141 research outputs found
Parametric phenomena of the particle dynamics in a periodic gravitational wave field
We establish exactly solvable models for the motion of neutral particles,
electrically charged point and spin particles (U(1) symmetry), isospin
particles (SU(2) symmetry), and particles with color charges (SU(3) symmetry)
in a gravitational wave background. Special attention is devoted to parametric
effects induced by the gravitational field. In particular, we discuss
parametric instabilities of the particle motion and parametric oscillations of
the vectors of spin, isospin, and color charge.Comment: 26 pages, to be published in J. Math. Phy
Time-Lapse Microscopy
Time-lapse microscopy is a powerful, versatile and constantly developing tool for real-time imaging of living cells. This review outlines the advances of time-lapse microscopy and refers to the most interesting reports, thus pointing at the fact that the modern biology and medicine are entering the thrilling and promising age of molecular cinematography
A bound on the scale of spacetime noncommutativity from the reheating phase after inflation
In an approach to noncommutative gauge theories, where the full
noncommutative behavior is delimited by the presence of the UV and IR cutoffs,
we consider the possibility of describing a system at a temperature T in a box
of size L. Employing a specific form of UV/IR relationship inherent in such an
approach of restrictive noncommutativity, we derive, for a given temperature T,
an upper bound on the parameter of spacetime noncommutativity Lambda_NC ~
|theta|^{-1/2}. Considering such epochs in the very early universe which are
expected to reflect spacetime noncommutativity to a quite degree, like the
reheating stage after inflation, or believable pre-inflation
radiation-dominated epochs, the best limits on Lambda_NC are obtained. We also
demonstrate how the nature and size of the thermal system (for instance, the
Hubble distance versus the future event horizon) can affect our bounds.Comment: 9 pages, a reference added, to appear in PL
Baryon number non-conservation and phase transitions at preheating
Certain inflation models undergo pre-heating, in which inflaton oscillations
can drive parametric resonance instabilities. We discuss several phenomena
stemming from such instabilities, especially in weak-scale models; generically,
these involve energizing a resonant system so that it can evade tunneling by
crossing barriers classically. One possibility is a spontaneous change of phase
from a lower-energy vacuum state to one of higher energy, as exemplified by an
asymmetric double-well potential with different masses in each well. If the
lower well is in resonance with oscillations of the potential, a system can be
driven resonantly to the upper well and stay there (except for tunneling) if
the upper well is not resonant. Another example occurs in hybrid inflation
models where the Higgs field is resonant; the Higgs oscillations can be
transferred to electroweak (EW) gauge potentials, leading to rapid transitions
over sphaleron barriers and consequent B+L violation. Given an appropriate
CP-violating seed, we find that preheating can drive a time-varying condensate
of Chern-Simons number over large spatial scales; this condensate evolves by
oscillation as well as decay into modes with shorter spatial gradients,
eventually ending up as a condensate of sphalerons. We study these examples
numerically and to some extent analytically. The emphasis in the present paper
is on the generic mechanisms, and not on specific preheating models; these will
be discussed in a later paper.Comment: 10 pages, 7 figures included, revtex, epsf, references adde
Analysis of measurement errors for a superconducting phase qubit
We analyze several mechanisms leading to errors in a course of measurement of
a superconducting flux-biased phase qubit. Insufficiently long measurement
pulse may lead to nonadiabatic transitions between qubit states and
, before tunneling through a reduced barrier is supposed to distinguish
the qubit states. Finite (though large) ratio of tunneling rates for these
states leads to incomplete discrimination between and .
Insufficiently fast energy relaxation after the tunneling of state may
cause the repopulation of the quantum well in which only the state is
supposed to remain. We analyze these types of measurement errors using
analytical approaches as well as numerical solution of the time-dependent
Schr\"{o}dinger equation.Comment: 14 pages, 14 figure
Evolution of Topological Defects During Inflation
Topological defects can be formed during inflation by phase transitions as
well as by quantum nucleation. We study the effect of the expansion of the
Universe on the internal structure of the defects. We look for stationary
solutions to the field equations, i.e. solutions that depend only on the proper
distance from the defect core. In the case of very thin defects, whose core
dimensions are much smaller than the de Sitter horizon, we find that the
solutions are well approximated by the flat space solutions. However, as the
flat space thickness parameter increases we notice a deviation from
this, an effect that becomes dramatic as approaches . Beyond this critical value we find no stationary solutions to the field
equations. We conclude that only defects that have flat space thicknesses less
than the critical value survive, while thicker defects are smeared out by the
expansion.Comment: 14 page
Extending Event-Driven Architecture for Proactive Systems
ABSTRACT Proactive Event-Driven Computing is a new paradigm, in which a decision is not made due to explicit users' requests nor is it made as a response to past events. Rather, the decision is autonomously triggered by forecasting future states. Proactive event-driven computing requires a departure from current event-driven architectures to ones capable of handling uncertainty and future events, and real-time decision making. We present a proactive event-driven architecture for Scalable Proactive Event-Driven Decision-making (SPEEDD), which combines these capabilities. The proposed architecture is composed of three main components: complex event processing, real-time decision making, and visualization. This architecture is instantiated by a real use case from the traffic management domain. In the future, the results of actual implementations of the use case will help us revise and refine the proposed architecture
Effective Field Theory Approach to String Gas Cosmology
We derive the 4D low energy effective field theory for a closed string gas on
a time dependent FRW background. We examine the solutions and find that
although the Brandenberger-Vafa mechanism at late times no longer leads to
radion stabilization, the radion rolls slowly enough that the scenario is still
of interest. In particular, we find a simple example of the string inspired
dark matter recently proposed by Gubser and Peebles.Comment: 19 pages, 2 figures, comments adde
On higher derivative corrections of tachyon action
We have examined the momentum expansion of the disk level S-matrix element of
two tachyons and two gauge fields to find, up to on-shell ambiguity, the
couplings of these fields in the world volume theory of N coincident non-BPS
D-branes to all order of . Using the proposal that the action of
D-brane-anti-D-brane is given by the projection of the action of two non-BPS
D-branes with , we find the corresponding couplings in the world
volume theory of the brane-anti-brane system. Using these infinite tower of
couplings, we then calculate the massless pole of the scattering amplitude of
one RR field, two tachyons and one gauge field in the brane-anti-brane theory.
We find that the massless pole of the field theory amplitude is exactly equal
to the massless pole of the disk level S-matrix element of one RR, two tachyons
and one gauge field to all order of .Comment: 22 pages, 1 figure, latex file, V2: minor change in notatio
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