7,564 research outputs found
Black Hole Superpartners and Fixed Scalars
Some bosonic solutions of supergravities admit Killing spinors of unbroken
supersymmetry. The anti-Killing spinors of broken supersymmetry can be used to
generate the superpartners of stringy black holes. This has a consequent
feedback on the metric and the graviphoton. We have found however that the
fixed scalars for the black hole superpartners remain the same as for the
original black holes. Possible phenomenological implications of this result are
discussed.Comment: 6 pages, Late
Instanton Corrected Non-Supersymmetric Attractors
We discuss non-supersymmetric attractors with an instanton correction in Type
IIA string theory compactified on a Calabi-Yau three-fold at large volume. For
a stable non-supersymmetric black hole, the attractor point must minimize the
effective black hole potential. We study the supersymmetric as well as
non-supersymmetric attractors for the D0-D4 system with instanton corrections.
We show that in simple models, like the STU model, the flat directions of the
mass matrix can be lifted by a suitable choice of the instanton parameters.Comment: Minor modifications, Corrected typos, 38 pages, 1 figur
Duality covariant non-BPS first order systems
We study extremal black hole solutions to four dimensional N=2 supergravity
based on a cubic symmetric scalar manifold. Using the coset construction
available for these models, we define the first order flow equations implied by
the corresponding nilpotency conditions on the three-dimensional scalar momenta
for the composite non-BPS class of multi-centre black holes. As an application,
we directly solve these equations for the single-centre subclass, and write the
general solution in a manifestly duality covariant form. This includes all
single-centre under-rotating non-BPS solutions, as well as their
non-interacting multi-centre generalisations.Comment: 31 pages, v2: Discussion of the quadratic constraint clarified,
references added, typos corrected, published versio
Multi-black holes from nilpotent Lie algebra orbits
For N \ge 2 supergravities, BPS black hole solutions preserving four
supersymmetries can be superposed linearly, leading to well defined solutions
containing an arbitrary number of such BPS black holes at arbitrary positions.
Being stationary, these solutions can be understood via associated non-linear
sigma models over pseudo-Riemaniann spaces coupled to Euclidean gravity in
three spatial dimensions. As the main result of this paper, we show that
whenever this pseudo-Riemanniann space is an irreducible symmetric space G/H*,
the most general solutions of this type can be entirely characterised and
derived from the nilpotent orbits of the associated Lie algebra Lie(G). This
technique also permits the explicit computation of non-supersymmetric extremal
solutions which cannot be obtained by truncation to N=2 supergravity theories.
For maximal supergravity, we not only recover the known BPS solutions depending
on 32 independent harmonic functions, but in addition find a set of non-BPS
solutions depending on 29 harmonic functions. While the BPS solutions can be
understood within the appropriate N=2 truncation of N=8 supergravity, the
general non-BPS solutions require the whole field content of the theory.Comment: Corrected version for publication, references adde
On the Stability of Non-Supersymmetric Quantum Attractors in String Theory
We study four dimensional non-supersymmetric attractors in type IIA string
theory in the presence of sub-leading corrections to the prepotential. For a
given Calabi-Yau manifold, the D0-D4 system admits an attractor point in the
moduli space which is uniquely specified by the black hole charges. The
perturbative corrections to the prepotential do not change the number of
massless directions in the black hole effective potential. We further study
non-supersymmetric D0-D6 black holes in the presence of sub-leading
corrections. In this case the space of attractor points define a hypersurface
in the moduli space.Comment: References Added, Typos Corrected, Appendix A.2 Reordere
Brane-anti-brane Democracy
We suggest a duality invariant formula for the entropy and temperature of
non-extreme black holes in supersymmetric string theory. The entropy is given
in terms of the duality invariant parameter of the deviation from extremality
and 56 SU(8) covariant central charges. It interpolates between the entropies
of Schwarzschild solution and extremal solutions with various amount of
unbroken supersymmetries and therefore serves for classification of black holes
in supersymmetric string theories. We introduce the second auxiliary 56 via
E(7) symmetric constraint. The symmetric and antisymmetric combinations of
these two multiplets are related via moduli to the corresponding two
fundamental representations of E(7): brane and anti-brane "numbers." Using the
CPT as well as C symmetry of the entropy formula and duality one can explain
the mysterious simplicity of the non-extreme black hole area formula in terms
of branes and anti-branes.Comment: LaTeX, 12 pages, no figure
Positive energy unitary irreducible representations of D=6 conformal supersymmetry
We give a constructive classification of the positive energy (lowest weight)
unitary irreducible representations of the D=6 superconformal algebras
osp(8*/2N). Our results confirm all but one of the conjectures of Minwalla (for
N=1,2) on this classification. Our main tool is the explicit construction of
the norms of the states that has to be checked for positivity. We give also the
reduction of the exceptional UIRs.Comment: 27 pages, TeX with harvmac, amssym.def, amssym.tex; v.2: minor
corrections and references added; v.3: minor corrections; v.4: to appear in
J. Phys.
Matrix Norms, BPS Bounds and Marginal Stability in N=8 Supergravity
We study the conditions of marginal stability for two-center extremal black
holes in N-extended supergravity in four dimensions, with particular emphasis
on the N=8 case. This is achieved by exploiting triangle inequalities satisfied
by matrix norms. Using different norms and relative bounds among them, we
establish the existence of marginal stability and split attractor flows both
for BPS and some non-BPS solutions. Our results are in agreement with previous
analysis based on explicit construction of multi-center solutions.Comment: 1+15 pages; v2: some new formulas added and misprints corrected; v3:
typos fixed, various refinements, Sec. 2.4 rewritten; to appear on JHE
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