to get started here. Excellent. Hello, hello, and welcome to today's edition. It's May 25th, believe it or not, of the Cardia User Group. And we're very excited today to have a guest speaker who will introduce in just a minute. But we need to get through a little bit of housekeeping. So I do want to cover that the Cardia Working Group is covered by the Hyperledger Antitrust Policy. You can find that here in our meeting notes. I will link the meeting notes in our chat for anybody who might not have that saved. There are also community meeting notes, so feel free to chime in and make adjustments as you feel fit. Additionally, we have a Hyperledger Code of Conduct, which to paraphrase, we're going to be nice to each other. We're going to encourage collaboration and communication among our community here. And hopefully, everybody feels welcome and encouraged to have a voice in this space. If you have any concerns, you can reach out to Ken or myself as co-chairs of this committee or you can reach out to Hyperledger directly through some of these links. They give you an opportunity to chime in there. Would anybody like to introduce themselves that's new or potentially it's been a while? We'd be happy to have you introduce yourself on today's call. OK, we've got a quiet bunch.  You are ready to go. We've got an exciting speaker and presenter today. So we have Sirot joining us. Sirot Pala, Ken, you have more personal experience. Would you like to do his introduction? Sirot is an entrepreneur and has taken at least one company that I'm aware of through a successful acquisition. And the reason that we contacted him is because he has some experience in workplace drug testing in order to enlighten the Cardio community. Those who are either attending today or watching the reporting about some of the challenges and perhaps opportunities for Cardio to improve the user experience and the privacy in workplace drug testing. So we welcome Sirot today. We're glad to have you here and hope to be enlightened by your experience so that we don't have to repeat some of the lessons learned that you've already taken into account. Oh, thank you. Thank you very much, Ken. Yes, I am glad to be here. I have been an accidental entrance to the, we would call workplace drug testing market because like you said, I'm an entrepreneur. I had previously started a few different companies, some successful and unsuccessful ones, but my path to drug testing started with my former company, Conform BioScience, which was like a commercialization company in the field of point of service testing. And initially, we started early 2000s with the goal of bringing testing to individuals and corporations. And we did not necessarily tackle workplace drug testing at the beginning, but as we evolve as a company and we've decided to focus more on cash basis testing and not so much reimbursement and health care and Medicare and so forth, we found that workplace drug testing was a growing market for obvious reasons. I mean, some of them are very unfortunate, as we know. And we're still going through the epidemic of drug abuse. And I think the last time I checked almost 100,000 people a year dying from drug abuse and overdose. So maybe I'll stop there and would love to see what could be the best way I can tackle some of the questions that you think I can answer and be a resource for the panel here. Hurt for those that are unfamiliar with drug testing, you said point of service testing. What are the implications of that? Point of service testing is basically bringing the test to where the action is. And it can happen in multiple ways. It can happen in an instant way, meaning if you're using an instant test. And many of the things that I will say, maybe we're talking about it from a drug testing perspective, but it can also apply to other type of wellness test as well. But when we talk about point of service testing, it can be either a test like a lateral flow test, which is like a very standard urine test that you might know, or pregnancy tests, where you give a sample in some sort of fluid, oral, or urine, or so forth. And then the test itself will react to the fluid and will give a result right there at the time. And that will be an instant test. But then you could also collect the sample again, urine, saliva here, and take the possession of the sample with a chain of custody, and then send the sample to a laboratory where the result will come from a lab result. So point of service covers those two different use cases. Both the collection of specimens that need to be sent to a lab and those that are immediately reactive and give an indication within five, 10 minutes, a half an hour, are they all very short or some take longer than that even though they're immediate tests? They all take less than three minutes, four minutes, the tops. And when we talk about instant testing, the drug testing world, we're basically talking about just two forms, which is urine and saliva. Urine being, my numbers might be a little bit outdated, but I would say still more than 85% of all drug testing in the workplace are still urine tests. It's still the main form of testing. Or the newcomer that is growing ground is the oral fluid-based testing. And both of these tests, some pros and cons. Maybe we can talk about that too. But there is, for obvious reasons, oral testing is more convenient and easier to make sure that there is no tampering with the sample. So it has been preferred more and more. But it also comes with some disadvantages because oral fluid testing tends to be detecting shorter amounts of time. It has less acceptance in some industries. It has higher detection levels. So sometimes things that can be detected in urine cannot be detected in oral and so forth. So what those are, the two main forms of instant testing is urine and saliva. Interesting. You mentioned, I want to start kind of at the beginning and talk about how a person holds in a test or participates in a test. What is the process for their consent being gathered, if any, and typically how is the test initiated? Is it requested by a workplace? Is it requested by the employee? What are the typical flow of starting a test to be taken? It is often time. When we talk about workplace drug testing, it's important to separate pre-employment drug testing and then regular drug testing that might happen in the course of an employment because of maybe a suspicion of use or some sort of accident that might happen at the workplace that might trigger a drug testing. So the first one I'd like to talk about is the pre-employment, which seems to be still 80% of the marketplace. Oftentimes someone will apply for a job. And it's a part of that process. There is a point where it can change from company to company. But in most cases, once they are offered the position and accept the position, they are told that they have to go to a drug testing. It's one of the check items. And often in the pre-employment screening scenario, drug testing and background screening happens almost concurrently. And there are a lot of users out there, a lot of service providers out there that actually combine those two and become a service provider for both. It's not necessarily the case. I think many of the background screening providers incorporate drug testing and use different contractors. But some employers might treat them separately and might contract out to two separate service providers to do that. But once an employer requests a prospective employee to take a drug testing, oftentimes they either send them an order form or something that will enable them to go to a laboratory to get the drug testing done. Some employers that are often more blue-color type of workplaces, they might have a high number of employees that they hire on a regular basis. Some employers might have resources or a clinic on site that could do the drug testing themselves right at the workplace itself. But in most cases, you as a prospective employee get an order form that instructs you to go and provide the sample at a collection center. As a part of that order, is the determination up front that the employer will receive or the prospective employer will receive the test results? Yes, the moment that the person provides their sample, again, it can happen in different ways. It can happen where the person is a part of the paperwork that they receive is being onboarded to the workplace. They could sign a consent, which gives the employer the right to ask for the drug testing to be done and get the results of the drug testing. So that can happen. Or if this particular process of drug testing is not so incorporated into the onboarding process, but could be a standalone order, then you might be sending as an employer to this person an order form to get their drug testing done, which is very much like an order form of a lab test that you would get as a part of your health test to your doctor. It could be very well, be a very similar process too. But the moment that if that's the case, and you get an order to go and provide the sample at a laboratory collection center, then it's a part of your signing process to give the sample at the clinic. You also give the consent of your sample to be analyzed and the result to be sent to the employer. Is that an expert? Do you understand that to be explicit consent where the employee is actually signing something? So either the employer is pre-collecting that if they have an established workflow in relationship with that lab organization would be my guess. Or they're deferring that to the collection lab for them to do it at the point of capture. So they're either bringing it with them because they already signed one with their employer or the lab is going to collect it directly. But it's explicit. It is very explicit. Like it is not something that you have to look for. It is important that this consent is explicit. Because in most cases, the result will be delivered. I mean, I would say pretty much all cases, I would say. The result will not be delivered to the donor in this case, where we will not get the result. It will be the employer that will get the result. So it's one of those very, I would say, unique cases as individuals. We will give a sample from our body where we will not, in most cases, have access to the result. Is that the initial access or never access? In most cases, the never access. You will have to go through additional steps to request the results. We have rights to get that result. But it is not a standard part of the process. Interesting. That's kind of a distinction between if I go to my regular primary care physician and have a test result, the lab almost always delivers the result to me as well as or can deliver there. I guess I have to request that as well. You do. Actually, there are some lab laws that say that the lab actually needs to go to the provider and they give the provider a certain amount of time to be in touch with you as the patient. You can imagine, for example, if you test positive for HIV, you don't want to be getting that from the lab directly and not have a doctor call you to say, you have HIV, let's talk about it. So there are some, and I would think these are probably, there's some federal laws, but there's probably also additional state law in the US that dictates that delay period where they give the provider like a jumpstart on contacting you before they issue the labs to you directly. And the workplace testing, does any of the test result go to a medical provider as well or is it strictly given to the