597 research outputs found
BPS black holes, quantum attractor flows and automorphic forms
We propose a program for counting microstates of four-dimensional BPS black
holes in N >= 2 supergravities with symmetric-space valued scalars by
exploiting the symmetries of timelike reduction to three dimensions. Inspired
by the equivalence between the four dimensional attractor flow and geodesic
flow on the three-dimensional scalar manifold, we radially quantize stationary,
spherically symmetric BPS geometries. Connections between the topological
string amplitude, attractor wave function, the Ooguri-Strominger-Vafa
conjecture and the theory of automorphic forms suggest that black hole
degeneracies are counted by Fourier coefficients of modular forms for the
three-dimensional U-duality group, associated to special "unipotent"
representations which appear in the supersymmetric Hilbert space of the quantum
attractor flow.Comment: 9 pages, revtex; v2: references added and typos correcte
Non-Supersymmetric Charged Domain Walls
We present general non-supersymmtric domain wall solutions with non-trivial
scalar and gauge fields for gauged five-dimensional N=2 supergravity coupled to
abelian vector multiplets.Comment: 11 pages, one ref. added. To appear in Physics Letters
Minimal unitary representation of SU(2,2) and its deformations as massless conformal fields and their supersymmetric extensions
We study the minimal unitary representation (minrep) of SO(4,2) over an
Hilbert space of functions of three variables, obtained by quantizing its
quasiconformal action on a five dimensional space. The minrep of SO(4,2), which
coincides with the minrep of SU(2,2) similarly constructed, corresponds to a
massless conformal scalar in four spacetime dimensions. There exists a
one-parameter family of deformations of the minrep of SU(2,2). For positive
(negative) integer values of the deformation parameter \zeta one obtains
positive energy unitary irreducible representations corresponding to massless
conformal fields transforming in (0,\zeta/2) ((-\zeta/2,0)) representation of
the SL(2,C) subgroup. We construct the supersymmetric extensions of the minrep
of SU(2,2) and its deformations to those of SU(2,2|N). The minimal unitary
supermultiplet of SU(2,2|4), in the undeformed case, simply corresponds to the
massless N=4 Yang-Mills supermultiplet in four dimensions. For each given
non-zero integer value of \zeta, one obtains a unique supermultiplet of
massless conformal fields of higher spin. For SU(2,2|4) these supermultiplets
are simply the doubleton supermultiplets studied in arXiv:hep-th/9806042.Comment: Revised with an extended introduction and additional references.
Typos corrected. 49 pages; Latex fil
Supertwistors as Quarks of SU(2,2|4)
The GS superstring on AdS_5 x S^5 has a nonlinearly realized, spontaneously
broken SU(2,2|4) symmetry. Here we introduce a two-dimensional model in which
the unbroken SU(2,2|4) symmetry is linearly realized. The basic variables are
supertwistors, which transform in the fundamental representation of this
supergroup.
The quantization of this supertwistor model leads to the complete oscillator
construction of the unitary irreducible representations of the centrally
extended SU(2,2|4). They include the states of d=4 SYM theory, massless and KK
states of AdS_5 supergravity, and the descendants on AdS_5 of the standard
massive string states, which form intermediate and long supermultiplets. We
present examples of such multiplets and discuss possible states of solitonic
and (p,q) strings.Comment: 12 pages, LaTeX, 1 EPS figur
Partition Functions, the Bekenstein Bound and Temperature Inversion in Anti-de Sitter Space and its Conformal Boundary
We reformulate the Bekenstein bound as the requirement of positivity of the
Helmholtz free energy at the minimum value of the function L=E- S/(2\pi R),
where R is some measure of the size of the system. The minimum of L occurs at
the temperature T=1/(2\pi R). In the case of n-dimensional anti-de Sitter
spacetime, the rather poorly defined size R acquires a precise definition in
terms of the AdS radius l, with R=l/(n-2). We previously found that the
Bekenstein bound holds for all known black holes in AdS. However, in this paper
we show that the Bekenstein bound is not generally valid for free quantum
fields in AdS, even if one includes the Casimir energy. Some other aspects of
thermodynamics in anti-de Sitter spacetime are briefly touched upon.Comment: Latex, 32 page
Explicit Orbit Classification of Reducible Jordan Algebras and Freudenthal Triple Systems
We determine explicit orbit representatives of reducible Jordan algebras and
of their corresponding Freudenthal triple systems. This work has direct
application to the classification of extremal black hole solutions of N = 2, 4
locally supersymmetric theories of gravity coupled to an arbitrary number of
Abelian vector multiplets in D = 4, 5 space-time dimensions.Comment: 18 pages. Updated to match published versio
