7,599 research outputs found
Gravity duals of supersymmetric gauge theories on three-manifolds
We study gravity duals to a broad class of N=2 supersymmetric gauge theories
defined on a general class of three-manifold geometries. The gravity
backgrounds are based on Euclidean self-dual solutions to four-dimensional
gauged supergravity. As well as constructing new examples, we prove in general
that for solutions defined on the four-ball the gravitational free energy
depends only on the supersymmetric Killing vector, finding a simple closed
formula when the solution has U(1) x U(1) symmetry. Our result agrees with the
large N limit of the free energy of the dual gauge theory, computed using
localization. This constitutes an exact check of the gauge/gravity
correspondence for a very broad class of gauge theories with a large N limit,
defined on a general class of background three-manifold geometries.Comment: 74 pages, 2 figures; v2: minor change
CHEMICAL ARTS AND RELIGION IN ANTIQUITY. AN INTRODUCTION
Introduction to the special issue dedicated to chemical arts and religion in Antiquit
Operator Counting and Eigenvalue Distributions for 3D Supersymmetric Gauge Theories
We give further support for our conjecture relating eigenvalue distributions
of the Kapustin-Willett-Yaakov matrix model in the large N limit to numbers of
operators in the chiral ring of the corresponding supersymmetric
three-dimensional gauge theory. We show that the relation holds for
non-critical R-charges and for examples with {\mathcal N}=2 instead of
{\mathcal N}=3 supersymmetry where the bifundamental matter fields are
nonchiral. We prove that, for non-critical R-charges, the conjecture is
equivalent to a relation between the free energy of the gauge theory on a three
sphere and the volume of a Sasaki manifold that is part of the moduli space of
the gauge theory. We also investigate the consequences of our conjecture for
chiral theories where the matrix model is not well understood.Comment: 27 pages + appendices, 5 figure
Operator Counting for N=2 Chern-Simons Gauge Theories with Chiral-like Matter Fields
The localization formula of Chern-Simons quiver gauge theory on nicely
reproduces the geometric data such as volume of Sasaki-Einstein manifolds in
the large- limit, at least for vector-like models. The validity of
chiral-like models is not established yet, due to technical problems in both
analytic and numerical approaches. Recently Gulotta, Herzog and Pufu suggested
that the counting of chiral operators can be used to find the eigenvalue
distribution of quiver matrix models. In this paper we apply this method to
some vector-like or chiral-like quiver theories, including the triangular
quivers with generic Chern-Simons levels which are dual to in-homogeneous
Sasaki-Einstein manifolds . The result is consistent
with AdS/CFT and the volume formula. We discuss the implication of our
analysis.Comment: 23 pages; v2. revised version; v3. corrected typos and clarified
argument
Semiclassical strings in marginally deformed toric AdS/CFT
We study string solutions in the beta-deformed Sasaki-Einstein gauge/gravity
dualities. We find that the BPS point-like strings move in the submanifolds
where the two U(1) circles shrink to zero size. In the corresponding T^3
fibration description, the strings live on the edges of the polyhedron, where
the T^3 fibration degenerates to T^1. Moreover, we find that for each deformed
Sasaki-Einstein manifold the BPS string solutions exist only for particular
values of the deformation parameter. Our results imply that in the dual field
theory the corresponding BPS operators exist only for these particular values
of the deformation parameter we find. We also examine the non-BPS strings,
derive their dispersion relations and compare them with the undeformed ones.
Finally, we comment on the range of the validity of our solutions and their
dependence on the deformation parameter.Comment: 29 pages, 9 figure
INTRAOPERATIVE CLINICAL TEST FOR KINEMATIC ASSESSMENT OF ACl GRAFT BEHAVIOUR WITH COMPUTER ASSISTED PROCEDURE
This paper describes a protocol for an accurate and extensive computer-assisted in vivo evaluation of joint laxities durinQl reconstructions of anterior cruciate ,ligament (ACL). The operating technique is a double bundle with over the top graft. Kinematic tests are performed, intraoperatively, before the ACL reconstruction, with ACL deficient knees, and after the ACL reconstruction. Results of first four in vivo cases, highlight that the reconstruction gives a complete restore of stability, in the antero-posterior direction, at 30° and 90° degrees giving and increased stability up to 73%, confirming the role of the ACL in the control of AP dislocation. Internal and external rotations were also satisfactorily restored after the graft fixation; in particular at 30° of tlexion, the reconstruction gives a good control of the joint, reducing laxity up to 43%
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
Excitonic Effects in Quantum Wires
We review the effects of Coulomb correlation on the linear and non-linear
optical properties of semiconductor quantum wires, with emphasis on recent
results for the bound excitonic states. Our theoretical approach is based on
generalized semiconductor Bloch equations, and allows full three-dimensional
multisubband description of electron-hole correlation for arbitrary confinement
profiles. In particular, we consider V- and T-shaped structures for which
significant experimental advances were obtained recently. Above band gap, a
very general result obtained by this approach is that electron-hole Coulomb
correlation removes the inverse-square-root single-particle singularity in the
optical spectra at band edge, in agreement with previous reports from purely
one-dimensional models. Strong correlation effects on transitions in the
continuum are found to persist also at high densities of photoexcited carriers.
Below bandgap, we find that the same potential- (Coulomb) to kinetic-energy
ratio holds for quite different wire cross sections and compositions. As a
consequence, we identify a shape- and barrier-independent parameter that
governs a universal scaling law for exciton binding energy with size. Previous
indications that the shape of the wire cross-section may have important effects
on exciton binding are discussed in the light of the present results.Comment: Proc. OECS-5 Conference, G\"ottingen, 1997 (To appear in Phys. Stat.
Sol. (b)
Emerging Non-Anomalous Baryonic Symmetries in the AdS_5/CFT_4 Correspondence
We study the breaking of baryonic symmetries in the AdS_5/CFT_4
correspondence for D3 branes at Calabi-Yau three-fold singularities. This
leads, for particular VEVs, to the emergence of non-anomalous baryonic
symmetries during the renormalization group flow. We claim that these VEVs
correspond to critical values of the B-field moduli in the dual supergravity
backgrounds. We study in detail the C^3/Z_3 orbifold, the cone over F_0 and the
C^3/Z_5 orbifold. For the first two examples, we study the dual supergravity
backgrounds that correspond to the breaking of the emerging baryonic symmetries
and identify the expected Goldstone bosons and global strings in the infra-red.
In doing so we confirm the claim that the emerging symmetries are indeed
non-anomalous baryonic symmetries.Comment: 65 pages, 15 figures;v2: minor changes, published versio
Post-test simulations for the NACIE-UP benchmark by STH codes
This paper illustrates the results obtained in the last phase of the NACIE-UP benchmark activity foreseen inside the EU SESAME Project. The purpose of this research activity, performed by system thermal–hydraulic (STH) codes, is finalized to the improvement, development and validation of existing STH codes for Heavy Liquid Metal (HLM) systems. All the participants improved their modelling of the NACIE-UP facility, respect to the initial blind simulation phase, adopting the actual experimental boundary conditions and reducing as much as possible sources of uncertainty in their numerical model. Four different STH codes were employed by the participants to the benchmark to model the NACIE-UP facility, namely: CATHARE for ENEA, ATHLET for GRS, RELAP5-3D© for the “Sapienza” University of Rome and RELAP5/Mod3.3(modified) for the University of Pisa. Three reference tests foreseen in the NACIE-UP benchmark and carried out at ENEA Brasimone Research Centre were analysed from four participants. The data from the post-test analyses, performed independently by the participant using different STH codes, were compared together and with the available experimental results and critically discussed
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