854 research outputs found
Relativistic Dynamics of Vector Bosons in the Field of Gravitational Radiation
We consider a model of the state evolution of relativistic vector bosons,
which includes both the dynamical equations for the particle four-velocity and
the equations for the polarization four-vector evolution in the field of a
nonlinear plane gravitational wave. In addition to the gravitational minimal
coupling, tidal forces linear in curvature tensor are suggested to drive the
particle state evolution. The exact solutions of the evolutionary equations are
obtained. Birefringence and tidal deviations from the geodesic motion are
discussed.Comment: 10 pages, no figures, Te
Spin-axion coupling
We establish a new covariant phenomenological model, which describes an
influence of pseudoscalar (axion) field on spins of test massive particles. The
model includes general relativistic equations of particle motion and spin
evolution in background pseudoscalar (axion), electromagnetic and gravitational
fields. It describes both the direct spin-axion coupling of the gradient type
and indirect spin-axion interaction mediated by electromagnetic fields. Special
attention is paid to the direct spin-axion coupling caused by the gradient of
the pseudoscalar (axion) field. We show that it describes a spin precession,
when the pseudoscalar (axion) field is inhomogeneous and/or non-stationary.
Applications of the model, which correspond to the three types of four-vectors
attributed to the gradient of the pseudoscalar (axion) field (time-like,
space-like, and null), are considered in detail. These are the spin precessions
induced by relic cosmological axions, axions distributed around spherically
symmetric static objects, and axions in a gravitational wave field,
respectively. We discuss features of the obtained exact solutions and some
general properties of the axionically induced spin rotation.Comment: 15 pages; replaced with the version accepted for publication in Phys.
Rev. D; new Subsection IVB and 13 references are adde
Dark Energy: A Unifying View
Different models of the cosmic substratum which pretend to describe the
present stage of accelerated expansion of the Universe like the CDM
model or a Chaplygin gas, can be seen as special realizations of a holographic
dark energy cosmology if the option of an interaction between pressurless dark
matter and dark energy is taken seriously. The corresponding interaction
strength parameter plays the role of a cosmological constant. Differences occur
at the perturbative level. In particular, the pressure perturbations are
intrinsically non-adiabatic.Comment: 9 pages, selected for "Honorable Mention" by the Gravity Research
Foundatio
The Maxwell--Boltzmann gas with non-standard self--interactions: a novel approach to galactic dark matter
Using relativistic kinetic theory, we study spherically symmetric, static
equilibrium configurations of a collisionless Maxwell-Boltzmann gas with
non-standard self-interactions, modelled by an effective one--particle force.
The resulting set of equilibrium conditions represents a generalization of the
classical Tolman-Oppenheimer-Volkov equations. We specify these conditions for
two types of Lorentz--like forces: one coupled to the 4-acceleration and the
4--velocity and the other one coupled to the Riemann tensor. We investigate the
weak field limits in each case and show that they lead to various Newtonian
type configurations that are different from the usual isothermal sphere
characterizing the conventional Newtonian Maxwell--Boltzmann gas. These
configurations could provide a plausible phenomenological and theoretical
description of galactic dark matter halo structures. We show how the
self--interaction may act phenomenologically as an effective cosmological
constant and discuss possible connections with Modified Newtonian
Dynamics(MOND).Comment: 12 pages, 2 figures, minor correction
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