787 research outputs found
Relation between Stochastic Resonance and Synchronization of Passages in a Double-Well System
We calculate, numerically, the residence times (and their distribution) of a
Brownian particle in a two-well system under the action of a periodic,
saw-tooth type, external field. We define hysteresis in the system. The
hysteresis loop area is shown to be a good measure of synchronization of
passages from one well to the other. We establish connection between this
stochastic synchronization and stochastic resonance in the system.Comment: To appear in PRE May 1997, figures available on reques
Beyond the Horizon
Cosmic horizons arise in general relativity in the context of black holes and
in certain cosmologies. Classically, regions beyond a horizon are inaccessible
to causal observers. However, quantum mechanical correlations may exist across
horizons that may influence local observations. For the case of de Sitter
space, we show how a single particle excitation behind the horizon changes the
density matrix governing local observables. As compared to the vacuum state, we
calculate the change in the average energy and entropy per unit volume. This
illustrates what may be a generic property allowing some features of spacetime
beyond a horizon to be inferred.Comment: 9 pages, 1 figur
Rite of Passage? Why Young Adults Become Uninsured and How New Policies Can Help, 2008 Update
Assesses the increase in young adults without health insurance -- their demographics and income levels, causes and implications, and federal and state actions taken -- and suggests targeted policy options to cover students and recent graduates
Rite of Passage? Why Young Adults Become Uninsured and How New Policies Can Help
Assesses the scope of the health insurance problem facing young adults, its causes and implications, and offers policy changes that could help them stay insured as they make the transition to independent living
Asymmetric motion in a double-well under the action of zero-mean Gaussian white noise and periodic forcing
Residence times of a particle in both the wells of a double-well system,
under the action of zero-mean Gaussian white noise and zero-averaged but
temporally asymmetric periodic forcings, are recorded in a numerical
simulation. The difference between the relative mean residence times in the two
wells shows monotonic variation as a function of asymmetry in the periodic
forcing and for a given asymmetry the difference becomes largest at an optimum
value of the noise strength. Moreover, the passages from one well to the other
become less synchronous at small noise strength as the asymmetry parameter
(defined below) differs from zero, but at relatively larger noise strengths the
passages become more synchronous with asymmetry in the field sweep. We propose
that asymmetric periodic forcing (with zero mean) could provide a simple but
sensible physical model for unidirectional motion in a symmetric periodic
system aided by a symmetric Gaussian white noise.Comment: Appeared in PRE March 1997, figures available on reques
Dispersionless motion in a driven periodic potential
Recently, dispersionless (coherent) motion of (noninteracting) massive
Brownian particles, at intermediate time scales, was reported in a sinusoidal
potential with a constant tilt. The coherent motion persists for a finite
length of time before the motion becomes diffusive. We show that such coherent
motion can be obtained repeatedly by applying an external zero-mean square-wave
drive of appropriate period and amplitude, instead of a constant tilt. Thus,
the cumulative duration of coherent motion of particles is prolonged. Moreover,
by taking an appropriate combination of periods of the external field, one can
postpone the beginning of the coherent motion and can even have coherent motion
at a lower value of position dispersion than in the constant tilt case.Comment: 4 pages, 4 figure
Rite of Passage? Why Young Adults Become Uninsured and How New Policies Can Help, 2009 Update
Provides an annual assessment of the uninsurance of 19- to 29-year-olds and their demographics, incomes, and health status. Outlines federal and state actions to expand access to coverage and suggests policy options to address the impact of the recession
Mobility and stochastic resonance in spatially inhomogeneous system
The mobility of an overdamped particle, in a periodic potential tilted by a
constant external field and moving in a medium with periodic friction
coefficient is examined. When the potential and the friction coefficient have
the same periodicity but have a phase difference, the mobility shows many
interesting features as a function of the applied force, the temperature, etc.
The mobility shows stochastic resonance even for constant applied force, an
issue of much recent interest. The mobility also exhibits a resonance like
phenomenon as a function of the field strength and noise induced slowing down
of the particle in an appropriate parameter regime.Comment: 14 pages, 12 figures. Submitted to Phys. Rev.
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