55 research outputs found
Entropy and Temperature of Black 3-Branes
We consider slightly non-extremal black 3-branes of type IIB supergravity and
show that their Bekenstein-Hawking entropy agrees, up to a mysterious factor,
with an entropy derived by counting non-BPS excitations of the Dirichlet
3-brane. These excitations are described in terms of the statistical mechanics
of a 3+1 dimensional gas of massless open string states. This is essentially
the classic problem of blackbody radiation. The blackbody temperature is
related to the temperature of the Hawking radiation. We also construct a
solution of type IIB supergravity describing a 3-brane with a finite density of
longitudinal momentum. For extremal momentum-carrying 3-branes the horizon area
vanishes. This is in agreement with the fact that the BPS entropy of the
momentum-carrying Dirichlet 3-branes is not an extensive quantity.Comment: 10 pages, LaTeX, minor revisions. v3: version that appeared in PR
Generic isolated horizons in loop quantum gravity
Isolated horizons model equilibrium states of classical black holes. A
detailed quantization, starting from a classical phase space restricted to
spherically symmetric horizons, exists in the literature and has since been
extended to axisymmetry. This paper extends the quantum theory to horizons of
arbitrary shape. Surprisingly, the Hilbert space obtained by quantizing the
full phase space of \textit{all} generic horizons with a fixed area is
identical to that originally found in spherical symmetry. The entropy of a
large horizon remains one quarter its area, with the Barbero-Immirzi parameter
retaining its value from symmetric analyses. These results suggest a
reinterpretation of the intrinsic quantum geometry of the horizon surface.Comment: 13 page
G2 Dualities in D=5 Supergravity and Black Strings
Five dimensional minimal supergravity dimensionally reduced on two commuting
Killing directions gives rise to a G2 coset model. The symmetry group of the
coset model can be used to generate new solutions by applying group
transformations on a seed solution. We show that on a general solution the
generators belonging to the Cartan and nilpotent subalgebras of G2 act as
scaling and gauge transformations, respectively. The remaining generators of G2
form a sl(2,R)+sl(2,R) subalgebra that can be used to generate non-trivial
charges. We use these generators to generalize the five dimensional Kerr string
in a number of ways. In particular, we construct the spinning electric and
spinning magnetic black strings of five dimensional minimal supergravity. We
analyze physical properties of these black strings and study their
thermodynamics. We also explore their relation to black rings.Comment: typos corrected (26 pages + appendices, 2 figures
Feynman Path Integral on the Noncommutative Plane
We formulate Feynman path integral on a non commutative plane using coherent
states. The propagator for a free particle exhibits UV cut-off induced by the
parameter of non commutativity.Comment: 7pages, latex 2e, no figures. Accepted for publication on J.Phys.
Fractional Conformal Descendants and Correlators in General 2D Orbifold CFTs at Large
We consider correlation functions in symmetric product () orbifold CFTs
at large with arbitrary seed CFT. Specifically, we consider correlators of
descendant operators constructed using both the full Virasoro generators
and fractional Virasoro generators . Using covering space
techniques, we show that correlators of descendants may be written entirely in
terms of correlators of ancestors, and further that the appropriate set of
ancestors are those operators that lift to conformal primaries on the cover. We
argue that the covering space data should cancel out in such calculations. To
back this claim, we provide some example calculations by considering a
three-point function of the form (4-cycle)-(2-cycle)-(5-cycle) that lifts to a
three-point function of arbitrary primaries on the cover, and descendants
thereof. In these examples we show that while the covering space is used for
the calculation, the final descent relations do not depend on covering space
data, nor on the details of which seed CFT is used to construct the orbifold,
making these results universal.Comment: 30 page
Non-supersymmetric Black Holes and Topological Strings
We study non-supersymmetric, extremal 4 dimensional black holes which arise
upon compactification of type II superstrings on Calabi-Yau threefolds. We
propose a generalization of the OSV conjecture for higher derivative
corrections to the non-supersymmetric black hole entropy, in terms of the one
parameter refinement of topological string introduced by Nekrasov. We also
study the attractor mechanism for non-supersymmetric black holes and show how
the inverse problem of fixing charges in terms of the attractor value of CY
moduli can be explicitly solved.Comment: 47 pages, harvmac. v2: footnote(4) expanded, references adde
Effect of Scalar Mass in the Absorption and Emission Spectra of Schwarzschild Black Hole
Following Sanchez's approach we investigate the effect of scalar mass in the
absorption and emission problems of 4d Schwarzschild black hole. The absorption
cross sections for arbitrary angular momentum of the scalar field are computed
numerically in the full range of energy by making use of the analytic
near-horizon and asymptotic solutions and their analytic continuations. The
scalar mass makes an interesting effect in the low-energy absorption cross
section for S-wave. Unlike the massless case, the cross section decreases with
increasing energy in the extremely low-energy regime. As a result the
universality, {\it i.e.} low-energy cross section for S-wave is equal to the
horizon area, is broken in the presence of mass. If the scalar mass is larger
than a critical mass, the absorption cross section becomes monotonically
decreasing function in the entire range of energy. The Hawking emission is also
calculated numerically. It turns out that the Planck factor generally
suppresses the contribution of higher partial waves except S-wave. The scalar
mass in general tends to reduce the emission rate.Comment: 20 pages, 8 figures, V2: few comments are added. version to appear in
Classical and Quantum Gravit
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