acts as an attractive interaction so this is the binding term this is responsible for the electron bound state appearing below the quasi particle band gap of the system and instead this partial contribution is normally much lower in value in magnitude than this in the semiconductor of interest to us so in general when we have this kernel we can find bound accidents ok so now let's switch to a different basis which is the transition basis as we can see we are now explicitly considering transition from the valence band so n1 is now a valence state to the conduction band so n2 is a conduction state so we can just label this double index with a single index the transition index and in this way we kind of simplify a little bit this equation because now it depends on 2 indices instead of 4 indices ok perfect now finally we are most at the end we can just do the Fourier transform of this since in the end it depends just on the difference of the times we can Fourier transform this and then if you ok try to do if we put k to 0 then it means we are putting to 0 the electron interaction and then we need to go back to the independent particles k and indeed if you do it you end up just with chi equals to this quantity so it is written in a kind of compact form but you can recognize it is the same chi not independent particle response function that we discussed yesterday but now we have an additional term this kernel and therefore finally we can write it as probably as it is most known the beta-salpeter equation as Dyson-like equation and this is kind of a kind of a diagrammatic representation this is the response function the box represents the fact that the electron and holes are interacting in a complicated way to this box we have first a non-interacting case the bubble diagram and then we have the interacting part ok and this is also the point of arrival of the other derivation approach that I outlined in the beginning the one based on Edin's equation in the end you get to this expression very good and of course the kernel is composed of these two terms that we just described perfect now we have to solve it so normally when you have a Dyson equation you try to invert it and this is what we are also doing here we try to factorize all the term with high on one side and then if we just keep omega alone we see that what is left as kind of the form of an effective Hamiltonian for two particle states so if we just call these h let's say then we can kind of invert it and place this on the other side of the equation ok so this we called h and then we invert it and we get something like this formally written so you see this actually starts looking more and more like a propagator like a green's function because in a green's function in a supercar space typically is the inverse of omega minus it's a relative Hamiltonian and in fact this is kind of the point here because now this Hamiltonian contains all the information that we were after at the beginning for example to describe excitonic corrections to optical absorption vector the eigen values of this Hamiltonian that is what is technically diagonalized inside the hambo give the exciton energies and instead the eigenvectors give the exciton coefficients that we were discussing before so now we can write this in this new lambda basis which is the exciton basis in which it is diagonal obviously since we diagonalized the two particle Hamiltonian and therefore finally if we want to go back to the transition basis we just have to perform a change of basis so basically we arrived at the end and we basically see that we have reduced let's say a problem that started from a complicated equation of motion for the response function to an external field of the system to basically just linear algebra problem just diagonalizing this effective Hamiltonian which contains enough diagonal part that encodes electron interactions in these hearty screen exchange approximation so these are all of course not time dependent, not frequency dependent all static interactions and this now this effective Hamiltonian that we need can just be computed with the techniques that we already know so for the energies here the single particle or quasi particle energies we will use DFT plus GW or various things the wave function we will use typically the DFT wave functions the conSAM wave functions and then we just have to compute the RPA screening to compute the W the statically screen interaction in the screen exchange approximation and that's it basically this is what kind of Yambo does in the next lecture Davide will enter into much more details about this and about also other technicalities so now I'm kind of skipping over many things but I thought at least in this way I can give you kind of initial understanding of what we mean and we say we derive the better equation we solve the two particle Hamiltonian we get the exciton information now I come to the last part in which I want just to give some examples of how we could use the BSE we could use an excitonic picture beyond or in addition to simple optical absorption not so simple but optical absorption measurements I think our guest speaker today will probably give a much better overview but still I will give you some examples so the first natural extension of what I said is okay so far you were implicitly considering the case of optical absorption therefore of macroscopic fields in which the momentum of the incoming field is much smaller than the extension of the deluene zone of the system but what happens if we instead we want to consider excitons with a finite momentum well then we would need to diagonalize the excitonica Hamiltonian for each finite momentum a different Hamiltonian for each momentum this is kind of similar if you know phonons to what is done in the matrix in the phonon case and then we have a q-dependent exciton basis and this describes you see a non-diagonal transition indirect transitions for example from a valent state at k minus q to a conduction state at ck so it's basically indirect transitions and when you solve the BSE at finite momentum for example compute exciton dispersion relations of what you do when you compute a phonon dispersions this is for example an example done with Yambo we are solving the BSE at values q's values transfer momenta in the deluene zone of monolayer MOS2 and basically we get the dispersion of the values excitons is a very badly made plot but just to give you an impression of what can be done but physically inside we can actually get from this paper maybe you will talk a bit more about it but I just want to mention some interesting things that can happen when you study exciton dispersion for example this is monolayer MOS2 and this is the exciton the first bright exciton of MOS2 da exciton it turns out this is a doubly degenerate exciton and when you go away from q equals 0 it splits and it has an interesting dispersion that goes parabolically and this is determined by the screen interaction that kind of gives this parabolic dispersion but the other one is dominated by the macroscopic component of the heart interaction which gives this linear behavior at least close to q equals 0 and another interesting case is this one of solid pentasin as you can see this bright exciton has kind of different energies at q equals 0 depending on the direction in which you take the q equals 0 limit in particular if your direction of q is parallel to the polarization of the incoming field so let's say it's a longitudinal direction you have a higher energy than the case in which the opposite case when the direction is orthogonal and so you have kind of a transverse direction and this is the so-called longitudinal transverse splitting of the exciton states maybe you know it from the phonons again the energy with the phonons is very nice maybe you know the L-O-T-O splitting longitudinal optical and transverse optical mode splitting this is a kind of a similar effect well obviously this ties into something that is very important at the moment for research which is basically ultrafast out-of-equilibrium experiments for example pump and probe experiments in this experimental setup what you do you first excite, create excitation in the system with a pump pulse then there is excitation and relaxation dynamics and then at a certain time you probe the system with a second pulse and check the state of the system and in system where excitonic effects are very important you kind of see complicated signatures in this pump and probe spectra for example this is a time-dependent arpes it means it's a kind of arpes that can probe also empty state also conduction states while regular arpes normally is confined to valence levels but here we don't see kind of a no parabolic conduction band or anything we see this blob and the authors of this experimental paper they say okay this is actually below the quasi-particle band, this is a kind of an exiton blob and actually if we wait a bit of time we start seeing some signal here and this could be because there is some kind of transfer of exiton from here to here for example some kind of complicated scattering process between exiton and phonons that could kind of move and change the momentum during the relaxation process of these exitonic states instead to the right we have another very interesting although very complicated type of experiment this is called a multi-dimensional optical spectroscopy and for example it is very useful to measure the broadening of the exiton peaks in general experimental sample you have many imperfections over the spatial distribution of the sample so it's not a perfect crystal you have defects, you have like distortions and whatever and this causes the various energy level to be a bit misaligned for example in absorption experiments but also in luminescence experiment and these adds a lot of noise to the broadening, to the width of the peak but with this technique you can actually remove all these noise and get to the true or so called homogeneous line width of the system which is the one that we compute when you do first principle calculations here you see the main diagonal is the line width of an exiton peak including these inomogeneities and instead the cross diagonal is the homogeneous line width so it's pure perfect crystal line width more or less of course this is a very difficult experiment and you see this is basically the cross section in the homogeneous direction and people found that the line width of the exiton peaks can be reduced by one order of magnitude between inomogeneous and homogeneous so this is quite important experimentally and where's the theory in all these well these are very difficult experiments to reproduce theoretically in a very convincing way let's say there's a lot of discussion about the important role that exitons certainly have in this kind of experiments but how to model this is pretty difficult here we can see some examples on the time dependent R-PES case on the left you see this is just a model so it's not first principle simulations and it gets what we kind of expect from experiment also this is the valence band this kind of dashed parabola is the conduction band