547 research outputs found
Constructing Lifshitz solutions from AdS
Under general assumptions, we show that a gravitational theory in d+1
dimensions admitting an AdS solution can be reduced to a d-dimensional theory
containing a Lifshitz solution with dynamical exponent z=2. Working in a d=4,
N=2 supergravity setup, we prove that if the AdS background is N=2
supersymmetric, then the Lifshitz geometry preserves 1/4 of the supercharges,
and we construct the corresponding Killing spinors. We illustrate these results
in examples from supersymmetric consistent truncations of type IIB
supergravity, enhancing the class of known 4-dimensional Lifshitz solutions of
string theory. As a byproduct, we find a new AdS4 x S1 x T(1,1) solution of
type IIB.Comment: 29 pages, no figures; v2 minor corrections, a reference adde
Control of macrophytes by grass carp (ctenopharyngodon idella) in a Waikato drain, New Zealand
Hornwort (Ceratophyllum demersum L.) and other aquatic macrophytes have historically been mechanically removed from the Rangiriri drain and Churchill East drain to maintain drain efficiency. As an alternative control method for the high plant biomass that accumulates at the end of summer, the effect of stocking diploid grass carp (Ctenopharyngodon idella L.) on the aquatic vegetation was evaluated in these Waikato drainage systems. At the start of the trial, both drains had a low diversity of aquatic macrophytes, and of the nine species (including the emergents), seven were exotic. Two months after grass carp were released to Churchill East drain (the treated drain) the four submerged and floating macrophyte species became scarce in the main drain. Over the same period, these species increased in biomass in Rangiriri drain (the untreated drain), where hornwort became dense and surface-reaching and remained so for the duration of the trial. However, grass carp did not control submerged vegetation in smaller side drains or the shallow, upper parts of the main drain, or the marginal sprawling species and emergent species. The cost of leasing the grass carp was similar to the cost of clearing the drains mechanically, but grass carp provided continuous weed control. However, subsequent to this trial, 62 dead grass carp were found in Churchill East drain in February 2001, and weed cover subsequently increased. This illustrates that grass carp management in New Zealand agricultural drains can be problematic due to periodic fish kills
Nonlinear Klein-Gordon-Maxwell systems with Neumann boundary conditions on a Riemannian manifold with boundary
Let (M,g) be a smooth compact, n dimensional Riemannian manifold, n=3,4 with
smooth n-1 dimensional boundary. We search the positive solutions of the
singularly perturbed Klein Gordon Maxwell Proca system with homogeneous Neumann
boundary conditions or for the singularly perturbed Klein Gordon Maxwell system
with mixed Dirichlet Neumann homogeneous boundary conditions. We prove that
stable critical points of the mean curvature of the boundary generates
solutions when the perturbation parameter is sufficiently small.Comment: arXiv admin note: text overlap with arXiv:1410.884
Holographic renormalization and supersymmetry
Holographic renormalization is a systematic procedure for regulating
divergences in observables in asymptotically locally AdS spacetimes. For dual
boundary field theories which are supersymmetric it is natural to ask whether
this defines a supersymmetric renormalization scheme. Recent results in
localization have brought this question into sharp focus: rigid supersymmetry
on a curved boundary requires specific geometric structures, and general
arguments imply that BPS observables, such as the partition function, are
invariant under certain deformations of these structures. One can then ask if
the dual holographic observables are similarly invariant. We study this
question in minimal N = 2 gauged supergravity in four and five dimensions. In
four dimensions we show that holographic renormalization precisely reproduces
the expected field theory results. In five dimensions we find that no choice of
standard holographic counterterms is compatible with supersymmetry, which leads
us to introduce novel finite boundary terms. For a class of solutions
satisfying certain topological assumptions we provide some independent tests of
these new boundary terms, in particular showing that they reproduce the
expected VEVs of conserved charges.Comment: 70 pages; corrected typo
Heterotic Flux Attractors
