61,397 research outputs found
Measurement-induced interference in an inhomogeneous gravitational field
A very interesting quantum mechanical effect is the emergence of
gravity-induced interference, which has already been detected. This effect also
shows us that gravity is at the quantum level not a purely geometric effect,
the mass of the employed particles appears explicitly in the interference
expression. In this work we will generalize some previous results. It will be
shown that the introduction of a second order approximation in the propagator
of a particle, immersed in the Earth's gravitational field, and whose
coordinates are being continuously monitored, allows us to include, in the
corresponding complex oscillator, a frequency which now depends on the geometry
of the source of the gravitational field, a fact that is absent in the case of
a homogeneous field. Using this propagator we will analyze the interference
pattern of two particle beams whose coordinates are being continuously
monitored. We will compare our results againt the case of a homogeneous field,
and also against the measurement ouputs of the Colella, Overhauser, and Werner
experiment, and find that the difference in the dependence upon the geometry of
the source of the gravitational field could render detectable differences in
their respective measurement outputs.Comment: 15 pages, accepted in Physics Letters
Group-theoretical structure of quantum measurements and equivalence principle
The transverse group associated to some continuous quantum measuring
processes is analyzed in the presence of nonvanishing gravitational fields.
This is done considering, as an exmaple, the case of a particle whose
coordinates are being monitored. Employing the so called restricted path
integral formalism, it will be shown that the measuring process could always
contain information concerning the gravitational field. In other words, it
seems that with the presence of a measuring process the equivalence principle
may, in some cases, break down. The relation between the breakdown of the
equivalence principle, at quantum level, and the fact that the gravitational
field could act always as a decoherence environment, is also considered. The
phenomena of quantum beats of quantum optics will allow us to consider the
possibility that the experimental corroboration of the equivalence principle at
quantum level could be taken as an indirect evidence in favor of the
quantization of the gravitational field, i.e., the quantum properties of this
field avoid the violation of the equivalence principle.Comment: 13 pages, accepted in Modern Physics Letters
Comment on "Chain Length Scaling of Protein Folding Time", PRL 77, 5433 (1996)
In a recent Letter, Gutin, Abkevich, and Shakhnovich (GAS) reported on a
series of dynamical Monte Carlo simulations on lattice models of proteins.
Based on these highly simplified models, they found that four different
potential energies lead to four different folding time scales tau_f, where
tau_f scales with chain length as N^lambda (see, also, Refs. [2-4]), with
lambda varying from 2.7 to 6.0. However, due to the lack of microscopic models
of protein folding dynamics, the interpretation and origin of the data have
remained somewhat speculative. It is the purpose of this Comment to point out
that the application of a simple "mesoscopic" model (cond-mat/9512019, PRL 77,
2324, 1996) of protein folding provides a full account of the data presented in
their paper. Moreover, we find a major qualitative disagreement with the
argumentative interpretation of GAS. Including, the origin of the dynamics, and
size of the critical folding nucleus.Comment: 1 page Revtex, 1 fig. upon request. Submitted to PR
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