44 research outputs found
D=7 / D=6 Heterotic Supergravity with Gauged R-Symmetry
We construct a family of chiral anomaly-free supergravity theories in D=6
starting from D=7 supergravity with a gauged noncompact R-symmetry, employing a
Horava-Witten bulk-plus-boundary construction. The gauged noncompact R-symmetry
yields a positive (de Sitter sign) D=6 scalar field potential. Classical
anomaly inflow which is needed to cancel boundary-field loop anomalies requires
careful consideration of the gravitational, gauge, mixed and local
supersymmetry anomalies. Coupling of boundary hypermultiplets requires care
with the Sp(1) gauge connection required to obtain quaternionic Kahler target
manifolds in D=6. This class of gauged R-symmetry models may be of use as
starting points for further compactifications to D=4 that take advantage of the
positive scalar potential, such as those proposed in the scenario of
supersymmetry in large extra dimensions.Comment: 43 pages, plain Latex; Clarification of discussion and references
adde
Non-singlet Baryons in Less Supersymmetric Backgrounds
We analyze the holographic description of non-singlet baryons in various
backgrounds with reduced supersymmetries and/or confinement. We show that they
exist in all AdS_5xY_5 backgrounds with Y_5 an Einstein manifold bearing five
form flux, for a number of quarks 5N/8< k< N, independently on the
supersymmetries preserved. This result still holds for gamma_i deformations. In
the confining Maldacena-Nunez background non-singlet baryons also exist,
although in this case the interval for the number of quarks is reduced as
compared to the conformal case. We generalize these configurations to include a
non-vanishing magnetic flux such that a complementary microscopical description
can be given in terms of lower dimensional branes expanding into fuzzy baryons.
This description is a first step towards exploring the finite 't Hooft coupling
region.Comment: 36 Pages, 1 figure, Latex, v2: few minor changes, JHEP versio
Wilson loops stability in the gauge/string correspondence
We study the stability of some classical string worldsheet solutions employed
for computing the potential energy between two static fundamental quarks in
confining and non-confining gravity duals. We discuss the fixing of the
diffeomorphism invariance of the string action, its relation with the
fluctuation orientation and the interpretation of the quark mass substraction
worldsheet needed for computing the potential energy in smooth (confining)
gravity background. We consider various dual gravity backgrounds and show by a
numerical analysis the existence of instabilities under linear fluctuations for
classical string embedding solutions having positive length function derivative
. Finally we make a brief discussion of 't Hooft loops in
non-conformal backgrounds.Comment: 34 pages, 36 figures. Reference added. Final version JHEP accepte
Six-dimensional (1,0) effective action of F-theory via M-theory on Calabi-Yau threefolds
The six-dimensional effective action of F-theory compactified on a singular
elliptically fibred Calabi-Yau threefold is determined by using an M-theory
lift. The low-energy data are derived by comparing a circle reduction of a
general six-dimensional (1,0) gauged supergravity theory with the effective
action of M-theory on the resolved Calabi-Yau threefold. The derivation
includes six-dimensional tensor multiplets for which the (anti-) self-duality
constraints are imposed on the level of the five-dimensional action. The vector
sector of the reduced theory is encoded by a non-standard potential due to the
Green-Schwarz term in six dimensions. This Green-Schwarz term also contains
higher curvature couplings which are considered to establish the full map
between anomaly coefficients and geometry. F-/M-theory duality is exploited by
moving to the five-dimensional Coulomb branch after circle reduction and
integrating out massive vector multiplets and matter hypermultiplets. The
associated fermions then generate additional Chern-Simons couplings at
one-loop. Further couplings involving the graviphoton are induced by quantum
corrections due to excited Kaluza-Klein modes. On the M-theory side integrating
out massive fields corresponds to resolving the singularities of the Calabi-Yau
threefold, and yields intriguing relations between six-dimensional anomalies
and classical topology.Comment: 55 pages, v2: typos corrected, discussion of loop corrections
improve
Gluon Scattering Amplitudes in Finite Temperature Gauge/Gravity Dualities
We examine the gluon scattering amplitude in N=4 super Yang-Mills at finite
temperature with nonzero R-charge densities, and in Non-Commutative gauge
theory at finite temperature. The gluon scattering amplitude is defined as a
light-like Wilson loop which lives at the horizon of the T-dual black holes of
the backgrounds we consider. We study in detail a special amplitude, which
corresponds to forward scattering of a low energy gluon off a high energy one.
