arXiv subjects

M. Cataldo

Publications and source records attributed to M. Cataldo.

34 records · Page 2Linked to original sources

arXiv2022

Reconstructing the neutrino energy for in-ice radio detectors

Starting in summer 2021, the Radio Neutrino Observatory in Greenland (RNO-G) will search for astrophysical neutrinos at energies >10 PeV by detecting the radio emission from particle showers in the ice around Summit Station, Greenland. We present an extensive simulation study that shows how RNO-G will be able to measure the energy of such particle cascades, which will in turn be used to estimate the energy of the incoming neutrino that caused them. The location of the neutrino interaction is determined using the differences in arrival times between channels and the electric field of the radio signal is reconstructed using a novel approach based on Information Field Theory. Based on these properties, the shower energy can be estimated. We show that this method can achieve an uncertainty of 13% on the logarithm of the shower energy after modest quality cuts and estimate how this can constrain the energy of the neutrino. The method presented in this paper is applicable to all similar radio neutrino detectors, such as the proposed radio array of IceCube-Gen2.

astro-ph.HE↗

arXiv2021

The IceCube-Gen2 Collaboration -- Contributions to the 37th International Cosmic Ray Conference (ICRC2021)

IceCube-Gen2 is a planned extension of the IceCube Neutrino Observatory at the South Pole. The extension is optimized to search for sources of astrophysical neutrinos from TeV to EeV, and will improve the sensitivity of the observatory to neutrino point sources by a factor of five. The science case of IceCube-Gen2 is built on a successful decade of observations with IceCube. This index of contributions to the 37th International Cosmic Ray Conference in Berlin, Germany (12-23 July 2021) describes research and development efforts for IceCube-Gen2. Included are performance studies of next-generation optical sensors that will detect Cherenkov radiation from TeV-PeV cosmic rays and neutrinos; optimizations of the geometries of the surface and in-ice optical arrays; and estimates of the sensitivity of the proposed IceCube-Gen2 radio array to Askaryan emission from PeV-EeV neutrinos. Contributions related to the existing instrument, IceCube, are available in a separate collection.

astro-ph.HE↗

arXiv2019

Probing galactic cosmic ray distribution with TeV gamma-ray sky

The distribution of cosmic rays in the Galaxy at energies above few TeVs is still uncertain and this affects the expectations for the diffuse gamma flux produced by hadronic interactions of cosmic rays with the interstellar gas. We show that the TeV gamma-ray sky can provide interesting constraints. Namely, we compare the flux from the galactic plane measured by Argo-YBJ, HESS, HAWC and Milagro with the expected flux due to diffuse emission and point-like and extended sources observed by HESS showing that experimental data can already discriminate among different hyphoteses for cosmic ray distribution. The constraints can be strengthened if the contribution of sources not resolved by HESS is taken into account.

astro-ph.HE↗

arXiv2004

On Magnetic solution to 2+1 Einstein--Maxwell gravity

The three--dimensional magnetic solution to the Einstein--Maxwell field equations have been considered by some authors. Several interpretations have been formulated for this magnetic spacetime. Up to now this solution has been considered as a two--parameter self--consistent field. We point out that the parameter related to the mass of this solution is just a pure gauge and can be rescaled to minus one. This implies that the magnetic metric has really a simple form and it is effectively one-parameter solution, which describes a distribution of a radial magnetic field in a 2+1 anti--de Sitter background space--time. We consider an alternative interpretation to the Dias--Lemos one for the magnetic field source.

hep-th↗

arXiv2003

A causal model for a closed universe

We study a closed model of a universe filled with viscous fluid and quintessence matter components. The dynamical equations imply that the universe might look like an accelerated flat Friedmann-Robertson-Walker (FRW) universe at low redshift. We consider here dissipative processes which obey a causal thermodynamics. Here, we account for the entropy production via causal dissipative inflation.

hep-th↗

arXiv2003

Relationship between (2+1) and 3+1)--Friedmann--Robertson--Walker cosmologies

In this work we establish the correspondence between solutions to the Friedmann--Robertson--Walker cosmologies for perfect fluid and scalar field sources, where both ones fulfill state equations of the form $p+ρ=γf(ρ)$, not necessarily linear ones. Such state equations are of common use in the case of matter--fluids, nevertheless, for a scalar field, they introduce relationships on the potential and kinetic scalar field energies which restrict the set of solutions. A theorem on this respect is demonstrated: From any given (3+1)--cosmological solution, obeying the quoted state equations, one can derive its (2+1)--cosmological counterpart or vice-versa. Some applications are given.

hep-th↗

arXiv2003

Supergravity with cosmological constant and the AdS group

It is shown that the supersymmetric extension of the Stelle-West formalism permits the construction of an action for $(3+1)$-dimensional N=1 supergravity with cosmological constant genuinely invariant under the $OSp(4/1).$ Since the action is invariant under the supersymmetric extension of the $AdS$ group, the supersymmetry algebra closes off shell without the need for auxiliary fields. The limit case $m\to 0$, i.e.$(3+1)$ -dimensional N=1 supergravity invariant under the Poincaré supergroup is also discussed.

