29 May, 2016

America runs on quarters

About two years ago, before leaving the United states, I've posted the following "study" friends-only on facebook. However, I feel that it might fit the format of this blog, so I'm reposting it here.

Everyone knows that the US monetary system is kind of screwed up. I you think America runs on Dunkin' Donuts – bullshit, America runs on quarters. Living in the US is a constant chase after the 25¢ coins: you need them for everything, whether it's parking, candy machines, or laundry.

The screwed up thing is that the rest of coins (1¢, 5¢, and 10¢) are absolutely useless. It's no Europe, in a store the cashier won't ever ask to look for ten cents, since she or he knows you don't have those. Instead, every American possesses a huge can at home where the coins are accumulated (you can cash them in a special machine later, to make sure that the worthless cycle continues).

And I was not an exception. This Mexican coffee tin filled up exactly by the end of my 3-year stay.

Recently, my old friend Valery Yundin was visiting and (after a couple of beers) we decided to estimate how much the coins were worth. Valery and I weighed the can (it was 3.5 kg) and looked up the mass of each coin on the Treasury Department website. Then we used two competing models to deduce the frequency with which 1¢, 5¢, and 10¢ occur:

(1) We assumed that the distribution of 1¢, 5¢, and 10¢ is uniform.

(2) We actually measured the coin distribution for a small sample of ~10 coins and assumed it is the same in the bulk.

Naively, one would expect (1) to be much less accurate than (2), since 1¢ is likely to occur 4 times more often than 5¢, for instance. However, this doesn't seem to be true: for the two cases we got very close estimates, of $57.33 and $57.48 respectively.*

Today I cashed the can and got $59.18 back.

You might be like: "Gosh, are you particle physicists or what?** Who else would get a 2.9% discrepancy and call it 'accurate' ?" Now watch my hands. Valery visited exactly 1 month ago, and I kept accumulating coins after he left. One month is 1/35th of my total stay in the US.

You know what I'm aiming at, alright. Linear extrapolation gives: $57.48 + $57.48/34 = $59.17

What do kids say these days? "Science works, bitches?" I guess that must be it.

Take care,


* Perhaps it's related to the way the prices are formed in the US – the xx.99¢ and xx.95¢ are too frequent, which biases the distribution. But I cannot prove that.

** Valery actually is.

15 May, 2016

The pressure to publish pushes down quality

An interesting read by Daniel Sarewitz in the recent Nature issue. It is a follow-up on the old discussion on the importance of the quality of the research papers as opposed to their quantity, and that the former should rather be taken into account to evaluate scientists for jobs, grants, and prizes.*

He gives an interesting example of poor quality, which is quite shocking from my naïve perspective:

"...The quality problem has been widely recognized in cancer science, in which many cell lines used for research turn out to be contaminated. For example, a breast-cancer cell line used in more than 1,000 published studies actually turned out to have been a melanoma cell line. The average biomedical research paper gets cited between 10 and 20 times in 5 years, and as many as one-third of all cell lines used in research are thought to be contaminated, so the arithmetic is easy enough to do: by one estimate, 10,000 published papers a year cite work based on contaminated cancer cell lines. Metastasis has spread to the cancer literature."

Take care,


* The main problem is, as usual, that the committee members rarely read the actual papers, and stick with the single-number estimates (such as journal impact-factors or h-index) instead.

20 April, 2016

More on bugs in Mathematica

In comments to my previous post, Rytis Jursenas pointed at an entire article in the Notices of AMS discussing several bugs in Mathematica. Since such problems are apparently quite common, I feel it deserves a separate post.

Here it comes:

(just in case, here is the preprint)

"...We have been using Mathematica as a tool in our mathematical research. All our computations with Mathematica have been symbolic, involving only integers (large integers, about 10 thousand digits long) and polynomials (with degree 60 at most), so no numerical rounding or instability can arise in them, and we completely trusted the results generated by Mathematica. However, we have obtained completely erroneous results."
"...Software bugs should not prevent us from continuing this mutually beneficial 
relationship in the future. However, for the time being, when dealing with a problem whose answer cannot be easily verified without a computer, it is highly advisable to perform the computations with at least two computer algebra systems."

