10,862 research outputs found
Scalar fields in the Lense-Thirring background with a cosmic string and Hawking radiation
We analyze the influence of the gravitational field produced by a slowly
rotating black hole with a cosmic string along the axis of symmetry on a
massive scalar field. Exact solutions of both angular and radial parts of the
Klein-Gordon equation in this spacetime are obtained, and are given in terms of
the confluent Heun functions. We emphasize the role of the presence of the
cosmic string in these solutions. We also investigate the solutions in regions
near and far from the event horizon. From the radial solution, we obtain the
exact wave solutions near the exterior horizon of the black hole, and discuss
the Hawking radiation of massive scalar particles.Comment: 6 page
Simple parametrization for the ground-state energy of the infinite Hubbard chain incorporating Mott physics, spin-dependent phenomena and spatial inhomogeneity
Simple analytical parametrizations for the ground-state energy of the
one-dimensional repulsive Hubbard model are developed. The charge-dependence of
the energy is parametrized using exact results extracted from the Bethe-Ansatz.
The resulting parametrization is shown to be in better agreement with highly
precise data obtained from fully numerical solution of the Bethe-Ansatz
equations than previous expressions [Lima et al., Phys. Rev. Lett. 90, 146402
(2003)]. Unlike these earlier proposals, the present parametrization correctly
predicts a positive Mott gap at half filling for any U>0. The construction is
extended to spin-dependent phenomena by parametrizing the
magnetization-dependence of the ground-state energy using further exact results
and numerical benchmarking. Lastly, the parametrizations developed for the
spatially uniform model are extended by means of a simple local-density-type
approximation to spatially inhomogeneous models, e.g., in the presence of
impurities, external fields or trapping potentials. Results are shown to be in
excellent agreement with independent many-body calculations, at a fraction of
the computational cost.Comment: New Journal of Physics, accepte
New records of moths (Insecta, Lepidoptera) from urban gardens on Terceira Island with new data on recently introduced species to the Azores
The urban Duque da Terceira Garden, in the main town of Angra do HeroĂsmo (Terceira, Azores), was investigated to describe the species composition of moths (Insecta, Lepidoptera). Moths were sampled with two methods: SLAM traps (between April and September 2017) and light trapping (two sessions in the summer of 2017). A total of 42 taxa were sampled with the addition of 19 new records for Duque da Terceira Garden, five of which were also new records for Terceira Island. The five species recorded as new for Terceira were subjected to an exhaustive taxonomic analysis. In addition, we revised the colonization status of some species. Our results show that urban gardens may help the establishment of exotic species and that it is necessary to monitor and control how these species established in urban environments.info:eu-repo/semantics/publishedVersio
The Anomalous Hall effect in re-entrant AuFe alloys and the real space Berry phase
The Hall effect has been studied in a series of AuFe samples in the
re-entrant concentration range, as well as in the spin glass range. The data
demonstrate that the degree of canting of the local spins strongly modifies the
anomalous Hall effect, in agreement with theoretical predictions associating
canting, chirality and a real space Berry phase. The canonical parametrization
of the Hall signal for magnetic conductors becomes inappropriate when local
spins are canted.Comment: 4 pages, 1 eps figur
Electron trapping and acceleration by the plasma wakefield of a self-modulating proton beam
It is shown that co-linear injection of electrons or positrons into the
wakefield of the self-modulating particle beam is possible and ensures high
energy gain. The witness beam must co-propagate with the tail part of the
driver, since the plasma wave phase velocity there can exceed the light
velocity, which is necessary for efficient acceleration. If the witness beam is
many wakefield periods long, then the trapped charge is limited by beam loading
effects. The initial trapping is better for positrons, but at the acceleration
stage a considerable fraction of positrons is lost from the wave. For efficient
trapping of electrons, the plasma boundary must be sharp, with the density
transition region shorter than several centimeters. Positrons are not
susceptible to the initial plasma density gradient.Comment: 9 pages, 9 figures, 1 table, 44 reference
On the extra phase correction to the semiclassical spin coherent-state propagator
The problem of an origin of the Solary-Kochetov extra-phase contribution to
the naive semiclassical form of a generalized phase-space propagator is
addressed with the special reference to the su(2) spin case which is the most
important in applications. While the extra-phase correction to a flat
phase-space propagator can straightforwardly be shown to appear as a difference
between the principal and the Weyl symbols of a Hamiltonian in the
next-to-leading order expansion in the semiclassical parameter, the same
statement for the semiclassical spin coherent-state propagator holds provided
the Holstein-Primakoff representation of the su(2) algebra generators is
employed.Comment: 19 pages, no figures; a more general treatment is presented, some
references are added, title is slightly changed; submitted to JM
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