99 research outputs found
A note on "symmetric" vielbeins in bimetric, massive, perturbative and non perturbative gravities
We consider a manifold endowed with two different vielbeins
and corresponding to two different metrics and
. Such a situation arises generically in bimetric or massive
gravity (including the recently discussed version of de Rham, Gabadadze and
Tolley), as well as in perturbative quantum gravity where one vielbein
parametrizes the background space-time and the other the dynamical degrees of
freedom. We determine the conditions under which the relation can be
imposed (or the "Deser-van Nieuwenhuizen" gauge chosen). We clarify and correct
various statements which have been made about this issue.Comment: 20 pages. Section 7, prop. 6 and 7. added. Some results made more
precis
Gravitomagnetism in Metric Theories: Analysis of Earth Satellites Results, and its Coupling with Spin
Employing the PPN formalism the gravitomagnetic field in different metric
theories is considered in the analysis of the LAGEOS results. It will be shown
that there are several models that predict exactly the same effect that general
relativity comprises. In other words, these Earth satellites results can be
taken as experimental evidence that the orbital angular momentum of a body does
indeed generate space--time geometry, notwithstanding they do not endow general
relativity with an outstanding status among metric theories. Additionally the
coupling spin--gravitomagnetic field is analyzed with the introduction of the
Rabi transitions that this field produces on a quantum system with spin 1/2.
Afterwards, a continuous measurement of the energy of this system is
introduced, and the consequences upon the corresponding probabilities of the
involved gravitomagnetic field will be obtained. Finally, it will be proved
that these proposals allows us, not only to confront against future experiments
the usual assumption of the coupling spin--gravotimagnetism, but also to
measure some PPN parameters and to obtain functional dependences among them.Comment: 10 page
Self-consistent Approach to Off-Shell Transport
The properties of two forms of the gradient expanded Kadanoff--Baym
equations, i.e. the Kadanoff--Baym and Botermans-Malfliet forms, suitable to
describe the transport dynamics of particles and resonances with broad spectral
widths, are discussed in context of conservation laws, the definition of a
kinetic entropy and the possibility of numerical realization. Recent results on
exact conservations of charge and energy-momentum within Kadanoff-Baym form of
quantum kinetics based on local coupling schemes are extended to two cases
relevant in many applications. These concern the interaction via a finite range
potential, and, relevant in nuclear and hadron physics, e.g. for the
pion--nucleon interaction, the case of derivative coupling.Comment: 35 pages, submitted to issue of Phys. Atom. Nucl. dedicated to S.T.
Belyaev on the occasion of his 80th birthday. Few references are adde
Currents and Superpotentials in classical gauge invariant theories I. Local results with applications to Perfect Fluids and General Relativity
E. Noether's general analysis of conservation laws has to be completed in a
Lagrangian theory with local gauge invariance. Bulk charges are replaced by
fluxes of superpotentials. Gauge invariant bulk charges may subsist when
distinguished one-dimensional subgroups are present. As a first illustration we
propose a new {\it Affine action} that reduces to General Relativity upon gauge
fixing the dilatation (Weyl 1918 like) part of the connection and elimination
of auxiliary fields. It allows a comparison of most gravity superpotentials and
we discuss their selection by the choice of boundary conditions. A second and
independent application is a geometrical reinterpretation of the convection of
vorticity in barotropic nonviscous fluids. We identify the one-dimensional
subgroups responsible for the bulk charges and thus propose an impulsive
forcing for creating or destroying selectively helicity. This is an example of
a new and general Forcing Rule.Comment: 64 pages, LaTeX. Version 2 has two more references and one misprint
corrected. Accepted in Classical and Quantum Gravit
Energy and directional signatures for plane quantized gravity waves
Solutions are constructed to the quantum constraints for planar gravity
(fields dependent on z and t only) in the Ashtekar complex connection
formalism. A number of operators are constructed and applied to the solutions.
These include the familiar ADM energy and area operators, as well as new
operators sensitive to directionality (z+ct vs. z-ct dependence). The
directionality operators are quantum analogs of the classical constraints
proposed for unidirectional plane waves by Bondi, Pirani, and Robinson (BPR).
It is argued that the quantum BPR constraints will predict unidirectionality
reliably only for solutions which are semiclassical in a certain sense. The ADM
energy and area operators are likely to have imaginary eigenvalues, unless one
either shifts to a real connection, or allows the connection to occur other
than in a holonomy. In classical theory, the area can evolve to zero. A quantum
mechanical mechanism is proposed which would prevent this collapse.Comment: 54 pages; LaTe
New Gauge Invariant Formulation of the Chern-Simons Gauge Theory
A new gauge invariant formulation of the relativistic scalar field
interacting with Chern-Simons gauge fields is considered. This formulation is
consistent with the gauge fixed formulation. Furthermore we find that canonical
(Noether) Poincar\'e generators are not gauge invariant even on the constraints
surface and do not satisfy the (classical) Poincar\'e algebra. It is the
improved generators, constructed from the symmetric energy-momentum tensor,
which are (manifestly) gauge invariant and obey the classical Poincar\'e
algebra.Comment: Shortened, to appear as Papid Communication-PRD/Nov/9
Relativistic conservation laws and integral constraints for large cosmological perturbations
For every mapping of a perturbed spacetime onto a background and with any
vector field we construct a conserved covariant vector density ,
which is the divergence of a covariant antisymmetric tensor density, a
"superpotential". is linear in the energy-momentum tensor
perturbations of matter, which may be large; does not contain the
second order derivatives of the perturbed metric. The superpotential is
identically zero when perturbations are absent.
By integrating conserved vectors over a part \Si of a hypersurface of
the background, which spans a two-surface \di\Si, we obtain integral
relations between, on the one hand, initial data of the perturbed metric
components and the energy-momentum perturbations on \Si and, on the other
hand, the boundary values on \di\Si. We show that there are as many such
integral relations as there are different mappings, 's, \Si's and
\di\Si's. For given boundary values on \di\Si, the integral relations may
be interpreted as integral constraints (e.g., those of Traschen) on local
initial data including the energy-momentum perturbations. Conservation laws
expressed in terms of Killing fields \Bar\xi of the background become
"physical" conservation laws.
In cosmology, to each mapping of the time axis of a Robertson-Walker space on
a de Sitter space with the same spatial topology there correspond ten
conservation laws. The conformal mapping leads to a straightforward
generalization of conservation laws in flat spacetimes. Other mappings are also
considered. ...Comment: This paper, published 7 years ago, was found useful by some
researchers but originally was not put on the gr-qc website. Now it has been
retyped with very minor changes: few wordings have been modified and several
misprints occurring in the printed version correcte
Lagrangian for the Majorana-Ahluwalia Construct
The equations describing self/anti-self charge conjugate states, recently
proposed by Ahluwalia, are re-written to covariant form. The corresponding
Lagrangian for the neutral particle theory is proposed. From a
group-theoretical viewpoint the construct is an example of the
Nigam-Foldy-Bargmann-Wightman-Wigner-type quantum field theory based on the
doubled representations of the extended Lorentz group. Relations with the
Sachs-Schwebel and Ziino-Barut concepts of relativistic quantum theory are
discussed.Comment: 10pp., REVTeX 3.0 fil
Extra Dirac Equations
This paper has rather a pedagogical meaning. Surprising symmetries in the
Lorentz group representation space are analyzed. The aim is
to draw reader's attention to the possibility of describing the particle world
on the ground of the Dirac "doubles". Several tune points of the variational
principle for this kind of equations are briefly discussed.Comment: REVTeX 3.0, 14p
- …