Well, I didn't expect such a conclusion to be drawn in 2014.

Take care,


17 April, 2016

A bug in Mathematica - 6 years later

In general, I'm a big fan of Wolfram Mathematica and their customer support. For instance, it happened that after my question "Do you guys have/plan to implement the X method to solve ordinary differential equations?" the support team would code and send me an implementation within a few days (although I obviously didn't ask for it).

Also, back to the day, when I found bugs in Mathematica routines I'd describe them in a blog post, and the support team would usually contact me very fast (sometimes within hours) and assist with solving the issue.

However, sometimes the bugs remain. One of the examples was a bug in evaluation of Clebsch-Gordan coefficients I've bumped into six years ago.

Today I mentioned it to a colleague ("...can you imagine how careful we had to be doing angular momentum algebra in grad school!"), and decided to check it, just for fun.

Here is my output from today:

Yep, after 6 years and 10 updates to Mathematica, it's still there...

Take care (especially using the Clebsch-Gordan routines),


13 April, 2016

Standing on the shoulders of giants

All of you have heard Newton's famous quote:
"If I have seen further, it is by standing on the shoulders of giants" *
It turns out that not only doesn't this quote originate from Newton, in fact, it was a very common saying at the time (such that Newton wouldn't even think there were people who hadn't heard it before).

That's how the "How to fly a horse" book describes it:

"Newton’s line was, in fact, close to a cliché at the time he wrote it. 
... Newton got it from George Herbert, who in 1651 wrote, "A dwarf on a giant’s shoulders sees farther of the two."
... Herbert got it from Robert Burton, who in 1621 wrote, "A dwarf standing on the shoulders of a giant may see farther than a giant himself."
... Burton got it from a Spanish theologian, Diego de Estella, also known as Didacus Stella, who probably got it from John of Salisbury, 1159: "We are like dwarfs on the shoulders of giants, so that we can see more than they, and things at a greater distance, not by virtue of any sharpness of sight on our part, or any physical distinction, but because we are carried high and raised up by their giant size."
... John of Salisbury got it from Bernard of Chartres, 1130: "We are like dwarfs standing upon the shoulders of giants, and so able to see more and see farther than the ancients." 
We do not know from whom Bernard of Chartres got it." 

Take care,


* Some of you might have heard Murray Gell-Mann's interpretation:
"If I have seen further than others, it is because I am surrounded by dwarfs."

10 April, 2016

Superfluidity and Bose-Einstein Condensation

A few times I heard people from the outside of the atomic physics community wondering why was the discovery of Bose-Einstein Condensation (BEC) in alkali gases so special, since the existence of BEC in superfluid helium was considered to be an accepted fact.

Of course, very soon after a BEC of ultracold atoms was created, the implication of the employed technology (as well as of several related developments) became crystal clear. By now, the field of ultracold gases grew into one of the mainstream areas of physics; it already allowed to use our knowledge about atoms and molecules to understand solid state physics, photonics, and even chemistry better.

However, a direct experimental observation of the BEC, as a novel state of matter, was of crucial importance.

Almost immediately after the discovery of superfluidity by Kapitza and Allen and Misener,* Fritz London suggested that this phenomenon was closely related to Bose-Einstein condensation. László Tisza, who was together with London in Paris (no pun intended) at the time, got excited and quickly elaborated on these ideas. Tisza developed the basis for what is known as the "two-fluid model." He conjectured that one can understand the superfluid phase of helium as a mixture of two components. The first, superfluid component, represents a Bose condensate of the atoms occupying the same single-particle quantum state. This results in a macroscopic coherence allowing a flux without friction or viscosity. The second, normal component, whose fraction depends on temperature, behaves as a regular viscous fluid.

Three years later, Lev Landau derived his version of the two-fluid model, based on the quantization of classical hydrodynamics equations. His theory was phenomenological and didn't require the particles to obey Bose statistics. Moreover, he started the paper by bluntly opposing the ideas of Tisza:

...Tisza’s well-known attempt to consider helium II as a degenerate Bose gas cannot be accepted as satisfactory – even putting aside the fact that liquid helium is not an ideal gas, nothing could prevent the atoms in the normal state from colliding with the excited atoms; i.e., when moving through the liquid they would experience friction and there would be no superfluidity at all.

