85 research outputs found
A New interpretation of MOND based on Mach principle and an Unruh like effect
A new interpretation is introduced for MOND based on the Sciama's
interpretation of Mach principle and an Unruh like effect, in the context of a
generalized equivalence principle. It is argued that in a locally accelerated
frame with acceleration the appearance of a Rindler horizon may give rise
to a constant acceleration as the local properties of cosmological
horizon or Hubble length. The total gravitational acceleration inside this
frame becomes the combination of with . For , the
conventional gravitational mass interacts with the dominant acceleration
as and application of Sciama's interpretation leads to the standard
Newtonian dynamics. For , however, a reduced gravitational mass
interacts with the dominant acceleration as and the
application of Sciama's interpretation on this reduced gravitational mass leads
to MOND. This introduces a third proposal for MOND: {\it The modification of
gravitational mass}.Comment: 11 pages, throughout revisio
A Note on the Integral Formulation of Einstein's Equations Induced on a Braneworld
We revisit the integral formulation (or Green's function approach) of
Einstein's equations in the context of braneworlds. The integral formulation
has been proposed independently by several authors in the past, based on the
assumption that it is possible to give a reinterpretation of the local metric
field in curved spacetimes as an integral expression involving sources and
boundary conditions. This allows one to separate source-generated and
source-free contributions to the metric field. As a consequence, an exact
meaning to Mach's Principle can be achieved in the sense that only
source-generated (matter fields) contributions to the metric are allowed for;
universes which do not obey this condition would be non-Machian. In this paper,
we revisit this idea concentrating on a Randall-Sundrum-type model with a
non-trivial cosmology on the brane. We argue that the role of the surface term
(the source-free contribution) in the braneworld scenario may be quite subtler
than in the 4D formulation. This may pose, for instance, an interesting issue
to the cosmological constant problem.Comment: 10 pages, no figures, accepted for publication in the General
Relativity and Gravitation Journa
An assessment of Evans' unified field theory II
Evans developed a classical unified field theory of gravitation and
electromagnetism on the background of a spacetime obeying a Riemann-Cartan
geometry. In an accompanying paper I, we analyzed this theory and summarized it
in nine equations. We now propose a variational principle for Evans' theory and
show that it yields two field equations. The second field equation is algebraic
in the torsion and we can resolve it with respect to the torsion. It turns out
that for all physical cases the torsion vanishes and the first field equation,
together with Evans' unified field theory, collapses to an ordinary Einstein
equation.Comment: 11 pages of late
The power spectrum of the circular noise
The circular noise is important in connection to Mach's principle, and also
as a possible probe of the Unruh effect. In this letter the power spectrum of
the detector following the Trocheries-Takeno motion in the Minkowski vacuum is
analytically obtained in the form of an infinite series. A mean distribution
function and corresponding energy density are obtained for this particular
detected noise. The analogous of a non constant temperature distribution is
obtained. And in the end, a brief discussion about the equilibrium
configuration is given.Comment: accepted for publication in GR
On the Machian Origin of Inertia
We examine Sciama's inertia theory: we generalise it, by combining rotation
and expansion in one unique model, we find the angular speed of the Universe,
and we stress that the theory is zero-total-energy valued. We compare with
other theories of the same null energy background. We determine the numerical
value of a constant which appears in the Machian inertial force expression
devised by Graneau and Graneau[2], by introducing the above angular speed. We
point out that this last theory is not restricted to Newtonian physics as those
authors stated but is, in fact, compatible with other cosmological and
gravitational theories. An argument by Berry[7] is shown in order to "derive"
Brans-Dicke relation in the present context.Comment: 10 pages including front one. New version was accepted to publication
by Astrophysics and Space Scienc
Sonoluminescence: Two-photon correlations as a test of thermality
In this Letter we propose a fundamental test for probing the thermal nature
of the spectrum emitted by sonoluminescence. We show that two-photon
correlations can in principle discriminate between real thermal light and the
quasi-thermal squeezed-state photons typical of models based on the dynamic
Casimir effect. Two-photon correlations provide a powerful experimental test
for various classes of sonoluminescence models.Comment: 6 pages, revtex 3; revised to include more discussion of finite
volume effects; physics conclusions unchanged; to appear in Physics Letters
'Universal' FitzGerald Contractions
The model of a universe with a preferred frame, which nevertheless shares the
main properties with traditional special and general relativity theories, is
considered. We adopt Mach's interpretation of inertia and show that the energy
balance equation, which includes the Machian energy of gravitational
interactions with the universe, can imitate standard relativistic formulas.Comment: The version accepted by Eur. Phys. J.
Four-fermion interaction from torsion as dark energy
The observed small, positive cosmological constant may originate from a
four-fermion interaction generated by the spin-torsion coupling in the
Einstein-Cartan-Sciama-Kibble gravity if the fermions are condensing. In
particular, such a condensation occurs for quark fields during the
quark-gluon/hadron phase transition in the early Universe. We study how the
torsion-induced four-fermion interaction is affected by adding two terms to the
Dirac Lagrangian density: the parity-violating pseudoscalar density dual to the
curvature tensor and a spinor-bilinear scalar density which measures the
nonminimal coupling of fermions to torsion.Comment: 6 pages; published versio
On the gravitodynamics of moving bodies
In the present work we propose a generalization of Newton's gravitational
theory from the original works of Heaviside and Sciama, that takes into account
both approaches, and accomplishes the same result in a simpler way than the
standard cosmological approach. The established formulation describes the local
gravitational field related to the observables and effectively implements the
Mach's principle in a quantitative form that retakes Dirac's large number
hypothesis. As a consequence of the equivalence principle and the application
of this formulation to the observable universe, we obtain, as an immediate
result, a value of Omega = 2. We construct a dynamic model for a galaxy without
dark matter, which fits well with recent observational data, in terms of a
variable effective inertial mass that reflects the present dynamic state of the
universe and that replicates from first principles, the phenomenology proposed
in MOND. The remarkable aspect of these results is the connection of the effect
dubbed dark matter with the dark energy field, which makes it possible for us
to interpret it as longitudinal gravitational waves.Comment: 18 pages, 4 figures. Final version: almost identical to the reference
journal; Cent. Eur. J. Phys. 201
Thermodynamic Gravity and the Schrodinger Equation
We adopt a 'thermodynamical' formulation of Mach's principle that the rest
mass of a particle in the Universe is a measure of its long-range collective
interactions with all other particles inside the horizon. We consider all
particles in the Universe as a 'gravitationally entangled' statistical ensemble
and apply the approach of classical statistical mechanics to it. It is shown
that both the Schrodinger equation and the Planck constant can be derived
within this Machian model of the universe. The appearance of probabilities,
complex wave functions, and quantization conditions is related to the
discreetness and finiteness of the Machian ensemble.Comment: Minor corrections, the version accepted by Int. J. Theor. Phy
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