Monthly Archives: May 2015

Battle of the Public Physicists

At the present time, there are a few (still living) people who represent the physics community in the eyes of the English-speaking public. The most popular are probably the following (in no particular order):

  1. Neil DeGrasse Tyson
  2. Michio Kaku
  3. Brian Greene
  4. Stephen Hawking
  5. Sean Carroll
  6. Bill Nye

There wasn’t a particular order, but Neil Degrasse Tyson, for me, is definitely #1. This is partly because of his central role in the remake of the popular educational series Cosmos: A Spacetime Odyssey With Neil deGrasse Tyson Revealed. The other traits that make him stand out among the others are: (a) he is a gifted, articulate public speaker, (b) he engages with comedians, pop stars, etc. on his podcast Star Talk in good humor unlike any other physicist can, and (c) he is not (or at least less) biased toward one particular subfield of physics. These traits are also shared by Bill Nye, though I would argue that Tyson is a more eloquent orator.

Michio Kaku is almost disingenuous in his attempts to draw in the public, marketing lofty ideas without concrete scientific backing. My criticisms of Brian Greene, Sean Carroll and Stephen Hawking, is that they are scientists first, and public engagement is a side-project to them. Of course this is in no way a true criticism, but when it comes to representing a field in the eyes of the public, I believe that Tyson has it won because he is willing to engage with others in topics outside his field of study. In his podcast, Tyson even goes so far as to talk about the origins of salt as well as the art of how to make a good wine.

More bluntly put, Neil Degrasse Tyson represents the different facets of physics much better than any high-energy or string theorist could, because they have nothing to say about my particular field of study, condensed matter physics (which incidentally is the largest subfield of physics). Tyson does not sell to the public any unverified theories (including string theory), but just sticks to what we know to be the best theories in describing the physical world. I would like to see him speak more about superconductivity, superfluidity and Bose-Einstein condensation every once in a while, but no one is perfect!  Jokes aside, I am proud to have Tyson representing our field in the eyes of the public, and I hope that he keeps the baton for many years to come.

Open-Access Publications

Imagine that taxes are collected from the public by the government, then the government uses some of that money to fund scientific research. Then imagine that after the scientific research is carried out, the scientists write up their results and submit their manuscript to a journal for peer review. The publisher of that journal selects the reviewers (who are not paid for these services). Soon after, the publisher hears back from the reviewers, forwards their comments to the papers’ authors and after some adjustments, publishes this paper.

This paper is then not available to the public, who has funded the research, and not even necessarily available to the government, unless the government agency has a subscription to the journal. In fact, the authors themselves are barred for a period of time from sharing their own work online. The work is owned by a third-party, the publisher.

Though this may seem absurd and overly-simplistic, this is not too much unlike how the current system of publishing in scientific journals actually works. I have argued previously, in Data and Plots for the Public, that it is important for the public to have access to data, plots and articles. It is also necessary for science journalists to be able to reprint these plots for articles that are more accessible to the public.

I am not alone in this point of view as it seems like open-access journals are becoming more popular in many fields, as reported recently in The Guardian. However, I do see a problem occurring with many of the current open-access journal models. These journals work by charging authors a fee for publication. It is easy for this model to become corrupted, as the more a journal publishes, the higher its revenue. Therefore, scientific quality will easily fade when faced with higher potential profits.

One way to rectify this situation is by charging the authors a fee for peer-review even if the paper may not be published. This method also has its drawbacks, however, as it may end up preventing some authors from submitting results to a journal altogether for fear of rejection.

There are a few ideas on how to solve these problems, but I think one thing is clear: the current model is unsustainable, unfair to the public and opposes scientific principles of openness. One wonders if public opinion would have been swayed sooner on the topics of climate change or nicotine addiction had the public been given access to the data and plots from scientific journals rather than having to intuit such information from secondary and tertiary sources. The current model of scientific publication is in need of reform.

Plastic Fantastic

In the past year, I got the chance to read Plastic Fantastic by Eugenie Samuel Reich, a nonfiction work following the short career of Jan Hendrik Schon. Just in case you haven’t heard of him, Schon was one of the biggest fraudsters in scientific history. In a short period between 2000-2001, Schon published a series of  subfield-creating results ranging from superconductivity at 117K in intercalated buckyballs to light-emitting field effect transistors. Most notably, he also announced the discovery of self-assembled molecular field effect transistors (SAMFETs), which would have had the potential to revolutionize the processors in one’s computer and thereby the economy. Most of his results, including the ones mentioned, were found to have been fabricated.

It is quite remarkable that Schon was able to publish 15 first-author papers in either Nature or Science in a time frame spanning from 2000-2001, while also publishing a whole slew of papers in other journals as well.  Is this the absurd length one must go to for one to get caught? While physicists tend to be quite rigorous when trying to explain data, they tend to generally be much more trusting of colleagues that produce the data.