employer for their review? In the context of workplace drug testing, there is another medical provider called Medical Review Officer, MRO, which is oftentimes these are medical doctors that gets these results, they look at the results before they endorse, I mean, they finalize it and release it to the employer, but they are in the middle as someone that acts to make sure the lab results could be determined to be a positive or a negative. And that's mainly because of the cases where you could be prescribed the medicine and that medicine can make you positive for a drug test, let's say opiates and so forth. So the Medical Review Officer at this point, once they get the positive result, would contact the donor and ask to see if they have any prescription or not, because if you do have a prescription for opiates and you get a result that says opiates positive, it is the job of the Medical Review Officer to qualify that and at the end give a negative result because assuming that everything else is negative but you are opiates positive, that way you would not necessarily fail the drug test result, even though you might be positive. So there is that Medical Review Officer institution that makes sure there is no illicit drug abuse, but if there is prescription that drug use is within the framework of that prescription. Is that Medical Review Officer affiliated with the lab or affiliated with the employer or independent? They are often independent individuals that gets the result from the lab, but they can be contracted by the lab provider, they can be contracted by the third party administrator. There's another institution called third party administrator. There could be just a partner for the employer to run their workplace drug testing. So if the third party administrator rounds the drug testing program for a corporation, they might contract out the lab portion to someone else. They might have an MRO inside and they can just make sure that all pieces of this process takes place in a seamless manner and then they give the result to the employer and even third party administrators could be responsible for what will happen if there is a positive result and how to deal with that positive result. And we started talking about pre-employment screening too, but then there are many different cases of drug testing that will happen not just for pre-employment purposes, but managing your employee pool. If you're an organization that is regulated by Department of Transportation, like your trucking company or an airline, or you have a manufacturing facility and you have random testing that needs to be done in your organization and you randomly drug test your regular workforce, these third party administrators will be the people that will be managing that entire program and they can get very complicated. So when we talk about just pre-employment screening, it's a white color individual working for a bank. You might have to be drug tested only once and that's it and you will never get drug tested again. But if you're a drug driver, then you have a lot of other ways that you might encounter the workplace drug testing. As you mentioned ongoing testing like for the trucking industry or airlines, is there a consent process that's done once or does it have to be repeated with each test? Do you know the differences there? I don't know the technicality of the differences but consent, as far as I know, you have to give explicit consent each time you provide the sample. Okay. On the ongoing testing, are there scheduled intervals that can be known and scheduled in advance or is some of it random or a mixture of both? I don't think there is any pre-scheduled ongoing tests in the workplace that is a standard. I'm sure like employment drug testing is a very, it's employment at will country here and you could customize a drug testing policy that can be very unique to your organization. So there might be very well cases for some companies to have that, but that is not very standard where you have a pre-scheduled timeline of when you will get drug tested. It is either random and it's random in a sense that everybody will get drug tested once a year at some point or it can be random in a sense that 10% of your workforce will be drug tested each year. So there is a randomization that happens and it is the responsibility of either the third party administrator or some randomization software to determine who's going to be get drug tested when and it does create complications because once you get a drug testing order you have to do it in a certain amount of time and you have to show up and do the drug testing otherwise it will impact the efficacy of the test because if you have two weeks to get drug tested and in most cases with saliva the detection window is less than a week or maybe two weeks then you could just wait it out if you want to avoid being getting positive results. So the randomization and what happens after the selection done and the timeline has to be a very strict policy and the the types of tests dictated by legislation or are they at the discretion of the employer? So you might have a test also for the same type of issue that could be your and test or saliva test are any of those things dictated by legislation or are they at the discretion of the employer? Yes, there are definitely regulated by the Department of Transportation and it is very strict I mean it is a very defined process it has its own laws and regulations so if you are regulated by the Department of Transportation as an employer you have to fulfill those requirements you cannot make shortcuts I'm sure you could add on additional restrictions you can do additional testing but at minimum you have to fulfill the Department of Transportation requirements then there are some federal employers like the military or some other federal agencies might have their own regulations for their employees and similarly states might very well do that with regards to their employees and we might be talking about law enforcement you know prison you know prisons that's not really an employee relationship but the prison guards might be subject to different type of drug testing that comes from the state regulations as well so it is a very when you think about it there is federal regulations involved there are state regulations involved there are many employment law related regulations there is privacy there is healthcare and that's really what makes workplace drug testing a really complicated manner overall because you have so many different jurisdictions and so many different considerations some of them federal some of them industry some of them state they are all layered on top of each other okay another question how does the lab know that I'm the one showing up to get my test done and it's not my brother-in-law who's drug free showing up to get a clear drug test for me on my behalf they do ID checks proper ID checks at the time of specimen collection but again it is not a very robust system because physical appearance might look similar to the ID even at the checking process I've noticed that at some collection centers you check in they check an ID but by the time you go give the sample there is not as strict of a flow that ensures that the donor is who the donor is supposed to be and plus in the cases of urine sample now you have the issue of privacy and how the collection is done and you might have to be in a restroom stall and they might not even know the sample that comes with you so that kind of that stall actually belongs to you and is freshly collected so there are a lot of there are a lot of failed areas when it comes to the authenticity of the sample that is being processed I have a question and I hope that I'm going to piggyback on Helen's question from the chat as well which is and this has been great, thank you very much when we talk about the lab is doing the lab test they are obviously doing it in a more granular way they are going to have the results those results are then being interpreted by the medical review officer which is either at the lab or the employer or a third party administrator who is managing the employment testing program for people are they then turning around and saying yes they can work or no they can't work or are they then sharing the detailed lab result with the employer it becomes a checklist item in the onboarding process they can move ahead it is the employer that will determine what is going to happen again going back to the employment screening pre-employment screening or ongoing testing you could very well have employers that will maybe give another chance or have some sort of other program for example if you are an existing employee to come back and get tested again it is not up to the third party administrator or MRO to say yes this person can be hired or can go to you to work it is whatever that employer's internal workflow that determines the next action the mayor role of it is like providing a background screening test background screening results you can have whatever you have on your background screening and you could have not a clean sheet or you can have issues but that doesn't necessarily automatically mean that you are not going to be working or you are not going to have to stop working and determine what to do with that person how are results transmitted to the medical review officer or the company is it through something like e-mail or mail to them you know I am old enough to remember those things were happening but they still do I am sure that faxes are still the thing but in most cases it is a part of the employee onboarding or employee management software system that incorporates those results or if you are that manages that process it could be a digital result provided to you by a lab or by your third party administrator and it can't even be an e-mail which is not really supposed to be because we are still operating with HIPAA and other considerations but it can be just a digital result in some shape or form encrypted or not depends I guess they are mostly if you are using a third party administrator or a lab you have to have passwords they are they are supposed to be encrypted but they fail to clarify about the instant drug testing and lab process results is the fact that when we talk about instant tests oftentimes those are not really confirmatory tests they are screening tests it is possible to have a urine test done instantly at a laboratory or clinic in an employer's factory and the result comes with a negative everything will be fine and you can continue it but whenever there is a non-negative it is not called positive and you have to go through a confirmatory process through a laboratory where the test results is provided to you by a formal lab process only then you could call it a confirmatory result where you can make a decision so non-negatives has to go through a laboratory process before they can be a positive I think we have all learned the nuances of those instant tests through our COVID experiences we are all well versed in their challenges and false negatives that would warrant the more comprehensive sensitive testing to follow up testing from that perspective yes and I don't know the Department of Transportation but for good reasons the Department of Transportation has very high standards where some of these screening tests might not be efficient and it cannot be used I like that fact and I know that the pilots are well tested is this an area of growth or is this something that is tapering off or is it flat over the last 10 