but we don't have this we have these exiton blobs below the conduction band and on the right you see instead the calculation done with the hambo by Davide actually of kind of the same thing this red parabola is the conduction band of lithium fluoride and then this energy the distance between the bottom of the parabola and this blob is the exiton binding energy and at the exiton binding energy there is this kind of signal which is a bit deformed with actually replicas of the valence bands so this is a kind of another complicated out of equilibrium process who can attempt to model it using the Bethe-Salpeter equation another important topic is exiton phonon coupling this is also a difficult concept to get around but for example it can be used I will give you two examples one example is to reproduce phonon assisted optical spectra so optical spectra that are determined by indirect band gaps mostly in this case we have bulk boron nitride and photo luminescent signal actually this is cathodoluminescent signal is determined by the emission, the recombination basically of some exiton at finite momentum and they can only recombine emitting light via the help of a phonon of several phonon modes and these are basically the satellites the phonon replicas that assist in this recombination because it turns out that for example the strength of this exiton phonon interaction is kind of proportional to the second derivative of our response function including the BSC with respect to atomic displacements along the various phonon modes another way to compute merge of the first principle types of calculations density function perturbation theory which is used to compute the phonons and many body BSC which is used to compute the exiton and then by doing this merging you can also get the exiton phonon and in this paper you see here this is not a band structure this is an exiton dispersion also of bulk exiton boron nitride and the colors represent the authors calculate as the relaxation times of the exitons so basically how much time typical time the exiton takes once it is excited by a pump pulse to relax and go to lower and lower energies so ok this is more or less were some examples from the literature of course this is a difficult problem as is the problem in general of non-equilibrium quantum mechanics in these condenser matter systems in many things that can be done here also a kind of a fundamental level I will give you just an example of something that we are trying with Yambo when you compute the phonons this you will see this better tomorrow you already include inside the phonon calculation the contribution of the electronic-arter interaction to get reasonable phonon frequencies but this contribution is also as we have seen inside the exiton so what we are trying to do now is to remove this double counting so for example to see what happens if we compute the exiton phonon coupling strength like removing the art interaction for the exitons and as you can see from these plots of the matrix elements these were done also with Yambo the orange is the one with the double counting and the blue is the one without double counting you see qualitatively we have of course the same structure the same symmetry, the same phonon modes coupled with the exitons this is monolayer molybdom disulfide but we can have also pretty different intensities as you can see this is not the final answer but it is just to say this is a very complicated problem there are many things to be studied many interesting approaches both theoretically, purely theoretically but also from the experimental side and from the explanation of the experimental signals there is also much to do so welcome to this field if you are interested and with this just conclude with a summary what we have seen that the independent particle picture is failing in the case of many semiconductors especially layer materials two dimensional semiconductors to reproduce important spectral features because we are not including in the standard treatment the electron interaction these we can get it in a very general framework in which we try to model the dynamics of the excited electron system out of equilibrium and for example from the question of motion of the response function then we can kind of recast it in a kind of effective to particle Hamiltonian form this is the standard better approach and this yields the exitonic picture that as we saw can be used to kind of improve our understanding on a variety of spectroscopic phenomena with this I thank you for your attention and before the end I just let me give you some references so basically if you are just interested in like learning about the derivation that I sketched in my slide without maybe too much context I would just suggest these two papers, the bottom two so these are papers in which this kind of derivation that I have shown is done very well with all the steps and everything if you are more interesting in also learning in the context of how one can do many body, physics in a time dependent framework of course there is the book of Karanoff and Beim and then there is the book that we already mentioned many times the book of Gianluca Stefanucci and Robert van Leuven honestly I don't know which one is more difficult Karanoff and Beim are actually ok, try the first five chapters of the Stefanucci then you tell me how it is and ok, it is really thank you for your attention so thankful you for this very nice talk so I recall you the first part was really focused on the Betis al Peter and what we can do with the Jambo code, computer excitons and absorption and then there was a second part which was more motivational to say you have the exciton, you can do much more there is a lot of physics you can explore and now the session is open for questions and I also remember that there will be a prize for those who are in presence and we call it a prize for the best attitude and doing questions is part of a good attitude in the participation of the school so we welcome many questions Alberto so first of all thank you for your nice talk and I hope this question is not out of topic but if you start from a GW bend structure you can also compute the finite lifetimes of the bends so is it possible to consider these lifetimes within the Betis al Peter equation? ok so this is actually a much deeper question than I hoped for but ok, try to reply just to say if you just plug in the complex part of the bends in the diagonal part this would be totally wrong ok because the BSc rest on the fact that you are using inside single particle well defined single particle states so you do not use the full spectral function that you get with GW you just use the spectral peak you just take the quasi particle energy and that's it otherwise it becomes all inconsistent then consider this if you put some kind of imaginary part of the let's say the electronic states inside the Betis al Peter equation which will describe the broadening relaxation and so on then the two particle Hamiltonian is not anymore pseudoimitian does not anymore give real eigenvalues and then you have to ask yourself like isn't it possible that I'm including something at the independent particle level that could be maybe cancelled if I include also dynamical interactions in the kernel this is actually the case so you cannot include higher order treatments just in the single particle case you kind of have to find a way to also describe in a consistent way a dynamical part of an electron interaction I don't know if this is clear or not but more or less this is there Thank you very much That was really interesting A question about the interactions that you include when you describe exit and phonons in two different ways one is the Bernadi-Tangali way that you showed exit and phonons from the kind of Hedins perspective from coupling excitons that you solve with phonons like here and you get lifetimes and the other is by real time GW real time propagation where you also include interactions with phonons so can you comment about the interactions you can include or not include in the two cases and I admit I will talk about it a little bit later but I'm interested mainly about the real time propagation part So I think in both cases what it boils down to is that you add the dynamical part of the kernel which depends on the first order on the phonon propagation so it's a kind of so basically you add for example the interaction of the conduction band of the electron with the phonon of the valence with the phonon and then the cross interaction between the two is called interference terms so it's a kind of first order correction in the phonons where the phonons are dynamical but then this correction is not if this makes sense re-summed in a dison-like way, it's just kept at first order and this I think is common to all kind of approaches this one, the equivalent one that was there at PLVG Kudatso and also kind of a real time approach however if you start your derivation because you can start your derivation and this is what was done here and also by Kudatso at the Bensal-Peter level like I have kind of the excitonic propagator I have the excitonic Hamiltonian now I kind of perturb it with an additional term with the phonons and then you get this go to the beginning of my slides and put electron for interaction inside the main general electronic Hamiltonian in this case you would be away from the standard artisex approximation, you will have to include a kind of vertex function in the phonon so you will have basically the GW interaction more or less is the artisex approximation plus a kind of fun type self energy so g times the phonon propagator times the vertex and this vertex will have to include all electronic interactions so also kind of an excitonic at the excitonic level within this vertex and if you do this it comes out very similar to this but with an important difference that basically is this one that the excitons since the vertex that you will include in some types of energy is the vertex without the heart interaction so it is irreducible vertex then you get excitons like this without the heart inside, with only W inside so you get slightly different and depending on the system Hamiltonian and then this is basically the difference for example for MOS2 in some unphysical exciton phonomatic elements in unphysical because these states are too far away to interact with a single phonon energy not because the calculation is wrong so you can see there can be kind of an effect so there is a difference and we are now finishing our work with Andrei Amaini in which we explain all of these very well with all the cases and yeah it remains to be seen what these entails for the future then in the next few minutes I don't know so yeah thank you for this very advanced discussion I mean here we are discussing things which are really different years of the present research I would like to have much more basic questions for the students I have a short question here as far as I know the YAMBO code can also use the Redesal Petri equation to calculate Magnon spectra to calculate sorry spectra from Magnon's oh ok, ok, yes could you say a few words on how