Although the book can be quite gossipy at times, it achieves the goal of imparting to the reader a sense of skepticism about published data. While he may have been the most egregious of the lot, Schon is not alone in perpetrating scientific dishonesty (the recent case of STAP cells comes to mind). It is pretty clear that many cases of “fudging” and/or fabrication occur that go unpunished and are never brought to light.

One aspect of the book that I found particularly disturbing is the effect that Schon’s results had on some careers of young scientists. Many graduate students spent years attempting to replicate his results without success in what is considered the most important years of one’s scientific development. Some young scientific careers were no doubt destroyed because of Schon’s outlandish claims.

One cannot stress enough the importance of scientific integrity and reporting accurate, reproducible data. This book may not be the best-written, but it serves an important purpose in opening one’s eyes to the ridiculous lengths to which one must go before being found out as a fraudster. This book has left no doubt in my mind that I have read papers containing “fudged” data and also that I will do so in the future. I just hope that I don’t spend years attempting to reproduce such a result.

Sign problems, Terry Tau, and open science

Recently a colleague of mine had a pretty amazing experience in open science. In brief, an outstanding conjecture in determinant quantum Monte Carlo about the sign problem was posed and answered by Terrance Tao and others on mathoverflow. The total turnaround time was approximately 3 days from beginning to finish, making it a wonderful example of the power of open science.

First some background. Pretty much any Monte Carlo simulation of fermions suffers from the notorious sign problem. In essence, because the exchange of two Fermi particle contributes a negative weight, any stochastic sampling of a Fermi distribution will result in approximately equal positive and negative parts. In fact, if one measures the sign weight throughout a Monte Carlo simulation, it can be seen to decay to zero exponentially with the number of states/particles and projection time/inverse temperature. There’s been some work by Troyer and Wiese that showed the sign problem in some specific instances falls into the NP-complete complexity class (http://arxiv.org/abs/cond-mat/0408370), though this deserves a blog post of its own. The upshot is it’s a HUGE hindrance to studying fermions and any progress on this front is generally considered very important.

Determinant quantum Monte Carlo (DQMC) is a specific breed of QMC that stochastically samples determinants representing all permutations of single particle fermion states. It was first introduced by some heavy hitters in the QMC committee to study the 2D Fermi Hubbard model (http://journals.aps.org/prb/abstract/10.1103/PhysRevB.80.075116), where they found that for the spin unpolarized system (equal spin-up and spin-down) there was no sign problem! Essentially the spin-up and spin-down signs could cancel each other. Later, Wu and Zhang extended the space of models that were sign problem free in DQMC (http://journals.aps.org/prb/abstract/10.1103/PhysRevB.71.155115). In both these works, however, the lack of a sign problem was found empirically without any hard proof.

Now, my friend and colleague Lei Wang wanted to know exactly why this true, and possibly if more models could fall under this category of sign problem free. Empirically, people see the following:

If Ai=(0 B_i^{T} // B_i 0), where B_i are real matrices and i=1,2,,N, then det(I+exp(A_1)exp(A_2)exp(A_N))0

For spin unpolarized systems it’s pretty clear why each A_i is of this form, but for others systems it’s not as clear. Anyways, this was the question he posed to mathoverflow. Amazingly people jumped on it, and it wasn’t long before Fields Medalist Terrance Tao got involved! It was then only a matter of 3 days before the conjecture was proven to be true in a mathematically rigorous way. For a full writeup of the proof, you can check out Tao’s blog.

When I found out about this, I was super excited to see the open science model working so incredibly well. Tao really is a leader on this front (though perhaps it’s much easier for him to command a crowd-sourced legion as well). At any rate, I would love to see more of this in the future, and I think we can take this instance as an excellent example of success.

The Value of “Wasting Time”

Science magazine this week published an article entitled Advice to a Young Scientist. There were some encouraging words from the Pedro Miguel Echenique in this regard. A lot of career advice nowadays is really geared towards what I often refer to as “careerism”. This is the kind of advice that emphasizes ones career, but is not directly related to improving oneself scientifically.

This article highlights five points that are infrequently discussed when it comes to scientific career advice. I point out the two that are the most rarely stressed:

1) Learn Broadly: Many times, a student of science gets pigeonholed in one particular aspect of a field and cannot see the broader picture. Studying different aspects of one’s scientific discipline (or even outside that) can help open one’s eyes to other avenues of interest and also help frame one’s own work within a larger scientific context.

2) Allow Yourself to Waste Time: The point is made in the article that one should chat with one’s colleagues, enjoy a tea or coffee break, and attend seminars to stimulate one’s mind. In my own experience, talking to other scientists has been a large part of my personal scientific development and has also taught me where there are gaps in my knowledge that need to be filled.

I appreciate Echenique’s sentiment on these points, as this kind of career advice is rarely given out. Sometimes, aspects of careerism can be important, but few things can replace good scientific development and curiosity.