years and expected to be flat in the future what is the trend line for this whole area you mean a workplace testing yes I might not be as fresh with my industry numbers but it has been a constant growth area it's a growth industry and it is going to continue to grow as the drug abuse increases this has to grow unfortunately the only challenges that will come to is the growth of drug abuse and growth of workplace drug testing correlation might come from the fact of unemployment rate and employment activity what I mean by that is in the times where it is hard to find employees you the rates are very low and you are in the market very competitive market try to hire people I see employers try to make shortcuts make decreases in the requests for drug testing because they want to work with a larger audience and they do not want to discourage people from applying to jobs in the times of low unemployment you see drug testing almost as a checklist item where employers will be very hoping that results will come back negative so that they can hire and that completely switches when it is time for recessions and unemployment is high then you not only use this as a way to really screen out you get more serious about drug testing and you can not only increase the number of tests but also the quality and efficacy of your tests because you want to make sure that the results are accurate but then I have seen in the last couple of recessions cycles where employers use this to increase their nutrition and decreasing their workforce because it is way cheaper to do this than try to fire people in general I am also curious there has been a lot of change at least in the US around state regulation both around cannabis and some other states that have decriminalized so there is some nuances around decriminalization but also then legalization of some recreational drug use and I am curious if you have thoughts on how that factors into it between state, federal, et cetera in terms of regulations that is a great question I was in the drug testing the company was in the drug testing business when this whole decriminalization wave was coming from Washington state honestly we did not know what to expect because Mariana has always been the number one test requested and conducted but it was very quickly clear to us that decriminalization of certain drugs do not necessarily decrease the amount of drug testing but it does not matter if it is legal to use THC they can still use it as a way to drug test their employees some states have specific laws that prevent that there is that level of complexity but keep in mind that alcohol and quite legal things to do it is just that employers can choose to test their employees for those substances as well but again they have to have valid reason for determining this abuse or use of these substances will have impact on the employment relationship and they cannot just use it very discretionary so there are not only laws that prevent in some states to drug test and use the result you have some legal exposure about why you are doing it even though it may be legal it might not be advised for a pilot or a truck driver to be consuming a particular substance because it might impair their ability to operate heavy equipment or other safety concerns first I know the Department of Transportation it is like screening the cut off levels are very specific and the Department of Transportation is very like it is a very streamlined very specific way of doing tests and yes of course that doesn't mean that just because you are in particular state that you could use THC and operate heavy machinery which segues me to a separate question related to Department of Transportation concepts one of the scenarios that we've discussed without knowledge so hopefully you can help us think this through is most and I don't know what statistics there are on this but certainly every Uber I've been in the driver almost always works for Lyft also and they end up being dual contractors and because those are transportation based roles I believe they are also subject to a lot of drug testing and in that case it seems like there could be some economy is gained by the reuse of recent drug testing so long as the results could be certified and vetted do you have any opinion about that or do you think everybody sort of wants their own and are willing to pay for it I do have some thoughts and I actually have some experience with these type of use cases even between these large providers and background screening companies providing services to these providers and how they could want to use some economies of scale there but before that regarding Uber Lyft being Department of Transportation regulated I'm always not an attorney but just because it is a transportation vehicle doesn't necessarily automatically make a Uber driver a DOT regulated driver there are different laws that would do that I think they're not surprised if they are because if they were Department of Transportation regulated then the bar would be so high I think a lot higher than what probably is right now for providers like Uber Lyft or others going back to the economies of scale I have seen and I've talked to customers providers about that inefficiency and not just from an economies of scale purposes but even for high-pining drivers onboarding drivers and so forth you could have a person sign up for Uber get through the Uber drug testing process and then next day go to Lyft to do the same and has to go through the process again and as far as I remember and this is not for any specific service provider but I think when we have done some research in the past we saw that people that are applying to Uber Lyft type of services almost up to 10% of the time they never end up going through the process of drug testing they decide not to show up not just because they might be using but just because of its inconvenience and their scheduling issues and so forth so the big companies like Uber Lyft have decided to make the drug testing process as seamless and as sufficient possible and they would love to be able to use piggyback on each other's results as long as it is comparable because that will make their workflow easier they will improve their hiring rates as well but because the results are the results and the better term belongs to the employers or prospective employers and there is no way for those results to be to share between potential employers you have these very inefficient situations somebody getting a drug drug testing that could be done four days in a row and you have these inefficiency and cost and inconvenience the only difference might be again I'm not talking about any specific companies here if the background screening companies are incorporating drug testing under their workflow and their result management system and they are doing service for multiple of these big companies they do have the option to share these so I think that not only the companies would benefit from that and now you have five different major clients you would really be able to improve your bottom line and your profitability if you can't figure out a way to share results still charge the clients the same I'm not going to go into that interesting I've kind of dominated this set of questions I wonder if there are any questions from our audience that you can answer Helen did we get your question answered I was more interested to hear if you have any experience or thoughts on the crossover between what we're talking about in drug testing and living organ donation and a lot of respects it's very similar in that you go and provide blood or whatever provide the sample and it goes off for privacy concerns so that the donor the person providing the sample doesn't see the health information that the person is looking for the donation you don't see those results so it's something where you provide the donation or you provide the sample it goes off and it's shared between numerous parties healthcare providers usually a donation center and then doctors several doctors who do the testing and review panels and boards and whatnot it just sounds like there's a lot of overlap I don't have any experience with that aspect of donation medical sample donation or if they're sort of apples and oranges a little bit you know what I don't actually like it's the many of the same things sound familiar similar in the way you're describing but I don't know anything about donation use cases and the flows to be able to make any connection or even comment on it I appreciate that when we were talking last year about expansion use cases for Cardia beyond COVID and travel I think we were looking at how can we provide and work as a community to build the technology that could be used by the most amount of people for the most amount of use cases and I think that it just sounds to me that if we were to focus on putting together a sort of implementation of Cardia specific to drug testing that it could be used in other types of medical testing environments as well besides drug testing and the expansion use cases for Cardia this is again I think another opportunity to bring more kind of use cases into the fold that's all thanks I guess the good and the bad thing about workplace drug testing is it because it's so complicated there are so many different layers of regulation there are a bunch of different substances we're talking about some of them being elicit some of them being elicit but you know might have an impact on the way someone can perform on a job site once you are able to build a robust workplace drug testing use case on a platform and flow I can definitely see potential of getting pieces out of there and using it more simpler straightforward more flat like work flow so I think there is definitely a chance of economies of scale there too absolutely thank you anybody else have questions they want to either type in the chat box or just come off mute and speak yes I'd like to know if there's a possibility for say in this use case the employer to allow an option for the employee candidate employment candidate to when they click on the consent form on the iPad or whatever is presented to them that they could also just enter their wallet ID so that the test could be electronically sent and placed into their wallet because some employees might have the concern that the employee that they want to make sure that they are trusted by them potential or candidate employee as a user interface I think that's a rather more philosophical question because yes I think I believe as individual we should have access the results should belong to us and that we should share with those results with whomever we want and we're just talking about workplace drug testing but keep in mind there's all kinds of pearl testing there's cases where trusts require there on a regular basis to get funding from trusts or your divorce cases so the use cases of drug testing is way beyond just workplace drug testing but employers for practical purposes I don't think unless they have to would want to allow that because it just opens up a whole quite set of questions you know you get a result and it says there are different cut off levels there's screening levels there's a bunch of different drugs if you look at a drug testing result it's a complicated result and it's also not the result that the employer might get a result that is filtered through and made it more simplified after an MRO decision but I would think that employers would rather not have prospective employees get their drug result