School of Physics Spring Colloquium Series-Dr. Vanderlei Bagnato

Speaker: Dr. Vanderlei Bagnato

Host: Carlos Sa De Melo

Title: Observation  of  Relaxation  Stages  in  a  Nonequilibrium  Closed  Quantum  System

Abstract: The dynamics of non-equilibrium closed quantum systems and their path to thermalization are of fundamental interest to diverse fields, from cosmology to particle physics.  However, a comprehensive description of nonequilibrium phenomena and evolutionary progress towards equilibrium still presents a significant challenge. In this presentation, we report the experimental observation of different stages during the relaxation of decaying turbulence in trapped Bose-Einstein condensates.  Our findings show a direct flow of particles from low to high momentum, a consequence of the injection of energy into the system, exhibiting a universal scaling feature. Prethermalization stage seems to be present preparing the system for the final stage of thermalization. This step is followed by a cascade of particles responsible for repopulating the previously depleted condensate. Both cascades can be explained through self-similar solutions predicted by wave turbulence theory.  These findings provide important information about the connection of many phenomena during the evolution of a nonequilibrium many bodies quantum system. Different possibilities and perspectives will be discussed.

Bio: Vanderlei S. Bagnato, is a Physicist from USP (1981) and Materials Engineer from UFSCar (1981), with a PhD from MIT (1987). He is currently a professor at IFSC-USP (in absence) and a Full professor at Texas A&M University. He works in the fields of optics, atomic and molecular physics with cold atoms and bio photonics.  He has published more than 750 scientific papers and advised more than 130 graduate students. He received several national and international awards. He is a member of the Brazilian Academy of Sciences, TWAS, the US National Academy of Science and the Vatican's Pontifical Academy of Sciences. He has several international collaborations. He coordinates several Brazilian, American and international projects. He has strong dedication to the diffusion of science and innovation besides the advances of basic science.