arXiv subjects

A. De Castro

Publications and source records attributed to A. De Castro.

15 recordsLinked to original sources

arXiv2016

The Latin American Giant Observatory: Contributions to the 34th International Cosmic Ray Conference (ICRC 2015)

The Latin American Giant Observatory (LAGO) is an extended cosmic ray observatory composed by a network of water-Cherenkov detectors spanning over different sites located at significantly different altitudes (from sea level up to more than $5000$\,m a.s.l.) and latitudes across Latin America, covering a huge range of geomagnetic rigidity cut-offs and atmospheric absorption/reaction levels. This detection network is designed to measure the temporal evolution of the radiation flux at ground level with extreme detail. The LAGO project is mainly oriented to perform basic research in three branches: high energy phenomena, space weather and atmospheric radiation at ground level. LAGO is built and operated by the LAGO Collaboration, a non-centralized collaborative union of more than 30 institutions from ten countries. These are the contributions of the LAGO Collaboration to the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands

astro-ph.IM↗

arXiv2009

Operating Water Cherenkov Detectors in high altitude sites for the Large Aperture GRB Observatory

Water Cherenkov Detectors (WCD) are efficient detectors for detecting GRBs in the 10 GeV - 1 TeV energy range using the single particle technique, given their sensitivity to low energy secondary photons produced by high energy photons when cascading in the atmosphere. The Large Aperture GRB Observatory (LAGO) operates arrays of WCD in high altitude sites (above 4500 m a.s.l.) in Bolivia, Mexico and Venezuela, with planned extension to Peru. Details on the operation and stability of these WCD in remote sites with high background rates of particles will be detailed, and compared to simulations. Specific issues due to operation at high altitude, atmospheric effects and solar activity, as well as possible hardware enhancements will also be presented.

astro-ph.HE↗

arXiv2009

The Large Aperture GRB Observatory

The Large Aperture GRB Observatory (LAGO) is aiming at the detection of the high energy (around 100 GeV) component of Gamma Ray Bursts, using the single particle technique in arrays of Water Cherenkov Detectors (WCD) in high mountain sites (Chacaltaya, Bolivia, 5300 m a.s.l., Pico Espejo, Venezuela, 4750 m a.s.l., Sierra Negra, Mexico, 4650 m a.s.l). WCD at high altitude offer a unique possibility of detecting low gamma fluxes in the 10 GeV - 1 TeV range. The status of the Observatory and data collected from 2007 to date will be presented.

astro-ph.HE↗

arXiv2009

Water Cherenkov Detectors response to a Gamma Ray Burst in the Large Aperture GRB Observatory

In order to characterise the behaviour of Water Cherenkov Detectors (WCD) under a sudden increase of 1 GeV - 1 TeV background photons from a Gamma Ray Burst (GRB), simulations were conducted and compared to data acquired by the WCD of the Large Aperture GRB Observatory (LAGO). The LAGO operates arrays of WCD at high altitude to detect GRBs using the single particle technique. The LAGO sensitivity to GRBs is derived from the reported simulations of the gamma initiated particle showers in the atmosphere and the WCD response to secondaries.

astro-ph.HE↗

arXiv2008

Noncommutative associative superproduct for general supersymplectic forms

We define a noncommutative and nonanticommutative associative product for general supersymplectic forms, allowing the explicit treatment of non(anti)commutative field theories from general nonconstant string backgrounds like a graviphoton field. We propose a generalization of deformation quantization a la Fedosov to superspace, which considers noncommutativity in the tangent bundle instead of base space, by defining the Weyl super product of elements of Weyl super algebra bundles. Super Poincare symmetry is not broken and chirality seems not to be compromised in our formulation. We show that, for a particular case, the projection of the Weyl super product to the base space gives rise the Moyal product for non(anti)commutative theories.

hep-th↗

arXiv2006

Non-singlet Q-deformed N=(1,0) and N=(1,1/2) U(1) actions

In this paper we construct N=(1,0) and N=(1,1/2) non-singlet Q-deformed supersymmetric U(1) actions in components. We obtain an exact expression for the enhanced supersymmetry action by turning off particular degrees of freedom of the deformation tensor. We analyze the behavior of the action upon restoring weekly some of the deformation parameters, obtaining a non trivial interaction term between a scalar and the gauge field, breaking the supersymmetry down to N=(1,0). Additionally, we present the corresponding set of unbroken supersymmetry transformations. We work in harmonic superspace in four Euclidean dimensions.

hep-th↗

arXiv2006

Non-singlet Q-deformations of N=2 gauge theories

We study a non-anticommutative chiral non-singlet deformation of the N=(1,1) abelian gauge multiplet in Euclidean harmonic superspace. We present a closed form of the gauge transformations and the unbroken N =(1,0) supersymmetry transformations preserving the Wess-Zumino gauge, as well as the bosonic sector of the N =(1,0) invariant action. This contribution is a summary of our main results in hep-th/0510013.