As a matter of fact, it took several decades to unify the ideas of Landau with the ones of London and Tisza. In the end of the 1950's and beginning of the 1960's, several hard-core many-body calculations allowed to theoretically prove that superfluidity is indeed accompanied by Bose-Einstein condensation of helium atoms.**

However, from the experimental side, establishing the existence of the BEC state in superfluid helium turned out to be extremely challenging. Namely, it was possible to obtain only indirect evidence that about 10% of the atoms form a condensate, based on high-energy neutron scattering and spectra of atoms evaporated from the helium surface.

Thus, it was the observation of a BEC in ultracold gases and later experiments on their superfluidity which allowed to establish a connection between the two concepts beyond all possible doubt.

Take care,


* While these two papers appeared back-to-back in Nature, only Kapitza was awarded a Nobel Prize for this discovery (and only 40 years later!). Quite unfortunately, even nowadays the contribution of Allen and Misener remains widely disregarded. There are several great articles discussing this peculiar story; there are even gossips that Kapitza refused to accept the prize together with Allen which made the Nobel committee postpone the decision for decades.

** Since the phenomenological theory of Landau happened to successfully reproduce the experimental data, the contributions of London and Tisza were not acknowledged as widely as they should have been. Among other things, it seems that Fritz London was the first person ever to recognize the effects of quantum mechanics at the macroscopic scale, and think about the emergence of quantum phenomena in many-particle systems. Phil Anderson wrote a nice essay about London's forgotten contributions, which resonates with his own "More is different"  very well.

07 April, 2016

"Ambulance chasing" in particle physics

The progress in particle physics crucially depends on a few large experiments, releasing new data to the entire community of theorists several times a year.

Such a format of theory-experiment interaction leads to what is called the "ambulance chasing" phenomenon. Namely, every time after an announcement of a preliminary experimental result (i.e. one with less than 6 sigma deviation), the arxiv.org preprint server explodes from the amount of theory submissions explaining it. Widely-known examples would be the detection of superluminal neutrinos five years ago, or the recent ATLAS observation of a two-photon peak at 750 GeV.

Quite often, it turns out that the result happened to be within an experimental error bar and is not confirmed by future measurements. However, whether right or wrong, the theory papers receive a fair amount of citations - the more the earlier the preprint appeared.

The race for priority is so intense that dozens of theory preprints are submitted within hours (!) after the official announcement, which means that they were written in advance based on some insider information from the experimentalists.

In any case, in a recent preprint Mihailo Backović (Catholic University of Louvain, Belgium) developed a theory describing the ambulance chasing phenomenon both qualitatively and quantitatively.

The analysis is based on the assumptions that the number of papers on a particular topic can be described using Poisson statistics, and that the interest in the topic as well as the number of available ideas decrease in time (he considers power-law and exponential decays). This resulted in a two-parameter model, which provided a perfect fit to 9 cases of ambulance chasing, considered by the author.

Thus, even if all these theory papers were wrong in explaining the measurements, they at least can be used to study universality in complex systems. :-)

Take care,


03 April, 2016

Surprisingly elegant expressions for fundamental constants and other applied numerology

A few years ago, when I was still at Harvard, Ariel Amir knocked on my door. Somehow, he bumped into my old blog post on the (probably) shortest physics article ever, and was wondering whether such a numerological coincidence is truly random or not.

I've seen this paper by Friedrich Lenz for the first time in the Fall of 2006, visiting the Fritz Haber Institute to interview for a PhD position (I cannot believe it was almost ten years ago). There was a talk by an experimentalist who was aiming to measure the change in the proton-to-electron mass ratio using a molecular fountain (I think that was someone from the Rick Bethlem's, but I'm not absolutely sure). There, the "shortest paper ever" was shown as a joke to spice up the introduction.

Since then I was somewhat puzzled whether Lenz actually meant what he wrote, or was basically trolling the scientific community.

Thus, Ariel and I chatted and decided that the only way to answer this was to do an actual calculation. It turned out that Tadashi Tokieda was on sabbatical at the Radcliffe Institute – basically around the corner – and we decided to discuss the idea with him first.

