143 research outputs found
Critical properties of phase transitions in lattices of coupled logistic maps
We numerically demonstrate that collective bifurcations in two-dimensional
lattices of locally coupled logistic maps share most of the defining features
of equilibrium second-order phase transitions. Our simulations suggest that
these transitions between distinct collective dynamical regimes belong to the
universality class of Miller and Huse model with synchronous update
Five-dimensional Superfield Supergravity
We present a projective superspace formulation for matter-coupled simple
supergravity in five dimensions. Our starting point is the superspace
realization for the minimal supergravity multiplet proposed by Howe in 1981. We
introduce various off-shell supermultiplets (i.e. hypermultiplets, tensor and
vector multiplets) that describe matter fields coupled to supergravity. A
projective-invariant action principle is given, and specific dynamical systems
are constructed including supersymmetric nonlinear sigma-models. We believe
that this approach can be extended to other supergravity theories with eight
supercharges in space-time dimensions, including the important case
of 4D N=2 supergravity.Comment: 18 pages, LaTeX; v2: comments added; v3: minor changes, references
added; v4: comments, reference added, version to appear in PL
Large-scale collective properties of self-propelled rods
We study, in two space dimensions, the large-scale properties of collections
of constant-speed polar point particles interacting locally by nematic
alignment in the presence of noise. This minimal approach to self-propelled
rods allows one to deal with large numbers of particles, revealing a
phenomenology previously unseen in more complicated models, and moreover
distinctively different from both that of the purely polar case (e.g. the
Vicsek model) and of active nematics.Comment: Submitted to Phys. Rev. Let
Low-dimensional chaos in populations of strongly-coupled noisy maps
We characterize the macroscopic attractor of infinite populations of noisy
maps subjected to global and strong coupling by using an expansion in order
parameters. We show that for any noise amplitude there exists a large region of
strong coupling where the macroscopic dynamics exhibits low-dimensional chaos
embedded in a hierarchically-organized, folded, infinite-dimensional set. Both
this structure and the dynamics occuring on it are well-captured by our
expansion. In particular, even low-degree approximations allow to calculate
efficiently the first macroscopic Lyapunov exponents of the full system.Comment: 16 pages, 9 figures. Progress of Theoretical Physics, to appea
"Barber pole turbulence" in large aspect ratio Taylor-Couette flow
Investigations of counter-rotating Taylor-Couette flow (TCF) in the narrow
gap limit are conducted in a very large aspect ratio apparatus. The phase
diagram is presented and compared to that obtained by Andereck et al. The
spiral turbulence regime is studied by varying both internal and external
Reynolds numbers. Spiral turbulence is shown to emerge from the fully turbulent
regime via a continuous transition appearing first as a modulated turbulent
state, which eventually relaxes locally to the laminar flow. The connection
with the intermittent regimes of the plane Couette flow (pCf) is discussed
Self-organized and driven phase synchronization in coupled maps
We study the phase synchronization and cluster formation in coupled maps on
different networks. We identify two different mechanisms of cluster formation;
(a) {\it Self-organized} phase synchronization which leads to clusters with
dominant intra-cluster couplings and (b) {\it driven} phase synchronization
which leads to clusters with dominant inter-cluster couplings. In the novel
driven synchronization the nodes of one cluster are driven by those of the
others. We also discuss the dynamical origin of these two mechanisms for small
networks with two and three nodes.Comment: 4 pages including 2 figure
Nonequilibrium Dynamics in the Complex Ginzburg-Landau Equation
We present results from a comprehensive analytical and numerical study of
nonequilibrium dynamics in the 2-dimensional complex Ginzburg-Landau (CGL)
equation. In particular, we use spiral defects to characterize the domain
growth law and the evolution morphology. An asymptotic analysis of the
single-spiral correlation function shows a sequence of singularities --
analogous to those seen for time-dependent Ginzburg-Landau (TDGL) models with
O(n) symmetry, where is even.Comment: 11 pages, 5 figure
Disordered Regimes of the one-dimensional complex Ginzburg-Landau equation
I review recent work on the ``phase diagram'' of the one-dimensional complex
Ginzburg-Landau equation for system sizes at which chaos is extensive.
Particular attention is paid to a detailed description of the spatiotemporally
disordered regimes encountered. The nature of the transition lines separating
these phases is discussed, and preliminary results are presented which aim at
evaluating the phase diagram in the infinite-size, infinite-time, thermodynamic
limit.Comment: 14 pages, LaTeX, 9 figures available by anonymous ftp to
amoco.saclay.cea.fr in directory pub/chate, or by requesting them to
[email protected]
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