because if they are let's say you get the job you assume that result was negative then you know what did the results say and you can still request results but then that can all become a whole new legal issue and a whole other set of you know state laws or employment laws can come into play so I think it is an employee or prospective employee having access to the result because things will probably become a problem when that person in some shape or form fails the test my question was basically as a user interface designer so I would like to know if hyper ledgers should offer the option of some employer or whatever it is allowing the employee to own their own data to say when they walk in there when they sign the consent form there will be lines fields that the potential employee or whatever could fill in and those fields could be say A send it to my wallet here's my wallet address B send it to Uber here's their wallet address whatever they're called here's their address D send it to Lyft here's their wallet address so that giving them the option to make their drug test available to others would that be or do you want to restrict hyper ledgers and user interface thank you I can't say anything about the hyper ledger how that might be but it is definitely I think a good use case for people to be able to do it and plus we could very well be in a situation in the future where as potential employees we could drug test ourselves if there was an option to be able to share the result I mean the employer's request to drug test results they're not testing because that's a part of their process but if there was trust in the system and there was a way to share between an authentic result employers would love not to pay for a drug test and would do it much easier so it couldn't even be a incentive for an employer to hire an employee that might already have a drug test results that they can share and they might even have paid for just to do a quick time check we're a couple of minutes over so I want to make sure we're not messing up everybody's day hopefully that answers the question I've taken some notes here feel free to review and adjust if you think I misinterpreted that I just want to take a minute and say thank you very much for this conversation it was enlightening we're very happy to have met you heard your input thank you thank you very much at our next meeting which is on June 8th we're going to have Sarah I think it's Samus from GCOM come and talk to us a lot about sort of the vaccination space but potentially some other topics as well and so I would encourage those of you who are here today to listen at our next meeting on the 8th with a different Zoom link so make sure you've got the calendar correct from Hyperledger thank you again Sir Hott we are very grateful for your time and expertise that you're willing to share with us thank you I'm glad it was somewhat useful it was thanks everybody thank you bye


How many kirtas do you own? I make four. Maybe five? Don't act like you're not impressed.   It's Corbin. I'm Rick. And you can follow us on Instagram and Twitter for more juice and content. It's so juicy. Sometimes separately, but most times together. Most times together, but sometimes it does. It's an interesting experience. If you haven't had it, you should try it. And they both says on Patreon, follow official Twitter, count ring the bell. We hope for them location. Ow! Today, hey, we are doing a movie review. Yep. It's a really loud camera. Our first film from Assam.  We just want to see if we want to represent everybody and we want to see good cinema. So we saw, what did we see, Rick? Amis. Amis. How do you pronounce it? Which on IMDB it says ravening? That doesn't make sense. No, because I'm pretty sure it means non-veg. Yeah, I think literally it means meat. Gotcha. Yeah. Yeah. That makes sense. I don't know what ravening is. Weird. But yes, it's a drama fantasy horror. I don't really want to read the synopsis, because it kind of gives stuff away. So we don't like to do non-spoilers, but I would say go watch this film and come back if you don't want to be spoiled. Yeah, because we've got to talk about everything that's in the thing. And truly, guys, do yourself a favor. Put pause, watch it. It's a short film. And then come back and see the review. OK, so, Rick, initial thoughts. Freaking low. Oh my god, it's so good. It's so freaking spectacularly good. Oh my god. It is. I've been bottling this up since I watched it last night. I know. I'm like, I wanted to post about it on Instagram. I just wanted the save review coming, but I didn't want to give anything away. This is an absolutely brilliant movie. If you haven't seen it yet, if you're still here, once again, stop. Go watch it and come back. We just told you it's amazing, OK? That's what you need to know. Go watch it. Don't go in knowing anything. That's what I want you to know. Yes. Anyways, but yes, it was. This movie deserves you. If you haven't seen it, this movie, like all stories, because that's my slogan, let the movie tell the story. This movie deserves the creators of this film. They deserve you to go in blind and let this thing unfold before your very eyes as you experience the film yourself without spoilers. So we're assuming you've seen it if you're still around, because now we're going to get into the meat of the review. But we know most of you haven't seen this, because it's from a small film industry and it's in a different language. Once again, as always, stop caring about subtitles and go watch films that are good films. And this is a very good film. And support good films no matter the region. It's India. It's cinema. The larger world of this is that we're talking about a great movie. This is not India. This is not a sum. This is the world of the motion picture. And this thing is great. Yeah, so I want to thank Anyard Khan. Obviously he didn't do anything with it, but he kind of, it was, in the trailer we watched, it was presented by, because he saw this and was like, more people need to see it. So he basically backed it. And no, no wonder why. Yeah, you could tell watching the film, why Anyard Khan, she outloves it. But anyway, let's get into the film. Directed and written by, say his name for me, Rick.  Directed and written by Bhaskar Hazarika, who I believe this was- It's first or second. Yeah, first or second. Just like the last film we saw, we're talking about some pretty impressive directing debuts, man. I think the budget was like little to none as well. Yeah, I'm sure. I believe the budget was like almost an independent film. Yeah, I'm sure. Style of budget. And I don't think a lot of the actors are known for anything either. They're not. The two stars were what you called debutants. I think they had done some work before, so this wasn't like an introducing, like never acted before, but I don't think they'd done anything remotely close. This was like their big screen debut, yes. Which is why it's so impressive, because one, there was very little thing. There was a few things acting wise that I didn't enjoy, but it wasn't anything huge and it wasn't from the main people. So I thought the two main people were very, very believable and also just a beautiful, thanks to the testament to the directing and the casting of it, a beautiful, weird pairing. Because that's how I just saw this movie. A very beautiful, warped, sadistic love story. Yeah, I would, I don't like the title of it. I wouldn't have called it meat. I would have maybe, I maybe would have called it flesh, a love story. Yeah, yeah. Yeah, something like that. Yeah, but yeah, it's weird because it, there's so many different areas to where you're like, oh my God, okay. So there's this young guy and he's just weird. He loves meat, weird. It's just, that's his thing. He loves meat, cool. Okay, you have this doctor.  And so is her sister. And so she's also having, well, she's more having an affair. This girl's having an emotional affair with this young guy. And then, and so there's a bunch of different stuff going on and you're like, okay, I don't know if they're good. I don't know if they're bad. I don't know if this girl's using him.  What? And you saw it coming the whole time, but like I didn't see that part coming. I didn't see like him wanting to get it out. I thought they were going to get to the point where they just wanted to like together eat a human. But what made it so beautiful is that, that's not where it went. It went like, this is their sex. Their sex is him taking meat out of him and her eating it. Yeah, he literally, he was literally trying to figure out a way. How do I, how do I get inside of her without violating the relationship because she's a married woman. So I need, I need, you know, he's got that. He's in love with her. He's smelling her clothes. He's dreaming about her. And he's moving toward the direction of I want to make love to this woman. So I can't get inside her that way. How can I get my meat? It is so. So warped and I love it. It's so warped and wonderful. And cause I wrote, I wrote a little paragraph as I am, as I am liking to do, right? And so I wrote, first of all, there's so many, I'll just say it. This is an absolutely brilliant film for me in the same league with Parasite. And I actually liked this one better than Parasite. Right after the end, I said, this is more creative and unique than Parasite. Yeah, more creative than Parasite. I like this film. And we love Parasite, by the way. And we love Parasite. Parasite is a wonderful motion picture. I like this one better. And it's depicting, the thing that's so brilliant about this on so many levels is it's depicting multiple moral truths at once. And it's doing so with a cinematic intelligence I wish was more present in cinema as a whole. Anyone who makes the mistake of thinking this is primarily a statement about meat eating controversies of the depicted region, which is something I know exists and know nothing about.  And we all have skeletons in our claws. That's just some of them have a little bit more meat on their bones. Those are all over the place. And that's just a few of the tasty morsels this film presents in an allegorical and metaphorical smorgasbord of cannibalistic delights. Your synopsis, as of late, have been really good, Rick. Thank you. Thank you. You're spending a lot of time on them, I can see. They're good. Yeah. That's truly, I only, as you know, I only will write something like that if I feel a film is really, really worthy and it evokes and draws that out of me. Like the last film we watched, it's just, I can't say enough about how good the movie is. And I knew you'd love it. Oh yeah, I loved it immediately. Thank you guys for recommending it to us. And I know a lot of people still haven't seen it and I'm hoping this will help. Please. From this review, I'm hoping that at least some Indians go see it as well because it's worthy of being seen. But yeah, there's so many things I loved about it in terms of the twists and turns it took and also the complexities that it had. I loved that at the beginning.  And she said right at the beginning, she said it wasn't the meat that caused your stomach. It was the gluttony. And that's essentially what happened to her. Right, yeah.  