For distribution

[CM ICTP - Trieste]

  JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINAR

	
Wednesday, 14 March    -    12:30 hrs.




Seminar Room - ICTP Main Building   (first floor)

		

S. FRANZ   ( The Abdus Salam I.C.T.P. )

" Modelling the evolution of the influenza virus "



Abstract

The evolution of the virus of influenza A presents paradoxical aspects: 
despite its rapid evolution to escape acquired immunity, the viral 
population remains concentrated with a behavior reminiscent of an 
evolving quasi-species.  After an introduction to the ecology and the 
evolution of Influenza, I will discuss recent proposals to understand 
this behaviour.

===



	
SEMINAR on   Disorder and strong electron correlations



Thursday, 15 March   -    11:00 a.m.



Lecture Room 204,  Main Bldg.- second floor



F.F. ASSAAD   ( Universität Würzburg )

"Magnetic phase diagram of the doped two-dimensional Kondo lattice 
model"


Abstract

The Kondo lattice model describes an array of magnetic impurities embed 
in a metallic host and is believed to capture the physics of heavy 
fermion systems.  Over the past years it has become possible to carry 
out approximation free auxiliary field quantum Monte Carlo simulations 
of the KLM for the special case of a particle-hole symmetric  
conduction band.  Those results allow an understanding of the interplay 
between the RKKY interaction and the Kondo effect which is at the 
origin of magnetic order-disorder quantum phase transitions in those 
models.  In the ordered phase, the  numerical results allow the 
interpretation of the coexistence, rather than the mutual exclusion, of 
magnetic ordering and Kondo screening.  The local moments are partially 
screened and the remnant moment orders magnetically.  The limitations 
of the above simulations lies in the  requirement of a particle-hole 
symmetric conduction band and invariably leads to insulating ground 
states.  To alleviate this restriction and to access metallic states,  
approximate methods have to be used.  We have opted for the dynamical 
cluster approximation (DCA)  with spin symmetry broken baths so as to 
account for magnetically ordered states.  In the special case of a 
particle-hole symmetric conduction band the overall features of the DCA 
results compare very favorably with  exact auxiliary field simulations. 
  Within the DCA, the magnetically ordered phase survives finite doping 
and allows the study of the evolution of the single particle spectral 
function from magnetic metallic states to paramagnetic heavy fermion 
states.