43,067 research outputs found
On new maximal supergravity and its BPS domain-walls
We revise the SU(3)-invariant sector of supergravity with
dyonic SO(8) gaugings. By using the embedding tensor formalism, analytic
expressions for the scalar potential, superpotential(s) and fermion mass terms
are obtained as a function of the electromagnetic phase and the
scalars in the theory. Equipped with these results, we explore
non-supersymmetric AdS critical points at for which
perturbative stability could not be analysed before. The -dependent
superpotential is then used to derive first-order flow equations and obtain new
BPS domain-wall solutions at . We numerically look at
steepest-descent paths motivated by the (conjectured) RG flows.Comment: 40 pages (30 pages + appendices), 3 tables, 6 figures. v2: References
added and discussion in section 4.2 clarified. v3: References added,
published version. v4: Fixed typo
BPS black hole horizons from massive IIA
The maximal four-dimensional supergravity with a dyonic ISO(7) gauging that
arises from the reduction of massive IIA on a six-sphere has recently been
shown to accommodate static BPS black holes with hyperbolic horizons. When
restricted to the N=2 subsector that retains one vector multiplet and the
universal hypermultiplet, the attractor mechanism was shown to fix both the
vector charges and the scalar fields at the horizon to a unique configuration
in terms of the gauging parameters. In order to assess the (non-)uniqueness of
BPS black hole horizons from massive IIA, we extend the study of the attractor
mechanism to other N=2 subsectors including additional matter multiplets. We
note that, while extending the hypermultiplet sector does not modify the set of
solutions to the attractor equations, the inclusion of additional vector
multiplets results in new hyperbolic/spherical horizons containing free
parameters. The model with three vector multiplets and the universal
hypermultiplet, which is the massive IIA analogue of the STU-model from
M-theory, may play a relevant role in massive IIA holography.Comment: 18 pages, 2 figures. v2: typos fixed, notation and presentation
improved, references added. v3: published versio
Vector fields, separatrices and Kato surfaces
We prove that a singular complex surface that admits a complete holomorphic
vector field that has no invariant curve through a singular point of the
surface is obtained from a Kato surface by contracting some divisor (in
particular, it is compact). We also prove that, in a singular Stein surface
endowed with a complete holomorphic vector field, a singular point of the
surface where the zeroes of the vector field do not accumulate is either a
quasihomogeneous or a cyclic quotient singularity. The proofs rely in a
combinatorial description of the vector field on a resolution of the singular
point based on previous work of Rebelo and the author. With the same tools, we
reprove some facts about the classification of compact complex surfaces
admitting holomorphic vector fields.Comment: post-referee versio
Hypermultiplet gaugings and supersymmetric solutions from 11D and massive IIA supergravity on H spaces
Supersymmetric , and asymptotically AdS black hole solutions are studied in
the context of non-minimal supergravity models involving
three vector multiplets (STU-model) and Abelian gaugings of the universal
hypermultiplet moduli space. Such models correspond to consistent subsectors of
the and gauged maximal
supergravities that arise from the reduction of 11D and massive IIA
supergravity on spaces down to four dimensions. A
unified description of all the models is provided in terms of a square-root
prepotential and the gauging of a duality-hidden symmetry pair of the universal
hypermultiplet. Some aspects of M-theory and massive IIA holography are
mentioned in passing.Comment: 10 pages, 3 tables. v2: Published version. v3: minor edits, added
clarification
Simulated and Actual Effects of the Brown Shrimp, Penaeus aztecus, Closure in Mexico
Simulations based on a yield-per-recruit model were performed to analyze the impact ofg rowth overfishing on brown shrimp, Penaeus aztecus, and to assess the effects of a closed season inshore and offshore of the Mexican States of Tamaulipas and Veracruz. Closure of both the inshore and offshore fisheries could enhance cohort yield by more than 300%. Cohon yield enhancement would be only about 60-80% if only the offshore season were closed. The closed season of 1993 gave better results as it covered a larger part of the brown shrimp peak recruitment period. Catch per unit of effort (CPUE) after closure in 1993, compared with 1994, was 2.4 times higher than the mean CPUE of the month. Total annual offshore yield increased 72% in 1993 (3,800 metric tons (t)) and 10% in 1994 (506 t) with respect to the mean annual offshore catch during the 10-year period prior to the 1993 closure. Simulation results could help identify alternatives that permit the coexistence of the inshore and offshore fisheries while maintaining high profitability of the brown shrimp fishery
