3,998 research outputs found
Long-Range Correlations in Self-Gravitating N-Body Systems
Observed self-gravitating systems reveal often fragmented non-equilibrium
structures that feature characteristic long-range correlations. However, models
accounting for non-linear structure growth are not always consistent with
observations and a better understanding of self-gravitating -body systems
appears necessary. Because unstable gravitating systems are sensitive to
non-gravitational perturbations we study the effect of different dissipative
factors as well as different small and large scale boundary conditions on
idealized -body systems. We find, in the interval of negative specific heat,
equilibrium properties differing from theoretical predictions made for
gravo-thermal systems, substantiating the importance of microscopic physics and
the lack of consistent theoretical tools to describe self-gravitating gas.
Also, in the interval of negative specific heat, yet outside of equilibrium,
unforced systems fragment and establish transient long-range correlations. The
strength of these correlations depends on the degree of granularity, suggesting
to make the resolution of mass and force coherent. Finally, persistent
correlations appear in model systems subject to an energy flow.Comment: 20 pages, 21 figures. Accepted for publication in A&
Dynamics in a Bistable-Element-Network with Delayed Coupling and Local Noise
The dynamics of an ensemble of bistable elements under the influence of noise
and with global time-delayed coupling is studied numerically by using a
Langevin description and analytically by using 1) a Gaussian approximation and
2) a dichotomous model. We find that for a strong enough positive feedback the
system undergoes a phase transition and adopts a non-zero stationary mean
field. A variety of coexisting oscillatory mean field states are found for
positive and negative couplings. The magnitude of the oscillatory states is
maximal for a certain noise temperature, i.e., the system demonstrates the
phenomenon of coherence resonance. While away form the transition points the
system dynamics is well described by the Gaussian approximation, near the
bifurcations it is more adequately described by the dichotomous model.Comment: 2 pages, 2 figures. To be published in the proceedings of "The 3rd
International Symposium on Slow Dynamics in Complex Systems", eds. M.
Tokuyama, I. Oppenheim, AIP Conf. serie
- …