Search results for "Variant"
showing 10 items of 1267 documents
Anisotropic deformations in a class of projectively-invariant metric-affine theories of gravity
2020
Among the general class of metric-affine theories of gravity, there is a special class conformed by those endowed with a projective symmetry. Perhaps the simplest manner to realise this symmetry is by constructing the action in terms of the symmetric part of the Ricci tensor. In these theories, the connection can be solved algebraically in terms of a metric that relates to the spacetime metric by means of the so-called deformation matrix that is given in terms of the matter fields. In most phenomenological applications, this deformation matrix is assumed to inherit the symmetries of the matter sector so that in the presence of an isotropic energy-momentum tensor, it respects isotropy. In th…
On the Weyl transverse frames in type I spacetimes
2004
We apply a covariant and generic procedure to obtain explicit expressions of the transverse frames that a type I spacetime admits in terms of an arbitrary initial frame. We also present a simple and general algorithm to obtain the Weyl scalars $\Psi_2^T$, $\Psi_0^T$ and $\Psi_4^T$ associated with these transverse frames. In both cases it is only necessary to choose a particular root of a cubic expression.
L-Rigidity in Newtonian approximation
2008
Newtonian limit of L-Rigidity is obtained. In this formalism, L-Rigidity is reduced to steady Newtonian rigid motions in a Newtonian frame of reference in which the observer is at rest.
Gauge-invariant Non-spherical Metric Perturbations of Schwarzschild Black-Hole Spacetimes
2005
The theory of gauge-invariant non-spherical metric perturbations of Schwarzschild black hole spacetimes is now well established. Yet, as different notations and conventions have been used throughout the years, the literature on the subject is often confusing and sometimes confused. The purpose of this paper is to review and collect the relevant expressions related to the Regge-Wheeler and Zerilli equations for the odd and even-parity perturbations of a Schwarzschild spacetime. Special attention is paid to the form they assume in the presence of matter-sources and, for the two most popular conventions in the literature, to the asymptotic expressions and gravitational-wave amplitudes. Besides…
Improved search for heavy neutrinos in the decay π→eν
2018
A search for massive neutrinos has been made in the decay π+→e+ν. No evidence was found for extra peaks in the positron energy spectrum indicative of pion decays involving massive neutrinos (π→e+νh). Upper limits (90% C.L.) on the neutrino mixing matrix element |Uei|2 in the neutrino mass region 60–135 MeV/c2 were set and are an order of magnitude improvement over previous results.
Observation of a Charged Charmoniumlike StructureZc(4020)and Search for theZc(3900)ine+e−→π+π−hc
2013
We study e(+)e(-) -> pi(+) pi(-)h(c) at center-of-mass energies from 3.90 to 4.42 GeV by using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections are measured at 13 energies and are found to be of the same order of magnitude as those of e(+)e(-) -> pi(+) pi(-) J/Psi but with a different line shape. In the pi(+/-)h(c) mass spectrum, a distinct structure, referred to as Z(c)(4020) is observed at 4. 02 GeV/c(2). The Z(c)(4020) carries an electric charge and couples to charmonium. A fit to the pi(+/-)h(c) invariant mass spectrum, neglecting possible interferences, results in a mass of (4022.9 +/- 0.8 +/- 2.7) MeV/c(2) and…
Direct Observation of aρDecay of theD13(1520)Baryon Resonance
2001
The reaction {gamma}p{yields}{pi}{sup +}{pi}{sup 0}n has been measured at MAMI for photon energies up to 820MeV. Invariant mass spectra of the particles in the final state ({pi}{sup +}n) , ({pi}{sup 0}n) , ({pi}{sup +}{pi}{sup 0}) have been determined for several bins of incident photon energy. Differences in {pi}{sup +}{pi}{sup 0} and simultaneously measured {pi}{sup 0}{pi}{sup 0} invariant mass distributions are assigned to a {rho} branch of the D{sub 13}(1520) nucleon resonance.
Unveiling the K1(1270) double-pole structure in the B¯→J/ψρK¯ and B¯→J/ψK¯*π decays
2021
By looking at the pseudoscalar-vector meson spectra in the $\overline{B}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\rho}\overline{K}$ and $\overline{B}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\overline{K}}^{*}\ensuremath{\pi}$ weak decays, we theoretically investigate the double-pole structure of the ${K}_{1}(1270)$ resonance by using the chiral unitary approach to account for the final-state interactions between the pseudoscalar ($P$) and vector ($V$) mesons. The ${K}_{1}(1270)$ resonance is dynamically generated through these interactions in coupled channels and influences the shape of the invariant mass distributions under consideration. We show how these shapes are affect…
Unitary chiral dynamics in decays and the role of scalar mesons
2004
We make a theoretical study of the J/psi decays into omegapipi, phipipi, omegaK (K) over bar and phiK (K) over bar using the techniques of the chiral unitary approach stressing the important role of the scalar resonances dynamically generated through the final state interaction of the two pseudoscalar mesons. We also discuss the importance of new mechanisms with intermediate exchange of vector and axial-vector mesons and the role played by the OZI rule in the J/ psi phipipi vertex, quantifying its effects. The results nicely reproduce the experimental data for the invariant mass distributions in all the channels considered. (C) 2004 Elsevier B.V. All rights reserved.
Intrinsic, deductive, explicit, and algorithmic characterization of the Szekeres-Szafron solutions
2018
We write the known invariant definition of the Szekeres-Szafron family of solutions in an intrinsic, deductive, explicit and algorithmic form. We also intrinsically characterize the two commonly considered subfamilies, and analyze other subclasses, also defined by first-order differential conditions. Furthermore, we present a Rainich-like approach to these metrics.