934 research outputs found
BPS Geometries and AdS Bubbles
Recently, 1/2-BPS AdS bubble solutions have been obtained by Lin, Lunin and
Maldacena, which correspond to Fermi droplets in phase space in the dual CFT
picture. They can be thought of as generalisations of 1/2-BPS AdS black hole
solutions in five or seven dimensional gauged supergravity. In this paper, we
extend these solutions by invoking additional gauge fields and scalar fields in
the supergravity Lagrangians, thereby obtaining AdS bubble generalisations of
the previously-known multi-charge AdS black solutions of gauged supergravity.
We also obtain analogous AdS bubble solutions in four-dimensional gauged
supergravity. Our solutions generically preserve supersymmetry fractions 1/4,
1/8 and 1/8 in seven, five and four dimensions respectively. They can be lifted
to M-theory or type IIB string theory, using previously known formulae for the
consistent Pauli sphere reductions that yield the gauged supergravities. We
also find similar solutions in six-dimensional gauged supergravity, and discuss
their lift to the massive type IIA theory.Comment: Latex, 11 page
ESSVCS: an enriched secret sharing visual cryptography
Visual Cryptography (VC) is a powerful technique that combines the notions of perfect ciphers and secret sharing in cryptography with that of raster graphics. A binary image can be divided into shares that are able to be stacked together so as to approximately recover the original image. VC is a unique technique in the sense that the encrypted message can be decrypted directly by the Human Visual System (HVS). The distinguishing characteristic of VC is the ability of secret restoration without the use of computation. However because of restrictions of the HVS, pixel expansion and alignment problems, a VC scheme perhaps can only be applied to share a small size of secret image. In this paper, we present an Enriched Secret Sharing Visual Cryptography Scheme (ESSVCS) to let the VC shares carry more secrets, the technique is to use cypher output of private-key systems as the input random numbers of VC scheme, meanwhile the encryption key could be shared, the shared keys could be associated with the VC shares. After this operation, VC scheme and secret sharing scheme are merged with the private-key system. Under this design, we implement a (k; t; n)-VC scheme. Compared to those existing schemes, our scheme could greatly enhance the ability of current VC schemes and could cope with pretty rich secrets
Semiclassical Quantization for the Spherically Symmetric Systems under an Aharonov-Bohm magnetic flux
The semiclassical quantization rule is derived for a system with a
spherically symmetric potential and an
Aharonov-Bohm magnetic flux. Numerical results are presented and compared with
known results for models with . It is shown that the
results provided by our method are in good agreement with previous results. One
expects that the semiclassical quantization rule shown in this paper will
provide a good approximation for all principle quantum number even the rule is
derived in the large principal quantum number limit . We also discuss
the power parameter dependence of the energy spectra pattern in this
paper.Comment: 13 pages, 4 figures, some typos correcte
Pseudo-supersymmetry, Consistent Sphere Reduction and Killing Spinors for the Bosonic String
Certain supergravity theories admit a remarkable consistent dimensional
reduction in which the internal space is a sphere. Examples include type IIB
supergravity reduced on S^5, and eleven-dimensional supergravity reduced on S^4
or S^7. Consistency means that any solution of the dimensionally-reduced theory
lifts to give a solution in the higher dimension. Although supersymmetry seems
to play a role in the consistency of these reductions, it cannot be the whole
story since consistent sphere reductions of non-supersymmetric theories are
also known, such as the reduction of the effective action of the bosonic string
in any dimension D on either a 3-sphere or a (D-3)-sphere, retaining the gauge
bosons of SO(4) or SO(D-2) respectively. We show that although there is no
supersymmetry, there is nevertheless a natural Killing spinor equation for the
D-dimensional bosonic string. A projection of the full integrability condition
for these Killing spinors gives rise to the bosonic equations of motion (just
as happens in the supergravity examples). Thus it appears that by extending the
notion of supersymmetry to "pseudo-supersymmetry" in this way, one may be able
to obtain a broader understanding of a relation between Killing spinors and
consistent sphere reductions.Comment: Latex, 15 page
Comparison of Genomes of Three Xanthomonas oryzae Bacteriophages
