3,781 research outputs found
Synchronization of non-chaotic dynamical systems
A synchronization mechanism driven by annealed noise is studied for two
replicas of a coupled-map lattice which exhibits stable chaos (SC), i.e.
irregular behavior despite a negative Lyapunov spectrum. We show that the
observed synchronization transition, on changing the strength of the stochastic
coupling between replicas, belongs to the directed percolation universality
class. This result is consistent with the behavior of chaotic deterministic
cellular automata (DCA), supporting the equivalence Ansatz between SC models
and DCA. The coupling threshold above which the two system replicas synchronize
is strictly related to the propagation velocity of perturbations in the system.Comment: 16 pages + 12 figures, new and extended versio
Transition to Stochastic Synchronization in Spatially Extended Systems
Spatially extended dynamical systems, namely coupled map lattices, driven by
additive spatio-temporal noise are shown to exhibit stochastic synchronization.
In analogy with low-dymensional systems, synchronization can be achieved only
if the maximum Lyapunov exponent becomes negative for sufficiently large noise
amplitude. Moreover, noise can suppress also the non-linear mechanism of
information propagation, that may be present in the spatially extended system.
A first example of phase transition is observed when both the linear and the
non-linear mechanisms of information production disappear at the same critical
value of the noise amplitude. The corresponding critical properties can be
hardly identified numerically, but some general argument suggests that they
could be ascribed to the Kardar-Parisi-Zhang universality class. Conversely,
when the non-linear mechanism prevails on the linear one, another type of phase
transition to stochastic synchronization occurs. This one is shown to belong to
the universality class of directed percolation.Comment: 21 pages, Latex - 14 EPS Figs - To appear on Physical Review
The String Tension in Gauge Theories
A review article on string tension concept and their relevance as
non-perturbative quantity on the study of quark confinement in lattice gauge
theories. A detailed description of a variety of methods to measure the string
tension on the lattice and an indication of the most promising developments is
proposed.Comment: Postscript file, 46 pages and 14 figure
The infrared dynamics of Minimal Walking Technicolor
We study the gauge sector of Minimal Walking Technicolor, which is an SU(2)
gauge theory with nf=2 flavors of Wilson fermions in the adjoint
representation. Numerical simulations are performed on lattices Nt x Ns^3, with
Ns ranging from 8 to 16 and Nt=2Ns, at fixed \beta=2.25, and varying the
fermion bare mass m0, so that our numerical results cover the full range of
fermion masses from the quenched region to the chiral limit. We present results
for the string tension and the glueball spectrum. A comparison of mesonic and
gluonic observables leads to the conclusion that the infrared dynamics is given
by an SU(2) pure Yang-Mills theory with a typical energy scale for the spectrum
sliding to zero with the fermion mass. The typical mesonic mass scale is
proportional to, and much larger than this gluonic scale. Our findings are
compatible with a scenario in which the massless theory is conformal in the
infrared. An analysis of the scaling of the string tension with the fermion
mass towards the massless limit allows us to extract the chiral condensate
anomalous dimension \gamma*, which is found to be \gamma*=0.22+-0.06.Comment: 29 pages, 16 figure
Problems in Lattice Gauge Fixing
We review many topics and results about numeric gauge fixing in lattice QCD.Comment: 47 pages, 16 eps figures. Review article sent to IJMP
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