the Redesal Petri equation can be extended to the magnetic interactions yeah so no I'm not doing that because the expert is Davide so I think he will probably talk about it a bit in his lecture there will be a slide on that so maybe we can check if there are questions from the audience of online hello just please hello a very nice presentation and actually I am curious about the ARPS plot that you have shown for excitons and what is the material actually you have chosen ARPS exciton plot so if I understand correctly you are asking me about which materials I have shown in these examples yeah yeah ARPS plot ah the ARPS so this one this one should be transition method like arcogenide tungsten something I think tungsten diselenide WS2 and I just want to ask here you have shown you are saying that this is the exciton when light is interacting so there must be many so is it a single one how are you explaining this exciton so you are still your question is still about this figure the left one is it a monolive? yeah ok thanks since this is a layered system in transition method like arcogenides you still have strongly bound excitons also for bulk systems so basically here they had some independent way to determine the position of the quasi particle bandga then they did this time dependent ARPS and they saw basically this signal this very weird looking signal below what should be in their determination the quasi particle bandga and therefore they assigned this to an electron all bound state they say ok this is an exciton and this is kind of this experiment ok then I've seen a nice question from Inizio Marinho from the online audience can unmute yourself so otherwise I do the question myself so the question is about the screening he says so we are doing all these complex BSc theory but then we still use the RPA screening so why do we do that well I mean let's say it's the simplest approximation and the most consistent with the many body treatments in general that are implemented in codes also you may think of this as a kind of improvement with respect to the RPA screening so the RPA screening is already a small improvement with respect to just the independent particle scales and then we kind of add even more physics inside it and from RPA it becomes BSc either the step before to go to the step after that if that makes sense ok and then I know the question from Rajet Dut if I spell it correctly if you can unmute yourself as well Rajet Dut thank you very nice presentation actually because we are talking about the exaltonic states so I'm wondering whether these exaltonic states can be used or to study the metallic optical optical spectra or is it it can help us to understand the metallic system as well ok so in general it's kind of a bad idea to try to apply betasalpeter to metals exactly because of the screening problem so metals are very heavy screen a gap and dynamical effects in this screening are extremely important while here the way we are taking electronic interaction is just at the static level so most likely if you try to do that you will get wrong results also even I mean in addition to the dynamical screening dynamical effect problems there are also some details inside the exaltonic Hamiltonian they didn't discuss about that need to be adjusted basically I'm referring to what is known as the thumb dunk of approximation this is a standard approximation that simplifies the exaltonic Hamiltonian but doesn't hold for metals maybe you will understand more about this in the talk of Davide Davide's talk in which he will explain these blocks of this Hamiltonian much better I mean much more basic answer is that in metals the screening is so strong that usually you also do not bind so you don't have excitons but you could have kind of modifications in the absorption sorry if I can add on that what you say is totally correct but still there are literature calculation on metals there is a famous paper in the still alloy group showing the existence of bound excitons in metallic current nano tubes so there is work on that and there are cases when you can find interesting results I would say in semi-metals not in metals semi-metals you are correct Any more questions from the audience here? I think Enesio Marino Junior asks to read the questions Yes, I think we already did that so I wonder if everything you said is also valid for core excitons is the physics still the same? I think generally yes but maybe Davide, you can answer to this I would say that in general for core excitons the electron binding energy is even more important because the oil is pretty much localized so it tends to interact a lot and there are at least two groups that worked on using beta salpator to describe core excitons and you can do that and it works pretty nicely We have time for one last question before the break May I please? Yes, sure Can we do bi exciton calculation using Yambo? There was also one question in chat box Same So in Yambo right now there is no response and charge excitations like that Ok, that was quick and also I see a raise the hand by Nea Kapila Sharba if you want to do your question I am sure they asked the hand in my hand You wanted to say something about bi excitons? No In Yambo we can calculate no linear properties You are calculating bi excitons functions and full point response functions You cannot disentangle bi excitons from single excitons but there you have free body interactions in uncontrolled way This is a type of simulation that the user can do like running Yambo So let's say the standard implementation of the BSE in frequency space you directly compute the response function and that is just for excitons In the real time propagation you can go beyond the linear regime and you can have much more effects somehow but in the implementation that we have at present in Yambo we linearize the kernel dependency with respect to the interaction so I think you will not capture bi excitons and these kind of effects but maybe we have to discuss so Let's say that at least the real time propagation formulation will be prone to include more easily these kind of effects OK, so time for the coffee break I think We are perfectly on time and we have half an hour of coffee break We will assume in half an hour


Hello friends welcome again to another session on number systems so far we were doing conversion of decimal numbers of terminating decimal numbers and pure form of non-terminating recurring decimal numbers in this session we are going to do conversion of decimal numbers which are mixed type non-terminating recurring right so what do I mean so in the earlier sessions we saw in the earlier sessions in the earlier sessions we saw that there are two types of decimal representation one is terminating terminating decimal representation and the other one is non-terminating non-terminating and repeating or recurring whichever way you want call it right recurring decimal representation so terminating example was let us say 0.25 another was 0.325 and things like that non-terminating would be 0.333 and it continues or 0.313131 like that right now in non-terminating recurring also we had two two types one is pure form pure form where it was all the decimals after the decimal point was repeating so for example this or 0.37 bar correct so all the digits will repeat now there is a mixed form also mixed form is you know what is mixed form so few decimals or few digits after the decimal will will not be repeating others will be repeating for example 0.223 bar that is this is nothing but 0.223223 so on and so forth right now in the previous two sessions we covered this fully how to convert terminating decimal numbers into p by q form we also followed covered this form your form how to convert in this session we are going to deal with mixed mixed decimal non-terminating recurring decimals so let us let us see how so let me take an example first so let me let me say I have to convert 0.231 bar into in the form of what p upon q our rational number we know that this is a rational number so it must be represented in the form of p by q so now look at the process carefully now if you if you see in the previous case when we were dealing with the pure form there let us say the number was simply 0.31 bar so in that case what did we used to do we used to count the number of repeating digits so in this case there are two isn't it n is equal to and hence we used to multiply first of all we will be calling this as x and then we will multiply the given number by one followed by how many zeros two zeros so one zero zero x in the left hand side and then on the right hand side it was again if you multiply 0.31 which is nothing but 0.313131 like that by 100 you will get 31.31 bar isn't it now what did we used to do you we used to subtract these two equation this is one and this is two so we used to get what 100 x minus x in the left hand side will be equal to 31.31 bar minus 0.31 bar and we used to get 31 right and hence 99 x was equal to 31 so hence you can find out x is equal to 31 upon 99 so easy to find out now in this case you can't really multiply this by 100 so here again if you see n is equal to two how many digits are getting repeated two right but if you multiply this let us say this is x but if you multiply this by 100 what will you get 100 x will be equal to 23.131313 so on and so forth isn't it now if you try to subtract let us say if you want to subtract 100 x 100 x and minus x and this is 0.2313131 like that it will be very difficult to subtract these two parts isn't it so it will not work it will not work so what do we do in this case first of all first of all shift the decimal to the position which position exactly before the repeating where the repeating starts right so two is not getting repeated so I will try to shift this decimal just next to two and before three right how can I do that so you can simply see you can multiply this by 10 right so hence if you multiply that by 10 you will get 10x is equal to 2.31 bar isn't it now this is my first step now I will repeat the process which I have learned in the previous session that is this one now again now count n n is equal to how much 2 how many digits are getting repeated 2 right now you multiply this now you call this equation as equation number 1 now multiply equation number 1 by 1 followed by 2 zeros right so 100 into 10x is equal to 100 into 2.31 bar so hence you'll get 1000 x is equal to 231.31 bar this is my second equation now you operate 2 minus 1 that means 1000 x is the left hand side minus 10x is equal to 231.31 bar minus 0.31 bar okay so what will you get you will get 990 x is equal to 231 isn't it 990 is I'm sorry no not 2.31 this will be this will not be 0.31 it will be 2.31 bar right so this is simply 2.31 bar so if you subtract it is nothing but 231 minus 2 or I'll write the full steps so hence you will get 231.31 bar minus 2.31 bar is nothing but so this 0.31 bar will cancel because of this you know so this both the 0.31 bar after the decimal will just get eliminated so it will be left with 231 minus 2 which is equal to 229 okay so hence x is 229 upon 900 sorry not 900 990 990 understood understood how to