3,314 research outputs found
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
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
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
SWOT Analysis of the horticultural farms in the Plovdiv region of Bulgaria
Agriculture/horticulture has traditionally been an important sector in the economy of Bulgaria. This paper reviews the changes in agriculture/horticulture in the Plovdiv region of Bulgaria after 1989 when the transition towards a free market economy began. In particular, it provides a review of the internal capabilities (strengths and weaknesses) of the horticultural farms and the impact upon them of the external environment (opportunities and threats). While many farmers regarded their experience as a strength, farmers having farms of different size identified additional different strengths, and different weaknesses and opportunities. Whereas, all of them were influenced by similar threats and the relative importance of these perceived threats did not varied depending upon the size of the farm
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
Rare Decay Modes of Quarter BPS Dyons
The degeneracy of quarter BPS dyons in N=4 supersymmetric string theories is
known to jump across walls of marginal stability on which a quarter BPS dyon
can decay into a pair of half BPS dyons. We show that as long as the electric
and magnetic charges of the original dyon are primitive elements of the charge
lattice, the subspaces of the moduli space on which a quarter BPS dyon becomes
marginally unstable against decay into a pair of quarter BPS dyons or a half
BPS dyon and a quarter BPS dyon are of codimension two or more. As a result any
pair of generic points in the moduli space can be connected by a path avoiding
these subspaces and there is no jump in the spectrum associated with these
subspaces.Comment: LaTeX file, 9 pages; v2: a minor logical error corrected with no
change in the result
Recounting Dyons in N=4 String Theory
A recently discovered relation between 4D and 5D black holes is used to
derive weighted BPS black hole degeneracies for 4D N=4 string theory from the
well-known 5D degeneracies. They are found to be given by the Fourier
coefficients of the unique weight 10 automorphic form of the modular group
Sp(2,Z). This result agrees exactly with a conjecture made some years ago by
Dijkgraaf, Verlinde and Verlinde.Comment: 5 page
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
On the dyon partition function in N=2 theories
We study the entropy function of two N =2 string compactifications obtained
as freely acting orbifolds of N=4 theories : the STU model and the FHSV model.
The Gauss-Bonnet term for these compactifications is known precisely. We apply
the entropy function formalism including the contribution of this four
derivative term and evaluate the entropy of dyons to the first subleading order
in charges for these models. We then propose a partition function involving the
product of three Siegel modular forms of weight zero which reproduces the
degeneracy of dyonic black holes in the STU model to the first subleading order
in charges. The proposal is invariant under all the duality symmetries of the
STU model. For the FHSV model we write down an approximate partition function
involving a Siegel modular form of weight four which captures the entropy of
dyons in the FHSV model in the limit when electric charges are much larger than
magnetic charges.Comment: 48 page
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