388 research outputs found
Detection of Gravitational Waves from Inflation
Recent measurements of temperature fluctuations in the cosmic microwave
background (CMB) indicate that the Universe is flat and that large-scale
structure grew via gravitational infall from primordial adiabatic
perturbations. Both of these observations seem to indicate that we are on the
right track with inflation. But what is the new physics responsible for
inflation? This question can be answered with observations of the polarization
of the CMB. Inflation predicts robustly the existence of a stochastic
background of cosmological gravitational waves with an amplitude proportional
to the square of the energy scale of inflation. This gravitational-wave
background induces a unique signature in the polarization of the CMB. If
inflation took place at an energy scale much smaller than that of grand
unification, then the signal will be too small to be detectable. However, if
inflation had something to do with grand unification or Planck-scale physics,
then the signal is conceivably detectable in the optimistic case by the Planck
satellite, or if not, then by a dedicated post-Planck CMB polarization
experiment. Realistic developments in detector technology as well as a proper
scan strategy could produce such a post-Planck experiment that would improve on
Planck's sensitivity to the gravitational-wave background by several orders of
magnitude in a decade timescale.Comment: 13 page, 4 figures. To appear in the proceedings of DPF2000,
Columbus, 9-12 August 2000 and (with slight revisions) in the proceedings of,
"Gravitational Waves: A Challenge to Theoretical Astrophysics," Trieste, 5-9
June 200
Cosmological constraints on pseudo-Nambu-Goldstone bosons
Particle physics models with pseudo-Nambu-Goldstone bosons (PNGBs) are characterized by two mass scales: a global spontaneous symmetry breaking scale, f, and a soft (explicit) symmetry breaking scale, Lambda. General model insensitive constraints were studied on this 2-D parameter space arising from the cosmological and astrophysical effects of PNGBs. In particular, constraints were studied arising from vacuum misalignment and thermal production of PNGBs, topological defects, and the cosmological effects of PNGB decay products, as well as astrophysical constraints from stellar PNGB emission. Bounds on the Peccei-Quinn axion scale, 10(exp 10) GeV approx. = or less than f sub pq approx. = or less than 10(exp 10) to 10(exp 12) GeV, emerge as a special case, where the soft breaking scale is fixed at Lambda sub QCD approx. = 100 MeV
Limits on Neutrino Radiative Decay from Sn1987a
We calculate limits on the properties of neutrinos using data from gamma-ray
detectors on the Pioneer Venus Orbiter and Solar Max Mission satellites. A
massive neutrino decaying in flight from the supernova would produce gamma rays
detectable by these instruments. The lack of such a signal allows us to
constrain the mass, radiative lifetime, and branching ratio to photons of a
massive neutrino species produced in the supernova. Presented at Beyond The
Standard Model III, June, 1992.Comment: 5 Pages, 2 Figures (avalable on request). LaTeX, WorldSci.st
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