835 research outputs found
Proton Decay Constraints on Low Scale AdS/CFT Unification
Dark matter candidates and proton decay in a class of models based on the
AdS/CFT correspondence are discussed. We show that the present bound on the
proton decay lifetime is inconsistent with SUSY, and strongly
constrains non-SUSY, low scale trinification type unification of
orbifolded AdS models.Comment: 10 page
Killing the Straw Man: Does BICEP Prove Inflation at the GUT Scale?
The surprisingly large value of , the ratio of power in tensor to scalar
density perturbations in the CMB reported by the BICEP2 Collaboration, if
confirmed, provides strong evidence for Inflation at the GUT scale. While the
Inflationary signal remains the best motivated source, a large value of
alone would still allow for the possibility that a comparable gravitational
wave background might result from a self ordering scalar field (SOSF)
transition that takes place later at somewhat lower energy. We find that even
without detailed considerations of the predicted BICEP signature of such a
transition, simple existing limits on the isocurvature contribution to CMB
anisotropies would definitively rule out a contribution of more than to
,. We also present a general relation for the allowed fractional
SOSF contribution to as a function of the ultimate measured value of .
These results point strongly not only to an inflationary origin of the BICEP2
signal, if confirmed, but also to the fact that if the GUT scale is of order
then either the GUT transition happens before Inflation or the
Inflationary transition and the GUT transition must be one and the same.Comment: 3 pages 2 figures, accepted for publication in Physics Letters B .
Accepted version revised slightly in response to referee's comment
A new perspective on the relation between dark energy perturbations and the late-time ISW effect
The effect of quintessence perturbations on the ISW effect is studied for a
mixed dynamical scalar field dark energy (DDE) and pressureless perfect fluid
dark matter. A new and general methodology is developed to track the growth of
the perturbations, which uses only the equation of state (EoS) parameter
of the scalar field DDE,
and the initial values of the the relative entropy perturbation (between the
matter and DDE) and the intrinsic entropy perturbation of the scalar field DDE
as inputs. We also derive a relation between the rest frame sound speed
of an arbitrary DDE component and its EoS . We show that the ISW signal differs from that expected in a
CDM cosmology by as much as +20% to -80% for parameterizations of
consistent with SNIa data, and about 20% for
parameterizations of consistent with SNIa+CMB+BAO data, at 95%
confidence. Our results indicate that, at least in principle, the ISW effect
can be used to phenomenologically distinguish a cosmological constant from DDE.Comment: Accepted for publication at PR
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