It was the gluttony of that she just kept wanting more and more and more and that they were like, okay, let's kill somebody now. Yeah. Is it incredible that it went that far? Yeah, even things like, so okay, so like my notes at the very beginning were very straightforward because the film is very straightforward at first. So I wrote, oh, he has a girlfriend, she's married. Hmm, I'm just straightforward. And then it got to the point, when you stay with the film, everything is either an allegory or a metaphor, even to the point when he vomits after he eats her. Yeah. That wasn't about him getting physically, he rejected her. Yeah. She was emotionally hurt because she was literally rejected. Yeah.  It basically took normal relationship stuff and just took out the sex and added cannibalism. Yes. Which is brilliant. But the other thing that it did that I love, and here's one example I'm gonna give technically that points to everything else about this film that I love the most, which is this. So I noticed early on the detail that the director took to making sure sound was, there were so many little depictions of things, example like that scene you just said when she went to go see the guy who was sick, right? Yeah. There was intestinal grumblings and moanings going on that sounded legitimate. Yeah. Little details like that throughout later on, she's pressing into the stomach of a person and you're getting all of those sounds. Then you also got the sounds of the food cooking, just these tiny little beautiful perfect things in the sound and the score that was an exact compliment to all of the other little things that were going on like as much as this is a larger story about obsession and lust and gluttony, it's also a story depicting about the power of the little things in intimacy, something as small as a smiley face in a text, something as little as the brushing of a finger. Like I love the fact, I went, oh my goodness, at the end when they had this moment. Because they've been waiting for that.  I was like, okay, why'd you have to ruin such a great film by like, okay, I get it. We're gonna wrap it up. Like cool, but I loved that at the end that shot made it perfect. It did.  Right. She doesn't care about you. She now just wants your flesh because that's what she's gotten the taste for and you're just like, I don't wanna see you sad so you're like, here have more of my flesh and so he was like limping around and all that cause and you started feeling really bad even though he's the one that initiated it, she started using him and you didn't know if also the entire time it was almost that relationship let her sister or friend said that you're leading them on and you're just using them to eat good food and get that relationship that you don't have with your husband. Right. But in the end that shot showed I believe that they actually really loved each other in the end and I thought that was a nice wrap up and a beautiful end shot for the film. Yeah. I mean, I don't know if you did this but I'm looking at the runtime on my thing as it's clicking down and I'm realizing there's only 10 minutes left in the film and I'm thinking, how are you gonna wrap this up without it being ruined? It was like, there's been many movies I've watched like that and I was like, please don't ruin this. It's been so great. Please don't ruin this. It's been so great. And just yeah, shout outs to Lima Das I believe is the name of the actress who plays Namali, the main woman. Is that, and then the young man is portrayed by Argadip, is that Barua, I believe? Yeah, I just thought they were both great. I thought everybody in the film did really good. The only one I had a problem with was the husband. I didn't think he was particularly strong. But it didn't bother me, but there wasn't, yeah. It didn't ruin the film or anything but that was one of my only gripes. Outside of, obviously I think one of the things that Parasite had going for it over this is Parasite had more money behind it because Bong Joon Ho, he has a name. People know the name Bong Joon Ho. And so he had a lot more cinematography and beautiful shots. This is like almost bare bones, like student film type. Exactly, yeah. In terms of the amount, like he just got a camera and he's like, okay, go stand over there. And there's gonna be cars passing.  At least that's what it looks like. I can't tell if that's actually what it is. But that's what it looked like. And so the quality of the film wasn't as good as like a Parasite, but it wasn't like a bad quality. That's not what I'm saying. It's just, that's the big difference. Like you'll see beautiful cinematography. You're not really gonna see beautiful cinematography in this because beautiful cinematography often takes money as well. 100%, and that's actually one of the things why I am more impressed with this than I was with Parasite.  He's a mathematician with his cinematography. I mean, his symmetry is extraordinary. But yeah, I guarantee he had a much higher quality camera and he had more cameras than one to use with much bigger production team. And I felt that this director and this crew did the absolute most they could with the little that they had. One of my favorite films I've ever seen out of India. And it would be one of my favorite films because I just, I think this could be sent to an American and they would thoroughly enjoy it without seeing any other Indian cinema. Oh yeah, it's on my list of my favorite all time films now, you know, like Gangs of Wasiper and Lunchbox. And this is one of my favorite, not just Indian films. This is one of my favorite films and what made it so wonderful. You know, when we're watching, when we're watching any film, we're rooting for it guys. We want the film, we don't want a film to be bad. Oh no, I value my time. Yeah, value our time and value the art form. And especially when we're setting foot for the first time in a region, we know that everybody in that region and that industry is wanting to present their best foot forward. And man, Assam just knocked it out of the park. 100%. So that was beautiful.  But let us know more from Assam. We'll watch it anyway. Let us know more from Assam that we should watch anything else from this director as well. I don't know if he's doing anything else right now. But he should. I hope Anurag takes him under his wing. Yeah, and become one of his disciples, 100%. So let us know more from Assam that we should be looking at and other stuff like that because this was great. Wonderful. I need some meat.


Right, so we have been looking at linear response theory from a specific point of view namely we decided to calculate corrections due to a small applied time dependent perturbation to the Hamiltonian. We calculated corrections to physical quantities like b some arbitrary quantity b by computing things in terms of the change in the density matrix. In other words if you recall what we did was to say that we start with some b and the expectation value of this b was equal to a b equilibrium plus a time dependent part which we call delta b and that would of course be t and we computed averages and the statement was that this to first order in the applied force was computed by computing first the change in the density operator. So in other words we use the fact that this was b with respect to rho equilibrium plus delta rho of t and we know b rho equilibrium was the equilibrium value time independent and then we computed this using the Liouville equation to first order etc. But you could equally well have done this by working in a more active picture in other words by working in terms of b of t itself in terms of rho equilibrium. So this means you would go to the Heisenberg picture with the full time dependent Hamiltonian correct to first order in it and then compute averages with respect to rho equilibrium. We did not explicitly do this we use this all this time. So what I would like to do is to make contact with what you would be more familiar with in the context of normal quantum mechanics and then we will put in the thermal fluctuations and average over things etc. We know the answer already we know the answer is given the Hamiltonian H of t equal to H not minus a f of t we know that the change delta b of t on the average this is equal to an integral from whenever you switched on the force which we took to be minus infinity in the most general case up to t dt prime f of t prime multiplied by the operator part of it and the operator part of it was this response function phi a b of t minus t prime that was the result that we got and for this we formulas among others for instance we discovered that this could be written as a of 0 comma b of t in the Heisenberg picture induced by the time independent part of the Hamiltonian trace with respect to the equilibrium density operator. So we had a formula like this and this we further simplified in the classical case in the quantum case and so on and so forth. What I would like to do is to now establish contact with the usual way of doing quantum mechanics we will do this in the Heisenberg picture just to clarify to you what we mean by going to the Heisenberg picture and so on. So it will become explicit in what I am going to do so let me call this contact with quantum mechanics with the usual perturbation theory formula in quantum mechanics. So I repeat we are just going to do something which will explicitly tell you how the commutator was up out here for this phi and we will re derive this formula from a slightly different view point. This will make it more familiar this will go through more familiar ground instead of the Louisville operator itself. So again I start with this and when we do not put any subscript on any Hamiltonian it is supposed to be in the Schrodinger picture. So this is a time independent there is no explicit time independent dependence in this operator it is a physical observable and we will take this to be the physical case a is a Hermitian operator. So the Hamiltonian is a Hermitian Hamiltonian if it is not I have the problem of writing this plus its conjugate dagger to make the Hamiltonian Hermitian but for simplicity of notation we will take this to be Hermitian operator here and the Hamiltonian to be Hermitian we will also take this to be real so that the hermiticity of the Hamiltonian is ensured right. Then we want to compute what the full system does and what would you normally do it is a whatever state you start with if you start with a state for example of the system then the Schrodinger equation would apply to the way that state evolves in time so formally one can write down a Schrodinger equation for the evolution of the state. Now it is convenient to introduce a time development operator u which is labeled by 2 time indices at t and an initial time t0. So I am going to take a general initial time t0 whatever be that etc. In general I take t0 to be the time introduced on the force and we will set it equal to minus infinity eventually but I want to make sure that we have a general formalism in other cases where you switch it on at finite times and so on so let us start with t t0. This takes you from the state of the system at t0 to the state of the system at time t and it satisfies of course the equation d over dt equal to h. In this case it is time dependent u of t. So this is the equation satisfied by the time development operator u. Because this is a Hermitian Hamiltonian we know that this time development operator must be unitary operator so that probabilities are conserved and so on. That is all we know about it to start with. You also have a boundary condition on this operator which we will write down subsequently little later. Now I repeat again there is no explicit time dependence here. So if you did not have this then the problem is utterly trivial, completely trivial. Then the solution to this