hep-th↗

arXiv2006

Non-singlet Q-deformation of the N=(1,1) gauge multiplet in harmonic superspace

We study a non-anticommutative chiral non-singlet deformation of the N=(1,1) abelian gauge multiplet in Euclidean harmonic superspace with a product ansatz for the deformation matrix, C^{(αβ)}_{(ik)} = c^{(αβ)}b_{(ik)}. This allows us to obtain in closed form the gauge transformations and the unbroken N=(1,0) supersymmetry transformations preserving the Wess-Zumino gauge, as well as the bosonic sector of the N=(1,0) invariant action. As in the case of a singlet deformation, the bosonic action can be cast in a form where it differs from the free action merely by a scalar factor. The latter is now given by \cosh^2 (2\barϕ\sqrt{c^2 b^2}}), with \barϕbeing one of two scalar fields of the N=(1,1) vector multiplet. We compare our results with previous studies of non-singlet deformations, including the degenerate case b^2=0 which preserves the N=(1,1/2) fraction of N=(1,1) supersymmetry.

hep-th↗

arXiv2004

N=2 Super-Born-Infeld from Partially Broken N=3 Supersymmetry in d=4

We employ the non-linear realization techniques to relate the N=1 chiral, and the N=2 vector multiplets to the Goldstone spin 1/2 superfield arising from partial supersymmetry breaking of N=2 and N=3 respectively. In both cases, we obtain a family of non-linear transformation laws realizing an extra supersymmetry. In the N=2 case, we find an invariant action which is the low energy limit of the supersymmetric Born-Infeld theory expected to describe a D3-brane in six dimensions.

hep-th↗

arXiv2004

On The Super Five Brane Hamiltonian

The explicit form of the Wess-Zumino term of the PST super 5-brane Lagrangian in 11 dimensions is obtained. A complete canonical analysis for a gauge fixed PST super 5-brane action reveals the expected mixture of first and second class constraints. The canonical Hamiltonian is quadratic in the antisymmetric gauge field. Finally, we find the light cone gauge Hamiltonian for the theory and its stability properties are commented.

hep-th↗

arXiv2004

Topologically Massive Models from Higgs Mechanism

A Higgs mechanism for Abelian theories over non-trivial background flat connections is proposed. It is found that the mass generated for the spin 1 excitation is the same as the one obtained from the standard Higgs mechanism over trivial backgrounds, however, the dynamical structure of the action for the Higgs scalar is completely different from the usual approach. There is a topological contribution to the mass term of the Higgs field. After functional integration over all backgrounds, it is shown that the action for the massive spin 1 excitation is dual to the Topologically Massive Models in any dimension.

hep-th↗

arXiv2003

M5-brane as a Nambu-Poisson geometry of a Multi D1-brane theory

We introduce a Nambu-Poisson bracket in the geometrical description of the D=11 M5-brane. This procedure allows us, under some assumptions, to eliminate the local degrees of freedom of the antisymmetric field in the M5-brane Hamiltonian and to express it as a D=11 p-brane theory invariant under symplectomorphisms. A regularization of the M5-brane in terms of a multi D1-brane theory invariant under the $SU(N)\times SU(N)$ group in the limit when $N\to\infty$ is proposed. Also, a regularization for the D=10 D4-brane in terms of a multi D0-brane theory is suggested.

hep-th↗

arXiv2002

Super Five Brane Hamiltonian and the Chiral Degrees of Freedom

We construct the Hamiltonian of the super five brane in terms of its physical degrees of freedom. It does not depend on the inverse of the induced metric. Consequently, some singular configurations are physically admissible, implying an interpretation of the theory as a multiparticle one. The symmetries of the theory are analyzed from the canonical point of view in terms of the first and second class constraints. In particular it is shown how the chiral sector may be canonically reduced to its physical degrees of freedom.

hep-th↗

arXiv2001

Master Canonical Action and BRST Charge of the M Theory Bosonic Five Brane

A complete analysis of the canonical structure for a gauge fixed PST bosonic five brane action is performed. This canonical formulation is quadratic in the dependence on the antisymmetric field and it has second class constraints. We remove the second class constraints and a master canonical action with only first class constraints is proposed. The nilpotent BRST charge and its BRST invariant effective theory is constructed. The construction does not assume the existence of the inverse of the induced metric. Singular configurations are then physical ones. We obtain the physical Hamiltonian of the theory and analyze its stability properties. Finally, by studying the algebra of diffeomorphisms we find under mild assumptions the general structure for the Hamiltonian constraint for theories invariant under 6 dimensional diffeomorphisms and we give an algebraic characterization of the constraint associated with the bosonic five brane action. We also identify the constraint for the bosonic five brane action upgraded with a cosmological term, it contains a Born-Infeld type term.

hep-th↗

arXiv1998

On the Interacting Chiral Gauge Field Theory in D=6 and the Off-Shell Equivalence of Dual Born-Infeld-Like Actions

A canonical action describing the interaction of chiral gauge fields in D=6 Minkowski space-time is constructed. In a particular partial gauge fixing it reduces to the action found by Perry and Schwarz. The additional gauge symmetries are used to show the off-shell equivalence of the dimensional reduction to D=5 Minkowski space-time of the chiral gauge field canonical action and the Born-Infeld canonical action describing an interacting D=5 Abelian vector field. Its extension to improve the on-shell equivalence arguments of dual D-brane actions to off-shell ones is discussed.

hep-th↗