5,636 research outputs found
Nonequilibrium charge dynamics of light-driven rings threaded by a magnetic flux
We study theoretically the charge polarization and the charge current
dynamics of a mesoscopic ring driven by short asymmetric electromagnetic pulses
and threaded by an external static magnetic flux. It is shown that the
pulse-induced charge polarization and the associated light-emission is
controllable by tuning the external magnetic flux. Applying two mutually
perpendicular pulses triggers a charge current in the ring. The interplay
between this nonequilibrium and the persistent currents is investigated and the
conditions under which the pulses stop the persistent current are identified.Comment: 6 pages, 2 figures; submitted to EP
Oscillatons revisited
In this paper, we study some interesting properties of a spherically
symmetric oscillating soliton star made of a real time-dependent scalar field
which is called an oscillaton. The known final configuration of an oscillaton
consists of a stationary stage in which the scalar field and the metric
coefficients oscillate in time if the scalar potential is quadratic. The
differential equations that arise in the simplest approximation, that of
coherent scalar oscillations, are presented for a quadratic scalar potential.
This allows us to take a closer look at the interesting properties of these
oscillating objects. The leading terms of the solutions considering a quartic
and a cosh scalar potentials are worked in the so called stationary limit
procedure. This procedure reveals the form in which oscillatons and boson stars
may be related and useful information about oscillatons is obtained from the
known results of boson stars. Oscillatons could compete with boson stars as
interesting astrophysical objects, since they would be predicted by scalar
field dark matter models.Comment: 10 pages REVTeX, 10 eps figures. Updated files to match version
published in Classical and Quantum Gravit
Quintessence and Scalar Dark Matter in the Universe
Continuing with previous works, we present a cosmological model in which dark
matter and dark energy are modeled by scalar fields and ,
respectively, endowed with the scalar potentials and . This model contains 95% of
scalar field. We obtain that the scalar dark matter mass is The solution obtained allows us to recover the success of the
standard CDM. The implications on the formation of structure are reviewed. We
obtain that the minimal cutoff radio for this model is Comment: 4 pages REVTeX, 3 eps color figures. Minor changes and references
updated. To appear in Classical and Quantum Gravity as a Letter to the
Editor. More information at http://www.fis.cinvestav.mx/~siddh/PHI
Quantum mechanical counterpart of nonlinear optics
Raman-type laser excitation of a trapped atom allows one to realize the
quantum mechanical counterpart of phenomena of nonlinear optics, such as
Kerr-type nonlinearities, parametric amplification, and multi-mode mixing.
Additionally, huge nonlinearities emerge from the interference of the atomic
wave function with the laser waves. They lead to a partitioning of the phase
space accompanied by a significantly different action of the time evolution in
neighboring phase-space zones. For example, a nonlinearly modified coherent
"displacement" of the motional quantum state may induce strong amplitude
squeezing and quantum interferences.Comment: 6 pages, 4 figures, to be published in Phys. Rev. A 55 (June
On the physics of the Gravitational Wave Background
It is a matter of fact that the universe lives on a Gravitational Wave
Background (GWB). This GWB is extra energy that is not contained in Einstein's
equations. In \cite{Matos:2021jef}, a new model was developed to explain the
accelerating expansion of the universe where a GWB was incorporated into
Einstein's equations by extending them as
, where is the Compton wavelength of the graviton. In
this paper, we continue to study this new paradigm. Due to GWB, quantum
particles cannot follow geodesics, but rather stochastic trajectories. In the
present work, we start by adding a stochastic term to the trajectories of
quantum particles and derive the corresponding field equations of a quantum
particle. We arrive at the Klein-Gordon equation in curved spacetime and from
it we obtain a generalized Schr\"odinger equation. This leads to the following
relevant result: the Schr\"odinger equation can be a direct consequence of the
fact that the universe lives on a GWB
Short-term movements and behaviour govern the use of road mitigation measures by a protected amphibian