We find attractor equations describing moduli stabilization for heterotic
compactifications with generic SU(3)-structure. Complex structure and K\"ahler
moduli are treated on equal footing by using SU(3)xSU(3)-structure at
intermediate steps. All independent vacuum data, including VEVs of the
stabilized moduli, is encoded in a pair of generating functions that depend on
fluxes alone. We work out an explicit example that illustrates our methods.Comment: 37 pages, references and clarifications adde
Hypermoduli Stabilization, Flux Attractors, and Generating Functions
We study stabilization of hypermoduli with emphasis on the effects of
generalized fluxes. We find a class of no-scale vacua described by ISD
conditions even in the presence of geometric flux. The associated flux
attractor equations can be integrated by a generating function with the
property that the hypermoduli are determined by a simple extremization
principle. We work out several orbifold examples where all vector moduli and
many hypermoduli are stabilized, with VEVs given explicitly in terms of fluxes.Comment: 45 pages, no figures; Version submitted to JHE
Consistent reduction of charged D3-D7 systems
We provide a consistent reduction to five dimensions of the system of
D3-branes at Calabi-Yau singularities coupled to D7-branes with world-volume
gauge flux. The D3-branes source the dual to would-be conformal quiver
theories. The D7-branes, which are homogeneously distributed in their
transverse directions, are dual to massless matter in the fundamental
representation at finite (baryon) density. We provide the five-dimensional
action and equations of motion, and discuss a few sub-truncations. The
reduction can be used in the study of transport properties and stability of
D3-D7 charged systems.Comment: 23 pages. v2: references added and minor change
A special road to AdS vacua
We apply the techniques of special Kaehler geometry to investigate AdS_4
vacua of general N=2 gauged supergravities underlying flux compactifications of
type II theories. We formulate the scalar potential and its extremization
conditions in terms of a triplet of prepotentials P_x and their special Kaehler
covariant derivatives only, in a form that recalls the potential and the
attractor equations of N=2 black holes. We propose a system of first order
equations for the P_x which generalize the supersymmetry conditions and yield
non-supersymmetric vacua. Special geometry allows us to recast these equations
in algebraic form, and we find an infinite class of new N=0 and N=1 AdS_4
solutions, displaying a rich pattern of non-trivial charges associated with
NSNS and RR fluxes. Finally, by explicit evaluation of the entropy function on
the solutions, we derive a U-duality invariant expression for the cosmological
constant and the central charges of the dual CFT's.Comment: 41 pages; v2, v3: minor improvements, references added, published
versio
Effective actions and N=1 vacuum conditions from SU(3) x SU(3) compactifications
We consider compactifications of type II string theory on general SU(3) x
SU(3) structure backgrounds allowing for a very large set of fluxes, possibly
nongeometric ones. We study the effective 4d low energy theory which is a
gauged N=2 supergravity, and discuss how its data are obtained from the
formalism of the generalized geometry on T+T*. In particular we relate
Hitchin's special Kaehler metrics on the spaces of even and odd pure spinors to
the metric on the supergravity moduli space of internal metric and B-field
fluctuations. We derive the N=1 vacuum conditions from this N=2 effective
action, as well as from its N=1 truncation. We prove a direct correspondence
between these conditions and an integrated version of the pure spinor equations
characterizing the N=1 backgrounds at the ten dimensional level.Comment: 54 pages. v2, v3: minor change
On N = 2 Truncations of IIB on T^{1,1}
We study the N=4 gauged supergravity theory which arises from the consistent
truncation of IIB supergravity on the coset T^{1,1}. We analyze three N=2
subsectors and in particular we clarify the relationship between true
superpotentials for gauged supergravity and certain fake superpotentials which
have been widely used in the literature. We derive a superpotential for the
general reduction of type I supergravity on T^{1,1} and this together with a
certain solution generating symmetry is tantamount to a superpotential for the
baryonic branch of the Klebanov-Strassler solution.Comment: 32 pages, v2:references adde
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