CSO superpotentials
Motivated by their application to holographic RG flows and hairy black holes
in Einstein-scalar systems, we present a collection of superpotentials driving
the dynamics of and four-dimensional
supergravities. These theories arise as consistent truncations of the
electric/magnetic families of maximal supergravities,
with , discovered by Dall'Agata et al. The and
truncations describe and invariant sectors, respectively, and contain AdS
solutions preserving supersymmetry within the full
theories, as well as various gauge symmetries. Realisations in terms of
non-geometric type IIB as well as geometric massive type IIA backgrounds are
also discussed. The aim of this note is to provide easy to handle
superpotentials that facilitate the study of gravitational and gauge aspects of
the maximal supergravities avoiding the
technicalities required in their construction.Comment: 10 pages, 1 table. v2: Published versio
Composite Operator Method analysis of the underdoped cuprates puzzle
The microscopical analysis of the unconventional and puzzling physics of the
underdoped cuprates, as carried out lately by means of the Composite Operator
Method (COM) applied to the 2D Hubbard model, is reviewed and systematized. The
2D Hubbard model has been adopted as it has been considered the minimal model
capable to describe the most peculiar features of cuprates held responsible for
their anomalous behavior. COM is designed to endorse, since its foundations,
the systematic emergence in any SCS of new elementary excitations described by
composite operators obeying non-canonical algebras. In this case (underdoped
cuprates - 2D Hubbard model), the residual interactions - beyond a 2-pole
approximation - between the new elementary electronic excitations, dictated by
the strong local Coulomb repulsion and well described by the two Hubbard
composite operators, have been treated within the Non Crossing Approximation.
Given this recipe and exploiting the few unknowns to enforce the Pauli
principle content in the solution, it is possible to qualitatively describe
some of the anomalous features of high-Tc cuprate superconductors such as large
vs. small Fermi surface dichotomy, Fermi surface deconstruction (appearance of
Fermi arcs), nodal vs. anti-nodal physics, pseudogap(s), kinks in the
electronic dispersion. The resulting scenario envisages a smooth crossover
between an ordinary weakly-interacting metal sustaining weak, short-range
antiferromagnetic correlations in the overdoped regime to an unconventional
poor metal characterized by very strong, long-but-finite-range
antiferromagnetic correlations leading to momentum-selective non-Fermi liquid
features as well as to the opening of a pseudogap and to the striking
differences between the nodal and the anti-nodal dynamics in the underdoped
regime.Comment: 30 PRB pages, 13 figures, 35 panel
The Hubbard model beyond the two-pole approximation: a Composite Operator Method study
Within the framework of the Composite Operator Method, a three-pole solution
for the two-dimensional Hubbard model is presented and analyzed in detail. In
addition to the two Hubbard operators, the operatorial basis comprises a third
operator describing electronic transitions dressed by nearest-neighbor spin
fluctuations. These latter, compared to charge and pair fluctuations, are
assumed to be preeminent in the region of model-parameter space - small doping,
low temperature and large on-site Coulomb repulsion - where one expects strong
electronic correlations to dominate the physics of the system. This assumption
and the consequent choice for the basic field, as well as the whole analytical
approximation framework, have been validated through a comprehensive comparison
with data for local and single-particle properties obtained by different
numerical methods on varying all model parameters. The results systematically
agree, both quantitatively and qualitatively, up to coincide in many cases.
Many relevant features of the model, reflected by the numerical data, are
exactly caught by the proposed solution and, in particular, the crossover
between weak and intermediate-strong correlations as well as the shape of the
occupied portion of the dispersion. A comprehensive comparison with other
-pole solutions is also reported in order to explore and possibly understand
the reasons of such good performance.Comment: 19 pages, 8 figures, 27 panel
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