find it out and if you can simplify this further you should simplify this fraction now let us take another example to check whether we learned it or not so let us say now x is equal to let us say you have to you have to convert 3.32123 bar this is the decimal number right this is non-terminating but repeating right you have to now convert this into which form p by q how to do first of all what is the step take the decimal point just next to the repeating digit so one is the first repeating digit so I'll have to shift this decimal here what to do how to do so you can shift that by two places by doing what multiplying by 100 so you'll get 332.123 bar now by this step I have ensured that after the decimal all the digits must repeat so now you see after the decimal all the digits are repeating now what to do next now you follow the same process so what is n here n is 3 because three digits are repeating so hence I will multiply equation number one by one followed by three zeros so it is nothing but hundred x into thousand is equal to 332.123 bar into thousand so LHS will become 1 0 0 0 0 x is equal to 332 123.123 bar now this is my equation number two now do what you know 2 minus 1 that means 1 0 0 0 0 0 0 x minus 100 x is equal to 332 123.123 bar minus what is that this is 332.123 bar now if you see we have we have equated or let's say you know we have got the same repetition after the decimal so that gets eliminated so it is simply nothing but 9 9 9 0 0 okay triple 9 99,900 right x is equal to what is it so it will be nothing but 332 123 123 be careful with the calculations because you may lead to it may lead to some calculation error so this is the most simplified form so 3 minus 2 is 1 12 minus 3 is 9 this becomes 10 10 minus 3 is 7 so 1 3 3 right so just check whether we have got the right calculation 1 plus 2 is 3 so how to check check 1 plus 2 is 3 right now 9 plus 3 is 12 carry 1 1 plus 7 8 8 plus 3 is 11 that is 1 here carry 1 again so 1 plus 1 is 2 3 and 3 so this is correct calculation so what is x now x is nothing but 3 3 1 7 9 1 upon 9 9 9 double 0 okay double 0 so now if you see the numerator and denominator both are multiples of 3 right so if you and for that matter yes it is multiple of 3 only not 9 so it is 11 0 I am now dividing the numerator by 3 so it is 11 and 0 and then 5 and then 9 and 7 okay and the denominator will be 3 3 3 double 0 right let us check if the numerator again is divisible by 3 no it's not no it's not so so let's check the calculation once again how to check multiply the numerator what you got by 3 to see whether you got you you get this number or not so 3 times 7 is 21 carry 2 3927 plus 2 is 9 carry 2 again 3 5s are 15 plus 2 17 carry 1 3 0 or 0 plus 1 is 1 and 3 1s are 3 and 3 1s are 3 so looks like the calculation is correct okay so you must also have a habit of checking the calculation so this is my representation of what this was x and what was x x was 3.3 2 1 2 3 bar so if you do this calculation you will get 3.3 2 1 2 3 bar okay so please check the problem solving sessions for more such problems and you know once you follow the steps you repeat it for some time you try some 56 problems you will be able to get a command over the process I hope you understood the process of converting a mixed non-terminating repeating decimal into p by q form thank you.


Hello and welcome to the part 2 of our lecture on network architectures. In this part I will talk about architecture of different types of networks. If I want to set up a small computer network in my lab or room connecting few computers, the only thing that I need is a switch and a few UTP patch cords and I can connect my computers using this UTP patch cords and the switch. The switch will provide the interconnection between these computers and I have a small network in my lab. If a switch is a 8 port switch, then I can connect 8 computers and in case I want to add more computers, I can simply add one more switch and cascade these two switches and add more computers. This is an ad hoc architecture, but if I want to extend this network to my building or my campus or a city or multiple cities, then I cannot scale this architecture because this is an ad hoc architecture. So the architecture that is used in different types of networks, I will briefly talk about. In case of a campus network where I have a few buildings in a campus, the architecture that we use is called as a three-tier architecture. In this architecture, we have a data center where we have application servers and in this data center, we have what is called as a backbone switch. So all the servers connect to the backbone switch. In each building, we have a distribution switch and this distribution switches in different buildings are connected to the backbone switch using fiber optic cables because these distances are typically long, a few kilometers each. So the backbone switch gets connected to the distribution switches using fiber optic cables and within each building, we place multiple access switches. The access switches on one hand connect to the end devices that is the computers or laptops and on the other hand connect to the distribution switch. So we have a inverted treat topology in which the backbone switch, the distribution switch and the access switches get interconnected to each other and provide connectivity to end computers and hence provide connectivity from one computer to other computer. In case I want to have a wireless network also, then I can connect wireless access points to different access switches and provide wireless connectivity in the region in which an access point has been provisioned. This is a very simple architecture which is used to provide connectivity in a campus environment and finally, the network would also have a firewall or a UTM device to connect it to the internet. Similarly, if I want to provide connectivity in residences, homes then two technology options are used. One is wired broadband and the other is wireless broadband. In wired broadband, what we do is that we use the telephone cables to provide the connectivity. This is also called as the DSL broadband connectivity. In this connectivity, you have a DSL modem at your residence. The voice signal from your telephone and the data signal from your computer are multiplexed and sent on the telephone wire that comes to your home. At the telephone exchange, these two signals are separated. The voice signal is sent to the voice exchange and the data signal is sent on the internet. So using the telephone wire that comes to your home and using a DSL modem, you can use the same telephone wire connectivity to provide data or the internet connectivity also. In wireless broadband in which we use the 2G or 3G wireless to provide data connectivity, what we have is that either we will have a 2G or 3G and these days even 4G dongles which I can connect to my laptop or desktop or in case of mobile phones, this is inbuilt. So using the data connectivity on 2G or 3G or 4G wireless networks, I can access the internet using that. The advantage of this kind of connectivity is that this can provide seamless data connectivity or internet connectivity on my mobile phones even when I am travelling. If I have a corporate network which means that I have multiple offices across multiple cities which I want to interconnect like the network of Microsoft. All the Microsoft offices across the globe are interconnected to each other. Similarly, examples would be for IBM, for Intel or any company which may have national or international presence. They interconnect their corporate offices, business offices across the globe and this network is used to provide data exchange between the offices. In most of the cases voice over IP also. So they built a voice over IP network across their multiple offices and they have a data network which can be used to share software and hardware resources across offices. The architecture that is used in this kind of corporate enterprise networks are multiple. One possibility could be that I can have a point to point least line network between multiple offices. I have point to point connectivity between multiple offices and I can use this point to point link to provide the data network connectivity. The second architecture or technology that is used to provide such connectivity is that I can use VPN over internet. Since each corporate office has got its own internet connectivity, I can build VPN or virtual private network over the internet to provide secure communication across these multiple offices. So instead of having separate dedicated point to point links between multiple corporate offices, I could use the standard internet connectivity that comes to these offices to provide the data communication between them. Another advantage of this architecture is that every organization would have users who are traveling or you may want to access the corporate data when you are at home. So what you can do is that while you are traveling or while you are at home, if you have any sort of internet connectivity using DSL connection, a cable connection or a wireless broadband connection, then you can use VPN client software on your laptop or desktop at home and using that client VPN software, you can over the internet, you can have a VPN connectivity to your corporate network and access data. So in this architecture, the open internet is used to provide secure communication between the offices and also between telecommuters who want to access the corporate data. The third architecture that is used to provide corporate connectivity is also called as the MPLS VPN architecture. In this architecture, what is done is that multiple offices are connected to a service provider network. So as we go along in part three of my lecture, I will tell you what is the architecture of service provider networks. So what you do is that you would have service providers which would have national presence or international presence and you interconnect all your corporate offices to the service provider networks. The service provider networks are used to provide internet services and voice services. So using the service provider network, you build a what is called as an MPLS VPN network which is a private network interconnecting multiple corporate offices and you can also provide internet VPN connectivity to the telecommuters through the service provider networks. So here the advantage is that you contract out the complete connectivity to one service provider which has national and international presence and they will provide connectivity to all your office locations as well as connectivity to your mobile telecommuters and they will provide you all types of services which would include data communication between the offices, internet access as well as voice over IP applications. So this in brief was different type of architectures which are used to set up a campus computer network or provide network connectivity in residences or to provide connectivity to corporate enterprise networks. With this we end the part two of this lecture and in the next part we will talk about the architecture of internet and how the web works. Thank you.