To prove the point, we considered all possible combinations of the 0-9 digits and standard mathematical constants (such as pi or e) and calculated the probability that a combination of three of them would reproduce a 5-digit number of the form xxxx.x.

The probability turned out to be as low as 1.2%!

In other words, the Lenz observation was indeed quite intriguing, in the sense that such an elegant expression for the proton-to-electron mass ratio might have signaled for some underlying physical theory. While, as far as I know, this theory has not ever been revealed (and later measurements actually deviate from 6pi^5), paying attention to such surprises might pay off and deepen our understanding of physics.

Tadashi, Ariel, and I wrote a little popular piece about such surprising coincidences, which will appear in the June issue of the American Mathematical Monthly.

I hope you will enjoy reading it!

Take care,


02 April, 2016

Blogging While Untenured and Other Extreme Sports

Hello there,

In the good old times I used to be a blogger. Moreover, this blog still appears on the first page of the Google output if one searches for my name.

Long story short, I decided to follow the classic piece by Christine Hurt and Tung Yin (or did I misunderstand their advice?) and give blogging another try after several years of silence.

As a faculty, I do not really have more time as I used to have being a postdoc, when blogging became a luxury that I could not afford. I feel, however, that now I might have more stories to tell, and those will be lost if I don't put them out somewhere.

Not much has changed concerning the things that excite me - it's still mostly funny stories from science and its history, although we'll see how it goes (and how long I will last as a blogger this time :-)

Take care,


06 July, 2012

Some stuff for 05.07.2012

(1) Stephen Hawking's party for time-travellers. I wonder whether it was organized in order to drag attention from the recent $100 bet he lost :-)

(2) Three (!) stories in the last Nature issue about the collapse of Spanish science happening right now: [1], [2], [3]

Take care,


10 June, 2012

FBI files on Richard Feynman published

In 1955 Richard Feynman got invited to a prestigious conference in Moscow, with all the expenses payed by the Soviets.

And here we go: "The FBI found out about the proposed trip while sifting through the trash of Soviet Union Ambassador Georgi Zaroubin’s office."

In the end of the day Feynman didn't go, but the FBI surveillance continued for another few years anyway. Now we can enjoy the original documents from that time.

Take care,


02 June, 2012

Barcode for scientists

Soon every scientist will be assigned a unique number, ORCID (Open Researcher and Contributor ID). That will be just a little tattoo on the inner side of the wrist... just kidding.

There aren't that many unique last names out there and looking for a paper by someone with a popular name might be a pain. For instance, according to statistics, the author named Y. Wang publishes more than 10 papers a day, and obviously it's not the same person :-)

Also, sometimes people change their names, use nicknames, or omit some of their initials, so introducing such unique ID's will be greatly appreciated.

The idea was around for quite a long time, with a few attempts of realization (one of those being the ResearcherID by Thomson Reuters). I hope it will work out this time.

Take care,


06 May, 2012

Two most useful papers of this week :-)

(1) D. Kobak, S. Shpilkin, M. S. Pshenichnikov, "Statistical anomalies in 2011-2012 Russian elections revealed by 2D correlation analysis", arXiv:1205.0741

A solid scientific base for what basically everyone knows already :-) Also, unlike previous analyses appearing on the internet, this one is in English, so everyone can understand it and spread the word.

(2) H. C. Mayer, R. Krechetnikov, "Walking with coffee: Why does it spill?", Phys. Rev. E 85, 046117 (2012). There is also a popular synopsis about it.

I was used to think that spilling coffee while walking (and then making innocent eyes and speeding up) was my own problem, because I basically break everything I touch. This article made me feel normal, just as everyone else. Finally, there is a scientific base for spilling coffee!

Take care,


29 April, 2012

Overlap with other authors

If you feel desperate this Saturday night and think life has no meaning – search for "by other authors" on arxiv.org. Of course, it doesn't mean all of these papers are plagiarized, but lots of fun anyway.

Take care,


14 April, 2012

Scientific Peer Review, ca. 1945

There were so many remakes on this war movie episode, but this one is probably the best. The embedding is disabled, so here we go: Scientific Peer Review, ca. 1945.

