1,892 research outputs found
Near-horizon modes and self-adjoint extensions of the Schroedinger operator
We investigate the dynamics of scalar fields in the near-horizon exterior
region of a Schwarzschild black hole. We show that low-energy modes are
typically long-living and might be considered as being confined near the black
hole horizon. Such dynamics are effectively governed by a Schroedinger operator
with infinitely many self-adjoint extensions parameterized by , a
situation closely resembling the case of an ordinary free particle moving on a
semiaxis. Even though these different self-adjoint extensions lead to
equivalent scattering and thermal processes, a comparison with a simplified
model suggests a physical prescription to chose the pertinent self-adjoint
extensions. However, since all extensions are in principle physically
equivalent, they might be considered in equal footing for statistical analyses
of near-horizon modes around black holes. Analogous results hold for any
non-extremal, spherically symmetric, asymptotically flat black hole.Comment: 10 pages, 1 fig, contribution submitted to the volume "Classical and
Quantum Physics: Geometry, Dynamics and Control. (60 Years Alberto Ibort
Fest)" Springer (2018
Spinless Matter in Transposed-Equi-Affine Theory of Gravity
We derive and discus the equations of motion for spinless matter:
relativistic spinless scalar fields, particles and fluids in the recently
proposed by A. Saa model of gravity with covariantly constant volume with
respect to the transposed connection in Einstein-Cartan spaces.
A new interpretation of this theory as a theory with variable Plank
"constant" is suggested.
We show that the consistency of the semiclassical limit of the wave equation
and classical motion dictates a new definite universal interaction of torsion
with massive fields.Comment: 29 pages, latex, no figures. New Section on semiclassical limit of
wave equation added; old references rearranged; new references, remarks,
comments, and acknowledgments added; typos correcte
On the renormalization of the electroweak chiral Lagrangian with a Higgs
We consider the scalar sector of the effective non-linear electroweak
Lagrangian with a light "Higgs" particle, up to four derivatives in the chiral
expansion. The complete off-shell renormalization procedure is implemented,
including one loop corrections stemming from the leading two-derivative terms,
for finite Higgs mass. This determines the complete set of independent chiral
invariant scalar counterterms required for consistency; these include bosonic
operators often disregarded. Furthermore, new counterterms involving the Higgs
particle which are apparently chiral non-invariant are identified in the
perturbative analysis. A novel general parametrization of the pseudoescalar
field redefinitions is proposed, which reduces to the various usual ones for
specific values of its parameter; the non-local field redefinitions reabsorbing
all chiral non-invariant counterterms are then explicitly determined. The
physical results translate into renormalization group equations which may be
useful when comparing future Higgs data at different energies
Gravitational wave recoil in Robinson-Trautman spacetimes
We consider the gravitational recoil due to non-reflection-symmetric
gravitational wave emission in the context of axisymmetric Robinson-Trautman
spacetimes. We show that regular initial data evolve generically into a final
configuration corresponding to a Schwarzschild black-hole moving with constant
speed. For the case of (reflection-)symmetric initial configurations, the mass
of the remnant black-hole and the total energy radiated away are completely
determined by the initial data, allowing us to obtain analytical expressions
for some recent numerical results that have been appeared in the literature.
