arXiv subjects

M. Campanelli

Publications and source records attributed to M. Campanelli.

133 records · Page 8Linked to original sources

arXiv1999

Second order gauge invariant gravitational perturbations of a Kerr black hole

We investigate higher than the first order gravitational perturbations in the Newman-Penrose formalism. Equations for the Weyl scalar $ψ_4,$ representing outgoing gravitational radiation, can be uncoupled into a single wave equation to any perturbative order. For second order perturbations about a Kerr black hole, we prove the existence of a first and second order gauge (coordinates) and tetrad invariant waveform, $ψ_I$, by explicit construction. This waveform is formed by the second order piece of $ψ_4$ plus a term, quadratic in first order perturbations, chosen to make $ψ_I$ totally invariant and to have the appropriate behavior in an asymptotically flat gauge. $ψ_I$ fulfills a single wave equation of the form ${\cal T}ψ_I=S,$ where ${\cal T}$ is the same wave operator as for first order perturbations and $S$ is a source term build up out of (known to this level) first order perturbations. We discuss the issues of imposition of initial data to this equation, computation of the energy and momentum radiated and wave extraction for direct comparison with full numerical approaches to solve Einstein equations.

gr-qc↗

arXiv1998

A medium baseline search for $ν_μ\toν_e$ oscillations at a $ν$ beam from muon decays

The accurate knowledge of the $\barν_e (ν_μ)$ beam produced in $μ^-$ decays and the absence of $ν_e (\barν_μ)$ contamination, make a future muon storage ring the ideal place to look for $\numunue$ ($\numubarnuebar$) oscillations. Using a detector capable of electron and muon identification with charge discrimination (e.g., the presently running NOMAD experiment), good sensitivities to $\numunue (\numubarnuebar)$ oscillations could be achieved. With the CERN-PS as a proton driver for a muon storage ring of the kind envisaged for a $μ$-collider, the LSND claim would be confirmed or disproved in a few years of running.

hep-ph↗

arXiv1998

Long baseline neutrino oscillation disappearance search using a $ν$ beam from muon decays

We study the feasibility of performing a $ν_μ$ disappearance long-baseline experiment using a neutrino beam coming from muon decays. The advantage of such a technique with respect to the production of neutrino beams from pions is that in a muon decay both muon and electron neutrinos are produced in the same quantity. In case of $ν_μ\toν_{τ,s}$ oscillations, the $ν_e$ charged current (CC) events can be used as a control sample, to predict in situ the $ν_μ$ rates, thus reducing the systematics due to the knowledge of the neutrino flux, which is the main source of uncertainties for disappearance experiments. We consider as our neutrino target, the ICARUS detector in its final mass configuration of 4.8 kton.

hep-ph↗

arXiv1996

Determination of the mass of the W boson

Previous studies of the physics potential of LEP2 indicated that with the design luminosity of 500 inverse picobarn one may get a direct measurement of the mass of the W-boson with a precision in the range 30 - 50 MeV. This report presents an updated evaluation of the estimated error on the mass of the W-boson based on recent simulation work and improved theoretical input. The most efficient experimental methods which will be used are also described.

hep-ph↗

arXiv1994

Perturbative Metric of Charged Black Holes in Quadratic Gravity

We consider perturbative solutions to the classical field equations coming from a quadratic gravitational lagrangian in four dimensions. We study the charged, spherically symmetric black hole and explicitly give corrections up to third order (in the coupling constant $β$ multiplying the $R_{μν}R^{μν}$ term) to the Reissner--Nordström hole metric. We consider the thermodynamics of such black holes, in particular, we compute explicitly its temperature and entropy--area relation which deviates from the usual $S=A/4$ expression.

gr-qc↗

arXiv1994

A Perturbative Method to solve fourth-order Gravity Field Equations

We develop a method for solving the field equations of a quadratic gravitational theory coupled to matter. The quadratic terms are written as a function of the matter stress tensor and its derivatives in such a way to have, order by order, a set of Einstein field equations with an effective $T_{μν}$. We study the cosmological scenario recovering the de Sitter exact solution, and the first order (in the coupling constants $α$ and $β$ appearing in the gravitational Lagrangian) solution to the gauge cosmic string metric and the charged black hole. For this last solution we discuss the consequences on the thermodynamics of black holes, and in particular, the entropy - area relation which gets additional terms to the usual ${1\over4} A$ value.

gr-qc↗

arXiv1993

"Are Black Holes in Brans-Dicke Theory precisely the same as in General Relativity?"

We study a three-parameters family of solutions of the Brans-Dicke field equations. They are static and spherically symmetric. We find the range of parameters for which this solution represents a black hole different from the Schwarzschild one. We find a subfamily of solutions which agrees with experiments and observations in the solar system. We discuss some astrophysical applications and the consequences on the "no hair" theorems for black holes.

gr-qc↗