67 research outputs found
On the Uniqueness of Supersymmetric Attractors
In this paper we discuss the uniqueness of supersymmetric attractors in four
dimensional N=2 supergravity theories coupled to n vector multiplets. We prove
that for a given charge configuration the supersymmetry preserving axion free
attractors are unique. We generalise the analysis to axionic attractors and
state the conditions for uniqueness explicitly. We consider the example of a
two-parameter model and find all solutions to the supersymmetric attractor
equations and discuss their uniqueness.Comment: 12 pages, Late
Multiple Single-Centered Attractors
In this paper we study spherically symmetric single-centered attractors in
N=2 supergravity in four dimensions. The attractor points are obtained by
extremising the effective black hole potential in the moduli space. Using the
4D-5D correspondence of critical points of the effective black hole potential
we argue the existence of multiple attractors in four dimensions and explicitly
construct a pair of multiple solutions in a simple two parameter model. We
further obtain explicit examples of two distinct non-supersymmetric attractors
in type IIA string theory compactified on K3 X T2 carrying D0-D4-D6 charges. We
compute the entropy of these attractors and analyse their stability in detail.Comment: Modifications in Section 3. Some incorrect results are removed and
the section is rewritte
Duality Symmetry and the Cardy Limit
We study supersymmetric and non-supersymmetric extremal black holes obtained
in Type IIA string theory compactified on K3 X T^2, with duality group
O(6,22,Z) X SL(2,Z). In the Cardy limit an internal circle combines with the
AdS_2 component in the near horizon geometry to give a BTZ black hole whose
entropy is given by the Cardy formula. We study black holes carrying D0-D4 and
D0-D6 brane charges. We find, both in the supersymmetric and non-supersymmetric
cases, that a generic set of charges cannot be brought to the Cardy limit using
the duality symmetries. In the non-supersymmetric case, unlike the
supersymmetric one, we find that when the charges are large, a small fractional
change in them always allows the charges to be taken to the Cardy limit. These
results could lead to a microscopic determination of the entropy for extremal
non-supersymmetric black holes, including rotating cases like the extreme Kerr
black hole in four dimensions.Comment: 46 pages, Latex, Some comments added in Introduction and Conclusions.
Minor changes made in sections 3.4 and
Born-Infeld Chern-Simons Theory: Hamiltonian Embedding, Duality and Bosonization
In this paper we study in detail the equivalence of the recently introduced
Born-Infeld self dual model to the Abelian Born-Infeld-Chern-Simons model in
2+1 dimensions. We first apply the improved Batalin, Fradkin and Tyutin scheme,
to embed the Born-Infeld Self dual model to a gauge system and show that the
embedded model is equivalent to Abelian Born-Infeld-Chern-Simons theory. Next,
using Buscher's duality procedure, we demonstrate this equivalence in a
covariant Lagrangian formulation and also derive the mapping between the
n-point correlators of the (dual) field strength in Born-Infeld Chern-Simons
theory and of basic field in Born-Infeld Self dual model. Using this
equivalence, the bosonization of a massive Dirac theory with a non-polynomial
Thirring type current-current coupling, to leading order in (inverse) fermion
mass is also discussed. We also re-derive it using a master Lagrangian.
Finally, the operator equivalence between the fermionic current and (dual)
field strength of Born-Infeld Chern-Simons theory is deduced at the level of
correlators and using this the current-current commutators are obtained.Comment: 27 pages, One reference added, minor changes in presentation and
typos corrected. To appear in Nucl. Phys.
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