Vitae & ShortBio

 
Ernesto Altshuler
Professor
"Henri Poincare" Group of Complex Systems
& Superconductivity Laboratory,
Physics Faculty-IMRE, University of Havana
University of Havana, 10400 Havana, Cuba
Phone:  +537 8327349
Fax:      +537 8783471
E-mails: ealtshuler (at) fisica.uh.cu, ealtshuler (at) yahoo.com

Updated Nov 01, 2010

I'm currently professor at the Physics Faculty, University of Havana, where I teach General Physics, Introduction to Superconductivity and Introduction to Complex Systems. I do research in the fields of Superconductivity, Avalanche Dynamics in diverse physical scenarios, Granular Matter, dynamics of social insects and other subjects, always with a strong experimental accent. I'm member of the Cuban Physical Society and of he American Phyiscal Society, and Regular Associate of the "Abdus Salam" ICTP. In the last years, I have maintained scientific exchange with the Group of Advanced Materials and Complex Systems at the University of Oslo, the ESPCI in Paris, the Physics Department at the University of Houston, and the Texas Center for Superconductivity. Besides teaching and doing research, I enjoy contributing to the popularization of Science at all levels, writing short stories, and composing a bit of music that will never be recorded. And, of course, the most important turns out to be the most difficult: trying to spend as much time as I can with my family and friends.
Scientific research...  

 

Avalanches in superconductors

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Avalanches come naturally to our mind when talking about mountains covered by snow. But they take place in incrediby distinct scenarios. One of them is the mixed state of Superconductors. When a big enough magnetic field is applied to a type II superconductor, tiny tornados of current called vortices penetrate the material, interacting repulsively amongst them, and attractively with the structural defects of the material. It can result in a discontinuos movement of the vortices that can eventually resemble the avalanches in a mountain or in a pile of sand as grains are slowly added from top (see my review on the subject here). Using microHall probes and Magnetooptical images, I and my collaborators have investigated how far one can pull the analogy by studying the statistics of such avalanches. We have proved that the statistical distribution of avalanche sizes in superconducting Nb follows a power law whose slope is quite independent from the "magnetic landscape" where it takes place.

Granular matter

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Granular materials lie somewhere between liquids and solids: while a pile of sand at rest looks solid, when you pour extra sand on it from above, you can either obtain a liquid-like flow of sand on the surface of the pile, or you can get intermittent avalanches. In such dynamics, solid-like and liquid-like phases coexist, even exchanging grains of sand between them. We have found strange phenomena such "revolving rivers" and "uphill solitons" in a misterious sand from "Santa Teresa" (Pinar del Rio province, western Cuba). These two phenomena were discovered in a serendipitous way, and turned out to be completely new for the granular community. We have also devoted years to the study of avalanches in laboratory piles of ball bearings (very fashionable in the tough, bicycle-crowded Havana of the early 1990's). More recently, our experiments have shown that avalanche prediction is indeed possible, if one considers not just the time series of avalanches, but the time series of the "structure factor" of the pile. World authority in Complex Systems H. Jensen (Imperial College) has said that our experiments "open the possibility for prediction" in real systems.

 

Dynamics of social insects

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After years of research dealing with vortices or grains of sand, one starts to search for more intelligent particles. Then you find ants. Ants, as social insects, are not very wise at the individual level, but collectively they can be quite smart, at least regarding "survival tasks" such as foraging and nest construction. I and my collaborators have been studying less explored sides of ants behaviour, such as the dynamics of a crowd of ants inside a cell with two symmetrical exits when they are in panic. Our experiments and simulations show that, when in panic, ants tend to use more one exit than the other sue to a "follow-the-crowd" rule apparently written in their genes. and So, when in panic, ants tend to resemble humans. The work has been featured by The American Naturalist and nicely described in a short paper appeared in Discover Magazine. I'm currently working in field experiments to probe self-organization of ants colonies using distributed sensors. Our preliminary results suggest that our system might transform the way to study ants in the wild. 



Transport in superconductors

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I'd say that polycrystals (specifically, ceramics) are regarded as the Cinderella of superconductors: they are too complicated to allow unveil their subtleties easily. But this turns to be attractive from the intellectual point of view. I have devoted several years in studying the high- temperature, low-field properties of polycrystalline High Temperature superconductors from all the highest Tc compounds: YBCO, BSCCO, TBCCO and HBCCO. Lately we have started to study the local, transversal transport properties of multi-filamentary BSCCO tapes (a strong candidate for power applications!) using a cute laser technique we have developed with the people of the Technical Laser Lab (IMRE, University of Havana). Another line of work –this one in collaboration with Prof. Tom Henning Johansen (University of Oslo)–, is the thermal visualization and modeling of “hot spots” in thin film YBCO superconducting bridges in the presence of transport currents: everybody knows that superconductivity breaks down at some point when the applied current is big enough –but we actually see it.

 

Other

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Lord Kelvin used to say that he only understood things when he had been able to construct in his mind a mechanical model of the phenomenon under consideration. I perfectly resonate with such idea. One of the teaching challenges that I have enjoyed the most is to devise a system of coupled pendula to understand systems of superconducting Josephson junctions. Our pendula are simple, but you can tune mechanical parameters that represent excitation currents, gauge-invariant phase differences and the like, and compare the output with its analogue in real junctions. You can read an opinion of this work by the president of the AAPT here. I and my collaborators have also worked theoretically in type II superconductors in cylindrical geometry, and in molecular sieves, specially a kind of zeolite called clinoptilolite, quite abundant in Cuba. It is not coincidence that my wife, A. Rivera, works full time in the subject.
   
 
...and beyond

 

As time goes by, you feel more and more confortable sitting in your ivory tower, producing papers and seminars that can be only understood by an intellectual elite. Then, you suddenly realize that you have lost compass: Science, and specially Physics, must be integrated to the rest of human culture --as Snow pointed out a few decades ago, sparking heavy debate to our days. Then, you start to write articles about Physics subjects that can be understood by a barman --at least I hope so--, and do other weird things that can be eventually regarded by some colleages as plain greed of publicity. Here you will find some products of this deformation of mine.

 

A century has passed since 1905, the Annuus Mirabilis when Einstein published seminal papers on the Photoelectric Effect, the Brownian Motion, and the Special Theory of Relativity. So we must celebrate. In fact, I'd rather say, we must shake it off, because Physics departments are shrinking: youngsters look eagerly at more "fashionable" disciplines such as Informatics, Telecommunications and Biochemistry. Physics --the substrate on which all of them rest-- must do all what is needed to keep itself alive. You will find here a poster I designed to complement a bit the beautiful series entitled "A Century of Physics" (by APS) and other ideas, such as a (seemingly) hopeless project to settle a statue of Albert Einstein in the stairs of the Physics Faculty, University of Havana.

Challenging the imagination: how one can manage to do some significant Physics in a developing country?. You may get some clues or, at least, a feeling of it, from this nice paper appeared in American Scientist

 

In this world where everything is ranked --from MTV hits to the most relevant personalities of the Millenium-- scientific journals do not escape the mainstream. Here I provide a "naive" introduction to some bibliographic indices used to "rank" scientific journals, and give some preliminary statistics and opinions on how publications authored by physicists in Cuba have found a trail in the entangled jungle of scientific impact.

 
Some images of my work and life (including the technically ugly ones, which are probably the dearest)