Upcoming QLS seminar - Monday 20 July at 11:00am

[Quantitative Life Sciences]

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  QUANTITATIVE LIFE SCIENCES SEMINAR
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Monday, 20 July at 11:00am
L. Stasi seminar room - ICTP, Leonardo building

Speaker: Clelia DE MULATIER (CEA Saclay et Universite Paris-Sud (LPTMS))

Title: Universal properties of branching random walks in confined geometries

Abstract:

Precisely quantifying the flow of radiation such as neutrons or photons 
through a structural material or a living body represents a 
long-standing problem in statistical physics. A fundamental question 
concerns the occupation statistics of the transported particles within 
the body when entering from the outer surface, i.e. the distribution of 
the travelled length I and the number of collisions Iperformed by the 
stochastic process in the body.
     Stochastic radiation transport is modeled by Pearson random walks, 
which can be coupled to a birth-death mechanism (neutron multiplication 
in fissile materials for instance): a random number of particles emerge 
from a collision, which leads to branching particle trajectories. In 
particular, branching Pearson random walks with exponentially 
distributed lengths stem from assuming that the traversed medium is 
homogeneous. In this case, the Markovian nature of the transport process 
leads to remarkably simple Cauchy-like formulas, relating the surface to 
the volume averages of /l/ and n.
     In many important applications of transport theory, the hypothesis 
of uncorrelated scattering centers is however deemed to fail, which thus 
calls for models based on non-exponential random walks. During this 
talk, we will see how such formulas strikingly carry over to the much 
broader class of branching processes with arbitrary jumps, and have thus 
a universal character.
     Our results are key to such technological issues as the analysis of 
radiation flow for nuclear reactor design and medical diagnosis and 
apply more broadly to physical and biological systems with diffusion, 
reproduction and death. The proposed formalism may also apply to animal 
search strategies in the presence of non-exponential displacements.



All those interested are welcome to attend.



-- 
Erica Sarnataro
Group Secretary
Quantitative Life Sciences
The Abdus Salam International Centre for Theoretical Physics (ICTP)
Trieste,  Italy
Tel. +39-040-2240623
e-mail:qls at ictp.it