Well good morning here in Washington and good evening in Afghanistan I'd like to welcome back back to our briefing room Marine Corps Major General John Tulen Jr. Commanding General of Regional Command Southwest. General Tulen assumed responsibility for RC Southwest on March 26th of this year he commands a multinational coalition of 30,000 service members drawn from the United States, United Kingdom, Estonia, Denmark, Georgia, Bahrain and Tonga. In partnership with the Afghan National Army's 250th Corps, his troops operate in the provinces of Helmand and Nimroz. The General last briefed us in June of this year and he joins us again from his headquarters at Camp Leatherneck. He will be joined today by Mr. Michael O'Neill, Britain's senior representative in Southern Afghanistan. He is also head of the Civil Military Mission and Provincial Reconstruction Team in Helmand. Mr. O'Neill assumed his position in October of last year and he leads a multinational team of specialists with expertise in development, diplomacy, policing, law, local government, education, agriculture and many other fields. The UK led multinational PRT works with Regional Command Southwest to assist the local Afghan government to deliver governance and security across the province. Mr. O'Neill last briefed us in January of this year. After some opening comments and we'll be glad to take your questions and with that general, sir, I'll turn it over to you for anything you want to open up with. That's great. Good morning to everyone back there in Washington. At this stage, we've not been, I've not been in command for about seven months and I've watched the progress move along pretty well and I'm pretty content with what I'm seeing. But I thought what I would do tonight is or is just tell you a little bit about my day today. I think it'll be a good story and we'll give you enough background information on what's going on here to maybe ask some good questions and get a feel for what's happening in Afghanistan. I just returned really just in a couple hours ago from a what we call a reintegration insurer. As you know, the shores are opportunities where the elders get together in their villages and they discuss items. We use the same term basically to meet a conference where we brought together, in this case today at Helmand Province, all the district governors as well as all the Afghan National Security Force leadership. So the Army, the police, the National Defense and the S representatives. And this sure was run by the governor, the governor of Helmand Province, whose name is Gulab, not Mongo. He's been the governor now for about three years. What I thought was interesting about today was the fact that reintegration is a concept and a practice that really it goes back to other case studies and counterinsurgency where we try to bring those individuals who have actually turned against the government to bring them back into the government. And it becomes a very powerful tool when it's used properly and when it actually brings back legitimate insurgents back into the fold. So this reintegration shore was run by the governor and reintegration in itself is a government process. So the effort today was to convince all the district governors and the leadership across the security spectrum that we needed to put a very concerted effort on convincing those insurgents, now Taliban, who have gone against the government, we want to bring them back into the fold. We want to offer them basically impunity from any prosecution or anything later on. So this conference was run and the speakers today were the governor and then there were the all the security leaders across the spectrum army police. And then they brought in the Mullahs from the Helmand province. Very powerful speeches from the Mullahs about what exactly it should be expected of good good Muslims and really trying to get a powerful talk to the district governors so that they could then use their Mullahs to spread that word out to the communities. So as the day went by, I think, you know, the point got across that reintegration here in Afghanistan and particularly in Helmand province was going to get a renewed effort. The reason why I bring that up is because reintegration in and of itself without any pressures is not going to work reintegration without having concerted pressure on the Taliban that they now realize this is not going well for them anymore, that the way the situation is developing in Helmand province, for example, these Taliban are realizing that they probably need to come back and join the Afghan government because they see positive results. What was interesting about my day today is that after the conference, I had a meeting with the Taliban commander out of Sengen province. And this individual came to me on his own volition, knowing that this reintegration offer was was now being pushed very heavily by myself and my colleagues here in Helmand province. And he offered to reintegrate. He also offered to lend to give over right now starting with 30 fighters and onwards of up to 300 within a month's time to the Afghan local police, which is an initiative where we bring the local the local elders come in and they swear that their sons, nephews or whatever will be good stewards of the community's law and order and that they will help protect the community. So this Taliban commander offered in a few days 30 fighters with a promise of up to 300 by the end of the month. Now he did this because he understands that at this stage in Helmand province, he sees the writing on the wall. He understands that we're making progress. He understands, for example, that in Sengen today, there is very, very little violence. And when you compare it with six months, five months a year ago, he realizes that this now is the time that actually has become sort of the motto is that now is the time Taliban to come back and join the government. He also realizes and he knows that currently, here in Helmand province at RC Southwest, we're in the process of putting on some major offensive operations to assume control of the Kajaki region and to begin what we hope will be a long term effort for re establishing the dam and the power projects and irrigation projects that are needed at the dam. So I think this is its reason why I bring this story up is because it's just indicative of the fact that what you really need in a counterinsurgency is you need relentless pressure on the enemy. You know, you can't be standing by you can't be sitting by, you've got to be constantly putting pressure on and that comes easy to us, particularly to the Marines out here in RC Southwest. We don't have a problem keeping the pressure on and they feel it and they know that the Taliban leadership that sponsored at Aquetta. Number one, the Taliban senior leadership is not coming into Helmand province because when they do, they get captured or killed. And that sends a powerful message to them to the mid level managers of the mid level Taliban who are operating in Helmand province. So their leadership is not there. There's also significant problems for the Taliban currently with the shortage of materials. We're constantly interdicting materials for IED making. We've captured hundreds of thousands of gallons of precursor chemicals that they're using to convert opium to heroin. We're just we're taking we're hurting them in the pocketbook and we're hurting them physically when they try to move into home in province. We're very aggressive in getting that message across that there is many splits in the Taliban hierarchy. There's arguments going on, etc. What that does is it's really created an environment again, where the Taliban leaders that are here living in the province are saying, it's time for me to go home. When I asked the Taliban commander this afternoon, I asked him, I said, Why are you changing your mind? What's the reason? Why are you willing to give up your Taliban ways?  During the years when Afghanistan was run by a very authoritarian government, he explained to me told me of times where he was beaten. He gave me names of people doubt Mohammed Khan, for example. And there are others who forced him to become Taliban because he said, I'm not going to take that kind of treatment. And the Taliban are going to offer me an opportunity to join them so that I can get rid of this government. I'm going to do that. And when you understand that environment, you understand that many of the Taliban that we're fighting or have been fighting or local, they're now turning their backs against the out the outsiders, the Taliban are coming in from Quetta and other places. They're turning their backs on and they're ready to fight them off. And they're ready to re engage with the government of Afghanistan. So this reintegration effort is extremely important. And as it progresses, we'll find that it was just, it'll the momentum will just take off. I think with that story that I just shared with you, I will turn it over to Mr. O'Neill so you can explain a little bit more about what we're doing on the governance and development side. Then we'll answer any questions you might have. Thank you. Well, good morning to everybody there. And I'm very glad to join General Tulan here and briefing you today. Let me just say the PRT, as the opening speaker said, is a multinational effort, civilians, military officers, police from several countries, including the US, UK, Denmark and others. And we work as part of a combined team with RC Southwest under General Tulan, and with the US Embassy Regional Platform, and the Paul Reed from the State Department. The reason it has to be a combined team is because all the work we do is closely integrated in security and governance and development. And across all those lines of operation, what we're all working here to do is help the Afghan authorities get into a position where they can run their own affairs in governance, but in security and in economic development. So