5 research outputs found
Acceleressence: Dark Energy from a Phase Transition at the Seesaw Scale
Simple models are constructed for "acceleressence" dark energy: the latent
heat of a phase transition occurring in a hidden sector governed by the seesaw
mass scale v^2/M_Pl, where v is the electroweak scale and M_Pl the
gravitational mass scale. In our models, the seesaw scale is stabilized by
supersymmetry, implying that the LHC must discover superpartners with a
spectrum that reflects a low scale of fundamental supersymmetry breaking.
Newtonian gravity may be modified by effects arising from the exchange of
fields in the acceleressence sector whose Compton wavelengths are typically of
order the millimeter scale. There are two classes of models. In the first class
the universe is presently in a metastable vacuum and will continue to inflate
until tunneling processes eventually induce a first order transition. In the
simplest such model, the range of the new force is bounded to be larger than 25
microns in the absence of fine-tuning of parameters, and for couplings of order
unity it is expected to be \approx 100 microns. In the second class of models
thermal effects maintain the present vacuum energy of the universe, but on
further cooling, the universe will "soon" smoothly relax to a matter dominated
era. In this case, the range of the new force is also expected to be of order
the millimeter scale or larger, although its strength is uncertain. A firm
prediction of this class of models is the existence of additional energy
density in radiation at the eV era, which can potentially be probed in
precision measurements of the cosmic microwave background. An interesting
possibility is that the transition towards a matter dominated era has occurred
in the very recent past, with the consequence that the universe is currently
decelerating.Comment: 10 pages, references adde
Sub-millimeter Tests of the Gravitational Inverse-square Law
Motivated by a variety of theories that predict new effects, we tested the
gravitational 1/r^2 law at separations between 10.77 mm and 137 microns using
two different 10-fold azimuthally symmetric torsion pendulums and rotating
10-fold symmetric attractors. Our work improves upon other experiments by up to
a factor of about 100. We found no deviation from Newtonian physics at the 95%
confidence level and interpret these results as constraints on extensions of
the Standard Model that predict Yukawa or power-law forces. We set a constraint
on the largest single extra dimension (assuming toroidal compactification and
that one extra dimension is significantly larger than all the others) of R <=
160 microns, and on two equal-sized large extra dimensions of R <= 130 microns.
Yukawa interactions with |alpha| >= 1 are ruled out at 95% confidence for
lambda >= 197 microns. Extra-dimensions scenarios stabilized by radions are
restricted to unification masses M >= 3.0 TeV/c^2, regardless of the number of
large extra dimensions. We also provide new constraints on power-law potentials
V(r)\propto r^{-k} with k between 2 and 5 and on the gamma_5 couplings of
pseudoscalars with m <= 10 meV/c^2.Comment: 34 pages, 38 figure
Bose-Einstein Condensation, Dark Matter and Acoustic Peaks
Scalar mediated interactions among baryons extend well above the Compton
wavelength, when they are embedded in a Bose-Einstein condensate composed of
the mediating particles. Indeed, this non-trivial environment results in an
infinite-ranged interaction. We show that if the Dark Matter of the Universe is
composed of such a condensate, the imprints of an interaction between baryonic
and Dark Matter could be manifest as anomalies in the peak structure of the
Cosmic Microwave Background.Comment: 11 pages, 2 figures; changes reflect published versio