7,938 research outputs found
The world-sheet corrections to dyons in the Heterotic theory
All the linear alpha-prime corrections, however excluding the gravitational
Chern-Simons correction, are studied in the toroidally compactified critical
Heterotic string theory. These corrections are computed to the entropy for a
BPS static spherical four dimensional dyonic black hole which represents a
wrapped fundamental string carrying arbitrary winding and momentum charges
along one cycle in the presence of KK-monopole and H-monopole charges
associated to another cycle. It is verified that after the inclusion of the
gravitational Chern-Simons corrections [hep-th/0608182], all the linear
alpha-prime corrections to the entropy for the supersymmetric dyon can be
reproduced by the inclusion of only the Gauss-Bonnet Lagrangian to the
supergravity approximation of the induced Lagrangian.Comment: JHEP style, 17 Pages; v2: a typo corrected ; v3: The coupling of the
gravitational Chern-Simons terms to the three form field strength taken into
account. The conclusion correcte
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
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
Entropy Function for Non-Extremal Black Holes in String Theory
We generalize the entropy function formalism to five-dimensional and
four-dimensional non-extremal black holes in string theory. In the near horizon
limit, these black holes have BTZ metric as part of the spacetime geometry. It
is shown that the entropy function formalism also works very well for these
non-extremal black holes and it can reproduce the Bekenstein-Hawking entropy of
these black holes in ten dimensions and lower dimensions.Comment: 19 pages, no figure, JHEP3 style, to appear in JHE
alpha'-Corrections to Extremal Dyonic Black Holes in Heterotic String Theory
We explicitly compute the entropy of an extremal dyonic black hole in
heterotic string theory compactified on T^6 or K3\times T^2 by taking into
account all the tree level four derivative corrections to the low energy
effective action. For supersymmetric black holes the result agrees with the
answer obtained earlier 1) by including only the Gauss-Bonnet corrections to
the effective action 2) by including all terms related to the curvature squared
terms via space-time supersymmetry transformation, and 3) by using general
arguments based on the assumption of AdS_3 near horizon geometry and space-time
supersymmetry. For non-supersymmetric extremal black holes the result agrees
with the one based on the assumption of AdS_3 near horizon geometry and
space-time supersymmetry of the underlying theory.Comment: LaTeX file, 18 pages; v3: some normalization conventions changed so
as to be compatible with standard conventio
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
Dying Dyons Don't Count
The dyonic 1/4-BPS states in 4D string theory with N=4 spacetime
supersymmetry are counted by a Siegel modular form. The pole structure of the
modular form leads to a contour dependence in the counting formula obscuring
its duality invariance. We exhibit the relation between this ambiguity and the
(dis-)appearance of bound states of 1/2-BPS configurations. Using this insight
we propose a precise moduli-dependent contour prescription for the counting
formula. We then show that the degeneracies are duality-invariant and are
correctly adjusted at the walls of marginal stability to account for the
(dis-)appearance of the two-centered bound states. Especially, for large black
holes none of these bound states exists at the attractor point and none of
these ambiguous poles contributes to the counting formula. Using this fact we
also propose a second, moduli-independent contour which counts the "immortal
dyons" that are stable everywhere.Comment: 27 pages, 2 figures; one minus sign correcte
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
Contribution of women\u27s fisheries substantial, but overlooked, in Timor-Leste
2020, The Author(s). A greater understanding of gendered roles in fisheries is necessary to value the often-hidden roles that women play in fisheries and households. We examine women\u27s contributions to household food and income using focus group discussions, market surveys, and landings data in six communities in Timor-Leste. Women were actively fishing more days per month than men. Gleaning was the most frequent activity and 100% of trips returned with catch for food and/or income. Mollusc and crab catches were common and exploitation appeared targeted on a dynamic reappraisal of changing food values and changing estimates of group needs. With as many as 80% of households in coastal areas involved in fishing, and at least 50% of women fishing, this highlights the current lack of women\u27s engagement as a critical gap in fisheries management approaches. The current androcentric dialogue limits social-ecological understanding of these systems and the potential for their effective stewardship
Extremal black holes in D=5: SUSY vs. Gauss-Bonnet corrections
We analyse near-horizon solutions and compare the results for the black hole
entropy of five-dimensional spherically symmetric extremal black holes when the
N=2 SUGRA actions are supplied with two different types of higher-order
corrections: (1) supersymmetric completion of gravitational Chern-Simons term,
and (2) Gauss-Bonnet term. We show that for large BPS black holes lowest order
\alpha' corrections to the entropy are the same, but for non-BPS are generally
different. We pay special attention to the class of prepotentials connected
with K3\times T^2 and T^6 compactifications. For supersymmetric correction we
find beside BPS also a set of non-BPS solutions. In the particular case of T^6
compactification (equivalent to the heterotic string on ) we
find the (almost) complete set of solutions (with exception of some non-BPS
small black holes), and show that entropy of small black holes is different
from statistical entropy obtained by counting of microstates of heterotic
string theory. We also find complete set of solutions for K3\times T^2 and T^6
case when correction is given by Gauss-Bonnet term. Contrary to
four-dimensional case, obtained entropy is different from the one with
supersymmetric correction. We show that in Gauss-Bonnet case entropy of small
``BPS'' black holes agrees with microscopic entropy in the known cases.Comment: 28 pages; minor changes, version to appear in JHE
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