hep-th↗

arXiv2002

Self--dual Lorentzian wormholes in n--dimensional Einstein gravity

A family of spherically symmetric, static and self--dual Lorentzian wormholes is obtained in n--dimensional Einstein gravity. This class of solutions includes the n--dimensional versions of the Schwarzschild black hole and the spatial--Schwarzschild traversable wormhole. Using isotropic coordinates we study the geometrical structure of the solution, and delineate the domains of the free parameters for which wormhole, naked singular geometries and the Schwarzschild black hole are obtained. It is shown that, in the lower dimensional Einstein gravity without cosmological constant, we can not have self--dual Lorentzian wormholes.

hep-th↗

arXiv2002

Duality mappings within three-dimensional nonlinear electrodynamics

In three-dimensional Einstein-Maxwell gravity the electrostatic Banados-Teitelboim-Zanelli solution and the magnetostatic Hirschmann-Welch solution are connected by a duality mapping. Here we point out that a similar duality mapping exists among circularly symmetric electrostatic and magnetostatic spacetimes, and electric and magnetic stationary solutions, for a nonlinear electrodynamics coupled to three-dimensional Einstein gravity.

hep-th↗

arXiv2002

Higher dimensional gravity invariant under the Poincare group

It is shown that the Stelle-West Grignani-Nardelli-formalism allows, both when odd dimensions and when even dimensions are considered, constructing actions for higher dimensional gravity invariant under local Lorentz rotations and under local Poincarè translations. It is also proved that such actions have the same coefficients as those obtained by Troncoso and Zanelli in ref. Class. Quantum Grav. 17 (2000) 4451.

gr-qc↗

arXiv2001

Supergravity and the Poincare group

An action for 3+1-dimensional supergravity genuinely invariant under the Poincare supergroup is proposed. The construction of the action is carried out considering a bosonic lagrangian invariant under both local Lorentz rotations and local Poincare translations as well as under diffeomorphism, and therefore the Poincare algebra closes off-shell. Since the lagrangian is invariant under the Poincare supergroup, the supersymmetry algebra closes off shell without the need of auxiliary fields.

gr-qc↗

arXiv2000

Viscous cosmologies in scalar-tensor theories for Kasner type metrics

In a viscous Bianchi type I metric of the Kasner form, it is well known that it is not possible to describe an anisotropic physical model of the universe, which satisfies the second law of thermodynamics and the dominant energy condition (DEC) in Einstein's theory of gravity. We examine this problem in scalar-tensor theories of gravity. In this theory we show that it is possible to describe the growth of entropy, keeping the thermodynamics and the dominant energy condition.

gr-qc↗

arXiv2000

(2+1)-Dimensional Black Hole with Coulomb-like Field

A (2+1)-static black hole solution with a nonlinear electric field is derived. The source to the Einstein equations is a nonlinear electrodynamics, satisfying the weak energy conditions, and it is such that the energy momentum tensor is traceless. The obtained solution is singular at the origin of coordinates. The derived electric field E(r) is given by $E(r)=q/r^2$, thus it has the Coulomb form of a point charge in the Minkowski spacetime. This solution describes charged (anti)--de Sitter spaces. An interesting asymptotically flat solution arises for $Λ=0$.

hep-th↗

arXiv2000

Comment on "Viscous cosmology in the Kasner metric"

We show in this comment that in an anisotropic Bianchi type I model of the Kasner form, it is not possible to describe the growth of entropy, if we want to keep the thermodynamics together with the dominant energy conditions. This consequence disagrees with the results obtained by Brevik and Pettersen [Phys. Rev. D 56, 3322 (1997)].

gr-qc↗

arXiv2000

BTZ black hole from (3+1) gravity

We propose an approach for constructing spatial slices of (3+1) spacetimes with cosmological constant but without a matter content, which yields (2+1) vacuum with $Λ$ solutions. The reduction mechanism from (3+1) to (2+1) gravity is supported on a criterion in which the Weyl tensor components are required to vanish together with a dimensional reduction via an appropriate foliation. By using an adequate reduction mechanism from the Plebański-Carter[A] solution in (3+1) gravity, the (2+1) BTZ solution can be obtained.

gr-qc↗

arXiv1993

Conformal Fourth-Rank Gravity

We consider the consequences of describing the metric properties of space- time through a quartic line element $ds^4=G_{μνλρ}dx^μdx^νdx^λdx^ρ$. The associated "metric" is a fourth-rank tensor $G_{μνλρ}$. We construct a theory for the gravitational field based on the fourth-rank metric $G_{μνλρ}$ which is conformally invariant in four dimensions. In the absence of matter the fourth-rank metric becomes of the form $G_{μνλρ}=g_{(μν}g_{λρ)}$ therefore we recover a Riemannian behaviour of the geometry; furthermore, the theory coincides with General Relativity. In the presence of matter we can keep Riemannianicity, but now gravitation couples in a different way to matter as compared to General Relativity. We develop a simple cosmological model based on a FRW metric with matter described by a perfect fluid. Our field equations predict that the entropy is an increasing function of time. For $k_{obs}=0$ the field equations predict $Ω\approx 4y$, where $y={p\overρ}$; for $Ω_{small}=0.01$ we obtain $y_{pred}=2.5\times 10^{-3}$. $y$ can be estimated from the mean random velocity of typical galaxies to be $y_{random}=1\times10^{-5}$. For the early universe there is no violation of causality for $t>t_{class}\approx10^{19}t_{Planck}\approx 10^{-24}s$.

gr-qc↗