that's really the task we're working to. And we need to do that so that the Afghan government can win back the confidence of people like the former Taliban fighters that John Tulan was describing. They need to win the confidence of ordinary people to put their trust in the government and not drift towards the insurgency. Now in the 12 months that I've been here in Helmand, I think we've seen real progress on all of those areas. I'll leave it to John to talk about security. But as a result of the improvements in security and freedom of movement that ISAF has achieved US Marines, British and other troops with their Afghan partners, we've been able to see governance and development spread steadily across this province. I just give you a couple of examples of that. You now have effective functioning bodies at the provincial level, a strong governor in Gulab Mangel, an elected provincial council of 15 members that includes four women. You have elected councils in seven of the districts, an interim council even in Sangin up in the north. You've also got 32 of the national line ministries now present in Helmand province in areas like health, education, agriculture, the other areas of business. You've got more judges and prosecutors and courthouses functioning, not only in Lashkargar, but in other districts. I'll give you a second example, education, vocational training, big areas for us. There are now more than double the number of schools that there were here in 2006. It's gone up from 47 to about 113. A huge increase in the numbers of kids in school, including girls. There were no girls in school at all here 10 years ago. There are now over 20,000 vocational training. We've got a big program that we're funding through an NGO called Mercy Corps. I went along two weeks ago to a graduation for 1000 young people, complete a three month training. 35% of those young people already had new jobs to go to. And that vocational training is being expanded. It's opened up this week in Goreshq, which is the main economic hub here. It's going to open in the next few weeks in Marja, in Gamsir, in other parts of Helmand. So there's been a lot of progress. Third example, I'll give you Cantonar Cotics. It's been a big focus for Governor Mangal. He's very much leading that effort. We work to support that in very close liaison with RC Southwest. And we've seen over the last three years in Helmand, probably a 40% reduction in poppy production, which is important because Helmand is the single biggest source of the poppy that produces heroin in the US, in Europe and in this country. So a 40% reduction is a huge step forward. We're continuing that effort this year and the program is going well. We've also seen and we've been able to help mentor a much more effective Afghan Cantonar Cotics police. And they've had multiple increases in seizures of heroin, of opium, and in the rest of drug traffickers. So there's been a lot of progress. Probably the single most important evidence of that was the beginning of transition for Lashkargarh here in July of this year, where the Afghans now formally taking control, running their own affairs. And that was a great step forward and a great symbol of progress. So for us in the PRT and I think all of us as coalition partners, we're looking at over the next three years to a new phase, which is about transition, putting the Afghans in the lead and helping them take control. So our task really now in the last two or three years that we're here is to make the progress that's been achieved more durable, to make it lasting and help the Afghans take that forward. And that will include in governance, helping them make their own systems of government stronger, with better connections between Kabul and the province between Lashkargarh and the districts. I think secondly, it means more investment in economic infrastructure. There's a lot of work going on by the US Marines, the PRT, USAID in roads, irrigation, power, all the things that are necessary for the economy to function, which takes me to the third bit, which is about getting the private sector moving. Because people here want security, obviously, they want health care and schools. Those things look much better now, but just like any other country in the world, they want jobs. And that isn't going to come from us or from the government of Afghanistan. It'll come from the private sector. So those are some of the challenges as we look forward. There's still a lot of work to do. We need to maintain that effort as we begin to draw down. But putting the Afghans in the lead is working in security and governments and developments. And that's what we need to consolidate. If I could just add two points that I failed to mention, and that is one, the reintegration program is all about creating opportunities for the returning insurgent. When an individual reintegrates, they're offered opportunities. First of all, they're offered some cash in the first couple of months for pay for work. But additionally, they're offered the opportunity, as Michael just described, is going to some vocational training and getting a skill. It's critically important that as they come back in society that we make them a worthy citizen that can produce and provide something to the community. So that's an important aspect. And I think that gives them hope. The other thing I wanted to mention in regards to the short today and a positive change is the fact that as I discussed that authoritarian government earlier and the abuse, the abusive way that some of the citizens of Helmand Province or Afghanistan were treated in the early days, that the police force, which is really the bridge between the country, the organization, the state itself, and the people. And when the police during that authoritarian period were extremely corrupt and extremely abusive and to turn the people against them. What we're seeing today is we're seeing a police force that's much improved. The police chief spoke today at the conference. And what was interesting in his comments is something I took away from was the fact that he said, you know, this is the first time in a long time that I even have a uniform that I could wear and a uniform that I could be proud of when I said in the days in the early days as a policeman, they didn't have uniforms. They didn't have equipment. It was a total mess. And they reiterated the fact that thanks to the organization and the structure that's been provided by NTMA and other organizations and by the regional commands themselves, they now have a sense of pride. They have a sense of mission. And they're not predatory in their corruption. And the people are starting to trust them. So all these things that contribute into this positive trend of reintegration and getting back coming out of the cold and joining back with their friends and families in Afghanistan. So I just wanted to add that I think we're we're finished with our statements and we'll open to questions. Thank you both gentlemen very much. I'll go ahead and make a I'll call on the reporters here in the room and they'll identify who they are with their question. Michael. General, it's my heavens from the London Times. Can I just check with you? Did you say it was the commander in Sangin or a commander in Sangin? In other words, you see the guy in charge of that whole area. And are you able to give us his name or is that too sensitive at this stage? I don't want to give you his name right now. But I think in probably 30 days time I'll be able to give you the name. I will tell you that there are several Taliban commanders. But the ones that are most important, the ones that will do the reintegration, the ones that have the influence in the community, the ones that can convince the local people to mobilize and support the government are the Taliban commanders who are homegrown. There are Taliban commanders that are from outside the area. And they're resented. And in my discussion with the Taliban commander today, you know, to be quite frank, he offered he offered to kill the outsider, the one that's that's sort of the connection between the senior leadership in Quetta and the insurgents that come from the Sangin area. So there are differences. But the one I'm talking about is an insurgent who is from the area of Sangin, has a lot of influence. And he's the one that's going to make the difference. General Otto Kressman, C-Power Magazine, you said you were going to start a significant offense of operation. But aren't you facing some reduction in your in your forces, both the US and and coalition in the near future? Right now, I am at maximum capacity. I have all my forces, and I'm making maximum use of all the assets that I have. We're in the process right now of making some major offensive pushes in a variety of different directions, specifically because we know we, as I said earlier, we figured out that you need to tip the scales by being relentless in the pursuit of the Taliban. And that's what we're doing right now. Yes, there are going to be some drawdowns. There will be a drawdown over the next 12 months. But right now it has, besides the planning, it has no effect on our operations. NBC News, if we can go back to the Taliban commander, who you spoke to today and from saying in, first off, how common is it that that someone like this would come to you? I was always sort of under the impression that these guys would go to an Afghan and that it was more of an Afghan led the wreck, the reintegration. But how common is that? And then also, I mean, when he offered to kill this other guy, this other intermediary, what did you say the US and the cold, the ISAF is is trying to capture or kill, presumably, this individual. So what was your response? Great questions. And the first question I failed to mention this, and this is very important, is actually I was with the governor, the governor of helmet and I went to go see this Taliban commander. And I really turned the conversation completely over to the governor. I was really just a listener. And the governor was the one who discussed with the Taliban commander, you know, how they would contribute the personnel to join the ALP and what what was meant by the ALP providing some financial support to the to the to the individuals that joined the ALP. He did all that discussion. I just listened. And then the governor looked at me and I said, Yes, I'm more than willing to to work with this this Taliban commander, because we do the mentoring on the Afghan local police, we're the ones that work with them, put them through the training, etc. So the governor is what did take the lead. And the Afghans are the ones that this is an Afghan program reintegration. We are just we are helping we are helping supporting it financially. And we're helping support it from a training perspective. Your second question. And you have to remind me how to respond. Oh, again, when he when he made that statement, he was actually talking to the governor. And the governor told him that his efforts, whatever efforts he contributed would be just fine. The Taliban out the Taliban leader that he was referring to is living in and around the same area. And we realize that as soon as reintegration is made public, this individual will become a target. And so the governor realizes that it's probably in everybody's best interest that this individual goes away. And so we're not given up on our targeting of that particular individual.  