Negative Energy in String Theory and Cosmic Censorship Violation
We find asymptotically anti de Sitter solutions in N=8 supergravity which
have negative total energy. This is possible since the boundary conditions
required for the positive energy theorem are stronger than those required for
finite mass (and allowed by string theory). But stability of the anti de Sitter
vacuum is still ensured by the positivity of a modified energy, which includes
an extra surface term. Some of the negative energy solutions describe classical
evolution of nonsingular initial data to naked singularities. Since there is an
open set of such solutions, cosmic censorship is violated generically in
supergravity. Using the dual field theory description, we argue that these
naked singularities will be resolved in the full string theory.Comment: 23 pages, 2 figures, v2: argument for forming naked singularities
clarified, references adde
Stable de Sitter Vacua in 4 Dimensional Supergravity Originating from 5 Dimensions
The five dimensional stable de Sitter ground states in N=2 supergravity
obtained by gauging SO(1,1) symmetry of the real symmetric scalar manifold (in
particular a generic Jordan family manifold of the vector multiplets)
simultaneously with a subgroup R_s of the R-symmetry group descend to four
dimensional de Sitter ground states under certain conditions. First, the
holomorphic section in four dimensions has to be chosen carefully by using the
symplectic freedom in four dimensions; and second, a group contraction is
necessary to bring the potential into a desired form. Under these conditions,
stable de Sitter vacua can be obtained in dimensionally reduced theories (from
5D to 4D) if the semi-direct product of SO(1,1) with R^(1,1) together with a
simultaneous R_s is gauged. We review the stable de Sitter vacua in four
dimensions found in earlier literature for N=2 Yang-Mills Einstein supergravity
with SO(2,1) x R_s gauge group in a symplectic basis that comes naturally after
dimensional reduction. Although this particular gauge group does not descend
directly from five dimensions, we show that, its contraction does. Hence, two
different theories overlap in certain limits. Examples of stable de Sitter
vacua are given for the cases: (i) R_s=U(1)_R, (ii) R_s=SU(2)_R, (iii) N=2
Yang-Mills/Einstein Supergravity theory coupled to a universal hypermultiplet.
We conclude with a discussion regarding the extension of our results to
supergravity theories with more general homogeneous scalar manifolds.Comment: 54 page
Flop Transitions in M-theory Cosmology
We study flop-transitions for M-theory on Calabi-Yau three-folds and their
applications to cosmology in the context of the effective five-dimensional
supergravity theory. In particular, the additional hypermultiplet which becomes
massless at the transition is included in the effective action. We find the
potential for this hypermultiplet which includes quadratic and quartic terms as
well as additional dependence on the Kahler moduli. By constructing explicit
cosmological solutions, it is demonstrated that a flop-transition can indeed by
achieved dynamically, as long as the hypermultiplet is set to zero. Once
excitations of the hypermultiplet are taken into account we find that the
transition is generically not completed but the system is stabilised close to
the transition region. Regions of moduli space close to flop-transitions can,
therefore, be viewed as preferred by the cosmological evolution.Comment: 18 pages, Latex, 8 eps-figures, typos correcte
Minimal Unitary Realizations of Exceptional U-duality Groups and Their Subgroups as Quasiconformal Groups
We study the minimal unitary representations of noncompact exceptional groups
that arise as U-duality groups in extended supergravity theories. First we give
the unitary realizations of the exceptional group E_{8(-24)} in SU*(8) as well
as SU(6,2) covariant bases. E_{8(-24)} has E_7 X SU(2) as its maximal compact
subgroup and is the U-duality group of the exceptional supergravity theory in
d=3. For the corresponding U-duality group E_{8(8)} of the maximal supergravity
theory the minimal realization was given in hep-th/0109005. The minimal unitary
realizations of all the lower rank noncompact exceptional groups can be
obtained by truncation of those of E_{8(-24)} and E_{8(8)}. By further
truncation one can obtain the minimal unitary realizations of all the groups of
the "Magic Triangle". We give explicitly the minimal unitary realizations of
the exceptional subgroups of E_{8(-24)} as well as other physically interesting
subgroups. These minimal unitary realizations correspond, in general, to the
quantization of their geometric actions as quasi-conformal groups as defined in
hep-th/0008063.Comment: 28 pages. Latex commands removed from the abstract for the arXiv. No
changes in the manuscrip
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