2,625 research outputs found
The gravity dual of supersymmetric gauge theories on a squashed
We present a new one-parameter family of supersymmetric solutions deforming
AdS_5. This is constructed as an asymptotically locally anti de Sitter (AlAdS)
solution of five-dimensional minimal gauged supergravity, with topology R x R^4
and a non-trivial graviphoton field, and can be uplifted to ten or eleven
dimensional supergravities. An analytic continuation of this solution yields
the gravity dual to a class of four-dimensional N=1 supersymmetric gauge
theories on a curved manifold with topology S^1 x S^3, comprising an SU(2) x
U(1)-symmetric squashed three-sphere, with a non-trivial background gauge field
coupling to the R-symmetry current. We compute the holographically renormalised
on-shell action and interpret it in terms of the Casimir energy of the dual
field theory. We also determine the holographic conserved charges of the
solution and discuss relations between them.Comment: 57 pages, 5 figures. v4: version published in JHE
Localization on Hopf surfaces
We discuss localization of the path integral for supersymmetric gauge
theories with an R-symmetry on Hermitian four-manifolds. After presenting the
localization locus equations for the general case, we focus on backgrounds with
S^1 x S^3 topology, admitting two supercharges of opposite R-charge. These are
Hopf surfaces, with two complex structure moduli p,q. We compute the localized
partition function on such Hopf surfaces, allowing for a very large class of
Hermitian metrics, and prove that this is proportional to the supersymmetric
index with fugacities p,q. Using zeta function regularisation, we determine the
exact proportionality factor, finding that it depends only on p,q, and on the
anomaly coefficients a, c of the field theory. This may be interpreted as a
supersymmetric Casimir energy, and provides the leading order contribution to
the partition function in a large N expansion.Comment: v2: discussion of background reality conditions modified and other
minor changes, references added; v3: further minor corrections, version
accepted for publication in JHE
Microscopic origin of the Bekenstein-Hawking entropy of supersymmetric AdS black holes
We present a holographic derivation of the entropy of supersymmetric
asymptotically AdS black holes. We define a BPS limit of black hole
thermodynamics by first focussing on a supersymmetric family of complexified
solutions and then reaching extremality. We show that in this limit the black
hole entropy is the Legendre transform of the on-shell gravitational action
with respect to three chemical potentials subject to a constraint. This
constraint follows from supersymmetry and regularity in the Euclidean bulk
geometry. Further, we calculate, using localization, the exact partition
function of the dual SCFT on a twisted with
complexified chemical potentials obeying this constraint. This defines a
generalization of the supersymmetric Casimir energy, whose Legendre transform
at large exactly reproduces the Bekenstein-Hawking entropy of the black
hole.Comment: v4: minor changes, version published in JHE
The large- limit of the 4d superconformal index
We systematically analyze the large- limit of the superconformal index of
superconformal theories having a quiver description. The index
of these theories is known in terms of unitary matrix integrals, which we
calculate using the recently-developed technique of elliptic extension. This
technique allows us to easily evaluate the integral as a sum over saddle points
of an effective action in the limit where the rank of the gauge group is
infinite. For a generic quiver theory under consideration, we find a special
family of saddles whose effective action takes a universal form controlled by
the anomaly coefficients of the theory. This family includes the known
supersymmetric black hole solution in the holographically dual AdS
theories. We then analyze the index refined by turning on flavor chemical
potentials. We show that, for a certain range of chemical potentials, the
effective action again takes a universal cubic form that is controlled by the
anomaly coefficients of the theory. Finally, we present a large class of
solutions to the saddle-point equations which are labelled by group
homomorphisms of finite abelian groups of order into the torus.Comment: 58 pages; v2: minor changes, published versio
Leptin Increases: Physiological Roles in the Control of Sympathetic Nerve Activity, Energy Balance, and the Hypothalamic-Pituitary-Thyroid Axis
: It is well established that decreases in plasma leptin levels, as with fasting, signal starvation and elicit appropriate physiological responses, such as increasing the drive to eat and decreasing energy expenditure. These responses are mediated largely by suppression of the actions of leptin in the hypothalamus, most notably on arcuate nucleus (ArcN) orexigenic neuropeptide Y neurons and anorexic pro-opiomelanocortin neurons. However, the question addressed in this review is whether the effects of increased leptin levels are also significant on the long-term control of energy balance, despite conventional wisdom to the contrary. We focus on leptin's actions (in both lean and obese individuals) to decrease food intake, increase sympathetic nerve activity, and support the hypothalamic-pituitary-thyroid axis, with particular attention to sex differences. We also elaborate on obesity-induced inflammation and its role in the altered actions of leptin during obesity
The Casimir Energy in Curved Space and its Supersymmetric Counterpart
We study -dimensional Conformal Field Theories (CFTs) on the cylinder,
, and its deformations. In the Casimir energy
(i.e. the vacuum energy) is universal and is related to the central charge .
In the vacuum energy depends on the regularization scheme and has no
intrinsic value. We show that this property extends to infinitesimally deformed
cylinders and support this conclusion with a holographic check. However, for
supersymmetric CFTs, a natural analog of the Casimir energy
turns out to be scheme independent and thus intrinsic. We give two proofs of
this result. We compute the Casimir energy for such theories by reducing to a
problem in supersymmetric quantum mechanics. For the round cylinder the vacuum
energy is proportional to . We also compute the dependence of the Casimir
energy on the squashing parameter of the cylinder. Finally, we revisit the
problem of supersymmetric regularization of the path integral on Hopf surfaces.Comment: 53 pages; v2: minor changes, references added, version published in
JHE
Supersymmetric counterterms from new minimal supergravity
We present a systematic classification of counterterms of four-dimensional
supersymmetric field theories on curved space, obtained as the rigid limit of
new minimal supergravity. These are supergravity invariants constructed using
the field theory background fields. We demonstrate that if the background
preserves two supercharges of opposite chirality, then all dimensionless
counterterms vanish, implying that in this case the supersymmetric partition
function is free of ambiguities. When only one Euclidean supercharge is
preserved, we describe the ambiguities that appear in the partition function,
in particular in the dependence on marginal couplings.Comment: 42 pages; v2: minor corrections, references adde
Comments on supersymmetric solutions of minimal gauged supergravity in five dimensions
We investigate supersymmetric solutions of minimal gauged supergravity in five dimensions, in the timelike class. We propose an ansatz based on a four-dimensional local orthotoric Kähler metric and reduce the problem to a single sixth-order equation for two functions, each of one variable. We find an analytic, asymptotically locally AdS solution comprising five parameters. For a conformally flat boundary, this reduces to a previously known solution with three parameters, representing the most general solution of this type known in the minimal theory. We discuss the possible relevance of certain topological solitons contained in the latter to account for the supersymmetric Casimir energy of dual superconformal field theories on . Although we obtain a negative response, our analysis clarifies several aspects of these solutions. In particular, we show that there exists a unique regular topological soliton in this family
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