Take care,


13 April, 2012

How to write awesome conclusions

A friend of mine Jerome Loreau sent me an article:

R. Breslow "Evidence for the Likely Origin of Homochirality in Amino Acids, Sugars, and Nucleosides on Prebiotic Earth", Published in the Journal of the American Chemical Society.

This part of conclusions is just awesome:

"...An implication from this work is that elsewhere in the universe there could be life forms based on D-amino acids and L-sugars, depending on the chirality of circular polarized light in that sector of the universe or whatever other process operated to favor the L-α-methyl amino acids in the meteorites that have landed on Earth. Such life forms could well be advanced versions of dinosaurs, if mammals did not have the good fortune to have the dinosaurs wiped out by an asteroidal collision, as on Earth. We would be better off not meeting them."

Take care,


UPD. The article was temporarily retracted for alleged duplication (self-plagiarism)

19 March, 2012

How long does it take for an article to be accepted?

I posted it on facebook at some point, but it certainly deserves a wider audience :-)

Take care,


17 March, 2012

A bit of computational sound art

Batuhan Bozkurt does good stuff. It's definitely worth checking out the Otomata - a music synthesizer based on cellular automata, and Circuli - another funny music toy.

They sound the best together, and you can add rain and fire to make it just perfect :-)

Take care,


11 March, 2012

The 1917 in mathematics

You probably know that in 1917 the October Revolution happened in Russia: the bolsheviks got power and created the Soviet Union five years later. The revolution split many lives into the "before" and "after" the 1917.

Here is how famous Russian mathematician Dmitrii Menshov tells about those times:

"...In 1915 we studied function series, in 1916 - orthogonal series. And then the 1917 happened. That was a very memorable year in our lives, this year there happened an event that had drastically affected our future lives: we started looking at trigonometric series."

source (in Russian)

I wish I could care that little about anything that's not science :-D

Take care,


10 March, 2012

Boycott Elsevier

It turns out that a number of people suddenly discovered my blog and I didn't update it for a while. In a nutshell: I moved to the US, changed the research subject a little (I just have to write a popular post about my research at some point!), and things of that sort, which is nothing but peanuts :-) Here comes some funny stuff.

After coming to the US I was surprised how many people are opposing Elsevier, and deny publishing, reviewing, or collaborating with them otherwise.

The reason is that Elsevier was actively pushing so-called Research Works Act, the directive that would prohibit open-access publishing of the federally funded research. Apart from just being unscientific, this directly contradicts the NIH policy stating that the taxpayers-funded research must be freely accessible online.

This very effort was triggered by mathematicians and spread widely across the general scientists' community, a good example is the website, where everyone can sign the "boycott petition."

Finally, Elsevier withdrew the support for the act, but it seems that most of the scientists' activity was prompted by Elsevier's pricing and things of that sort alone, without people discussing the Journal of Chaos Solitons and Fractals (Google it) and 6 fake medical journals they've been publishing. A few years ago my PhD institution and I had a funny story related to it, which made some established scientists join the boycott movement (if we met - ask me in person :-).

Apparently, all that is a consequence of Elsevier being run as a money-making machine, as juxtaposed to many publishing houses ran by scientific societies, like APS, ACS, AAAS, and so on.

It's nice that we don't hear such stories about the Nature magazine that also belongs to the commercial publisher.

Take care,


01 August, 2011

The Journal of Irreproducible Results

I didn't know that a predecessor of the famous Annals of Improbable Research (whose staff runs the Ig Nobel Prize award) was The Journal of Irreproducible Results.

It was founded almost 60 years ago and apparently became a very credible scientific magazine. At least, some people take it very seriously:

"...JIR received attention from American military intelligence when a copy of one of their articles was found among other papers in an abandoned terrorist headquarters in the Middle East. The article was a highly unrealistic and farcical explanation of how to build a nuclear weapon that some unwitting Al Qaida member had filed away. Nonetheless the discovery prompted a short-lived official investigation..." (wiki)

Take care,


31 July, 2011

Vavilov, Cherenkov, and credit for discoveries

We all know that accelerated charged particles emit light - that's how modern high-intensity light sources, synchrotrons, function. Interestingly, uniformly moving particles can emit light too.

