QLS Guest Seminar - Wed. 5 September 11h00

[Quantitative Life Sciences]

QLS GUEST SEMINAR
Wednesday, 5 September 2018 11h00
ICTP, Central Area, 2nd floor, old SISSA building, Via Beirut 2 
https://goo.gl/maps/qotEd4RyXGJ2
Web: http://indico.ictp.it/event/8677/

Speaker:  Marco Baity-Jesi - Columbia University, New York (NY), USA

Title: Trap Models and their Connection to more Realistic Glasses

Abstract:

At low temperatures, the dynamics of glasses suffer a dramatic slowing 
down. The system becomes stuck in metastable configurations called 
traps, which are rarely abandoned, through a process called activation. 
The Trap Model (TM), that de- scribe the motion between different traps, 
provides a simplified framework to un- derstand activated dynamics. Even 
though signs of TM-like behavior were found in realistic systems, it is 
not clear (i) whether the dynamics of most models is the one predicted 
by the TM, (ii) to what extent the TM description applies to other 
glasses and (iii) which are the relevant features for this dynamics to 
be found. We show that the TM description does apply to other glassy 
models, such as the Ran- dom Energy Model [1], if one defines the traps 
dynamically, through the time series of the energy [2]. We then extend 
our analysis to systems with correlated energy levels, and see that the 
trap behavior holds as long as the correlations are weak [3]. Once the 
correlations are strong enough, as it happens in a Hamiltonian system, 
it is unclear whether the dynamic behavior of the glass can be 
completely described through the simple picture provided by the TM.

Comparing Dynamics of Glasses with Deep Neural Networks

Time permitting, a second section on Deep Learning is presented. We 
study dynam- ics and energy (or loss) landscape of feedforward Deep 
Neural Networks [4], with an emphasis on their Mean Square Displacement, 
and find that they exhibit aging on a finite time scale. Later, they 
start diffusing at the bottom of the landscape. Further, we argue that 
the slow dynamics is due rather to flat directions in the landscape than 
to barrier crossing, and we show evidence of an under- to 
over-parametrized phase transition.


Everyone interested is most 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
www.ictp.it/research/qls.aspx
e-mail:qls at ictp.it