58 research outputs found
Interacting Dark Energy and the Cosmic Coincidence Problem
The introduction of an interaction for dark energy to the standard cosmology
offers a potential solution to the cosmic coincidence problem. We examine the
conditions on the dark energy density that must be satisfied for this scenario
to be realized. Under some general conditions we find a stable attractor for
the evolution of the Universe in the future. Holographic conjectures for the
dark energy offer some specific examples of models with the desired properties.Comment: 8 pages, 3 figures, Phys. Rev. D versio
Combined flavor symmetry violation and lepton number violation in neutrino physics
Heavy singlet neutrinos admit Majorana masses which are not possible for the
Standard Model particles. This suggest new possibilities for generating the
masses and mixing angles of light neutrinos. We present a model of neutrino
physics which combines the source of lepton number violation with the flavor
symmetry responsible for the hierarchy in the charged lepton and quark sector.
This is accomplished by giving the scalar field effecting the lepton number
violation a nonzero charge under the horizontal flavor symmetry. We find an
economical model which is consistent with the measured values of the
atmospheric and solar neutrino mass-squares and mixing angles.Comment: 6 pages, no figures (published version
An Interacting Dark Energy Model for the Expansion History of the Universe
We explore a model of interacting dark energy where the dark energy density
is related by the holographic principle to the Hubble parameter, and the decay
of the dark energy into matter occurs at a rate comparable to the current value
of the Hubble parameter. We find this gives a good fit to the observational
data supporting an accelerating Universe, and the model represents a possible
alternative interpretation of the expansion history of the Universe.Comment: 6 pages, 2 figures, Phys. Rev. D versio
Signals for Low Scale Gravity in the Process
We investigate the sensitivity of future photon-photon colliders to low scale
gravity scenarios via the process where the Kaluza-Klein
boson exchange contributes only when the initial state photons have opposite
helicity. We contrast this with the situation for the process where the and channel also contribute. We include
the one-loop Standard Model background whose interference with the graviton
exchange determines the experimental reach in measuring any deviation from the
Standard Model expectations and explore how polarization can be exploited to
enhance the signal over background. We find that a 1 TeV linear collider has an
experimental reach to mass scale of about 4 TeV in this channel.Comment: 20 pages, 8 figure
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