54 research outputs found
Strong quantum violation of the gravitational weak equivalence principle by a non-Gaussian wave-packet
The weak equivalence principle of gravity is examined at the quantum level in
two ways. First, the position detection probabilities of particles described by
a non-Gaussian wave-packet projected upwards against gravity around the
classical turning point and also around the point of initial projection are
calculated. These probabilities exhibit mass-dependence at both these points,
thereby reflecting the quantum violation of the weak equivalence principle.
Secondly, the mean arrival time of freely falling particles is calculated using
the quantum probability current, which also turns out to be mass dependent.
Such a mass-dependence is shown to be enhanced by increasing the
non-Gaussianity parameter of the wave packet, thus signifying a stronger
violation of the weak equivalence principle through a greater departure from
Gaussianity of the initial wave packet. The mass-dependence of both the
position detection probabilities and the mean arrival time vanish in the limit
of large mass. Thus, compatibility between the weak equivalence principle and
quantum mechanics is recovered in the macroscopic limit of the latter. A
selection of Bohm trajectories is exhibited to illustrate these features in the
free fall case.Comment: 11 pages, 7 figure
Testing the Principle of Equivalence by Solar Neutrinos
We discuss the possibility of testing the principle of equivalence with solar
neutrinos. If there exists a violation of the equivalence principle quarks and
leptons with different flavors may not universally couple with gravity. The
method we discuss employs a quantum mechanical phenomenon of neutrino
oscillation to probe into the non-universality of the gravitational couplings
of neutrinos. We develop an appropriate formalism to deal with neutrino
propagation under the weak gravitational fields of the sun in the presence of
the flavor mixing. We point out that solar neutrino observation by the next
generation water Cherenkov detectors can improve the existing bound on
violation of the equivalence principle by 3-4 orders of magnitude if the
nonadiabatic Mikheyev-Smirnov-Wolfenstein mechanism is the solution to the
solar neutrino problem.Comment: Latex, 17 pages + 6 uuencoded postscript figures, KEK-TH-396,
TMUP-HEL-9402 (unnecessary one reference was removed
A Neutron Interferometric Method to Provide Improved Constraints on Non-Newtonian Gravity at the Nanometer Scale
In recent years, an energetic experimental program has set quite stringent
limits on a possible "non - 1/r^2" dependence on gravity at short length
scales. This effort has been largely driven by the predictions of theories
based on compactification of extra spatial dimensions. It is characteristic of
many such theories that the strength and length scales of such anomalous
gravity are not clearly determined from first principles. As a result, it is
productive to extend the current limits the range and strength of such
hypothetical interactions. As a heavy, neutral, and (almost) stable particle,
the neutron provides an ideal probe for the study of such hypothetical
interactions at very short range. In this work, we describe methods based on
neutron interferometry which have the capability to provide improved
sensitivity non-Newtonian forces down to length scales at and below an
nanometer.Comment: PDF-fil
Back reaction of a long range force on a Friedmann-Robertson-Walker background
It is possible that there may exist long-range forces in addition to gravity.
In this paper we construct a simple model for such a force based on exchange of
a massless scalar field and analyze its effect on the evolution of a
homogeneous Friedmann-Robertson-Walker cosmology. The presence of such an
interaction leads to an equation of state characterized by positive pressure
and to resonant particle production similar to that observed in preheating
scenarios.Comment: 14 pages, 6 color Postscript figures, LaTe
Neutrinos in a gravitational background: a test for the universality of the gravitational interaction
In this work we propose an extended formulation for the interaction between
neutrinos and gravitational fields. It is based on the parametrized
post-Newtonian aproach, and includes a violation of the universality of the
gravitational interaction which is non diagonal in the weak flavor space. We
find new effects that are not considered in the standard scenario for violation
of the equivalence principle. They are of the same order as the effects
produced by the Newtonian potential, but they are highly directional dependent
and could provide a very clean test of that violation. Phenomenological
consequences are briefly discussed.Comment: 18 pages, revtex, no figure
Cosmic strings in dilaton gravity
We examine the metric of an isolated self-gravitating abelian-Higgs vortex in
dilatonic gravity for arbitrary coupling of the vortex fields to the dilaton.
We look for solutions in both massless and massive dilaton gravity. We compare
our results to existing metrics for strings in Einstein and Jordan-Brans-Dicke
theory. We explore the generalization of Bogomolnyi arguments for our vortices
and comment on the effects on test particles.Comment: 24 pages plain TEX, 4 figures -- references amended, some additional
comments added, version to appear in journa
The fundamental constants and their variation: observational status and theoretical motivations
This article describes the various experimental bounds on the variation of
the fundamental constants of nature. After a discussion on the role of
fundamental constants, of their definition and link with metrology, the various
constraints on the variation of the fine structure constant, the gravitational,
weak and strong interactions couplings and the electron to proton mass ratio
are reviewed. This review aims (1) to provide the basics of each measurement,
(2) to show as clearly as possible why it constrains a given constant and (3)
to point out the underlying hypotheses. Such an investigation is of importance
to compare the different results, particularly in view of understanding the
recent claims of the detections of a variation of the fine structure constant
and of the electron to proton mass ratio in quasar absorption spectra. The
theoretical models leading to the prediction of such variation are also
reviewed, including Kaluza-Klein theories, string theories and other
alternative theories and cosmological implications of these results are
discussed. The links with the tests of general relativity are emphasized.Comment: 56 pages, l7 figures, submitted to Rev. Mod. Phy
A Possible Violation of the Equivalence Principle by Neutrinos
We consider the effect of a long range, flavor changing tensor interaction of
possible gravitational origin. Neutrino mixing experiments provide the most
sensitive probe to date for such forces---testing the equivalence principle at
levels below . Here we justify and generalize a formalism for
describing such effects. The constraints from neutrino mixing experiments on
gravitationally induced mixing are calculated. Our detailed analysis of the
atmospheric neutrino data confirms a remarkable result: the atmospheric
neutrino data implies the same size force as does the solar neutrino data.
Additional tests of this suggestive result are discussed.Comment: 45 pages of text, 5 figures available upon request to
[email protected]
The Confrontation between General Relativity and Experiment
The status of experimental tests of general relativity and of theoretical
frameworks for analysing them are reviewed. Einstein's equivalence principle
(EEP) is well supported by experiments such as the E\"otv\"os experiment, tests
of special relativity, and the gravitational redshift experiment. Future tests
of EEP and of the inverse square law will search for new interactions arising
from unification or quantum gravity. Tests of general relativity at the
post-Newtonian level have reached high precision, including the light
deflection, the Shapiro time delay, the perihelion advance of Mercury, and the
Nordtvedt effect in lunar motion. Gravitational wave damping has been detected
to half a percent using the binary pulsar, and new binary pulsar systems may
yield further improvements. When direct observation of gravitational radiation
from astrophysical sources begins, new tests of general relativity will be
possible.Comment: 103 pages, 10 figures, accepted for publication in Living Reviews in
Relativit
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