Road mitigation infrastructure for pond‐breeding amphibians aims to provide a safe and sustainable passage for individuals between critical habitat patches. However, relatively little is known about how amphibians interact with mitigation systems because of the challenges of documenting movements at sufficiently large sample sizes. The effect of real or perceived barriers to short‐term movement could ultimately determine the success or failure of road mitigation schemes. We quantified behavioural responses of the protected great crested newt Triturus cristatus in a complex road mitigation system in the UK. We used fluorescent paint to mark individuals in order to measure distance travelled and trajectory orientation over two seasons (spring when adults migrate to breeding ponds and autumn when newts disperse) and in three components of the mitigation system (fences, tunnel entrances and inside the tunnels). A total of 250 juveniles and 137 adult great crested newts were marked and tracked during 38 survey nights. Adults were individually identified using belly‐pattern recognition. There was substantially greater activity along the fences during autumn (82% of newt captures) compared to spring. Triturus cristatus typically moved short distances each night (3.21 m per night in spring and 6.72 m per night in autumn), with a maximum of 25.6 m travelled inside a tunnel. Adult recapture rates were low (9.7%) and only 3% of the newts found along the fences reached the tunnel entrances. Movements were straighter in spring and inside the tunnels and newts had higher crossing rates in autumn compared to spring. Overall, behaviour and seasonal movement patterns significantly influenced the use of the mitigation system, in a way that could impact landscape connectivity for T. cristatus over the long‐term. Adequate incorporation of fine‐scale movement dynamics could help develop new behavioural models, inform our understanding of amphibian ecology and substantially improve future road mitigation projects
Quantum-state synthesis of multi-mode bosonic fields: Preparation of arbitrary states of 2-D vibrational motion of trapped ions
We present a universal algorithm for an efficient deterministic preparation
of an arbitrary two--mode bosonic state. In particular, we discuss in detail
preparation of entangled states of a two-dimensional vibrational motion of a
trapped ion via a sequence of laser stimulated Raman transitions. Our formalism
can be generalized for multi-mode bosonic fields. We examine stability of our
algorithm with respect to a technical noise.Comment: 8 pages, revtex, including 2 ps-figures, section about physical
implementation added, references updated, submitted to Phys. Rev. A, computer
program available at http://www.savba.sk/sav/inst/fyzi/qo
A Note on the Local Cosmological Constant and the Dark Energy Coincidence Problem
It has been suggested that the Dark Energy Coincidence Problem could be
interpreted as a possible link between the cosmological constant and a massive
graviton. We show that by using that link and models for the graviton mass a
dark energy density can be obtained that is indeed very close to measurements
by WMAP. As a consequence of the models, the cosmological constant was found to
depend on the density of matter. A brief outline of the cosmological
consequences such as the effect on the black hole solution is given
Case Report: Varicella Associated Neuropsychiatric Syndrome (VANS) in Two Pediatric Cases
Background: Viral or bacterial infections can trigger auto-immune inflammatory reactions and conditions in children. Self-reactivity arises due to similarities in molecular structures between pathogenic microorganisms and regular body structures with consequent immune-cross reactions. Reactivation of latent Varicella Zoster Virus (VZV) infections can cause neurological sequalae, including cerebellitis, post-herpetic neuralgias, meningo/encephalitis, vasculopathy and myelopathy. We propose a syndrome caused by auto-immune reactivity triggered by molecular mimicry between VZV and the brain, culminating in a post-infectious psychiatric syndrome with childhood VZV infections.
Case presentation: Two individuals, a 6-year-old male and 10-year-old female developed a neuro-psychiatric syndrome 3-6 weeks following a confirmed VZV infection with intrathecal oligoclonal bands. The 6-year-old male presented with a myasthenic syndrome, behavior deterioration and regression in school, he was poorly responsive to IVIG and risperidone, however had a pronounced response to steroid treatment. The 10-year-old female presented with marked insomnia, agitation, and behavioral regression as well as mild bradykinesia. A trial of neuroleptics and sedatives resulted in a mild unsustained reduction in psychomotor agitation and IVIG was also unsuccessful, however the patient was very responsive to steroid therapy.
Conclusion: Psychiatric syndromes with evidence of intrathecal inflammation temporally related to VZV infections that are responsive to immune modulation have not been described before. Here we report two cases demonstrating neuro-psychiatric symptoms following VZV infection, with evidence of persistent CNS inflammation following the resolution of infection, and response to immune modulation.info:eu-repo/semantics/publishedVersio
- …