Moreover, by using the Galerkin spectral method to analyze the non-linear
regime of the Robinson-Trautman equations, we show that the recoil velocity can
be estimated with good accuracy from some asymmetry measures (namely the first
odd moments) of the initial data. The extension for the non-axisymmetric case
and the implications of our results for realistic situations involving head-on
collision of two black holes are also discussed.Comment: 9 pages, 6 figures, final version to appear in PR
Quantum dynamics of non-relativistic particles and isometric embeddings
It is considered, in the framework of constrained systems, the quantum
dynamics of non-relativistic particles moving on a d-dimensional Riemannian
manifold M isometrically embedded in . This generalizes recent
investigations where M has been assumed to be a hypersurface of . We
show, contrary to recent claims, that constrained systems theory does not
contribute to the elimination of the ambiguities present in the canonical and
path integral formulations of the problem. These discrepancies with recent
works are discussed.Comment: Revtex, 14 page
Neutron star in presence of torsion-dilaton field
We develop the general theory of stars in Saa's model of gravity with
propagating torsion and study the basic stationary state of neutron star. Our
numerical results show that the torsion force decreases the role of the gravity
in the star configuration leading to significant changes in the neutron star
masses depending on the equation of state of star matter. The inconsistency of
the Saa's model with Roll-Krotkov-Dicke and Braginsky-Panov experiments is
discussed.Comment: 29 pages, latex, 24 figures, final version. Added: 1)comments on
different possible mass definitions; 2)new sections: a)the inconsistency of
the Saa's model with Roll-Krotkov-Dicke and Braginsky-Panov experiments;
b)stability analysis via catastrophe theory; 3)new figers added and some
figures replaced. 4)new reference
Scale-invariant gauge theories of gravity: Theoretical foundations
We consider the construction of gauge theories of gravity, focussing in particular on the extension of local PoincarĂ© invariance to include invariance under local changes of scale. We work exclusively in terms of finite transformations, which allow for a more transparent interpretation of such theories in terms of gauge fields in Minkowski spacetime. Our approach therefore differs from the usual geometrical description of locally scale-invariant PoincarĂ© gauge theory (PGT) and Weyl gauge theory (WGT) in terms of RiemannâCartan and WeylâCartan spacetimes, respectively. In particular, we reconsider the interpretation of the Einstein gauge and also the equations of motion of matter fields and test particles in these theories. Inspired by the observation that the PGT and WGT matter actions for the Dirac field and electromagnetic field have more general invariance properties than those imposed by construction, we go on to present a novel alternative to WGT by considering an âextendedâ form for the transformation law of the rotational gauge field under local dilations, which includes its ânormalâ transformation law in WGT as a special case. The resulting âextendedâ Weyl gauge theory (eWGT) has a number of interesting features that we describe in detail. In particular, we present a new scale-invariant gauge theory of gravity that accommodates ordinary matter and is defined by the most general parity-invariant eWGT Lagrangian that is at most quadratic in the eWGT field strengths, and we derive its field equations. We also consider the construction of PGTs that are invariant under local dilations assuming either the ânormalâ or âextendedâ transformation law for the rotational gauge field, but show that they are special cases of WGT and eWGT, respectively.This is the final version of the article. It first appeared from the American Institute of Physics via http://dx.doi.org/10.1063/1.496314
Quantum effects and superquintessence in the new age of precision cosmology
Recent observations of Type Ia supernova at high redshifts establish that the
dark energy component of the universe has (a probably constant) ratio between
pressure and energy density . The
conventional quintessence models for dark energy are restricted to the range
, with the cosmological constant corresponding to .
Conformally coupled quintessence models are the simplest ones compatible with
the marginally allowed superaccelerated regime (). However, they are
known to be plagued with anisotropic singularities.
We argue here that the extension of the classical approach to the
semiclassical one, with the inclusion of quantum counterterms necessary to
ensure the renormalization, can eliminate the anisotropic singularities
preserving the isotropic behavior of conformally coupled superquintessence
models. Hence, besides of having other interesting properties, they are
consistent candidates to describe the superaccelerated phases of the universe
compatible with the present experimental data.Comment: 7 pages. Essay selected for "Honorable Mention" in the 2004 Awards
for Essays on Gravitation, Gravity Research Foundatio
Frames of reference in spaces with affine connections and metrics
A generalized definition of a frame of reference in spaces with affine
connections and metrics is proposed based on the set of the following
differential-geometric objects:
(a) a non-null (non-isotropic) vector field,
(b) the orthogonal to the vector field sub space,
(c) an affine connection and the related to it covariant differential
operator determining a transport along the given non-null vector filed.
On the grounds of this definition other definitions related to the notions of
accelerated, inertial, proper accelerated and proper inertial frames of
reference are introduced and applied to some mathematical models for the
space-time. The auto-parallel equation is obtained as an Euler-Lagrange's
equation. Einstein's theory of gravitation appears as a theory for
determination of a special frame of reference (with the gravitational force as
inertial force) by means of the metrics and the characteristics of a material
distribution.
PACS numbers: 0490, 0450, 1210G, 0240VComment: 17 pages, LaTeX 2
Auto-parallel equation as Euler-Lagrange's equation in spaces with affine connections and metrics
The auto-parallel equation over spaces with affine connections and metrics is
considered as a result of the application of the method of Lagrangians with
covariant derivatives (MLCD) on a given Lagrangian density.Comment: 19 pages, LaTe
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