[This is the old program from SS 2008. The current program and contact information can be found here.]

18 April 2008, 16:00

Alessandro Torcini (Istituto dei Sistemi Complessi, CNR, Sesto Fiorentino, Italy)
Stability of the splay state in pulse-coupled networks  

Abstract:
The stability of the dynamical states characterized by a uniform firing rate ("splay states") is analyzed in a network of globally coupled leaky integrate-and-fire neurons. This is done by reducing the set of differential equations to a map that is investigated in the limit of large network size. We show that the stability of the splay state depends crucially on the ratio between the pulse--width and the inter-spike interval. More precisely, the spectrum of Floquet exponents turns out to consist of three components: (i) one that coincides with the predictions of the mean-field analysis [Abbott-van Vreesvijk, PRE - 1993]; (ii) a component measuring the instability of ``finite-frequency" modes; (iii) a number of ``isolated" eigenvalues that are connected to the characteristics of the single pulse and may give rise to strong instabilities (the Floquet exponent being proportional to the network size). Finally, we find that the splay state can be stable even for inhibitory coupling.

References:
L.F. Abbott and C. van Vreeswijk, Phys. Rev. E 48, 1483 (1993).
R. Zillmer, R. Livi, A. Politi, and A. Torcini, Phys. Rev. E 76, 046102 (2007).

09 May 2008, 16:00

Andreas Bausch (Biophysik (E22), Technische Universität München)
Physics of complex actin networks: from molecules to networks [Abstract] 

30 May 2008, 16:00

Otto E. Rössler (Institut für Physikalische und Theoretische Chemie, Universität Tübingen)
New statistical mechanics - Clausisus and Chandrasekhar [Abstract] 

06 June 2008, 16:00

Hiroya Nakao (Abteilung Physikalische Chemie, Fritz-Haber-Institut, Berlin)
Diffusion-induced instabilities on random networks [Abstract]