1,119 research outputs found
Exact Counting of Black Hole Microstates
The exact entropy of two-charge supersymmetric black holes in N=4 string
theories is computed to all orders using Wald's formula and the supersymmetric
attractor equations with an effective action that includes the relevant higher
curvature terms. Classically, these black holes have zero area but the
attractor equations are still applicable at the quantum level. The quantum
corrected macroscopic entropy agrees precisely with the microscopic counting
for an infinite tower of fundamental string states to all orders in an
asymptotic expansion.Comment: 4 pages, latex, minor change
Violating the string winding number maximally in Anti-de Sitter space
We study n-string scattering amplitudes in three-dimensional Anti-de Sitter
space (AdS3). We focus our attention on the processes in which the winding
number conservation is violated maximally; that is, those processes in which it
is violated in n-2 units. A worldsheet conformal field theory calculation leads
us to confirm a previous conjecture about the functional form of these
observables.Comment: 15 pages. V2 references added and minor typo corrected. V3, V4
addendum on an alternative derivation of the main formula for short string
Higher Derivative Corrections, Dimensional Reduction and Ehlers Duality
Motivated by applications to black hole physics and duality, we study the
effect of higher derivative corrections on the dimensional reduction of
four-dimensional Einstein, Einstein Liouville and Einstein-Maxwell gravity to
one direction, as appropriate for stationary, spherically symmetric solutions.
We construct a field redefinition scheme such that the one-dimensional
Lagrangian is corrected only by powers of first derivatives of the fields,
eliminating spurious modes and providing a suitable starting point for
quantization. We show that the Ehlers symmetry, broken by the leading
corrections in Einstein-Liouville gravity, can be restored by including
contributions of Taub-NUT instantons. Finally, we give a preliminary discussion
of the duality between higher-derivative F-term corrections on the vector and
hypermultiplet branches in N=2 supergravity in four dimensions.Comment: 21 pages, uses JHEP3.cls; v3: minor corrections, final version
published in JHE
tt* Geometry and Closed String Tachyon Potential
We propose a closed string tachyon action including kinetic and potential
terms for non-supersymmetric orbifolds. The action is given in terms of
solutions to equations which captures the geometry of vacua of the
corresponding N=2 worldsheet theory. In certain cases the solutions are well
studied. In case of tachyons of , solutions to affine toda
equations determine the action. We study the particular case of in detail and find that the Tachyon action is determined in terms of a
solution to Painleve III equation.Comment: 10 page
Black Holes, Elementary Strings and Holomorphic Anomaly
In a previous paper we had proposed a specific route to relating the entropy
of two charge black holes to the degeneracy of elementary string states in N=4
supersymmetric heterotic string theory in four dimensions. For toroidal
compactification this proposal works correctly to all orders in a power series
expansion in inverse charges provided we take into account the corrections to
the black hole entropy formula due to holomorphic anomaly. In this paper we
demonstrate that similar agreement holds also for other N=4 supersymmetric
heterotic string compactifications.Comment: LaTeX file, 28 pages, reference added, minor changes in appendix
Veneziano Amplitude for Winding Strings
String configurations with nonzero winding number describe soliton string
states. We compute the Veneziano amplitude for the scattering of arbitrary
winding states and show that in the large radius limit the strings always
scatter trivially and with no change in the individual winding numbers of the
strings. In this limit, then, these states scatter as true solitons.Comment: 7 page
Counting all dyons in N =4 string theory
For dyons in heterotic string theory compactified on a six-torus, with
electric charge vector Q and magnetic charge vector P, the positive integer I =
g.c.d.(Q \wedge P) is an invariant of the U-duality group. We propose the
microscopic theory for computing the spectrum of all dyons for all values of I,
generalizing earlier results that exist only for the simplest case of I=1. Our
derivation uses a combination of arguments from duality, 4d-5d lift, and a
careful analysis of fermionic zero modes. The resulting degeneracy agrees with
the black hole degeneracy for large charges and with the degeneracy of
field-theory dyons for small charges. It naturally satisfies several physical
requirements including integrality and duality invariance. As a byproduct, we
also derive the microscopic (0,4) superconformal field theory relevant for
computing the spectrum of five-dimensional Strominger-Vafa black holes in ALE
backgrounds and count the resulting degeneracies
How Does a Fundamental String Stretch its Horizon?
It has recently been shown that if we take into account a class of higher
derivative corrections to the effective action of heterotic string theory, the
entropy of the black hole solution representing elementary string states
correctly reproduces the statistical entropy computed from the degeneracy of
elementary string states. So far the form of the solution has been analyzed at
distance scales large and small compared to the string scale. We analyze the
solution that interpolates between these two limits and point out a subtlety in
constructing such a solution due to the presence of higher derivative terms in
the effective action. We also study the T-duality transformation rules to
relate the moduli fields of the effective field theory to the physical
compactification radius in the presence of higher derivative corrections and
use these results to find the physical radius of compactification near the
horizon of the black hole. The radius approaches a finite value even though the
corresponding modulus field vanishes. Finally we discuss the non-leading
contribution to the black hole entropy due to space-time quantum corrections to
the effective action and the ambiguity involved in comparing this result to the
statistical entropy.Comment: LaTeX file, 38 pages; v2: minor changes and added reference
Branes, Black Holes and Topological Strings on Toric Calabi-Yau Manifolds
We develop means of computing exact degerenacies of BPS black holes on toric
Calabi-Yau manifolds. We show that the gauge theory on the D4 branes wrapping
ample divisors reduces to 2D q-deformed Yang-Mills theory on necklaces of
P^1's. As explicit examples we consider local P^2, P^1 x P^1 and A_k type ALE
space times C. At large N the D-brane partition function factorizes as a sum
over squares of chiral blocks, the leading one of which is the topological
closed string amplitude on the Calabi-Yau. This is in complete agreement with
the recent conjecture of Ooguri, Strominger and Vafa.Comment: 50 pages, 6 figures, harvma
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