is with the time independent Hamiltonian is just the exponential of this Hamiltonian multiplied by time. But the question is what is it with the time dependence present here. And we have to be careful because there is no guarantee that h at time t commutes with h at any other time. Two operators at different times of time need not commute the same operator at different instance of time need not commute at all because the Hamiltonian gets in between if you like. So what would one do? One would like to find the solution to this but first let us see what happens in the absence of this fellow here. So if h prime so this is what I called h not plus h prime of t. If h prime is absent then of course you have a time independent development operator d over dt and let us call that u not the time development operator in the absence of h prime okay the unperturbed problem. And what would you do there? You would say this is t. Let us take the initial time here. There is no switching on force or anything like that. So I will say that t equal to 0. The system is given to you and then I look at it at any later time. Just one time argument here. This is equal to h not u not of t with the initial condition u not of 0 equal to 1 okay and then the solution implies u not of t equal to e to the there is an h not divided by h cross so it is e to the power minus i h not t over h cross times u not of 0 which is 1 okay. So that is a very trivial problem to do this. Once you have this then I can go back and ask what does this look like the solution to this equation look like. But first let me define the Heisenberg picture for you. So the Heisenberg picture we are talking about is a transformation from the Schrodinger picture to a time system which has time dependent operators. The time dependence comes from h not alone as I have been saying. So any operator B now becomes time dependent this is defined as e to the power as u not dagger of t B u not of t. This is the definition or if you like I write a Heisenberg equation for it. This is solution of i h cross d B over d t is equal to h not B with h not. That is the Heisenberg equation of motion. I solve this and I get this out here okay and this is equal to e to the power i h not t over h cross B e to the minus i h not t over h cross. So if I write an operator without any time argument at all by that I understood. We mean the Schrodinger picture operator which coincides with the Heisenberg picture operator at t equal to 0. Is that clear? So yeah we are still doing the case when h prime is 0 because we are going to switch on h prime and I am still going to do this first and after that take care of h prime separately okay. You will see as we go along what that entails. So we are still doing this and we are going to always continue to define a time dependence of an operator like B via this. But of course once I switch this on, once this is switched on then there could be a time dependence in the operator coming from the fact that you in the time development operator is you and not you not. I have to take that into account I would like to do it to first order in F. So that is the problem really. Now of course you can also ask what is the general solution to this for an arbitrary h of t to all orders arbitrary h of t. It is not an exponential, it is not an exponential because this follow is explicitly time dependent. So you cannot trivially do that. You need an integrating factor as you know and even classically even without operators along the line when you have a thing like d y over d x plus p of x y equal to q of x. If this were a constant this would be a trivial problem but if this were a function then of course you have an integrating factor to take into account. You have to do an definite integral of some kind put correct boundary conditions and things like that. Now it becomes much harder in the case of an operator because of this commutativity problem. You have a formal solution available it is called a Dyson time ordered exponential but we are not interested in that here. We are interested in things to first order in F. So let us see what to do. So is this clear whenever I write this I mean this always and we will use that notation. Of course when you switch this on B has time dependence because of this 2 this portion 2. I will call that B total of t the total time dependence if you like for lack of better notation but I would like to retain B of t for this guy here. And notice that in earlier derivations and linear response theory all the arguments of the function of the various operators refer to this kind of thing. They all refer to this with a nation not alone but I am now making this thing explicit here. You could ask what sort of picture is this where I take the time dependence of the operator to come from the unperturbed Hamiltonian but then I am including the interaction in some way. It is called the interaction picture but I am trying to do this without using that terminology but it will become obvious because I need only first order. Now what should I do for this? I have to now deal with this full problem. So let us use an Anzart's or trial solution and that would be let us put u of t t0 to be equal to u0 of t saying that this fellow will go on evolving due to h0 all the time multiplied by u prime of t and t0. That is a trial solution. It may work, it may not work. We will see what happens. We know this. We know this function. We know u0 of t is this guy here explicitly. We need to put an equation for u prime. So what happens? This is equal to h0 minus a f of t in this fashion u0 of t u prime t0 just substituting for h and substituting this Anzart's for u. On the left hand side I have ih cross d over dt so you have du0 t over dt times u prime of t t0. That is the first term in the derivative here plus ih cross u0 of t d over dt u prime of t t0 and that is equal to this fellow here. That is equal to h0 u 0 of t u prime of t t0 minus there is an f of t which comes out a u0 of t u prime of t just substituting. But look at this term versus that. We already know ih du0 over dt is h0 u0 of t. We already know that. So this term says this term cancels against that even though they are operators. You operate on both sides of this equation. You operate with u prime of t t0. You get the same answer. So this term cancels against this term and we have an equation for this alone. But u0 of t is a unitary operator. It is e to the minus ih0 whatever it is. So this implies that ih cross du over dt u prime of t and t0. This is equal to minus f of t and then e to the power let us move this u0 to the other side. That becomes u0 dagger because u0 is unitary. So this becomes e to the power ih0 t over h cross a e to the minus ih t over h cross on this side. That is u0 and then a u prime of t. This is h0 of t u prime of t which is of course this quantity here is what we have called a u of t. For any operator that is the definition of the Heisenberg picture operator as induced by h0. So this is equal to minus f of t a of t u prime of t t0. Now what is the boundary condition on this fellow here? Boundary condition u prime of t0 t0 equal to 1 because this is due to the switching on the perturbation. And it is switched on at time t0 equal to at any t0. So at that instant of time it is the identity operator. It starts with that and then it goes off to whatever it is. No, no. I am actually going to put t0 equal to minus infinity. Right now it is arbitrary, completely arbitrary. I have defined my Heisenberg picture operator to coincide with the Schrodinger picture operator at t equal to 0 as is conventional. No, no, no, no. Because there is always this evolution due to h0 going on. So I want to keep track of that. And I simply want these 2 pictures coincide at some arbitrary t equal to 0. I call that the origin of time. So this is the boundary condition I want to impose. And that is a differential equation except this is an operator. This fellow is an operator and we have to be careful. This is a number. It is some function. It is a C number, classical number. So we need to solve this equation using this condition and there is this ih cross sitting here on this side. Now what is the way to solve this differential equation? It looks like I have exchanged one problem for another. This is again time dependent and it is an operator. And we do not know how it commutes with that. We have no idea at all at the moment. So we have not done anything significant except that now I am going to say let us convert this differential equation to an integral equation which will incorporate the boundary condition that u prime of t0 t0 equal to 1. So this will imply, this thing implies that u prime of t t0 equal to 1 and let us move the ih cross down here plus i over h cross integral from t0 up to t because that integral whatever it is at t equal to t0 will vanish and then you will get this equal to 1 on this side. So this is the correct inhomogeneous term to take into account that boundary condition times d t prime f of t prime a of t prime u prime of t prime t0. Why is that? Because if I first of all if t0 t equal to t0 this goes to 0 and u prime of t0 t0 equal to 1 which is our boundary condition. Second if I differentiate both sides, if I differentiate this fellow and multiply by ih cross I end up with precisely this because the only t dependence is sitting here and I use the formula for differentiation under the integral sign. There is no t dependence here so there is no partial derivative. There is t dependence here and you are supposed to set the integration variable equal to this limit and differentiate the limit with respect to t which is 1 and if you do that you get f of t a of t u prime of t t. So the integral equation is exact no approximation made here etc and it will tell you how this Dyson series is generated as you can see because now I solve this by iteration I say this is small so I will do first order, second order, third order etc and what is this to first order to 0th order in f it is equal to 1. To first order in f it is an integral again with this quantity here with the second integration variable etc right. So by iteration I can get the solution the exact solution but I am not interested in that I am interested in that to first order. So therefore u prime of t t not is equal to and this means to first order the perturbation this is equal to 1 plus I over h cross integral t not to t dt prime f of t prime a of t prime times 1 because that is the solution to 0th order and there is already an f here.  