The idea goes back to the 1904 Sommerfeld's paper, where he studied the motion of charged particles in a vacuum, and demonstrated that particles flying faster than the speed of light emit radiation even when moving uniformly [1]. Of course, the special relativity theory that appeared next year, rendered Sommerfeld's discovery just a funny mathematical result that has nothing to do with reality, since according to the special relativity no particle can move faster than light in a vacuum.

It's worth noting that the velocity restrictions imposed by the special relativity apply only to a single particle (a group velocity of a bunch of particles can be anything) moving in a vacuum (the speed of light in a medium is much smaller than in a vacuum and particles can move faster than that). However, it took more than 30 years to generalize the Sommerfeld idea to the case of charged particles propagating through a material.

Pavel Cherenkov was pursuing a PhD under Sergey Vavilov, a brother of a famous geneticist Nikolai Vavilov (who was imprisoned and eventually killed by the Soviet regime). Cherenkov was studying the luminescence of uranium salts in solutions irradiated by gamma-rays, and was quite surprised to see the "luminescence" of a pure liquid (sulfuric acid it was), with no salts added. Actually, he was convinced that his PhD work was completely ruined [2].

And it was Vavilov who suggested that this radiation was not luminescence but something completely new, and encouraged Cherenkov to continue the measurements. Indeed, very soon Igor Tamm and Ilya Frank developed a theory for the effect, showing that the radiation is emitted by electrons propagating faster than the speed of light in this particular solution. In 1958 Cherenkov, Tamm, and Frank shared a Nobel Prize for this discovery (unfortunately, without Vavilov who deceased in 1951).

Although Russians call it the "Vavilov-Cherenkov effect", it seems that the name of Vavilov is omitted in the rest of the world where people simply refer to the "Cherenkov Radiation". Why do they?

The funny thing is that immediately after the discovery Vavilov (himself) wrote a paper and submitted it to Nature, where it was rejected (!), and then to Physical Review. This paper had a single author - Cherenkov [3].

I wonder whether such an extreme academic generosity would be possible nowadays :-)

Take care,


[1] A. Sommerfeld, Göttingen Nachrichten 9, 363 (1904); 201 (1905)
[2] V. L. Ginsburg "About science and about myself" (2001)
[3] P. A. Čerenkov, Phys. Rev. 52, 378 (1937)

11 July, 2011


I have no idea whether Google+ will last more than Wave and whether it's any better than facebook, but you can add me to circles here :-)


27 April, 2011

Some stuff for 27.04.11

1) retractionwatch.wordpress.com - a very nice blog about misconduct, fraud, cheating, and other things we all love

2) A Harvard entrance exam from 1899

3) The world is producing more PhDs than ever before. Is it time to stop? (Nature)

4) Reform the PhD system or close it down (Nature)

5) "Down with Determinants!" by Sheldon Axler. The paper presents a different approach to linear algebra, the one without determinants.

Take care,


26 April, 2011

How to Publish a Scientific Comment

A nice essay by Prof. Rick Trebino from Georgia Tech (here is the comment he finally published). I heard people complaining that publishing comments is hard  - a lot of politics involved, journal editors don't want to confess in publishing wrong articles, and so on.

Perhaps, it might be a good idea to make a separate journal publishing only comments and replies to them, as guys propose here (in Russian). In such a way one may highlight all the fraud/misconduct/delusion cases via peer-reviewed comments and replies, without any troubles due to politics of a given journal.

No, really, why don't people do that.

Take care,


Fibonacci salad

Bad food in the university cantine can be described by simple math. Every day they feed us with Fibonacci Salad - it's when you mix a yesterday salad with a salad from two days ago to get the salad for today.

(via Valera Yundin)

Take care,


01 April, 2011

What's so wrong with Comic Sans?



Second, a great affair failed due to comic sans - an old 1978 flyer turned out to be fake. Look at the "land" in "England", it's comic sans. And comic sans was invented in 1994.


Take care,


20 March, 2011

For you, little angular momentum fans

- Why in the Varshalovich book active and passive rotations are defined in opposite way to the book of Edmonds?

- Because in Soviet Russia you don't rotate a coordinate system. Coordinate system rotates you.

Take care,