146 research outputs found
Field Configurations and their Instability Induced by Higher Dimensions of Spacetime: An Example
We use the model of L. Randall et al to investigate the stability of allowed quantum field configurations. Firstly, we find that due to the topology of this 5 dimensional model, there are 2 possible configurations of the scalar field, untwisted and twisted. Secondly, when allowed to interact the untwisted field is shown to be unstable even if it is at the true vacuum groundstate as a result of one-loop corrections that arise from coupling with the twisted field. The twisted field can make the two 3-branes (that are otherwise identical in their properties and geometry) distinguishable. That is due to the antiperiodicity of the twisted fields, when rotating with to go from one 3-brane to the other. This toy model is simple enough to use to illustrate a point that can be important for the general case of any high dimension model, namely: higher dimensions, besides many other effects can also induce more than one field configuration and that can have consequences (e.g. instabilities) even after reducing the problem to 4 dimensions
Why the Universe Started from a Low Entropy State
We show that the inclusion of backreaction of massive long wavelengths
imposes dynamical constraints on the allowed phase space of initial conditions
for inflation, which results in a superselection rule for the initial
conditions. Only high energy inflation is stable against collapse due to the
gravitational instability of massive perturbations. We present arguments to the
effect that the initial conditions problem {\it cannot} be meaningfully
addressed by thermostatistics as far as the gravitational degrees of freedom
are concerned. Rather, the choice of the initial conditions for the universe in
the phase space and the emergence of an arrow of time have to be treated as a
dynamic selection.Comment: 12 pages, 2 figs. Final version; agrees with accepted version in
Phys. Rev.
Kinematical solution of the UHE-cosmic-ray puzzle without a preferred class of inertial observers
Among the possible explanations for the puzzling observations of cosmic rays
above the GZK cutoff there is growing interest in the ones that represent
kinematical solutions, based either on general formulations of particle physics
with small violations of Lorentz symmetry or on a quantum-gravity-motivated
scheme for the breakup of Lorentz symmetry. An unappealing aspect of these
cosmic-ray-puzzle solutions is that they require the existence of a preferred
class of inertial observers. Here I propose a new kinematical solution of the
cosmic-ray puzzle, which does not require the existence of a preferred class of
inertial observers. My proposal is a new example of a type of relativistic
theories, the so-called "doubly-special-relativity" theories, which have
already been studied extensively over the last two years. The core ingredient
of the proposal is a deformation of Lorentz transformations in which also the
Planck scale (in addition to the speed-of-light scale ) is described
as an invariant. Just like the introduction of the invariant requires a
deformation of the Galileian transformations into the Lorentz transformations,
the introduction of the invariant requires a deformation of the Lorentz
transformations, but there is no special class of inertial observers. The
Pierre Auger Observatory and the GLAST space telescope should play a key role
in future developments of these investigations. I also emphasize that the
doubly-special-relativity theory here proposed, besides being the first one to
provide a solution for the cosmic-ray puzzle, is also the first one in which a
natural description of macroscopic bodies is achieved, and may find
applications in the context of a recently-proposed dark-energy scenario.Comment: LaTex (revtex), 9 page
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