22,661 research outputs found
Rotating binary Bose-Einstein condensates and vortex clusters in quantum droplets
Quantum droplets may form out of a gaseous Bose-Einstein condensate,
stabilized by quantum fluctuations beyond mean field. We show that multiple
singly-quantized vortices may form in these droplets at moderate angular
momenta in two dimensions. Droplets carrying these precursors of an Abrikosov
lattice remain self-bound for certain timescales after switching off an initial
harmonic confinement. Furthermore, we examine how these vortex-carrying
droplets can be formed in a more pertubation-resistant setting, by starting
from a rotating binary Bose-Einstein condensate and inducing a metastable
persistent current via a non-monotonic trapping potential.Comment: 5 page, 4 figure
Spinorial cohomology and maximally supersymmetric theories
Fields in supersymmetric gauge theories may be seen as elements in a
spinorial cohomology. We elaborate on this subject, specialising to maximally
supersymmetric theories, where the superspace Bianchi identities, after
suitable conventional constraints are imposed, put the theories on shell. In
these cases, the spinorial cohomologies describe in a unified manner gauge
transformations, fields and possible deformations of the models, e.g.
string-related corrections in an alpha' expansion. Explicit cohomologies are
calculated for super-Yang-Mills theory in D=10, for the N=(2,0) tensor
multiplet in D=6 and for supergravity in D=11, in the latter case from the
point of view of both the super-vielbein and the super-3-form potential. The
techniques may shed light on some questions concerning the alpha'-corrected
effective theories, and result in better understanding of the role of the
3-form in D=11 supergravity.Comment: 23 pp, plain tex. v2: Minor changes, references adde
Towards a practical approach for self-consistent large amplitude collective motion
We investigate the use of an operatorial basis in a self-consistent theory of
large amplitude collective motion. For the example of the
pairing-plus-quadrupole model, which has been studied previously at
equilibrium, we show that a small set of carefully chosen state-dependent basis
operators is sufficient to approximate the exact solution of the problem
accuratly. This approximation is used to study the interplay of quadrupole and
pairing degrees of freedom along the collective path for realistic examples of
nuclei. We show how this leads to a viable calculational scheme for studying
nuclear structure, and discuss the surprising role of pairing collapse.Comment: 19 pages, 8 figures Revised version To be published in Phys. Rev.
On the ground--state energy of finite Fermi systems
We study the ground--state shell correction energy of a fermionic gas in a
mean--field approximation.
Considering the particular case of 3D harmonic trapping potentials, we show
the rich variety of different behaviors (erratic, regular, supershells) that
appear when the number--theoretic properties of the frequency ratios are
varied. For self--bound systems, where the shape of the trapping potential is
determined by energy minimization, we obtain accurate analytic formulas for the
deformation and the shell correction energy as a function of the particle
number . Special attention is devoted to the average of the shell correction
energy. We explain why in self--bound systems it is a decreasing (and negative)
function of .Comment: 10 pages, 5 figures, 2 table
Expansion of CORE-SINEs in the genome of the Tasmanian devil
Background: The genome of the carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii, Order: Dasyuromorphia), was sequenced in the hopes of finding a cure for or gaining a better understanding of the contagious devil facial tumor disease that is threatening the species’ survival. To better understand the Tasmanian devil genome, we screened it for transposable elements and investigated the dynamics of short interspersed element (SINE) retroposons.
Results: The temporal history of Tasmanian devil SINEs, elucidated using a transposition in transposition analysis, indicates that WSINE1, a CORE-SINE present in around 200,000 copies, is the most recently active element. Moreover, we discovered a new subtype of WSINE1 (WSINE1b) that comprises at least 90% of all Tasmanian devil WSINE1s. The frequencies of WSINE1 subtypes differ in the genomes of two of the other Australian marsupial orders. A co-segregation analysis indicated that at least 66 subfamilies of WSINE1 evolved during the evolution of Dasyuromorphia. Using a substitution rate derived from WSINE1 insertions, the ages of the subfamilies were estimated and correlated with a newly established phylogeny of Dasyuromorphia. Phylogenetic analyses and divergence time estimates of mitochondrial genome data indicate a rapid radiation of the Tasmanian devil and the closest relative the quolls (Dasyurus) around 14 million years ago.
Conclusions: The radiation and abundance of CORE-SINEs in marsupial genomes indicates that they may be a major player in the evolution of marsupials. It is evident that the early phases of evolution of the carnivorous marsupial order Dasyuromorphia was characterized by a burst of SINE activity. A correlation between a speciation event and a major burst of retroposon activity is for the first time shown in a marsupial genome
Electronic structure of GaAs1-xNx alloy by soft-X-ray absorption and emission: Origin of the reduced optical efficiency
The local electronic structure of N atoms in a diluted GaAs1-xNx (x=3%)
alloy, in view of applications in optoelectronics, is determined for the first
time using soft-X-ray absorption (SXA) and emission (SXE). Deviations from
crystalline GaN, in particular in the conduction band, are dramatic. Employing
the orbital character and elemental specificity of the SXE/SXA spectroscopies,
we identify a charge transfer from the N atoms at the valence band maximum,
reducing the overlap with the wavefunction in conduction band minimum, as the
main factor limiting the optical efficiency of GaAs1-xNx alloys. Moreover, a
k-conserving process of resonant inelastic x-ray scattering involving the L1
derived valence and conduction states is discovered.Comment: 3 pages, physica status solidi (Rapid Research Notes), in pres
On the dependence between UV luminosity and Lyman-alpha equivalent width in high redshift galaxies
We show that with the simple assumption of no correlation between the
Ly-alpha equivalent width and the UV luminosity of a galaxy, the observed
distribution of high redshift galaxies in an equivalent width - absolute UV
magnitude plane can be reproduced. We further show that there is no dependence
between Ly-alpha equivalent width and Ly-alpha luminosity in a sample of
Ly-alpha emitters. The test was expanded to Lyman-break galaxies and again no
dependence was found. Simultaneously, we show that a recently proposed lack of
large equivalent width, UV bright galaxies (Ando et al. 2006) can be explained
by a simple observational effect, based on too small survey volumes.Comment: 7 pages, 3 figures, 2 tables, accepted in MNRA
Role of low- component in deformed wave functions near the continuum threshold
The structure of deformed single-particle wave functions in the vicinity of
zero energy limit is studied using a schematic model with a quadrupole deformed
finite square-well potential. For this purpose, we expand the single-particle
wave functions in multipoles and seek for the bound state and the Gamow
resonance solutions. We find that, for the states, where is
the -component of the orbital angular momentum, the probability of each
multipole components in the deformed wave function is connected between the
negative energy and the positive energy regions asymptotically, although it has
a discontinuity around the threshold. This implies that the
resonant level exists physically unless the component is inherently large
when extrapolated to the well bound region. The dependence of the multipole
components on deformation is also discussed
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