Seminars coming up soon

[Cond.Matt. & Stat.Mech.Section]

INFORMAL SEMINAR
 
 

Friday, 25 February   -    11:30 a.m.
 
 
Luigi Stasi Seminar Room -  Leonardo Bldg. - first floor
 
  
 
Alkaterini MANDILARA   ( Universite' Libre de Bruxelles )
 
 

"On the uncertainty and positivity of Wigner functions of one-dimensional mixed states"

 
Abstract
 
 
We present a new uncertainty relation for one-dimensional mixed states given its purity and degree of non-Gaussianity. This relation extends the purity-bounded uncertainty re- lation for mixed states derived by V. V. Dodonov and V. I. Man’ko. For the special case of pure states it provides us with an extended version of the Robertson-Schro ̈dinger uncer- tainty relation, saturated by a set of states which includes all the eigenstates of the quantum harmonic oscillator. We represent our results as a bound in a three-dimensional parametric space of mixed states and identify the regions of the bound realized by states with non- negative Wigner function. This takes us closer to a proper extension of Hudson’s theorem to mixed states and permits us to visualize and compare the set of states with non-negative Wigner function and the set of states which minimize the newly derived uncertainty relation.

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JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINAR



Tuesday, 1 March   -   11:30 hrs.

 

Luigi Stasi Seminar Room,  ICTP Leonardo Building - 1st floor

 


Evgeny KOZIK    ( Eidgenossische Technische Hochschule Zurich )

 

"Diagrammatic Monte Carlo for    correlated fermions"


Abstract


One of the important goals promising a major impact on the field of condensed matter and far beyond, is being able to describe properties of correlated fermionic systems quantitatively accurately without uncontrolled approximations.  In this talk, I will focus on the family of diagrammatic Monte Carlo (DiagMC) methods introduced recently to meet this challenge.  The Determinant DiagMC technique allowed to obtain the most accurate so far prediction of the critical temperature curve across the crossover from the Bardeen-Cooper-Schrieffer pairing to the Bose-Einstein condensate of molecules (the BCS-BEC crossover) in a two-component Fermi gas.  A new generation of DiagMC methods based on sampling irreducible Feynman diagrams directly in the thermodynamic limit features an unprecedented tolerance to the notorious fermionic sign problem, which makes it a promising technique for unbiased solution of generic many-body fermionic systems.  I will substantiate this promise with accurate results for the repulsive Hubbard model in the correlated Fermi liquid regime and a very recent calculation of the equation of state of the unitary Fermi gas.