Just one more follow up, General Tulin. How do you vet someone like this? Before you bring him and any of these fighters? And, you know, we saw President Rabani was assassinated by someone who was allegedly coming in to reconcile. How do you vet them to make sure that they're not infiltrating? Well, as you probably know, I mean, this business that we're in is all about risk and managing risk and mitigating risk. And so there's risk. There's risk associated with bringing anybody in from the Taliban and bringing them into society and then trying to reintegrate them and give them jobs, make them responsible people. So there's risk associated. That's probably why it's a good reason that this is an afghan program, because I think in many ways, the governor mango when his conversation, his conversation with me after the fact, we talked about the level of sincerity. And this in this individual, particular individual was known to the governor before. So there is a certain feel. There are other ways of making sure that their past record is is at least documented. And we have a system. I'm sure many of you heard of the bats and hide system where we take their fingerprints, we take their retinal scan, and then we have a database. It's not like our FBI records and files, but it's getting pretty good. And it gives us some insights as to what that person has done in the past, and what can be attributed to that person. But that's that's really the extent. The reality is also to that the people that reintegrate, there is a very detailed process that the governor will begin in helmet province. But it actually that whole package takes about three months for it to come back down through the system and be finally approved. It actually goes through some some processes with what we call the Joint Secretariat, which is a group of elders from the province. And then there's the High Peace Council up in Kabul that goes through the government process, and then comes back down. So it gets a pretty good vetting, but you can't eliminate all the rest. USA Today, general, how many people in Helmand have been reintegrated so far? And how many are in pipeline and you anticipate this program is increasing dramatically in coming months? Unfortunately, in Helmand province, we have not had very many reintegrates. And the process, as I mentioned earlier, is that, you know, we got to keep the pressure on. And in the past six months, we've been able to maintain a pretty pretty good security bubble in the populated centers. And we're making this concerted effort to really close the last bastion of insurgent activity in Helmand province up there in Kajaki. So with all that pressure going on, on top of the fact that really our commander, General Allen, about two months ago made reintegration a major effort. And he stressed that the time was now that we need to push reintegration effort. So in Helmand province, we don't have too many. Today was really, in my mind, a very big success story. We've got we brought all the local government figures in. We've got the governor firmly behind the program, the security leadership. And we got a Taliban commander who was willing to come in from the call. If I'm just gonna add one thing to what General Tulen has said, the process of formal reintegration in Helmand has been slow for the reason that John described the process still quite slow. We hope it's going to move forward after today's event. But I think if you were taught to Governor Mangel, he would also talk to you about what he describes as informal reintegration or quiet reintegration, which is where fighters decide to stop fighting. And they don't necessarily come in through some formal program, but they stop fighting, which achieves the same effect. And so Governor Mangel has spent a lot of time, and I think increasingly General Tulen, with me and other colleagues, Paul Reed, spending a lot of time engaged in political dialogue with community leaders, tribal leaders from Northern Helmand, places like the Upper Sangin Valley, the Upper Goreshk Valley, Kajaki, and with the key tribes up there who have often been alienated, like the Alizei, Yashaksai, and the purpose of Governor Mangel in that effort, which we're supporting, is really to try and push forward local peace deals, local agreements, which mean that people stop fighting. And some of those young people who stop fighting might join the Afghan local police. And there's a pretty good vetting system for that, which is under the control of district authorities, police chiefs. So the formal process is still too slow and needs to move forward, but there has been progress in that informal track. And we want to continue on that as well. It's just the war report online, the Taliban leader that you met with today. Was he promised immunity for what he may or may not have done in the past? And the 30 or 300 that he promised to bring in, would they also be given immunity? And were there any officer money to any or all of these individuals? In the process of reintegration, when they formally vetted through the process, takes a couple of months, when that finally comes back, during that near and while they're waiting, they do receive a small amount of money, I believe it's $100 a month, which basically allows them the opportunity and during that same timeframe, we offer vocational training. And we're trying to get them to find a job, find employment, become a productive member of society. So that's how that particular case is handled. As far as the fighters, it's initial 30 fighters that are going to come and join the Afghan local police. I mean, they actually will get a job right away and they'll get training and work for the Afghan local police. I think I answered your questions. I think there was another part. But maybe could I just add one other thing to that, which is going back to something John said a few minutes ago, the process. Questions for you. Every. Okay, I'm going to go. It's Justin from Fox with two bigger picture questions. Every six months or so, you hear about this trend that the Taliban has researched and gained strength in the north. And we're hearing that particularly because of your efforts in the south to crack down. Is that happening now? And how do you stop that? And I do have a second question. Well, I think as far as the Taliban effort, what we're finding, I think in Afghanistan right now is that in the south, the Taliban are pretty much being kept under close wraps. They're not able to expand. As I mentioned earlier, they're having internal problems that are creating dysfunction among the Taliban. There are increased efforts. I'm sure you've read about the Connie network and some of the activities that are being conducted on the east in the arts regional command east area and into Kabul. There appears to be increased effort in that area. But generally speaking, I think what you'll find is that as the effort in the south has done a pretty good job of maintaining a squash in the Taliban. It's having an impact on the rest of the country. Yes, it's pushed some Taliban out to some of the peripheral areas. But there is so spread out that it's not having the kind of impact that it had, for example, here in the south a couple of years ago. I'd love for you to expand and you may have talked about a little bit already, but if you want to expand on the internal problems that the Taliban is having, I'd like to hear more about that. And then finally, as you probably know, tomorrow is 10 years since the invasion of Afghanistan. Just, you know, where we made the most progress and where do we have the most progress to make? The fissures that I discussed in regards to the Taliban, it's really a direct result of a couple of things is Mr. O'Neill brought up earlier. You know, we've had a counter-narcotic effort. That has really been very effective of taking away the drug labs and some of the large stores of drugs. But really what it's done is it's taken money out of the Taliban's purse. And so therefore, they haven't been able to buy the materials that they need to supply the Taliban in the area. So the IEDs, for example, which are the most prevalent is the most prevalent tactic of the Taliban. They really no longer can face us. Mano imano. So that effort has really hurt them in the purse, hurt them in the pocketbook. And so what it's done is it's taken the Taliban who are operating in these areas in Afghanistan who are not getting supplies. They're not getting guidance from