555 research outputs found
Black Ring Deconstruction
We present a sample microstate for a black ring in four and five dimensional
language. The microstate consists of a black string microstate with an
additional D6-brane. We show that with an appropriate choice of parameters the
piece involving the black string microstate falls down a long AdS throat, whose
M-theory lift is AdS_3 X S^2. We wrap a spinning dipole M2-brane on the S^2 in
the probe approximation. In IIA, this corresponds to a dielectric D2-brane
carrying only D0-charge. We conjecture this is the first approximation to a
cloud of D0-branes blowing up due to their non-abelian degrees of freedom and
the Myers effect.Comment: 10 pages, 2 figure
The F-Landscape: Dynamically Determining the Multiverse
We evolve our Multiverse Blueprints to characterize our local neighborhood of
the String Landscape and the Multiverse of plausible string, M- and F-theory
vacua. Building upon the tripodal foundations of i) the Flipped SU(5) Grand
Unified Theory (GUT), ii) extra TeV-Scale vector-like multiplets derived out of
F-theory, and iii) the dynamics of No-Scale Supergravity, together dubbed
No-Scale F-SU(5), we demonstrate the existence of a continuous family of
solutions which might adeptly describe the dynamics of distinctive universes.
This Multiverse landscape of F-SU(5) solutions, which we shall refer to as the
F-Landscape, accommodates a subset of universes compatible with the presently
known experimental uncertainties of our own universe. We show that by
secondarily minimizing the minimum of the scalar Higgs potential of each
solution within the F-Landscape, a continuous hypervolume of distinct minimum
minimorum can be engineered which comprise a regional dominion of universes,
with our own universe cast as the bellwether. We conjecture that an
experimental signal at the LHC of the No-Scale F-SU(5) framework's
applicability to our own universe might sensibly be extrapolated as
corroborating evidence for the role of string, M- and F-theory as a master
theory of the Multiverse, with No-Scale supergravity as a crucial and pervasive
reinforcing structure.Comment: 15 Pages, 7 Figures, 1 Tabl
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
Two Centered Black Holes and N=4 Dyon Spectrum
The exact spectrum of dyons in a class of N=4 supersymmetric string theories
is known to change discontinuously across walls of marginal stability. We show
that the change in the degeneracy across the walls of marginal stability can be
accounted for precisely by the entropy of two centered small black holes which
disappear as we cross the walls of marginal stability.Comment: LaTeX file, 12 pages; v3: added footnote 2 regarding overall sign of
the index, expanded footnote 3, added reference
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
Unifying gauge couplings at the string scale
Using the current precision electroweak data, we look for the minimal
particle content which is necessary to add to the standard model in order to
have a complete unification of gauge couplings and gravity at the weakly
coupled heterotic string scale. We find that the addition of a vector-like
fermion at an intermediate scale and a non-standard hypercharge normalization
are in general sufficient to achieve this goal at two-loop level. Requiring the
extra matter scale to be below the TeV scale, it is found that the addition of
three vector-like fermion doublets with a mass around 700 GeV yields a perfect
string-scale unification, provided that the affine levels are , as in the string-GUT. Furthermore,
if supersymmetry is broken at the unification scale, the Higgs mass is
predicted in the range 125 GeV - 170 GeV, depending on the precise values of
the top quark mass and parameter.Comment: 11 pages, 4 eps figures, using jpconf style, talk given at CORFU2005,
RTN meeting ``The Quest for Unification: Theory Confronts Experiment'', 11 -
18 September 2005, Corfu, Greec
Kahler Stabilized, Modular Invariant Heterotic String Models
We review the theory and phenomenology of effective supergravity theories
based on orbifold compactifications of the weakly-coupled heterotic string. In
particular, we consider theories in which the four-dimensional theory displays
target space modular invariance and where the dilatonic mode undergoes Kahler
stabilization. A self-contained exposition of effective Lagrangian approaches
to gaugino condensation and heterotic string theory is presented, leading to
the development of the models of Binetruy, Gaillard and Wu. Various aspects of
the phenomenology of this class of models are considered. These include issues
of supersymmetry breaking and superpartner spectra, the role of anomalous U(1)
factors, issues of flavor and R-parity conservation, collider signatures, axion
physics, and early universe cosmology. For the vast majority of
phenomenological considerations the theories reviewed here compare quite
favorably to other string-derived models in the literature. Theoretical
objections to the framework and directions for further research are identified
and discussed.Comment: Invited review article for International Journal of Modern Physic
Black Holes in Supergravity: the non-BPS Branch
We construct extremal, spherically symmetric black hole solutions to 4D
supergravity with charge assignments that preclude BPS-saturation. In
particular, we determine the ground state energy as a function of charges and
moduli. We find that the mass of the non-BPS black hole remains that of a
marginal bound state of four basic constituents throughout the entire moduli
space and that there is always a non-zero gap above the BPS bound.Comment: 29 pages, one appendix, no figures; v2. few comments and references
added and a missing sign included; v3. further references adde
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
Enhanced Symmetries in Multiparameter Flux Vacua
We give a construction of type IIB flux vacua with discrete R-symmetries and
vanishing superpotential for hypersurfaces in weighted projective space with
any number of moduli. We find that the existence of such vacua for a given
space depends on properties of the modular group, and for Fermat models can be
determined solely by the weights of the projective space. The periods of the
geometry do not in general have arithmetic properties, but live in a vector
space whose properties are vital to the construction.Comment: 32 pages, LaTeX. v2: references adde
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