883 research outputs found
Scanning the Landscape of Flux Compactifications: Vacuum Structure and Soft Supersymmetry Breaking
We scan the landscape of flux compactifications for the Calabi-Yau manifold
with two K\" ahler moduli by varying the value of
the flux superpotential over a large range of values. We do not include
uplift terms. We find a rich phase structure of AdS and dS vacua. Starting with
we reproduce the exponentially large volume scenario, but as
is reduced new classes of minima appear. One of them corresponds to the
supersymmetric KKLT vacuum while the other is a new, deeper non-supersymmetric
minimum. We study how the bare cosmological constant and the soft supersymmetry
breaking parameters for matter on D7 branes depend on , for these classes
of minima. We discuss potential applications of our results.Comment: draft format remove
Exact solutions for supersymmetric stationary black hole composites
Four dimensional N=2 supergravity has regular, stationary, asymptotically
flat BPS solutions with intrinsic angular momentum, describing bound states of
separate extremal black holes with mutually nonlocal charges. Though the
existence and some properties of these solutions were established some time
ago, fully explicit analytic solutions were lacking thus far. In this note, we
fill this gap. We show in general that explicit solutions can be constructed
whenever an explicit formula is known in the theory at hand for the
Bekenstein-Hawking entropy of a single black hole as a function of its charges,
and illustrate this with some simple examples. We also give an example of
moduli-dependent black hole entropy.Comment: 13 pages, 1 figur
Effective action for the field equations of charged black holes
In this article, we consistently reduce the equations of motion for the
bosonic N = 2 supergravity action, using a multi-centered black hole ansatz for
the metric. This reduction is done in a general, non-supersymmetric setup, in
which we extend concepts of BPS black hole technology. First of all we obtain a
more general form of the black hole potential, as part of an effective action
for both the scalars and the vectors in the supergravity theory. Furthermore,
we show that there are extra constraints specifying the solution, which we
calculate explicitly. In the literature, these constraints have already been
studied in the one-center case. We also show that the effective action we
obtain for non-static metrics, can be linked to the "entropy function" for the
spherically symmetric case, as defined by Sen and Cardoso et al.Comment: 18 pages, (v2: small corrections, version to be published in CQG
The Non-BPS Black Hole Attractor Equation
We study the attractor mechanism for extremal non-BPS black holes with an
infinite throat near horizon geometry, developing, as we do so, a physical
argument as to why such a mechanism does not exist in non-extremal cases. We
present a detailed derivation of the non-supersymmetric attractor equation.
This equation defines the stabilization of moduli near the black hole horizon:
the fixed moduli take values specified by electric and magnetic charges
corresponding to the fluxes in a Calabi Yau compactification of string theory.
They also define the so-called double-extremal solutions. In some examples,
studied previously by Tripathy and Trivedi, we solve the equation and show that
the moduli are fixed at values which may also be derived from the critical
points of the black hole potential.Comment: 32 Pages, 2 Figures, LaTeX; v2: typos corrected, references adde
Non-Supersymmetric Attractors in String Theory
We find examples of non-supersymmetric attractors in Type II string theory
compactified on a Calabi Yau three-fold. For a non-supersymmetric attractor the
fixed values to which the moduli are drawn at the horizon must minimise an
effective potential. For Type IIA at large volume, we consider a configuration
carrying D0, D2, D4 and D6 brane charge. When the D6 brane charge is zero, we
find for some range of the other charges, that a non-supersymmetric attractor
solution exists. When the D6 brane charge is non-zero, we find for some range
of charges, a supersymmetry breaking extremum of the effective potential.
Closer examination reveals though that it is not a minimum of the effective
potential and hence the corresponding black hole solution is not an attractor.
Away from large volume, we consider the specific case of the quintic in CP^4.
Working in the mirror IIB description we find non-supersymmetric attractors
near the Gepner point.Comment: Added a few clarification
How many black holes fit on the head of a pin?
The Bekenstein-Hawking entropy of certain black holes can be computed
microscopically in string theory by mapping the elusive problem of counting
microstates of a strongly gravitating black hole to the tractable problem of
counting microstates of a weakly coupled D-brane system, which has no event
horizon, and indeed comfortably fits on the head of a pin. We show here that,
contrary to widely held beliefs, the entropy of spherically symmetric black
holes can easily be dwarfed by that of stationary multi-black-hole
``molecules'' of the same total charge and energy. Thus, the corresponding
pin-sized D-brane systems do not even approximately count the microstates of a
single black hole, but rather those of a zoo of entropically dominant
multicentered configurations.Comment: 4 pages, fourth prize in the Gravity Research Foundation Essay
competition 200
Intersoliton forces in the Wess-Zumino model
The spectrum of supersymmetric domain wall solitons of the Wess-Zumino model
is known to be discontinuous across a curve (of marginal stability) in the
moduli space of quartic superpotentials. Here we show how this phenomenon can
be understood from the behavior of the long-range inter-soliton force, which we
compute by a method due to Manton.Comment: 10 pages, 4 figures, latex. Version 3, to appear in PLB, corrects
minor error
Type IIB Flux Vacua from M-theory via F-theory
We study in detail some aspects of duality between type IIB and M-theory. We
focus on the duality between type IIB string theory on K3 x T^2/Z_2 orientifold
and M-theory on K3 x K3, in the F-theory limit. We give the explicit map
between the fields and in particular between the moduli of compactification,
studying their behavior under the F-theory limit. Turning on fluxes generates a
potential for the moduli both in type IIB and in M-theory. We verify that the
type IIB analysis gives the same results of the F-theory analysis. In
particular, we check that the two potentials match.Comment: 24 pages; reference correcte
Gaugino Condensation and Nonperturbative Superpotentials in Flux Compactifications
There are two known sources of nonperturbative superpotentials for K\"ahler
moduli in type IIB orientifolds, or F-theory compactifications on Calabi-Yau
fourfolds, with flux: Euclidean brane instantons and low-energy dynamics in D7
brane gauge theories. The first class of effects, Euclidean D3 branes which
lift in M-theory to M5 branes wrapping divisors of arithmetic genus 1 in the
fourfold, is relatively well understood. The second class has been less
explored. In this paper, we consider the explicit example of F-theory on with flux. The fluxes lift the D7 brane matter fields, and stabilize
stacks of D7 branes at loci of enhanced gauge symmetry. The resulting theories
exhibit gaugino condensation, and generate a nonperturbative superpotential for
K\"ahler moduli. We describe how the relevant geometries in general contain
cycles of arithmetic genus (and how divisors can
contribute to the superpotential, in the presence of flux). This second class
of effects is likely to be important in finding even larger classes of models
where the KKLT mechanism of moduli stabilization can be realized. We also
address various claims about the situation for IIB models with a single
K\"ahler modulus.Comment: 24 pages, harvmac, no figures, references adde
A Barren Landscape?
We consider the generation of a non-perturbative superpotential in F-theory
compactifications with flux. We derive a necessary condition for the generation
of such a superpotential in F-theory. For models with a single volume modulus,
we show that the volume modulus is never stabilized by either abelian
instantons or gaugino condensation. We then comment on how our analysis extends
to a larger class of compactifications. From our results, it appears that among
large volume string compactifications, metastable de Sitter vacua (should any
exist) are non-generic.Comment: 14 pages, comments adde
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