8,341 research outputs found
Lifshitz and Schrodinger Vacua, Superstar Resolution in Gauged Maximal Supergravities
We consider the subset of gauged maximal supergravities that consists of the
SO(n+1) gauge fields A^{ij} and the scalar deformation T^{ij} of the S^n in the
spherical reduction of M-theory or type IIB. We focus on the Abelian Cartan
subgroup and the diagonal entries of T^{ij}. The resulting theories can be
viewed as the STU models with additional hyperscalars. We find that the
theories with only one or two such vectors can be generalized naturally to
arbitrary dimensions. The same is true for the D=4 or 5 Einstein-Maxwell theory
with such a hyperscalar. The gauge fields become massive, determined by
stationary points of the hyperscalars a la the analogous Abelian Higgs
mechanism. We obtain classes of Lifshitz and Schrodinger vacua in these
theories. The scaling exponent z turns out to be rather restricted, taking
fractional or irrational numbers. Tweaking the theories by relaxing the mass
parameter or making a small change of the superpotential, we find that
solutions with z=2 can emerge. In a different application, we find that the
resolution of superstar singularity in the STU models by using bubbling-AdS
solitons can be generalized to arbitrary dimensions in our theories. In
particular, we obtain the smooth AdS solitons that can be viewed as the
resolution of the Reissner-Nordstrom superstars in general dimensions.Comment: Latex, 24 page
Thermodynamics of Lifshitz Black Holes
We specialize the Wald formalism to derive the thermodynamical first law for
static black holes with spherical/torus/hyperbolic symmetries in a variety of
supergravities or supergravity-inspired theories involving multiple scalars and
vectors. We apply the formula to study the first law of a general class of
Lifshitz black holes. We analyse the first law of three exact Lifshitz black
holes and the results fit the general pattern. In one example, the first law is
where are the electric potential and charge of the
Maxwell field. The unusual vanishing of mass in this specific solution
demonstrates that super-extremal charged black holes can exist in asymptotic
Lifshitz spacetimes.Comment: 27 page
Scalar Charges in Asymptotic AdS Geometries
We show that for n-dimensional Einstein gravity coupled to a scalar field
with mass-squared m_0^2=-n(n-2)/(4\ell^2), the first law of thermodynamics of
(charged) AdS black holes will be modified by the boundary conditions of the
scalar field at asymptotic infinity. Such scalars can arise in gauged
supergravities in four and six dimensions, but not in five or seven. The result
provides a guiding principle for constructing designer black holes and solitons
in general dimensions, where the properties of the dual field theories depend
on the boundary conditions.Comment: Latex, 9 pages, references adde
Nonlocal noise cross-correlation mediated by entangled Majorana fermions
Due to their nonlocality, qubits nested in Majorana bound states may be the
key to realize decoherence-free quantum computation. Majorana bound states
could be achieved at the ends of a one-dimensional topological superconductor.
However, when the bound states couple directly to electron reservoirs their
nonlocal correlation is quenched by local Andreev reflections. Here we propose
a scheme to generate nonlocal noise cross correlation between two
well-separated quantum dots, mediated by a pair of Majorana bound states. Both
positive and negative cross correlations can be obtained by tuning the gate
voltages applied to the dots. Within a limited range of finite temperatures,
the cross correlation is not suppressed by thermal fluctuations. Furthermore,
we show how the local Andreev reflections suppress the noise cross correlation
when multiple dot energy levels are coupled to the Majorana bound states. The
measurable cross correlation is expected to serve as a sensitive indicator for
the generation of Majorana fermions.Comment: 8 pages, 5 figure
Light Front Approach for Strong and Weak Decays of Pentaquarks
Strong and weak decays of pentaquarks are studied in the framework of the
light-front approach.Comment: 3 pages, talk given at the 2004 DPF Meeting, Riverside, CA. Aug
26-31, 200
Holographic Heat Current as Noether Current
We employ the Noether procedure to derive a general formula for the radially
conserved heat current in AdS planar black holes with certain transverse and
traceless perturbations, for a general class of gravity theories. For Einstein
gravity, the general higher-order Lovelock gravities and also a class of
Horndeski gravities, we derive the boundary stress tensor and show that the
resulting boundary heat current matches precisely the bulk Noether current.Comment: Latex, 27 pages, typos corrected, comments added, references adde
Generation of Atomic Cluster States through the Cavity Input-Output Process
We propose a scheme to implement a two-qubit controlled-phase gate for single
atomic qubits, which works in principle with nearly ideal success probability
and fidelity. Our scheme is based on the cavity input-output process and the
single photon polarization measurement. We show that, even with the practical
imperfections such as atomic spontaneous emission, weak atom-cavity coupling,
violation of the Lamb-Dicke condition, cavity photon loss, and detection
inefficiency, the proposed gate is feasible for generation of a cluster state
in that it meets the scalability criterion and it operates in a conclusive
manner. We demonstrate a simple and efficient process to generate a cluster
state with our high probabilistic entangling gate
Quasi-Topological Ricci Polynomial Gravities
Quasi-topological terms in gravity can be viewed as those that give no
contribution to the equations of motion for a special subclass of metric
ans\"atze. They therefore play no r\^ole in constructing these solutions, but
can affect the general perturbations. We consider Einstein gravity extended
with Ricci tensor polynomial invariants, which admits Einstein metrics with
appropriate effective cosmological constants as its vacuum solutions. We
construct three types of quasi-topological gravities. The first type is for the
most general static metrics with spherical, toroidal or hyperbolic isometries.
The second type is for the special static metrics where is
constant. The third type is the linearized quasi-topological gravities on the
Einstein metrics. We construct and classify results that are either dependent
on or independent of dimensions, up to the tenth order. We then consider a
subset of these three types and obtain Lovelock-like quasi-topological
gravities, that are independent of the dimensions. The linearized gravities on
Einstein metrics on all dimensions are simply Einstein and hence ghost free.
The theories become quasi-topological on static metrics in one specific
dimension, but non-trivial in others. We also focus on the quasi-topological
Ricci cubic invariant in four dimensions as a specific example to study its
effect on holography, including shear viscosity, thermoelectric DC
conductivities and butterfly velocity. In particular, we find that the
holographic diffusivity bounds can be violated by the quasi-topological terms,
which can induce an extra massive mode that yields a butterfly velocity unbound
above.Comment: Latex, 56 pages, discussion on shear viscosity revise
Thermodynamics of Einstein-Proca AdS Black Holes
We study static spherically-symmetric solutions of the Einstein-Proca
equations in the presence of a negative cosmological constant. We show that the
theory admits solutions describing both black holes and also solitons in an
asymptotically AdS background. Interesting subtleties can arise in the
computation of the mass of the solutions and also in the derivation of the
first law of thermodynamics. We make use of holographic renormalisation in
order to calculate the mass, even in cases where the solutions have a rather
slow approach to the asymptotic AdS geometry. By using the procedure developed
by Wald, we derive the first law of thermodynamics for the black hole and
soliton solutions. This includes a non-trivial contribution associated with the
Proca "charge." The solutions cannot be found analytically, and so we make use
of numerical integration techniques to demonstrate their existence.Comment: 35 pages, Improved discussion of cases with logarithmic asymptotic
fall off
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