488 research outputs found
Harrison transformation and charged black objects in Kaluza-Klein theory
We generate charged black brane solutions in dimensions in a theory of
gravity coupled to a dilaton and an antisymmetric form, by using a
Harrison-type transformation. The seed vacuum solutions that we use correspond
to uplifted Kaluza-Klein black strings and black holes in -dimensions. A
generalization of the Marolf-Mann quasilocal formalism to the Kaluza-Klein
theory is also presented, the global charges of the black objects being
computed in this way. We argue that the thermodynamics of the charged solutions
can be derived from that of the vacuum configurations. Our results show that
all charged Kaluza-Klein solutions constructed by means of Harrison
transformations are thermodynamically unstable in a grand canonical ensemble.
The general formalism is applied to the case of nonuniform black strings and
caged black hole solutions in Einstein-Maxwell-dilaton gravity, whose
geometrical properties and thermodynamics are discussed. We argue that the
topology changing transition scenario, which was previously proposed in the
vacuum case, also holds in this case. Spinning generalizations of the charged
black strings are constructed in six dimensions in the slowly rotating limit.
We find that the gyromagnetic ratio of these solutions possesses a nontrivial
dependence on the nonuniformity parameter.Comment: 42 pages, 12 figure
Nuclear Structure Corrections to Deuterium Hyperfine Structure and Lamb Shift
The low-energy theorem for the forward Compton scattering is generalized to
the case of an arbitrary target spin. The generalization is used to calculate
the corresponding contribution to the deuterium hyperfine structure. The
nuclear-structure corrections are quite essential in this case due to the
deuteron large size. Corrections of this type calculated here remove the
discrepancy between the theoretical and experimental values of the deuterium
hyperfine splitting. Explicit analytical result is obtained also for the
deuteron polarizability contribution to the Lamb shift.Comment: 14 pages, latex, no figure
Entanglement via Barut-Girardello coherent state for quantum algebra: bipartite composite system
Using noncocommutative coproduct properties of the quantum algebras, we
introduce and obtain, in a bipartite composite system, the Barut-Girardello
coherent state for the q-deformed algebra. The quantum coproduct
structure ensures this normalizable coherent state to be entangled. The
entanglement disappears in the classical limit, giving rise to a
factorizable state.Comment: 12 page
Instability of generalised AdS black holes and thermal field theory
We study black holes in AdS-like spacetimes, with the horizon given by an
arbitrary positive curvature Einstein metric. A criterion for classical
instability of such black holes is found in the large and small black hole
limits. Examples of large unstable black holes have a B\"ohm metric as the
horizon. These, classically unstable, large black holes are locally
thermodynamically stable. The gravitational instability has a dual description,
for example by using the version of the AdS/CFT
correspondence. The instability corresponds to a critical temperature of the
dual thermal field theory defined on a curved background.Comment: 1+16 pages. 1 figure. LaTeX. Minor clarification
Rotating nonuniform black string solutions
We explore via linearized perturbation theory the Gregory-Laflamme
instability of rotating black strings with equal magnitude angular momenta. Our
results indicate that the Gregory-Laflamme instability persists up to
extremality for all even dimensions between six and fourteen. We construct
rotating nonuniform black strings with two equal magnitude angular momenta in
six dimensions. We see a first indication for the occurrence of a topology
changing transition, associated with such rotating nonuniform black strings.
Charged nonuniform black string configurations in heterotic string theory are
also constructed by employing a solution generation technique.Comment: 36 pages, 10 figures, final versio
New nonuniform black string solutions
We present nonuniform vacuum black strings in five and six spacetime
dimensions. The conserved charges and the action of these solutions are
computed by employing a quasilocal formalism. We find qualitative agreement of
the physical properties of nonuniform black strings in five and six dimensions.
Our results offer further evidence that the black hole and the black string
branches merge at a topology changing transition. We generate black string
solutions of the Einstein-Maxwell-dilaton theory by using a Harrison
transformation. We argue that the basic features of these solutions can be
derived from those of the vacuum black string configurations.Comment: 30 pages, 12 figures; v2: more details on numerical method,
references added; v3: references added, minor revisions, version accepted by
journa
New stable phase of non uniform black strings in
We consider the non uniform black string equations in arbitrary number
of dimension in a perturbative approach up to order 2 and in a non
perturbative. We restrict the study in the perturbative approach to the
backreacting modes, since they provide the first relevant corrections on the
thermodynamical quantities of the solutions. We also present some preliminary
results in the construction of non-perturbative solutions, in particular, we
present a first part of the non uniform - uniform black string phase diagram.
Our results suggests the existence of a new stable phase for non uniform
black strings, namely long non uniform black string, with the extra direction
length of the order of the curvature.Comment: Results extended. 14 pages, 5 figure
Non Uniform Black Strings and Critical Dimensions in
We study the equations of black strings in spacetimes of arbitrary dimensions
with a negative cosmological constant and construct numerically non uniform
black strings solutions. Our results suggest the existence of a localised black
hole in asymptotically locally spacetime. We also present evidences for a
dependence of the critical dimension on the horizon radius.The critical
dimension represents the dimension where the order of the phase transition
between uniform and non uniform black string changes. Finally, we argue that
both, the regular asymptotically locally solution and black string
solutions with a very small horizon radius, present a negative tension. This
turns out to be an unexpected feature of the solutions.Comment: 13 pages, 5 figure
About the possibility of five-dimensional effective theories for low-energy QCD
The AdS/QCD models suggest an interesting idea that the effective theory of
low-energy QCD may be formulated as a 5-dimensional field theory in the weak
coupling regime in which the fifth coordinate plays a role of inverse energy
scale. Taking the point of view that this is just an efficient parametrization
of the non-perturbative dynamics of strong interactions, we discuss on a
qualitative level an alternative possibility for a simpler 5-dimensional
parametrization of main phenomena in the low-energy QCD. We propose to
interpret the effect of chiral symmetry breaking as an effective appearance of
compactified extra dimension with the radius of the order of inverse scale of
chiral symmetry breaking. Following some heuristic arguments two dual scenarios
for the emergence of the excited light mesons are introduced: In the first
scenario, the meson resonances are interpreted as the effects of Kaluza-Klein
excitations of quarks inside mesons, in the second one, as the formation of
gluon strings wound around the compactified dimension an appropriate number of
times. Matching of these scenarios permits to express the slope of radial Regge
trajectories through the order parameters of the chiral symmetry breaking, with
the compactification radius being excluded. This example shows qualitatively
that the extra dimension may play an auxiliary role providing a short way for
deriving new relations.Comment: 11 pages, accepted by Eur. Phys. J.
Holography: 2-D or not 2-D?
As was recently pointed out by Cadoni, a certain class of two-dimensional
gravitational theories will exhibit (black hole) thermodynamic behavior that is
reminiscent of a free field theory. In the current letter, a direct
correspondence is established between these two-dimensional models and the
strongly curved regime of (arbitrary-dimensional) anti-de Sitter gravity. On
this basis, we go on to speculatively argue that two-dimensional gravity may
ultimatley be utilized for identifying and perhaps even understanding
holographic dualities.Comment: 8 pages, Revtex; (v2) references and footnote added; (v3) discussion
on page 5 revise
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