So now let us look at the case that we are interested in so let us set t not equal to minus infinity that is the most general case I can of course put a theta function so that this ensures suppose this f is switched on at some finite time t not I can always put a t prime minus t not here a unit step function here that take care of it. So this is the most general case so what does u become even before I do that what does u of t not t t not after all that is what we are interested in what does this become this quantity is u not of t just sitting here multiplying this whole thing times 1 plus i over h cross integral t not to t d t prime f of t prime a of t therefore u of t minus infinity is this so we have our exact expression to first order the correct expression to first order and notice how the Heisenberg picture as a has already got the Heisenberg picture evolution in it and the full time development operator has a correction this is the uncorrected one unperturbed part but then there is a perturbed part which is the product of this u of t with this integral all the way here. Now let us look at what the time dependence of some physical quantity like B is so let us look at what is B and I want the total of t so let us put a total because I have already used the symbol B of t for this quantity so I have already said B of t has been defined by mean to be u not of t dagger B and this is the B Schrodinger or B of 0 but now I want with this full thing and what will this be well if the state vector or the states of the system are governed by the time development operator u then the operators are governed by u dagger operator u so this of course is by definition u of t minus infinity B u of t minus infinity with the dagger here where I found this quantity to first order but had I found it to full glory to all orders this would have been the exact time development of this quantity of any quantity here pardon me yeah we are going to check that we are going to check that yeah it will be as you can see because I have to take the dagger of this it will become this fellow go on the right hand side and then this would become a minus and this is Hermitian so to first order it will be second order you got to check order by order consistently but it is the full thing is the full thing is as long as the Hamiltonian is Hermitian so the model of the story is that if the Hamiltonian is time independent and Hermitian then e to the power i Hamiltonian times t over h cross is a unitary operator but the statement is even if the Hamiltonian is time dependent as long as it is Hermitian the time development operator is unitary it is a complicated time ordered exponential but it is still unitary and you can show that order by order so now let us see what this fellow does so this therefore implies that B total of t equal to u dagger so it is this fellow goes to the right hand side and we have to write 1 minus i over h cross integral minus infinity to t dt prime f of t prime a of t prime because a equal to a dagger I have taken that to be the case if it were not the case then you have to add a portion to the Hamiltonian which will make it Hermitian so you have to add minus a f of t minus a dagger f star of t so that the sum becomes Hermitian quantity sometimes you would see in books plus h c to show that it is Hermitian conjugate has been understood to be added but the fact is that I am now going to look at the simple case where a is Hermitian just for notational simplicity so the minus here and you have this multiplied by u naught dagger so this is u naught dagger of t and then the quantity B and then a u which is u naught of t on this side and then 1 plus i over h cross integral minus infinity to t dt prime f of t prime a of t prime okay but we have to keep this only to first order for consistency there is a second order term here due to this f times that f but we have to throw that out because we do not have the answer correct to second order we do not have the time development operator correct to second order so keeping that second order term would be inconsistent which is equal to this times this will just give you a B of t the Heisenberg picture B of t governed by u naught evolution and then you need this times that and then this times that so let us put this times that first plus i over h cross integral minus infinity to t dt prime f of t prime times what well this is always a B of t so this portion is B of t I am multiplying 1 with B of t so B of t and then an A of t prime and in the opposite order it is A of t prime with B of t okay. So let us do the following let us write this as minus 1 over i h cross is that correct I have to be careful here I want to be careful so let us not mess around with these signs so let us take this term first so minus i over h cross integral minus infinity t dt prime f of t prime A of t prime B of t that is this times that with the minus sign and take it the other way there is an x i over plus i over h cross so I will put a minus sign inside the bracket so let us this write this as plus over i h cross which is equal to B of t plus integral minus infinity t dt prime f of t prime and then a commutator of A of t prime with B of t over i h cross but this is precisely what we call the response function well it is actually t minus t prime that is not hard to show that is really hard to show you put in those e to the i h s and etc are not quite not quite so let us not do that yet let us not be in a hurry so we have this expression here and now the last step is to say B total of t average value now we are going to take averages and with respect to what should we take the averages with respect to row equilibrium because we have already put in all the time dependence in the operators we solve the equation of motion for the operators by writing a time development operator acting on the operators and finding out what that does explicitly and computing to first order so this average is now with respect to row equilibrium that is equal to average value of B of t in equilibrium row equilibrium which I call equilibrium plus integral minus infinity to t dt prime f of t prime times the expectation value of A of t prime commutator B of t in equilibrium over i h cross by the way this is time independent B equilibrium this part of it is identically equal to B equilibrium it is time independent why is that why does that happen because yeah because what you need here is e to the minus beta h naught you have to take a trace of e to the minus beta h naught B of t but B of t e to the i h naught t over h cross B e to the minus i h naught t over h cross by the cyclic invariance of the trace move this portion across to this side and of course it commutes with itself it cancels against this and you have trace e to the minus beta h naught B which is equal to B so this portion of it is harmless it is just you can compute it at any time it does not matter in the Schrodinger or Eisenberg picture does not matter it is just the equilibrium average so this part is what we defined as delta B of t by definition this was the change and we are back to the formula we had for delta B of t so delta B of t this quantity is exactly precisely so this we can write now as integral minus infinity to t dt prime f of t prime phi AB of t minus t prime because the expectation value of A of t prime B of t commutator equilibrium is equal to and that we did we explicitly did this we wrote out this quantity and put in all the e to the minus beta h naught and took it across it so that is how we did that is one way of now explicitly deriving so what we what have we done we have done first order perturbation theory in the Eisenberg picture it also tells you how to generate the higher orders so in principle if you are interested you can go on to the next order and find out what is the correction etc. So again go back to the integral equation for u prime and work it out work out the solution to the second order consistent a lot of algebra it would not be linear response theory anymore definitely but it will be second order perturbation theory and then of course we also showed that phi AB of tau this quantity was equal to the bracket that we wrote here A of 0 B of tau this quantity in equilibrium this was also equal to in the classical case just beta A dot of 0 B of tau equilibrium and in the quantum case it was equal to integral 0 to beta d lambda trace of e to the minus beta h naught times e to the lambda h naught A dot of 0 e to the minus lambda h naught B of tau which we wrote as the same thing with the semicolon here by definition so all the non-commutativity of quantum mechanics the complications arise from here from this complex expression relatively complicated expression because you have this sandwiching this is sandwich between these two operate and then all the rest of the properties of this semicolon this common this response function namely the fact that it is stationary it is real for A and B Hermitian it is symmetric function if you interchange the A and B even though they do not commute with each other etc those things follow because of the cyclic property of the trace so I thought I would do this just to show you explicitly that the same answer is obtained from perturbation theory first order perturbation theory by choosing that particular answers for the time development operator okay and what is it that you are doing in choosing that answer you are simply saying that this operator is basically the unperturbed operator but for the perturbation you got an extra piece which satisfies a separate time dependent equation and that equation can be solved by converting it to an integral equation and iterating term by term so that is one way of solving such operator equations with time dependent on inside the operator. Now there is one more thing that we need to do and that is to connect this with dissipation after all you are in a force to the system so there is some kind of energy that is increasing or decreasing some energy is being dissipated and we would like to see how the system absorbs energy if it is a quantum mechanical system it is obviously going to be able to absorb energy only if it takes you from one level to another or brings you down from one level to another one of the two so we should be able to see that explicitly. I am just going to outline the steps here and leave the rest of it as an exercise for you to work out so let us do that case and for simplicity let us look at the case where B is equal to A itself then remember that Phi AA of tau equal to the equilibrium expectation value of the commutator of A of 0, A of tau and A is Hermitian when what is it we want to compute? We have a Hamiltonian which is now time dependent so there is an H of t equal to H0 minus A f of t. We would like to find the rate of change of this the expectation value of this Hamiltonian of the internal energy of the system so we would like to find what is this d over dt H of t and that comes from the time dependence here so this quantity is minus A of t expectation f dot of t I should say A total and the explicit time dependence is sitting here and that is the quantity I want to compute but this quantity so this thing here is equal to so let us compute minus of this fellow this is equal to A equilibrium f dot of t is a term sitting here that is a harmless term you can see plus and this is the interesting part plus an integral from minus infinity to t dt prime f dot of t out here times Phi AA of what? f dot of t minus t prime f of t prime in this fashion. We have an expression for this fellow here in fact we can go all the way back and write this expression in terms of the spectral function they have an explicit expression for the spectral function in terms of e to the i omega t and things like that and you can do this integral because the time integral finally this fellow here is a function of tau and that will become 0 to infinity in tau do the integral and it will essentially give you once you put in time dependences here if you put a Fourier mode it will give you the susceptibility at some temperature at some value of the frequency. So now let us say we now put in a physical case we say f of t equal to the real part of f not e to the minus i omega t so I am trying to find out what happens if you hit the system with a force at some frequency omega which is equal to f not e to the minus i omega t plus f not star e to the i omega t over 2. So f dot of t is trivial this is equal to minus i omega over 2 times f not e to the minus i omega t minus f not star e to the i. f not is some