4,997 research outputs found
Universality in the Gravitational Stretching of Clocks, Waves and Quantum States
There are discernible and fundamental differences between clocks, waves and
physical states in classical physics. These fundamental concepts find a common
expression in the context of quantum physics in gravitational fields; matter
and light waves, quantum states and oscillator clocks become quantum synonymous
through the Planck-Einstein-de Broglie relations and the equivalence principle.
With this insight, gravitational effects on quantum systems can be simply and
accurately analyzed. Apart from providing a transparent framework for
conceptual and quantitative thinking on matter waves and quantum states in a
gravitational field, we address and resolve with clarity the recent
controversial discussions on the important issue of the relation and the
crucial difference between gravimetery using atom interferometers and the
measurement of gravitational time dilation.Comment: Gravity Research Foundation honorable mention, 201
Can cosmological observations uniquely determine the nature of dark energy ?
The observational effect of all minimally coupled scalar field models of dark
energy can be determined by the behavior of the following two parameters : (1)
equation of state parameter , which relates dark energy pressure to its
energy density, and (2) effective speed of sound , which relates
dark energy pressure fluctuation to its density fluctuation. In this paper we
show that these two parameters do not uniquely determine the form of a scalar
field dark energy Lagrangian even after taking into account the perturbation in
the scalar field. We present this result by showing that two different forms of
scalar field Lagrangian can lead to the same values for these paired
parameters. It is well known that from the background evolution the Lagrangian
of the scalar field dark energy cannot be uniquely determined. The two models
of dark energy presented in this paper are indistinguishable from the evolution
of background as well as from the evolution of perturbations from a FRW metric.Comment: 9 pages, 2 figures, few references adde
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