1,347 research outputs found
Multifractal characterization of stochastic resonance
We use a multifractal formalism to study the effect of stochastic resonance
in a noisy bistable system driven by various input signals. To characterize the
response of a stochastic bistable system we introduce a new measure based on
the calculation of a singularity spectrum for a return time sequence. We use
wavelet transform modulus maxima method for the singularity spectrum
computations. It is shown that the degree of multifractality defined as a width
of singularity spectrum can be successfully used as a measure of complexity
both in the case of periodic and aperiodic (stochastic or chaotic) input
signals. We show that in the case of periodic driving force singularity
spectrum can change its structure qualitatively becoming monofractal in the
regime of stochastic synchronization. This fact allows us to consider the
degree of multifractality as a new measure of stochastic synchronization also.
Moreover, our calculations have shown that the effect of stochastic resonance
can be catched by this measure even from a very short return time sequence. We
use also the proposed approach to characterize the noise-enhanced dynamics of a
coupled stochastic neurons model.Comment: 10 pages, 21 EPS-figures, RevTe
Monopoles at Finite Volume and Temperature in SU(2) Lattice Gauge Theory
We resolve a discrepancy between the SU(2) spacial string tension at finite
temperature, and the value obtained by monopoles in the maximum Abelian gauge.
Previous work had incorrectly omitted a term due to Dirac sheets. When this
term is included, the monopole and full SU(2) determinations of the spacial
string tension agree to within the statistical errors of the monopole
calculation.Comment: 8 pages, Latex files: msum.tex,msum.aux packaged with uufile
Codimension-2 surfaces and their Hilbert spaces: low-energy clues for holography from general covariance
We argue that the holographic principle may be hinted at already from
low-energy considerations, assuming diffeomorphism invariance, quantum
mechanics and Minkowski-like causality. We consider the states of finite
spacelike hypersurfaces in a diffeomorphism-invariant QFT. A low-energy
regularization is assumed. We note a natural dependence of the Hilbert space on
a codimension-2 boundary surface. The Hilbert product is defined dynamically,
in terms of transition amplitudes which are described by a path integral. We
show that a canonical basis is incompatible with these assumptions, which opens
the possibility for a smaller Hilbert-space dimension than canonically
expected. We argue further that this dimension may decrease with surface area
at constant volume, hinting at holographic area-proportionality. We draw
comparisons with other approaches and setups, and propose an interpretation for
the non-holographic space of graviton states at asymptotically-Minkowski null
infinity.Comment: 13 pages, 9 eps figures. Added Section VI, improved presentation.
Expanded and split the Introduction into two sections. Added Section VII.
Added reference
Evaluation of be-38 percent al alloy final report, 27 jun. 1964 - 28 feb. 1965
Mechanical properties, microstructural features, and general metallurgical quality of beryllium- aluminum allo
Relativistic Hydrodynamics with General Anomalous Charges
We consider the hydrodynamic regime of gauge theories with general triangle
anomalies, where the participating currents may be global or gauged, abelian or
non-abelian. We generalize the argument of arXiv:0906.5044, and construct at
the viscous order the stress-energy tensor, the charge currents and the entropy
current.Comment: 13 pages, Revte
Noise Induced Complexity: From Subthreshold Oscillations to Spiking in Coupled Excitable Systems
We study stochastic dynamics of an ensemble of N globally coupled excitable
elements. Each element is modeled by a FitzHugh-Nagumo oscillator and is
disturbed by independent Gaussian noise. In simulations of the Langevin
dynamics we characterize the collective behavior of the ensemble in terms of
its mean field and show that with the increase of noise the mean field displays
a transition from a steady equilibrium to global oscillations and then, for
sufficiently large noise, back to another equilibrium. Diverse regimes of
collective dynamics ranging from periodic subthreshold oscillations to
large-amplitude oscillations and chaos are observed in the course of this
transition. In order to understand details and mechanisms of noise-induced
dynamics we consider a thermodynamic limit of the ensemble, and
derive the cumulant expansion describing temporal evolution of the mean field
fluctuations. In the Gaussian approximation this allows us to perform the
bifurcation analysis; its results are in good agreement with dynamical
scenarios observed in the stochastic simulations of large ensembles
Anomalies in Superfluids and a Chiral Electric Effect
We analyze the chiral transport terms in relativistic superfluid
hydrodynamics. In addition to the spontaneously broken symmetry current, we
consider an arbitrary number of unbroken symmetries and extend the results of
arXiv:1105.3733. We suggest an interpretation of some of the new transport
coefficients in terms of chiral and gravitational anomalies. In particular, we
show that with unbroken gauged charges in the system, one can observe a chiral
electric conductivity - a current in a perpendicular direction to the applied
electric field. We present a motivated proposal for the value of the associated
transport coefficient, linking it to the triangle anomaly. Along the way we
present new arguments regarding the interpretation of the anomalous transport
coefficients in normal fluids. We propose a natural generalization of the
chiral transport terms to the case of an arbitrary number of spontaneously
broken symmetry currents.Comment: 30 pages; v2: Onsager-relations argument corrected, references added;
v3: fixed missing line in eq. (38
An Analytical Study of Coupled Two-State Stochastic Resonators
The two-state model of stochastic resonance is extended to a chain of coupled
two-state elements governed by the dynamics of Glauber's stochastic Ising
model. Appropriate assumptions on the model parameters turn the chain into a
prototype system of coupled stochastic resonators. In a weak-signal limit
analytical expressions are derived for the spectral power amplification and the
signal-to-noise ratio of a two-state element embedded into the chain. The
effect of the coupling between the elements on both quantities is analysed and
array-enhanced stochastic resonance is established for pure as well as noisy
periodic signals. The coupling-induced improvement of the SNR compared to an
uncoupled element is shown to be limited by a factor four which is only reached
for vanishing input noise.Comment: 29 pages, 5 figure
Collective dynamics of two-mode stochastic oscillators
We study a system of two-mode stochastic oscillators coupled through their
collective output. As a function of a relevant parameter four qualitatively
distinct regimes of collective behavior are observed. In an extended region of
the parameter space the periodicity of the collective output is enhanced by the
considered coupling. This system can be used as a new model to describe
synchronization-like phenomena in systems of units with two or more oscillation
modes. The model can also explain how periodic dynamics can be generated by
coupling largely stochastic units. Similar systems could be responsible for the
emergence of rhythmic behavior in complex biological or sociological systems.Comment: 4 pages, RevTex, 5 figure
Impact of AIRS Thermodynamic Profiles on Precipitation Forecasts for Atmospheric River Cases Affecting the Western United States
No abstract availabl
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