amplitude which is necessarily got to be complex because I want the force to be real so f not plus f not star put that in put this expression in for f of t prime put this expression in for f dot of t t collect the exponentials together when you do that you are going to get e to the i omega t minus t prime everywhere sometimes t plus t prime 2 you get that term as well right you are going to get both kinds of terms in there integral is minus infinity to t change variables to t minus t prime equal to tau and wherever you recognize e to the i omega tau times phi a a of tau replace it with chi of omega and in terms with the wrong sign e to the 2 t plus t prime what should you do subtract twice t so make that t minus t prime inside and then there will be e to the 2 i omega t outside right. So that big mess the huge in my I do not I do not want to write it down here because it will be quite a large number of terms due to this fellow here and what we want to find is the average rate of dissipation so average then over time t from 0 to pi over omega which is the time period over a full cycle of this force that will give you the average rate of dissipation so are the steps clear it will give you may be a constant we do not know you will have e to the 2 i omega t you have to integrate over full period may give you 0 may not etc so in general it will disappear as you can see but at the end of the day at the end of the day you would expect this quantity this quantity to be proportional to mod f naught square that is not too surprising right time something which involves the susceptibility and I want you to show that it is proportional to chi imaginary times constant there is some omegas and stuff like that now you can come you can write this down in terms of the spectral function and a is Hermitian so the spectral function is going to involve weight factors a n m b m n those are going to now become a n m b m n and then there will be summations and things like that so those are called oscillator strings and then there would be all the transition frequencies of the system so that the term which corresponds to absorption and then the term which corresponds to emission they are both there in quantum mechanics so there is always stimulated emission along with absorption and finally you will discover that you have got time dependent first order perturbation theory the Fermi golden rule but with a finite temperature so there are always things weighted by the Boltzmann factor so compute this I am going to give this write the answer down in the problem sheets and then you will see check against what you have done so this kind of brings me to the end of formal linear response theory the rest of it will be in the form of exercises which we will put in the notes but I would like you to go through this derivation step by step all over again and complete this complete this piece of algebra I would do this except for the fact that they did not let it carry over to next time and it is a lengthy slightly lengthy piece of algebra but you see the strategy that is involved and once you do this for one frequency you know the answer for all frequencies because you superpose for an arbitrary force history okay that kind of completes what I wanted to say about linear response theory we still have to make contact with another way of doing this whole business which is to introduce a random force into the system and then compute various quantities once you have a stochastic model for the system including dissipation now that is not easy to do in quantum mechanics because including friction and quantum mechanics is a non trivial task we have sidestep that task but the difficulty with that are the more powerful very powerful way of doing things is that you have to make some assumptions about the nature of the stochastic force that you have and when you have quantum mechanics you also have to worry about commutativity and so on makes it more complicated the formalism of linear response theory on the other hand gives you a very general framework for solving such problems plus points and minus points this is more general than the other case but the other case is very specific and it will go further in term once you make a detailed model of the stochastic force or whatever is driving that fluctuations then you can go little further here there is a fluctuation dissipation theorem here too and that is the relation between we already know in this case kind of intuitively you can see we have a formula for this quantity for A of 0 B of tau in equilibrium this was our response function and we have a formula for its Fourier transform which is essentially phi tilde of omega right if you like that is like taking care of this quantity here is taking care of the response of the system that is what the response is when you apply the force on the other hand the fluctuations themselves would be given by things like what happens under pure thermal fluctuations not the commutator but the anticommutator would give you a measure of the fluctuations especially if you set A equal to B then you get a mean square values that will give you fluctuations the variance of that quantity etc and you know that there is a relation which says that if you took the anticommutator here we could see that this went like an integral d omega phi A B tilde of omega times this quantity this e beta omega over omega whereas this fellow was just the spectral function the Fourier transform of the response function right which measured the dissipation in the system if you like so there is a connection which says that the power spectrum of this quantity which is Fourier transform is related to the power spectrum which measures the dissipation namely phi tilde by this formula one of them is phi tilde and the other is phi tilde times this quantity so that is the generalized fluctuation dissipation theorem you have not used any model for the random force or anything like that but it is a relation between fluctuations and dissipation because the dissipation is governed finally by this quantity which comes from the response function and the fluctuations are governed by the power spectrum of this one the Fourier transform of this quantity so if you like that is the fluctuation dissipation theorem in this problem without any reference to the stochastic force or anything like that which is the way it appears in the Langevin model here so this is intrinsic to it we have not assumed any specific model of stochasticity and yet the thermal fluctuations are getting connected to the dissipation in the system so I will write that expression out explicitly in the handout so you can see and check what happens and you can also compute now things like the mean square displacement of a harmonic oscillator quantum mechanical oscillator at finite temperature at very high temperatures this would be essentially k T and very low temperatures it would be related to h cross omega but in between temperatures it comes from using these some rules here for the spectral function so some of these things I will give us exercises for you to check out so with that we stop here and the next thing we are going to do is to go back backtrack a little bit and fill in a gap we had not filled in earlier which is to connect up the Langevin model with the corresponding differential equation for the and for the probability distributions themselves so things like the Fokker-Planck equation and so on and we take it from there next time.


Just what happened except I thought it would come more quickly. I was overly optimistic about how long it would take I thought we would likely see gravitational waves by 2000 the team has closed the detectors down for about 16 months to improve them this takes a long time, but if we if the team can make these improvements, so we see three times farther than the volume of the universe we see is three cubed or 27 times bigger And so instead of seeing one pair of black holes collide each month when the detectors are operating They should see approximately one every day That's the main reason I have done science My grandfather when I was four years old said to me If you find a job when you grow up that is like play, then you will have succeeded in life And science for me was like play and so yes, I I've maintained that enthusiasm all the way through I had a telephone call as people in America do in the middle of the night and the voice on the other end I From the Nobel committee said it will not surprise you that we are awarding the Nobel Prize to you To Barry bearish and to Rainer Weiss for your contributions to LIGO. I said it does not surprise me at all I was expecting it, but I'm disappointed And I was disappointed I have been disappointed because the discovery of gravitational waves is the result of the efforts of a team of a thousand people and It's really the entire team that deserves the credit and not the three of us who got the prize and I told the Nobel committee they really have an obligation to the people of the world to educate people outside science about the importance of Collaborations and that certain kinds of big discoveries can only be done through large Collaborations where people work together in a very effective and very organized way Why do I do it one? It's fun. I Was a Conventional professor for nearly 50 years. I've been there. I had done that. I wanted to do something different I enjoy working with brilliant people who are very creative who are different than I am and filmmakers artists musicians who are my My collaborators now on my projects They're very different, but they're very creative and very interesting and we each bring different Different skills and experiences to a collaboration. So it's enjoyable But it also is a way to inspire people especially young people about science The goal in that movie from the outset from the very beginning was to do a movie that is based on real science But a movie that also Bridges over the boundary of our current knowledge So there are pieces of the movie that are spec very speculative in regions where we don't understand the laws of nature Very well so-called laws of quantum gravity and then other areas that are very well understood Like the physics of black holes as turns out very well understood we had a guideline that we agreed to that Nothing in the movie would violate well-established laws of physics and all of the speculations would come from science and not come from just the mind of a screenwriter and Christopher Nolan Agreed to that so long as it did not in the way of making a great movie He was afraid at the beginning that I would be what he called the science police But he quickly came to and I was I was afraid that he wouldn't respect the science But with within an hour or two of working together it became clear to both of us that That we had the same goals and that we were working together to brainstorm together to find ways to do the science in a really interesting manner. I have a Book that I'm very enthusiastic about that I hope to finish this year That's a collaboration with a painter Her name is Leah Halloran, and it's her paintings of Warped space and time black holes the birth of the universe things where Space and time are strongly warped and it was originally my words that went with that, but I very carefully improved the wording so it would flow beautifully like her Paintings and then a book designer broke my words up into Segments that look like poetry and I decided gee this could be poetry So I'm trying to turn it into real poetry