16,806 research outputs found
Quantum anti-quenching of radiation from laser-driven structured plasma channels
We demonstrate that in the interaction of a high-power laser pulse with a
structured solid-density plasma-channel, clear quantum signatures of stochastic
radiation emission manifest, disclosing a novel avenue to studying the
quantized nature of photon emission. In contrast to earlier findings we observe
that the total radiated energy for very short interaction times, achieved by
studying thin plasma channel targets, is significantly larger in a quantum
radiation model as compared to a calculation including classical radiation
reaction, i.e., we observe quantum anti-quenching. By means of a detailed
analytical analysis and a refined test particle model, corroborated by a full
kinetic plasma simulation, we demonstrate that this counter-intuitive behavior
is due to the constant supply of energy to the setup through the driving laser.
We comment on an experimental realization of the proposed setup, feasible at
upcoming high-intensity laser facilities, since the required thin targets can
be manufactured and the driving laser pulses provided with existing technology.Comment: 6 pages, 3 figure
Thermodynamics of an accelerated expanding universe
We investigate the laws of thermodynamics in an accelerating universe driven
by dark energy with a time-dependent equation of state. In the case we consider
that the physically relevant part of the Universe is that envelopped by the
dynamical apparent horizon, we have shown that both the first law and second
law of thermodynamics are satisfied. On the other hand, if the boundary of the
Universe is considered to be the cosmological event horizon the thermodynamical
description based on the definitions of boundary entropy and temperature breaks
down. No parameter redefinition can rescue the thermodynamics laws from such a
fate, rendering the cosmological event horizon unphysical from the point of
view of the laws of thermodynamics.Comment: 13 pages, 2 figure
Lyapunov Spectra in SU(2) Lattice Gauge Theory
We develop a method for calculating the Lyapunov characteristic exponents of
lattice gauge theories. The complete Lyapunov spectrum of SU(2) gauge theory is
obtained and Kolmogorov-Sinai entropy is calculated. Rapid convergence with
lattice size is found.Comment: 7pp, DUKE-TH-93-5
Strong energy enhancement in a laser-driven plasma-based accelerator through stochastic friction
Conventionally, friction is understood as an efficient dissipation mechanism
depleting a physical system of energy as an unavoidable feature of any
realistic device involving moving parts, e.g., in mechanical brakes. In this
work, we demonstrate that this intuitive picture loses validity in nonlinear
quantum electrodynamics, exemplified in a scenario where spatially random
friction counter-intuitively results in a highly directional energy flow. This
peculiar behavior is caused by radiation friction, i.e., the energy loss of an
accelerated charge due to the emission of radiation. We demonstrate
analytically and numerically how radiation friction can enhance the performance
of a specific class of laser-driven particle accelerators. We find the
unexpected directional energy boost to be due to the particles' energy being
reduced through friction whence the driving laser can accelerate them more
efficiently. In a quantitative case we find the energy of the laser-accelerated
particles to be enhanced by orders of magnitude.Comment: 14 pages, 3 figure
Breaking scale invariance from a singular inflaton potential
In this paper we break the scale invariance of the primordial power spectrum
of curvature perturbations of inflation. Introducing a singular behaviour due
to spontaneous symmetry breaking in the inflaton potential, we obtain fully
analytic expressions of scale dependent oscillation and a modulation in power
on small scale in the primordial spectrum. And we give the associated cosmic
microwave background and matter power spectra which we can observe now and
discuss the signature of the scale dependence. We also address the possibility
of whether some inflationary model with featured potential might mimic the
predictions of the scale invariant power spectrum. We present some examples
which illustrate such degeneracies.Comment: 20 pages, 9 figures; Discussion expanded and references added;
Miscellaneous typos correcte
Thermodynamical properties of dark energy
We have investigated the thermodynamical properties of dark energy. Assuming
that the dark energy temperature and considering that the volume
of the Universe enveloped by the apparent horizon relates to the temperature,
we have derived the dark energy entropy. For dark energy with constant equation
of state and the generalized Chaplygin gas, the derived entropy can be
positive and satisfy the entropy bound. The total entropy, including those of
dark energy, the thermal radiation and the apparent horizon, satisfies the
generalized second law of thermodynamics. However, for the phantom with
constant equation of state, the positivity of entropy, the entropy bound, and
the generalized second law cannot be satisfied simultaneously.Comment: 5 two column pages, 2 figures; v2: discussion on thermal equilibrium
with the horizon is added, v3: minor corrections, published in PR
Persistence of locality in systems with power-law interactions
Motivated by recent experiments with ultra-cold matter, we derive a new bound
on the propagation of information in -dimensional lattice models exhibiting
interactions with . The bound contains two terms: One
accounts for the short-ranged part of the interactions, giving rise to a
bounded velocity and reflecting the persistence of locality out to intermediate
distances, while the other contributes a power-law decay at longer distances.
We demonstrate that these two contributions not only bound but, except at long
times, \emph{qualitatively reproduce} the short- and long-distance dynamical
behavior following a local quench in an chain and a transverse-field Ising
chain. In addition to describing dynamics in numerous intractable long-range
interacting lattice models, our results can be experimentally verified in a
variety of ultracold-atomic and solid-state systems.Comment: 5 pages, 4 figures, version accepted by PR
- âŠ