Seminars coming up tomorrow and day after

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

INFORMAL SEMINAR on    Statistical Physics
 

Tuesday, 24 July -  11:30 a.m.

 

Luigi Stasi Seminar Room, Leonardo Building - first floor

 



Satya N. MAJUMDAR    ( Université XI - Paris Sud  )

 

"Diffusion with stochastic resetting"

 

Abstract

We study a simple model of search where the searcher undergoes normal diffusion, but once in a while resets to its initial starting point stochastically with rate  r.  The effect of a finite resetting rate  r  turns out to be rather drastic.  It leads to finite mean search time which, as a function of  r,  has a minimum at an optimal resetting rate r_c.

This makes the search process efficient.

We then generalize this model to study multiple searchers.

Resetting alters fundamentally the late time decay of the survival probability of a stationary target when there are multiple searchers: while the typical survival probability decays exponentially with time, the average decays as a power law with an exponent depending continuously on the density of searchers.  We also consider various generalisations of this simple model.

 

Refs:

 M.R. Evans and S.N. Majumdar, "Diffusion with Stochastic Resetting", Phys. Rev. Lett. 106, 160601 (2011).

 M.R. Evans and S.N. Majumdar, "Diffusion with Optimal Resetting", J. Phys. A-Math. & Theor. 44, 435001 (2011).





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JOINT ICTP/SISSA   COLLOQUIUM

 ON CONDENSED MATTER PHYSICS

 

 

Wednesday, 25 July -  4:00 p.m.

 

Luigi Stasi Seminar Room,    ICTP Leonardo Building (1st floor)

 



Roberto CAR    ( Princeton University )

 

" X-ray absorption spectra of water and ice"



Abstract

X-ray absorption spectroscopy (XAS) is a powerful tool to investigate matter at the molecular scale, but requires a good theory of the excitation process as a prerequisite to a consistent experimental interpretation.  New XAS calculations, based on the GW approximation for the self-energy of the excited quasi-electron in presence of a static core hole, are in good agreement with experiment in liquid water, hexagonal (Ih) ice, high pressure ice VIII, and the two amorphous ice forms LDA (low density amorphous ice) and HDA (high density amorphous ice).  Good models of disorder are essential to achieve experimental agreement, and disorder associated to the quantal dynamics of the nuclei plays an important role.  Analysis of the spectral features yields valuable information on the unifying aspects of short- and intermediate-range order in these systems.