729 research outputs found
Hawking Radiation from a (4+n)-Dimensional Rotating Black Hole on the Brane
We study the emission of Hawking radiation in the form of scalar fields from
a (4+n)-dimensional, rotating black hole on the brane. We perform a numerical
analysis to solve both the radial and angular parts of the scalar field
equation, and derive exact results for the radial wavefunction and angular
eigenvalues, respectively. We then determine the Hawking radiation energy
emission rate, and find that, as the angular momentum increases, it is
suppressed in the low-energy regime but enhanced in the intermediate and
high-energy regimes. Our results agree with previous analytical studies,
derived in the low-angular momentum and low-energy approximation, and
generalize them to include angular momentum and energy regimes that were until
now unexplored. We also investigate the energy amplification due to
super-radiance and we find that, in the presence of extra dimensions, the
effect is significantly enhanced.Comment: 9 pages, Latex file, 5 figures, a new figure and a paragraph have
been added along with some clarifying comments, version to appear in Phys.
Lett.
Static, non-SUSY -branes in diverse dimensions
We give explicit constructions of static, non-supersymmetric -brane (for
, where is the space-time dimensionality and including
or D-instanton) solutions of type II supergravities in diverse dimensions. A
subclass of these are the static counterpart of the time dependent solutions
obtained in [hep-th/0309202]. Depending on the forms of the non-extremality
function defined in the text, we discuss various possible solutions and
their region of validity. We show how one class of these solutions interpolate
between the -brane--anti -brane solutions and the usual BPS -brane
solutions in , while the other class, although have BPS limits, do not
have such an interpretation. We point out how the time dependent solutions
mentioned above can be obtained by a Wick rotation of one class of these static
solutions. We also discuss another type of solutions which might seem
non-supersymmetric, but we show by a coordinate transformation that they are
nothing but the near horizon limits of the various BPS -branes already
known.Comment: 29 pages, typos corrected, references adde
A black hole hologram in de Sitter space
In this paper we show that the entropy of de Sitter space with a black hole
in arbitrary dimension can be understood using a modified Cardy-Verlinde
entropy formula. We also comment on the observer dependence of the de Sitter
entropy.Comment: 13 pages. Final version accepted for publication in JHEP. Added
references and improved presentatio
Twisted K-Theory from Monodromies
RR fluxes representing different cohomology classes may correspond to the
same twisted K-theory class. We argue that such fluxes are related by
monodromies, generalizing and sometimes T-dual to the familiar monodromies of a
D7-brane. A generalized theta angle is also transformed, but changes by a
multiple of 2pi. As an application, NS5-brane monodromies modify the twisted
K-theory classification of fluxes. Furthermore, in the noncompact case K-theory
does not distinguish flux configurations in which dG is nontrivial in compactly
supported cohomology. Such fluxes are realized as the decay products of
unstable D-branes that wrapped nontrivial cycles. This is interpreted using the
E8 bundle formalism.Comment: 24 Pages, 6 eps figure
Didactic Software for Autistic Children
In this paper we describe the aims and requirements of a project devoted to designing and developing Open Source didactic Software (SW) for children in the autism disorder spectrum, conforming to the Applied Behaviour Analysis (ABA) learning technique. In this context, participatory design with therapists and child?s parents is necessary to ensure a usable product that responds to these children?s special needs and respects education principles and constraints of the ABA methodology
Warped Phenomenology of Higher-Derivative Gravity
We examine the phenomenological implications at colliders for the existence
of higher-derivative gravity terms as extensions to the Randall-Sundrum model.
Such terms are expected to arise on rather general grounds, e.g., from string
theory. In 5-d, if we demand that the theory be unitary and ghost free, these
new contributions to the bulk action are uniquely of the Gauss-Bonnet form. We
demonstrate that the usual expectations for the production cross section and
detailed properties of graviton Kaluza-Klein resonances and TeV-scale black
holes can be substantially altered by existence of these additional
contributions. It is shown that measurements at future colliders will be highly
sensitive to the presence of such terms.Comment: 29 pages, 8 figure
A Comparison of Real Time Thermal Rating Systems in the U.S. and the UK
Real-Time Thermal Rating is a smart grid technology that allows the rating of electrical conductors to be increased based on local weather conditions. Overhead lines are conventionally given a conservative, constant seasonal rating based on seasonal and regional worst case scenarios rather than actual, say, local hourly weather predictions. This paper provides a report of two pioneering schemes—one in the United States of America and one in the United Kingdom—in which Real-Time Thermal Ratings have been applied. Thereby, we demonstrate that observing the local weather conditions in real time leads to additional capacity and safer operation. Secondly, we critically compare both approaches and discuss their limitations. In doing so, we arrive at novel insights which will inform and improve future Real-Time Thermal Rating projects
Interacting Open Wilson Lines in Noncommutative Field Theories
In noncommutative field theories, it was known that one-loop effective action
describes propagation of non-interacting open Wilson lines, obeying the flying
dipole's relation. We show that two-loop effective action describes cubic
interaction among `closed string' states created by open Wilson lines. Taking
d-dimensional noncommutative [\Phi^3] theory as the simplest setup, we compute
nonplanar contribution at low-energy and large noncommutativity limit. We find
that the contribution is expressible in a remarkably simple cubic interaction
involving scalar open Wilson lines only and nothing else. We show that the
interaction is purely geometrical and noncommutative in nature, depending only
on sizes of each open Wilson line.Comment: v1: 27 pages, Latex, 7 .eps figures v2: minor wording change +
reference adde
Brane/flux annihilation transitions and nonperturbative moduli stabilization
By extending the calculation of Kahler moduli stabilization to account for an
embiggened antibrane, we reevaluate brane/flux annihilation in a warped throat
with one stabilized Kahler modulus. We find that depending on the relative size
of various fluxes three things can occur: the decay process proceeds
unhindered, the anti-D3-branes are forbidden to decay classically, or the
entire space decompactifies. Additionally, we show that the Kahler modulus
receives a contribution from the collective 3-brane tension. This allows for a
significant change in compactified volume during the transition and possibly
mitigates some fine tuning otherwise required to achieve large volume.Comment: 25 pages, 6 figures, LaTeX. v2: references adde
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