8,879 research outputs found
Effective phase description of noise-perturbed and noise-induced oscillations
An effective description of a general class of stochastic phase oscillators
is presented. For this, the effective phase velocity is defined either by
invariant probability density or via first passage times. While the first
approach exhibits correct frequency and distribution density, the second one
yields proper phase resetting curves. Their discrepancy is most pronounced for
noise-induced oscillations and is related to non-monotonicity of the phase
fluctuations
Symmetric Brownian motor
In this paper we present a model of a symmetric Brownian motor (SBM) which
changes the sign of its velocity when the temperature gradient is inverted. The
velocity, external work and efficiency are studied as a function of the
temperatures of the baths and other relevant parameters. The motor shows a
current reversal when another parameter (a phase shift) is varied. Analytical
predictions and results from numerical simulations are performed and agree very
well. Generic properties of this type of motors are discussed.Comment: 8 pages and 10 figure
Geometric scaling of purely-elastic flow instabilities
We present a combined experimental, numerical and theoretical investigation
of the geometric scaling of the onset of a purely-elastic flow instability in a
serpentine channel. Good qualitative agreement is obtained between experiments,
using dilute solutions of flexible polymers in microfluidic devices, and
two-dimensional numerical simulations using the UCM model. The results are
confirmed by a simple theoretical analysis, based on the dimensionless
criterion proposed by Pakdel-McKinley for onset of a purely-elastic
instability
Bi-Laplacian Growth Patterns in Disordered Media
Experiments in quasi 2-dimensional geometry (Hele Shaw cells) in which a
fluid is injected into a visco-elastic medium (foam, clay or
associating-polymers) show patterns akin to fracture in brittle materials, very
different from standard Laplacian growth patterns of viscous fingering. An
analytic theory is lacking since a pre-requisite to describing the fracture of
elastic material is the solution of the bi-Laplace rather than the Laplace
equation. In this Letter we close this gap, offering a theory of bi-Laplacian
growth patterns based on the method of iterated conformal maps.Comment: Submitted to PRL. For further information see
http://www.weizmann.ac.il/chemphys/ander
Autonomous stochastic resonance in fully frustrated Josephson-junction ladders
We investigate autonomous stochastic resonance in fully frustrated
Josephson-junction ladders, which are driven by uniform constant currents. At
zero temperature large currents induce oscillations between the two ground
states, while for small currents the lattice potential forces the system to
remain in one of the two states. At finite temperatures, on the other hand,
oscillations between the two states develop even below the critical current;
the signal-to-noise ratio is found to display array-enhanced stochastic
resonance. It is suggested that such behavior may be observed experimentally
through the measurement of the staggered voltage.Comment: 6 pages, 11 figures, to be published in Phys. Rev.
An Upper Bound on the Higgs Boson Mass from a Positivity Condition on the Mass Matrix
We impose the condition that the eigenvalues of the mass matrix in the
shifted Lagrangian density be positive at \phi=\phi_{0}, the vacuum expectation
value of the scalar field. Using the one-loop effective potential of the
standard model, this condition leads to an upper bound on the Higgs boson mass
m_{H}: m_{H}<230GeV, for a top quark mass of 175GeV.Comment: LaTex, 5 page
Dynamical Gauge Symmetry Breaking in Extension of the Standard Model
We study the extension of the Standard model with a
strong U(1) coupling. We argue that current experiments limit this coupling to
be relatively large. The model is dynamically broken to the Standard model at the scale of a few TeV with all the extra gauge bosons
and the exotic quarks acquiring masses much larger than the scale of
electroweak symmetry breaking. Furthermore we find that the model leads to
large dynamical mass of the top quark and hence also breaks the electroweak
gauge symmetry. It therefore leads to large dynamical effects within the
Standard model and can partially replace the Higgs interactions.Comment: 4 pages, revtex, no figures; revised version predicting realistic
mass spectru
Drift and Diffusion in Periodically Driven Renewal Processes
We consider the drift and diffusion properties of periodically driven renewal
processes. These processes are defined by a periodically time dependent waiting
time distribution, which governs the interval between subsequent events. We
show that the growth of the cumulants of the number of events is asymptotically
periodic and develop a theory which relates these periodic growth coefficients
to the waiting time distribution defining the periodic renewal process. The
first two coefficients, which are the mean frequency and effective diffusion
coefficient of the number of events are considered in greater detail. They may
be used to quantify stochastic synchronization.Comment: 29 pages, 6 figures, submitted to Journal of Statistical Physic
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