For this kinematic configuration in the considered backgrounds, we find the
corresponding minimal surface which is directly related to the gluon scattering
amplitude. We find that for increasing the chemical potential or the
non-commutative parameter, the on-shell action corresponding to our Wilson loop
in the T-dual space decreases. For all of our solutions the length of the short
side of the Wilson loop is constrained by an upper bound which depends on the
temperature, the R-charge density and the non-commutative parameter. Due to
this constraint, in the limit of zeroth temperature our approach breaks down
since the upper bound goes to zero, while by keeping the temperature finite and
letting the chemical potential or the non-commutative parameter to approach to
zero the limit is smooth.Comment: 30 pages, 16 figures, minor corrections (plus improved numerical
computation for the non-commutative case
Towards multi-scale dynamics on the baryonic branch of Klebanov-Strassler
We construct explicitly a new class of backgrounds in type-IIB supergravity
which generalize the baryonic branch of Klebanov-Strassler. We apply a
solution-generating technique that, starting from a large class of solutions of
the wrapped-D5 system, yields the new solutions, and then proceed to study in
detail their properties, both in the IR and in the UV. We propose a simple
intuitive field theory interpretation of the rotation procedure and of the
meaning of our new solutions within the Papadopoulos-Tseytlin ansatz, in
particular in relation to the duality cascade in the Klebanov-Strassler
solution. The presence in the field theory of different VEVs for operators of
dimensions 2, 3 and 6 suggests that this is an important step towards the
construction of the string dual of a genuinely multi-scale (strongly coupled)
dynamical model.Comment: 37 pages, 7 figures. References added, version to appear in JHE
A Double Sigma Model for Double Field Theory
We define a sigma model with doubled target space and calculate its
background field equations. These coincide with generalised metric equation of
motion of double field theory, thus the double field theory is the effective
field theory for the sigma model.Comment: 26 pages, v1: 37 pages, v2: references added, v3: updated to match
published version - background and detail of calculations substantially
condensed, motivation expanded, refs added, results unchange
Global aspects of the space of 6D N = 1 supergravities
We perform a global analysis of the space of consistent 6D quantum gravity
theories with N = 1 supersymmetry, including models with multiple tensor
multiplets. We prove that for theories with fewer than T = 9 tensor multiplets,
a finite number of distinct gauge groups and matter content are possible. We
find infinite families of field combinations satisfying anomaly cancellation
and admitting physical gauge kinetic terms for T > 8. We find an integral
lattice associated with each apparently-consistent supergravity theory; this
lattice is determined by the form of the anomaly polynomial. For models which
can be realized in F-theory, this anomaly lattice is related to the
intersection form on the base of the F-theory elliptic fibration. The condition
that a supergravity model have an F-theory realization imposes constraints
which can be expressed in terms of this lattice. The analysis of models which
satisfy known low-energy consistency conditions and yet violate F-theory
constraints suggests possible novel constraints on low-energy supergravity
theories.Comment: 41 pages, 1 figur
Probing strongly coupled anisotropic plasma
We calculate the static potential, the drag force and the jet quenching
parameter in strongly coupled anisotropic N=4 super Yang-Mills plasma. We find
that the jet quenching is in general enhanced in presence of anisotropy
compared to the isotropic case and that its value depends strongly on the
direction of the moving quark and the direction along which the momentum
broadening occurs. The jet quenching is strongly enhanced for a quark moving
along the anisotropic direction and momentum broadening happens along the
transverse one. The parameter gets lower for a quark moving along the
transverse direction and the momentum broadening considered along the
anisotropic one. Finally, a weaker enhancement is observed when the quark moves
in the transverse plane and the broadening occurs on the same plane. The drag
force for quark motion parallel to the anisotropy is always enhanced. For
motion in the transverse space the drag force is enhanced compared to the
isotropic case only for quarks having velocity above a critical value. Below
this critical value the force is decreased. Moreover, the drag force along the
anisotropic direction is always stronger than the force in the transverse
space. The diffusion time follows exactly the inverse relations of the drag
forces. The static potential is decreased and stronger decrease observed for
quark-antiquark pair aligned along the anisotropic direction than the
transverse one. We finally comment on our results and elaborate on their
similarities and differences with the weakly coupled plasmas.Comment: 1+44 pages, 18 Figures; Added results on static force; Added
references; version published in JHE
Generalized Geometry and M theory
We reformulate the Hamiltonian form of bosonic eleven dimensional
supergravity in terms of an object that unifies the three-form and the metric.
For the case of four spatial dimensions, the duality group is manifest and the
metric and C-field are on an equal footing even though no dimensional reduction
is required for our results to hold. One may also describe our results using
the generalized geometry that emerges from membrane duality. The relationship
between the twisted Courant algebra and the gauge symmetries of eleven
dimensional supergravity are described in detail.Comment: 29 pages of Latex, v2 References added, typos fixed, v3 corrected
kinetic term and references adde