the senior leadership who won't leave Quetta because when they leave Quetta, they get themselves either captured or killed. So it's just gotten inside their decision cycle and it's really made the Taliban, local Taliban, think twice about whether or not it's better to join the government of Afghanistan, which looks like it's on an upward trend. It's got decent cops. It's got decent army and it's got projects, potential for jobs if they reintegrate, et cetera. As far as the second question is concerned, we're really celebrated the 10th anniversary of 9-11 when we were out here in Afghanistan. I think that to us was a far more significant date than 10 years of fighting in Afghanistan. Because really when you look at the 10 years, you're looking at different levels of forces, different levels of attention given to Afghanistan. If you really look at the problem and you look at the effort that's been put into Afghanistan, when we searched about a year and a half ago, it changed everything. And I think that change is going to be lasting. I'll turn over to Michael if you've got any. Yeah, well, I agree. I think the progress that I've seen in the 12 months I've been here, but which started before that, was hugely pushed forward by the US military surge, the better troop numbers there now are, but also the better capacity to train Afghan forces. You have a lot more Afghan army, police, they're better trained. All those things have come about as a result of the surge and they've made other progress possible. And I think you can measure that progress in lots of ways in Helmand. The key challenge now is not so much has there been progress, but how do we all make sure that is lasting? And I would say as my closing comment, the tone for all of us now, and this is going to increase over the next couple of years, is about putting the Afghans in the lead. And that's happening. You know, it's happening in governance. They're making their own plans, they're proving their own projects. On reintegration, which General Thun was describing earlier, you know, the key decisions around all of that are made by the Afghans. You see security in Lashkar provided by the Afghans. So putting them in front is the key task. And the other thing in my view, what's more important than what we think about progress, you know, in Washington or in London, is what the Afghans think. And you know, we just got the latest set of data from polling that we do every three months, several thousand people in Helmand. And what that showed we got this last week is most people in Helmand think security has got better in their area. They've got more confidence in the Afghan army and police. And in the end, that's the key test, really. That matters more than what they think about us. They've got more confidence than their own army and police. And they've got more confidence in their own government at local and provincial level. So really consolidating all of that is the key task now, which we'll work towards. Thank you. If you could just stand by for one minute. I would like to just say that, you know, one more question, Barb, you get the last question and then we're gonna give it over to the general, Mr. O'Neill, if they have any closing comments. Barbara Starr from CNN. I'm not sure I heard an answer to the immunity question. So my question is, was this man, this Taliban commander and his fighters responsible for the deaths of any American U.S. Marines? Any coalition forces? Are they getting immunity for it? And now that you've identified him relatively publicly and except for his name, do you have any concerns about his security? Are you providing any security for him? Well, as one of the questions earlier, brought up the fact that, you know, they wanted to know the name.  And it certainly takes a very brave and courageous person to step up and want to reintegrate. And this individual is one of those people. So yes, I will protect him as much as we possibly can. And part of that protection is to go after the Taliban that are not gonna reintegrate, the Taliban that are from out of the area and try to assist them. Secondly, as I mentioned earlier, we're in a major move, major offensive move. We, one of the reasons why that reintegration is timed so well is that we're already closed in on Sengen and we had that place pretty well under wraps. So I'm concerned about his safety, but you know, this individual knew what he was doing and I think he's got a pretty good hand on the situation. In regards to immunity, the reintegration is a process that brings people like the story I expressed about why they turned Taliban in the first place.  And so when they reintegrate, there's no going back and trying to determine the evidence based on what this person did, et cetera. That person's reintegrated into the system after he's vetted through the process, through the province, up to the national level and then back down. And that's a government of Afghanistan process. They do that vetting and they make the final decision. So it's not really for us to decide at that point. Can I just follow up very quickly and ask, do you have any information? If he controls 300 fighters, that's not insignificant. Is his network, do you believe his network has been responsible for the deaths of coalition forces, including U.S. Marines? If anybody is a Taliban, they're responsible for doing damage to the coalition forces in this region as well as other regions. I wouldn't doubt that at all. Thank you very much for your time. I'm going to toss it over to you, Sir, if you have any closing comments and as you as well, Mr. O'Neill. I just wanna say these close with the fact that, you know, this whole effort over here has done one individual at a time. And I have two just quick stories. One is about a seaman apprentice, Brian McGill, who was from Petal, Mississippi, a native and Navy corpsman, and works with us here in the R.C. Southwest. The kind of work that's done out here is done in a variety of different ways. And in seaman apprentice McGill's case, it was just recently, on September 11th actually, he revived, saved a little Afghan toddler who was actually drowning in a canal, went in, saved the girl, gave her CPR, restored her breathing, and sort of a heroic little effort on his part, but the kinds of things that go on all the time that sort of build that bond and trust between people. Yeah, I really need to mention one of our sergeants, Ricardo Ramirez, who just came back, is just going back home. He was from 1st Battalion, 5th Marines. One of the first Marines to be allowed to re-enlist, he's got a hook for a right arm, lost it when he was in 1-5 back out here in Afghanistan. And he's out there doing the same infantry grunt things he was doing with two hands, he's now doing with one and a hook. These are the kinds of people that we have over here, and that's the reason why we're making such a significant difference. Thank you. Maybe I could just close with two quick comments. One, just to illustrate, I think some of the progress that's been made over the last year, 18 months here, I'm going to take Marja, which, as you know, for most of 2010, was the Centre of Operation Mashtarak, difficult operation that involved a lot of sacrifice. And I came out here on a recce visit in July last year, went to Marja, and I was not able to leave the base because of the security concerns. In December, when I'd started my job here, I went back and we were walking around the centre of town, talking to local people. We visited a restaurant that had just opened. Then at the beginning of March this year, Marja had elections for the first time. They've now got an elected district council, which is a great sign of the extension of governance. And just in the last couple of weeks, there's now an internet cafe in Marja. Now, those are just anecdotal things, but I think they give an illustration of the kind of progress and the transformation that we've seen down here. And we get a lot of Afghan visitors who come down from Kabul, senior ministers and others, who go away saying they can't believe the transformation that has happened here in Helmand. And the very last point I would make is, you know, for all of us, US Marines, the PRT, the British military and others, you know, we're all looking now at moving into transition, the beginnings of drawdown over the next couple of years. All I would say about that is, you know, that is a necessary and healthy process because for the efforts that we've all been making here to last, to be successful in the long term, it's got to be the Afghans in the lead. And the only way we're going to get there is by putting them forward, us drawing back. So we need to manage that in an orderly way. It needs to be carefully planned and it is being planned. But as we go forward, I think transition, our drawdown, putting the Afghans in the lead, you know, that is the way forward and that is the sign to achieving what we all came here to achieve. Gentlemen, thank you very, very much for your time this evening. We know how very busy you are. We appreciate it. Thank you so much. Thank you. Bye bye.


Just a few hours later, also took the courts against Crookston, starting with four singles. Bemidji's Bailey Harris, he had the drop shot work and that's called placement, six-one winner in straight sets to three singles. Wyatt Haram, he says, anything you can do, I can do better. I can work the drop shot better than you. He cruises six-zero, six-three to doubles. Jonah Furman and Eric Guida at number three. Look at them work the net for the volley winner, six-three, six-one straight sets and finally two doubles, the Hest Brothers, Luke and Silas, Silas the serve here, ace it up, they went in two, six-four, six-zero. Crookston does steal one at number one doubles, the Jax win their second of the day, same score, six-one. If you enjoyed this segment of Lakeland News, please consider making a tax-deductible contribution to Lakeland PBS.