Tuesday, February 28, 2006

Reading QFT

The problem with reading Quantum Field Theory is not a lack of concentration, but rather the sapping of the wish or energy to do anything else. It leads to insomnia and crankiness. Also, it is a form of isolation, nobody around me can follow where I go.

But this, for me, may not be a big price to pay.


Savya said...

Hi Arun,

I have been reading your blog for a while now. I had a couple of questions for you:

1. I have placed a link to your blog on mine. Is that ok?

2. Would you recommend P&S or Siegel's book for QFT for someone who has had a n intro grad course in particle physics?



Arun said...

Hi Savya,

Blogs are meant to be freely linked to. So link away!

From the overview I'd prefer Siegel to Peskin and Schroeder; but it really depends on what you want to learn.

Siegel says about his book:

It is NOT:

* a history book.
o All the other recent, comprehensive field theory texts take the "traditional" approach of covering topics in chronological (rather than logical) order, in storybook fashion. (This is strongly reminiscent of introductory classical mechanics courses that still teach Newton's laws before energy-momentum conservation.)
o This book takes advantage of hindsight, using what we now know to be the most efficient and general approaches. (For example, these other texts still quantize QED canonically, even though they know that method is inadequate for QCD. Some even claim path integrals are less rigorous, even though constructive quantum field theory has shown the opposite to be true.)
o Whenever I have questioned anyone who prefers the traditional approach, after eliminating all the spurious clichés, it all boils down to nostalgia. (I have even heard the excuse that it is useful to learn the less useful approaches simply because they ultimately failed --- certainly an excellent reason to relegate these topics to true history courses, for those who have the time and interest.) This really means that most professors simply teach things the way they learned them, and (ironically) will not bother to learn a new way, or even to check if it has any advantages. (Unfortunately, similar remarks often apply to research.)
* a cookbook. Some books race to Feynman diagrams as quickly as possible, because they either consider them the only useful part of field theory, or they think such an approach is an introductory one. One consequence is that the Higgs effect must take a back seat, and thus weak interactions are underemphasized or explained more phenomenologically.
* a concept book. All the recent texts that use a modern approach, although giving the appearance of being comprehensive except for conciseness, are curiously deficient in explicit S-matrix calculations, especially for QCD. This book both includes modern concepts and calculates with them, since the dualistic approach of concept book plus calculation book has always proved deficient for lack of two good books that work well together.
* a survey. With few exceptions, theories are described in this book at a level that allows explicit calculations.
* an art book. It covers topics that have proven useful, not those that have appealed to certain tastes.