Title: Chimera states and collective chaos in pulse-coupled neural networks Speaker: Simona Olmi, from Institute for Complex Systems-CNR, Florence Italy Time: Thursday, 3rd November, 2011, at 14:00 Place: Room 1520-732 Abstract: We study the dynamics of two symmetrically coupled populations of identical leaky integrate-and-fire neurons characterized by an excitatory coupling. Upon varying the coupling strength, we find symmetry-breaking transitions that lead to the onset of various chimera states as well as to a new regime, where the two populations are characterized by a different degree of synchronization. Symmetric collective states of increasing dynamical complexity are also observed. The computation of the the finite-amplitude Lyapunov exponent allows us to establish the chaoticity of the (collective) dynamics in a finite region of the phase plane. The further numerical study of the standard Lyapunov spectrum reveals the presence of several positive exponents, indicating that the microscopic dynamics is high-dimensional. Alberto Imparato _____