5,404 research outputs found
Quantization of the universe as a black hole
It has been shown that black holes can be quantized by using Bohr's idea of
quantizing the motion of an electron inside the atom. We apply these ideas to
the universe as a whole. This approach reinforces the suggestion that it may be
a way to unify gravity with quantum theory.Comment: 7 pages. Accepted for publication in Astrophysics & Space Science in
25th Octuber 201
Seeable universe and its accelerated expansion: an observational test
From the equivalence principle, one gets the strength of the gravitational
effect of a mass on the metric at position r from it. It is proportional to
the dimensionless parameter , which normally is .
Here is the gravitational constant, the mass of the gravitating body,
the position of the metric from the gravitating body and the speed of
light. The seeable universe is the sphere, with center at the observer, having
a size such that it shall contain all light emitted within it. For this to
occur one can impose that the gravitational effect on the velocity of light at
is zero for the radial component, and non zero for the tangential one.
Light is then trapped. The condition is given by the equality ,
where represents the radius of the {\it seeable} universe. It is the
gravitational radius of the mass . The result has been presented elsewhere
as the condition for the universe to be treated as a black hole. According to
present observations, for the case of our universe taken as flat (), and
the equation of state as , we prove here from the Einstein's
cosmological equations that the universe is expanding in an accelerated way as
, a constant acceleration as has been observed. This implies that the
gravitational radius of the universe (at the event horizon) expands as .
Taking as constant, observing the galaxies deep in space this means deep in
time as , linear. Then, far away galaxies from the observer that we see
today will disappear in time as they get out of the distance ct that is . The accelerated expanding vacuum will drag them out of sight. This may be
a valid test for the present ideas in cosmology. Previous calculations are here
halved by our results.Comment: 15 pages, 2 figure
Three-Dimensional Wave Packet Approach for the Quantum Transport of Atoms through Nanoporous Membranes
Quantum phenomena are relevant to the transport of light atoms and molecules
through nanoporous two-dimensional (2D) membranes. Indeed, confinement provided
by (sub-)nanometer pores enhances quantum effects such as tunneling and zero
point energy (ZPE), even leading to quantum sieving of different isotopes of a
given element. However, these features are not always taken into account in
approaches where classical theories or approximate quantum models are
preferred. In this work we present an exact three-dimensional wave packet
propagation treatment for simulating the passage of atoms through periodic 2D
membranes. Calculations are reported for the transmission of He and He
through graphdiyne as well as through a holey graphene model. For
He-graphdiyne, estimations based on tunneling-corrected transition state theory
are correct: both tunneling and ZPE effects are very important but competition
between each other leads to a moderately small He/He selectivity. Thus,
formulations that neglect one or another quantum effect are inappropriate. For
the transport of He isotopes through leaky graphene, the computed transmission
probabilities are highly structured suggesting widespread selective adsorption
resonances and the resulting rate coefficients and selectivity ratios are not
in agreement with predictions from transition state theory. Present approach
serves as a benchmark for studies of the range of validity of more approximate
methods.Comment: 4 figure
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