| Oct 22, 2013 |
Oleksandr Burylko
(National Academy of Sciences Kyiv, Ukraine) |
Analysis of bifurcations and the study of competition in phase oscillator networks with positive and negative coupling |
| A globally coupled phase oscillators of Kuramoto type with positive (conformist)
and negative (contrarian) couplings are considered in (Hong & Strogatz (HS), 2011).
Here we generalize the HS system to include a phase shift at the interaction function.
The system is analyzed by using bifurcation theory as well as a detailed study of geometry of the invariant manifolds.
Results include a rich repertoire of dynamical regimes (multistability, complex heteroclinic cycles, chaos, etc).
Some of these interesting regimes are not possible in HS system. |
Oct 28, 2013
(Monday) |
Alexander Skubachevskii
(Peoples' Friendship University of Russia, Russia) |
The Vlasov–Poisson equations in infinite cylinder and controlled plasma |
We consider the first mixed problem for the Vlasov-Poisson equations
in infinite cylinder, describing evolution of densities for ions and electrons in rarefied plasma with external magnetic
field. We construct in explicate form a stationary solution with densities of charged particles in interior cylinder.
In a neighborhood of stationary solution it is proved existence and uniqueness of classical solution with supports
of densities of charged particles locating at some positive distance from cylindrical boundary. This work was
supported by the RFBR (grant No. 12-01-00524).
Talk will take place at 3:15 p.m.
at the Free University Berlin, Room 140, Arnimallee 7 (rear building), 14195 Berlin. |
Oct 28, 2013
(Monday) |
Dmitrii Turaev
(Imperial College London, UK) |
Arnold diffusion in the a priori chaotic case |
Let a real-analytic Hamiltonian system have a normally-hyperbolic cylinder such that the Poincare map on the cylinder has a twist property. Let the stable and unstable manifolds of the cylinder intersect transversely. The homoclinic channel is a small neighbourhood of the union of the cylinder and the homoclinic. We show that generically (in the real-analytic
category) in the channel there always exist orbits which deviate from the initial condition unboundedly.
Talk will take place at 4:45 p.m.
at the Free University Berlin, Room 140, Arnimallee 7 (rear building), 14195 Berlin. |
| Oct 29, 2013 |
SFB 647
und Workshop am WIAS |
| Nov 5, 2013 |
DFG Research Center MATHEON - Center Days |
| Nov 12, 2013 |
CANCELLED |
| Nov 19, 2013 |
Antonio Politi
(University of Aberdeen, UK) |
Coarsening processes in Discrete Nonlinear Schroedinger-type models |
| The Discrete Nonlinear Schroedinger equation (DNLSE) is a paradigmatic
model used to describe both Bose-Einstein condensates and propagation in
waveguides. The DNLSE behaviour is discussed from the point of view of
statistical mechanics, with a particular emphasis given to the
convergence to the equilibrium state in the regime of the so-called
negative (absolute) temperatures. The observed coarsening is studied
with the help of simplified models of exclusion-process type. |
| Nov 26, 2013 |
SFB 647 |
| Dec 3, 2013 |
CANCELLED |
| Dec 10, 2013 |
CANCELLED |
Dec 17, 2013
3:15 p.m. |
Atsushi Mochizuki
(RIKEN Advanced Science Institute, Japan) |
Rate sensitivity of biochemical reaction systems: A function-free approach |
| tba |
Dec 17, 2013
4:45 p.m. |
Jan Sieber
(University of Exeter, UK) |
Periodic orbits in equations with state-dependent delay |
| tba |
| Jan 7, 2014 |
SFB 647 |
| Jan 14, 2014 |
CANCELLED |
| Jan 21, 2014 |
Josef Ladenbauer
(Technical University Berlin) |
Modeling populations of adaptive neurons: spike train properties and network dynamics
|
| Many types of neurons exhibit spike rate adaptation, a gradual decrease
in spiking activity following a sudden increase in stimulus intensity.
This phenomenon is typically produced by slowly deactivating
transmembrane potassium currents, which effectively inhibit neuronal
responses and can be controlled by neuromodulators. In this talk I will
present recent theoretical work on (networks of) model neurons, showing
(i) how these adaptation currents change the relationship between
fluctuating synaptic input, spike rate output and the spike train
statistics of single neurons and (ii) how they contribute to spike
synchronization as well as spike rate oscillations in recurrent networks
of excitatory and inhibitory neurons. |
| Jan 28, 2014 |
Philipp Hövel
(Technical University Berlin) |
Dynamics of two neural oscillators in the presence of heterogeneous coupling delays
|
Investigations of nonlinear dynamics in coupled systems have seen a
huge increase in interest during the last years. The size of considered systems ranges from a few coupled elements to complex
networks, and collective dynamics may arise in various patterns, of which in-phase (or zero-lag) synchronization is just the most
prominent one. The signal transmission between coupled elements is often not instantaneous. Thus, non-zero transmission times have to be
taken into account as crucial quantities that influence the dynamics of network nodes to a large extent.
In this presentation, I will discuss synchronization effects in the presence of delayed coupling for two excitable neural systems. In
particular, I will investigate the effects of heterogeneous delays in the coupling [1]. Depending upon the coupling strengths and the time
delays in the mutual and self-coupling, the compound system exhibits different types of synchronized oscillations of variable period. I
will present an analysis of this behavior based on the interplay of the different time delays. The numerical results are supported by
analytical findings. In addition, I elaborate on bursting-like dynamics with two competing timescales on the basis of the
autocorrelation function.
[1] A. Panchuk, D. P. Rosin, P. Hövel, and E. Schöll: Synchronization of coupled neural oscillators with heterogeneous delays
Int. J. Bif. Chaos 23, 1330039 (2013).
|
| Feb 4, 2014 |
SFB 647 |
| Feb 11, 2014 |
Irina Kmit
(Humboldt University Berlin) |
Hopf bifurcation for one-dimensional hyperbolic PDEs
|
| tba
|
Tea and coffee will be served at 2:45 p.m. on the ground floor.
Guests are always welcome !
Last change: Feb. 7, 2014
