59 research outputs found
Adding Charges to N=4 Dyons
The spectrum of dyons in a class of N=4 supersymmetric string theories has
been found for a specific set of electric and magnetic charge vectors. We
extend the analysis to more general charge vectors by considering various
charge carrying collective excitations of the original system.Comment: LaTeX file, 16 page
Vortex solutions in the noncommutative torus
Vortex configurations in the two-dimensional torus are considered in
noncommutative space. We analyze the BPS equations of the Abelian Higgs model.
Numerical solutions are constructed for the self-dual and anti-self dual cases
by extending an algorithm originally developed for ordinary commutative space.
We work within the Fock space approach to noncommutative theories and the
Moyal-Weyl connection is used in the final stage to express the solutions in
configuration space.Comment: 18 pages, 5 figure
Dyon Spectrum in Generic N=4 Supersymmetric Z_N Orbifolds
We find the exact spectrum of a class of quarter BPS dyons in a generic N=4
supersymmetric Z_N orbifold of type IIA string theory on K3\times T^2 or T^6.
We also find the asymptotic expansion of the statistical entropy to first
non-leading order in inverse power of charges and show that it agrees with the
entropy of a black hole carrying same set of charges after taking into account
the effect of the four derivative Gauss-Bonnet term in the effective action of
the theory.Comment: LaTeX file, 39 pages; minor change
Dyon Spectrum in N=4 Supersymmetric Type II String Theories
We compute the spectrum of quarter BPS dyons in freely acting Z_2 and Z_3
orbifolds of type II string theory compactified on a six dimensional torus. For
large charges the result for statistical entropy computed from the degeneracy
formula agrees with the corresponding black hole entropy to first non-leading
order after taking into account corrections due to the curvature squared terms
in the effective action. The result is significant since in these theories the
entropy of a small black hole, computed using the curvature squared corrections
to the effective action, fails to reproduce the statistical entropy associated
with elementary string states.Comment: LaTeX file, 32 pages; v2:minor change
Walls of Marginal Stability and Dyon Spectrum in N=4 Supersymmetric String Theories
The spectrum of quarter BPS dyons in N=4 supersymmetric string theories can
change as the asymptotic moduli cross walls of marginal stability on which the
dyon can break apart into a pair of half BPS states. In this paper we classify
these marginal stability walls and examine this phenomenon in the context of
exact dyon spectrum found in a class of N=4 supersymmetric string theories. We
argue that the dyon partition functions in different domains separated by
marginal stability walls are the same, but the choice of integration contour
needed for extracting the degeneracies from the partition function differ in
these different regions. We also find that in the limit of large charges the
change in the degeneracy is exponentially suppressed compared to the leading
contribution. This is consistent with the fact that in the computation of black
hole entropy we do not encounter any change as the asymptotic moduli fields
move across the walls of marginal stability. Finally we carry out some tests of
S-duality invariance in the theory.Comment: LateX file, 1 figure, 42 pages; v2 more tests of S-duality added with
complete proof for all N<7; v3: minor change
Bogomolny equations for vortices in the noncommutative torus
We derive Bogomolny-type equations for the Abelian Higgs model defined on the
noncommutative torus and discuss its vortex like solutions. To this end, we
carefully analyze how periodic boundary conditions have to be handled in
noncommutative space and discussed how vortex solutions are constructed. We
also consider the extension to an model, a simplified
prototype of the noncommutative standard model.Comment: 23 pages, no figure
Dyon Death Eaters
We study general two-body decays of primitive and non-primitive 1/4-BPS dyons
in four-dimensional type IIB string compactifications. We find a ``master
equation'' for marginal stability that generalises the curve found by Sen for
half-BPS decay, and analyse this equation in a variety of cases including
decays to 1/4-BPS products. For half-BPS decays, an interesting and useful
relation is exhibited between walls of marginal stability and the mathematics
of Farey sequences and Ford circles. We exhibit an example in which two curves
of marginal stability intersect in the interior of moduli space.Comment: 24 pages, 1 figure, v2: section on non-primitive dyons slightly
modified and expanded, few other small change
CHL Dyons and Statistical Entropy Function from D1-D5 System
We give a proof of the recently proposed formula for the dyon spectrum in CHL
string theories by mapping it to a configuration of D1 and D5-branes and
Kaluza-Klein monopole. We also give a prescription for computing the degeneracy
as a systematic expansion in inverse powers of charges. The computation can be
formulated as a problem of extremizing a duality invariant statistical entropy
function whose value at the extremum gives the logarithm of the degeneracy.
During this analysis we also determine the locations of the zeroes and poles of
the Siegel modular forms whose inverse give the dyon partition function in the
CHL models.Comment: LaTeX file, 48 pages; v2: typos correcte
The mixed black hole partition function for the STU model
We evaluate the mixed partition function for dyonic BPS black holes using the
recently proposed degeneracy formula for the STU model. The result factorizes
into the OSV mixed partition function times a proportionality factor. The
latter is in agreement with the measure factor that was recently conjectured
for a class of N=2 black holes that contains the STU model.Comment: 14 page
Three String Junction and N=4 Dyon Spectrum
The exact spectrum of dyons in a class of N=4 supersymmetric string theories
gives us information about dyon spectrum in N=4 supersymmetric gauge theories.
This in turn can be translated into prediction about the BPS spectrum of three
string junctions on a configuration of three parallel D3-branes. We show that
this prediction agrees with the known spectrum of three string junction in
different domains in the moduli space separated by walls of marginal stability.Comment: LaTeX file, 14 page
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