Friday, April 12, 2013

Local Author Interview Series: Thad Walker

The flurry of new books by local authors seems to have subsided.  We're going to take this opportunity to go back to books published within the past several years by local authors and give them the chance for their moment in the blog spotlight.  In this post we're talking to Thad Walker.  Thad co-wrote a book, Optically Pumped Atoms, with William Happer and Yuan-Yu Jau in 2010.

What was one of the most surprising things you learned in writing Optically Pumped Atoms?

The purpose of the book was to present a new approach to making practical calculations of the evolution of atoms subjected to light fields,  including not only effects like spontaneous and stimulated emission, but collisions, diffusion, etc.  In other words, present the fairly well-known theory of these processes in a unified manner that facilitates accurate computer modeling of real experiments.  What surprised me is that the resulting formalism was actually simpler and easier to understand than the usual methods.  It also made for surprisingly simple codes for doing very sophisticated modeling.  A key part of this is that the book is written using Liouville space in which the NxN density matrix in the usual approach becomes an N^2 element vector.  This greatly facilitates dealing with dissipative processes in a clear, compact, and easily programmable manner.

Did you come across any unexpected challenges while writing? 

Communication between three distant co-authors was one of the challenges.  Another was getting sleep.  Getting all the equations right, both from physics and typesetting, was nightmarish.  However, I'm fairly proud of only having found 9 errors in it after 3 years.  Especially considering the awful state of the original proofs given us by the publisher.  I spent many hours pouring over the proofs in the library, fixing all the superscript  and subscript errors inserted by the publisher.  It seemed almost a willful intent to mess up the equations.

How is writing a book different than writing a journal article?

In this case, there was quite a bit of original work so in that sense it was similar to writing an extremely long journal article.  It was different in the sense that the book did not undergo peer review.  We had to be extremely careful to get things right.  There was an extensive amount of effort that went into checking the physics by writing simulation codes.  I don't think my co-authors were aware that I was writing my codes in a different language (Mathematica) than they were using (Matlab), and was used for the published codes in the book.  It was a good test of the formalism, that it works well in multiple languages.

The codes were also a different experience as compared to journal articles, in which codes rarely explicitly appear.  The book contains many short codes that illustrate example simulations.  That they could appear verbatim in the book is testimony to the concise formulation we achieved in the book.  We also published the codes electronically.  For this we took advantage of a nice service of the UW libraries, called MINDS@UW, where we deposited the codes with a permanent URL and with the promise of the library to maintain access to the codes permanently.  [See

I think it is going to take some time for the book to make its full impact.  A year or so ago I was contacted by someone from the Navy who was trying to model an atomic clock.  Their ability to understand the clock using the model was greatly hampered by the fact that the model took a week to run (no joke).  Using the methods from the book, I was able in a few hours work to produce a model that could calculate in 30 seconds what they were getting out in a week.  This example was likely exceptional, but I think that after a few more incidents like that people will take the time to learn our new approach.

Do you have any advice for the aspiring physicist or suggestions for the young student about further studies, etc.

Physics has been and continues to be an exciting and fulfilling way to spend my life.  My advice is to find your passion, i.e. physics, and then--"Whatever your hand finds to do, do it with all your might", says the Teacher.  For students: remember, the classroom is an artificial environment.  The real way to learn and experience physics is to get going on research.

What are some books that have inspired you, either professionally or personally?

I think everyone wanting to do something never done before should read "The Last Place on Earth", by Roland Huntford.  It's far and away the best account of the race to the South Pole in 1911-1912.  That book will show how to, and how not to, get it done.

Physics books are rarely inspiring, though journal articles sometimes are.  Helpful, yes; inspiring, no.  Books are usually published after their contents are scientifically mature.  They are great for learning what is well-known, for getting background in a new area, but the real good stuff is in the journals and on the archive.

I do find biographies of famous physicists sometimes inspiring for the same reasons I like the book mentioned above;  you get some insight into how the best people go about making marvelous discoveries.

Most people, even in the supposedly impersonal physics world, will attest to inspiration coming from other people.  In my case 2 professors at Abiliene Christian University, my Ph. D. advisor at Princeton, and my post-doctoral advisor at JILA were all exceptional people who somehow saw promise in a gawky young lad long ago.  They ignored the superficial evidence and gave me some great opportunities to take advantage of.  

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