<p>Abstract</p> <p>Background</p> <p>Xp10 and OP1 are phages of <it>Xanthomonas oryzae </it>pv. oryzae (Xoo), the causative agent of bacterial leaf blight in rice plants, which were isolated in 1967 in Taiwan and in 1954 in Japan, respectively. We recently isolated the Xoo phage Xop411.</p> <p>Results</p> <p>The linear Xop411 genome (44,520 bp, 58 ORFs) sequenced here is 147 bp longer than that of Xp10 (60 ORFs) and 735 bp longer than that of OP1 (59 ORFs). The G+C contents of OP1 (51%) and Xop411 and Xp10 (52% each) are less than that of the host (65%). The 9-bp 3'-overhangs (5'-GGACAGTCT-3') in Xop411 and Xp10 are absent from OP1. More of the deduced Xop411 proteins share higher degrees of identity with Xp10 than with OP1 proteins, while the right end of the genomes of Xp10 and OP1, containing all predicted promoters, share stronger homology. Xop411, Xp10, and OP1 contain 8, 7, and 6 freestanding HNH endonuclease genes, respectively. These genes can be classified into five groups depending on their possession of the HNH domain (HNN or HNH type) and/or AP2 domain in intact or truncated forms. While the HNN-AP2 type endonuclease genes dispersed in the genome, the HNH type endonuclease genes, each with a unique copy, were located within the same genome context. Mass spectrometry and N-terminal sequencing showed nine Xop411 coat proteins, among which three were identified, six were assigned as coat proteins (4) and conserved phage proteins (2) in Xp10. The major coat protein, in which only the N-terminal methionine is removed, appears to exist in oligomeric forms containing 2 to 6 subunits. The three phages exhibit different patterns of domain duplication in the N-terminus of the tail fiber, which are involved in determination of the host range. Many short repeated sequences are present in and around the duplicated domains.</p> <p>Conclusion</p> <p>Geographical separation may have confined lateral gene transfer among the Xoo phages. The HNN-AP2 type endonucleases were more likely to transfer their genes randomly in the genome and may degenerate after successful transmission. Some repeated sequences may be involved in duplication/loss of the domains in the tail fiber genes.</p
Evaluation of the BCS Approximation for the Attractive Hubbard Model in One Dimension
The ground state energy and energy gap to the first excited state are
calculated for the attractive Hubbard model in one dimension using both the
Bethe Ansatz equations and the variational BCS wavefunction. Comparisons are
provided as a function of coupling strength and electron density. While the
ground state energies are always in very good agreement, the BCS energy gap is
sometimes incorrect by an order of magnitude, particularly at half-filling.
Finite size effects are also briefly discussed for cases where an exact
solution in the thermodynamic limit is not possible. In general, the BCS result
for the energy gap is poor compared to the exact result.Comment: 25 pages, 5 Postscript figure
AdS Wormholes
We obtain a large class of smooth Lorentzian p-brane wormholes in
supergravities in various dimensions. They connect two asymptotically flat
spacetimes. In cases where there is no dilaton involved in the solution, the
wormhole can connect an AdS_n\times S^m in one asymptotic region to a flat
spacetime in the other. We obtain explicit examples for (n,m)=(4,7), (7,4),
(5,5), (3,3), (3,2). These geometries correspond to field theories with UV
conformal fixed points, and they undergo decompactification in the IR region.
In the case of AdS_3, we compute the central charge of the corresponding
conformal field theory.Comment: 20 pages, references adde
New supersymmetric solutions of N=2, D=5 gauged supergravity with hyperscalars
We construct new supersymmetric solutions, including AdS bubbles, in an N=2
truncation of five-dimensional N=8 gauged supergravity. This particular
truncation is given by N=2 gauged supergravity coupled to two vector multiples
and three incomplete hypermultiplets, and was originally investigated in the
context of obtaining regular AdS bubble geometries with multiple active
R-charges. We focus on cohomogeneity-one solutions corresponding to objects
with two equal angular momenta and up to three independent R-charges.
Curiously, we find a new set of zero and negative mass solitons asymptotic to
AdS_5/Z_k, for k \ge 3, which are everywhere regular without closed timelike
curves.Comment: Latex 3 times, 42 page
Phase diagram of the one-dimensional extended attractive Hubbard model for large nearest-neighbor repulsion
We consider the extended Hubbard model with attractive on-site interaction U
and nearest-neighbor repulsions V. We construct an effective Hamiltonian
H_{eff} for hopping t<<V and arbitrary U<0. Retaining the most important terms,
H_{eff} can be mapped onto two XXZ models, solved by the Bethe ansatz. The
quantum phase diagram shows two Luttinger liquid phases and a region of phase
separation between them. For density n<0.422 and U<-4, singlet superconducting
correlations dominate at large distances. For some parameters, the results are
in qualitative agreement with experiments in BaKBiO.Comment: 6 pages, 3 figures, submitted to Phys. Rev.
Spectral functions of the Falicov-Kimball model with electronic ferroelectricity
We calculate the angular resolved photoemission spectrum of the
Falicov-Kimball model with electronic ferroelectricity where - and
-electrons have different hoppings. In mix-valence regimes, the presence of
strong scattering processes between - excitons and a hole, created by
emission of an electron, leads to the formation of pseudospin polarons and
novel electronic structures with bandwidth scaling with that of -
excitons. Especially, in the two-dimensional case, we find that flat regions
exist near the bottom of the quasiparticle band in a wide range of the - and
-level energy difference.Comment: 5 pages, 5 figure
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