arXiv subjects

Ion I. Cotaescu

Publications and source records attributed to Ion I. Cotaescu.

78 records · Page 5Linked to original sources

arXiv2001

Remarks on a solvable cosmological model

We present an exact analytical solution of the Einstein equations with cosmological constant in a spatially flat Robertson-Walker metric. This is interpreted as an isotropic Lemaitre-type version of the cosmological Friedmann model. Implications in the recent discovered cosmic acceleration of the universe and in the theory of an inflationary model of the universe are in view. Some properties of this solution are pointed out as a result of numerical investigations of the model.

gr-qc↗

arXiv2001

Polarized Dirac fermions in de Sitter spacetime

The tetrad gauge invariant theory of the free Dirac field in two special moving charts of the de Sitter spacetime is investigated pointing out the operators that commute with the Dirac one. These are the generators of the symmetry transformations corresponding to isometries that give rise to conserved quantities according to the Noether theorem. With their help the plane wave spinor solutions of the Dirac equation with given momentum and helicity are derived and the final form of the quantum Dirac field is established. It is shown that the canonical quantization leads to a correct physical interpretation of the massive or massless fermion quantum fields.

hep-th↗

arXiv2000

Classical Oscilators in General Relativity

It is shown that in general relativity some static metrics are able to simulate oscillatory motions. Their form depends on two arbitrary real parameters which determine the specific oscillation modes. The conclusion is that these metrics can be used for new geometric models of closed or even open bags. Pacs: 04.02.-q and 04.02.Jb

gr-qc↗

arXiv2000

External symmetry in general relativity

We propose a generalization of the isometry transformations to the geometric context of the field theories with spin where the local frames are explicitly involved. We define the external symmetry transformations as isometries combined with suitable tetrad gauge transformations and we show that these form a group which is locally isomorphic with the isometry one. We point out that the symmetry transformations that leave invariant the equations of the fields with spin have generators with specific spin terms which represent new physical observables. The examples we present are the generators of the central symmetry and those of the maximal symmetries of the de Sitter and anti-de Sitter spacetimes derived in different tetrad gauge fixings. Pacs: 04.20.Cv, 04.62.+v, 11.30.-j

gr-qc↗

arXiv1997

The Dirac equation in Cartesian gauge

It is shown that in the case of the spherically symmetric static backgrounds there is a gauge in which the Dirac equation is manifestly covariant under rotations. This allows us to separate the spherical variables like in the flat space-time, obtaining a pair of radial equations and a specific form of the radial scalar product.

gr-qc↗

arXiv1997

A new class of (3+1) quantum geometric models

A new family of analytically solvable quantum geometric models is proposed. The structure of the energy spectra as well as the form of the corresponding eigenfunctions are presented pointing out their main specific properties.

gr-qc↗