214 research outputs found
Energy Density in Expanding Universes as Seen by Unruh's Detector
We consider the response of an Unruh detector to scalar fields in an
expanding space-time. When combining transition elements of the scalar field
Hamiltonian with the interaction operator of detector and field, one finds at
second order in time-dependent perturbation theory a transition amplitude,
which actually dominates in the ultraviolet over the first order contribution.
In particular, the detector response faithfully reproduces the particle number
implied by the stress-energy of a minimally coupled scalar field, which is
inversely proportional to the energy of a scalar mode. This finding disagrees
with the contention that in de Sitter space, the response of the detector drops
exponentially with particle energy and therefore indicates a thermal spectrum.Comment: 15 pages, 1 figur
Baryogenesis from the amplification of vacuum fluctuations during inflation
We propose that the baryon asymmetry of the Universe may originate from the
amplification of quantum fluctuations of a light complex scalar field during
inflation. CP-violation is sourced by complex mass terms, which are smaller
than the Hubble rate, as well as non-standard kinetic terms. We find that, when
assuming 60 e-folds of inflation, an asymmetry in accordance with observation
can result for models where the energy scale of inflation is of the order of
10^16 GeV. Lower scales may be achieved when assuming substantially larger
amounts of e-folds.Comment: 18 page
Case Study of Multiyear Precipitation Variations and the Hydrology of Fort Cobb Reservoir
Impacts of decadal precipitation variations on reservoir inflow, flood releases, and pool elevation were investigated for the Fort Cobb Reservoir, which controls runoff from a 787 km2 agricultural watershed in central Oklahoma. The difference in mean annual precipitation between multiyear dry and wet periods was 33% of the long-term mean and led to a corresponding 100% change in mean reservoir inflow, 170% change in mean annual flood releases from the reservoir, and a maximum drop in conservation pool elevation of 2 m. From a reservoir operations perspective, only the frequency of controlled flood releases was impacted by decadal precipitation variations. These flood releases were sporadic in nature, and the more frequent releases during wet periods were not believed to appreciably enhance stream habitat and riparian vegetation downstream of the reservoir. It was further reasoned that large differences in annual reservoir inflow due to decadal precipitation variations would likely be accompanied by related changes in upstream soil erosion and reservoir sediment loading. With regard to hydrologic and environmental modeling, it was argued that decadal precipitation variations had important implications for model calibration, verification, and subsequent application. Overall, this case study demonstrated watershed and reservoir hydrology were sensitive to decadal precipitation variations and suggested that decadal precipitation variations deserved careful consideration in hydrologic and water quality investigations in central Oklahoma
Lepton-mediated electroweak baryogenesis
We investigate the impact of the tau and bottom Yukawa couplings on the
transport dynamics for electroweak baryogenesis in supersymmetric extensions of
the Standard Model. Although it has generally been assumed in the literature
that all Yukawa interactions except those involving the top quark are
negligible, we find that the tau and bottom Yukawa interaction rates are too
fast to be neglected. We identify an illustrative "lepton-mediated electroweak
baryogenesis" scenario in which the baryon asymmetry is induced mainly through
the presence of a left-handed leptonic charge. We derive analytic formulae for
the computation of the baryon asymmetry that, in light of these effects, are
qualitatively different from those in the established literature. In this
scenario, for fixed CP-violating phases, the baryon asymmetry has opposite sign
compared to that calculated using established formulae.Comment: 26 pages, 5 figure
Unruh response functions for scalar fields in de Sitter space
We calculate the response functions of a freely falling Unruh detector in de
Sitter space coupled to scalar fields of different coupling to the curvature,
including the minimally coupled massless case. Although the responses differ
strongly in the infrared as a consequence of the amplification of superhorizon
modes, the energy levels of the detector are thermally populated.Comment: 16 pages, 1 figure, accepted for publication by Classical and Quantum
Gravit
Yukawa Interactions and Supersymmetric Electroweak Baryogenesis
We analyze the quantum transport equations for supersymmetric electroweak
baryogenesis including previously neglected bottom and tau Yukawa interactions
and show that they imply the presence of a previously unrecognized dependence
of the cosmic baryon asymmetry on the spectrum of third generation quark and
lepton superpartners. For fixed values of the CP-violating phases in the
supersymmetric theory, the baryon asymmetry can vary in both magnitude and sign
as a result of the squark and slepton mass dependence. For light, right-handed
top and bottom quark superpartners, the baryon number creation can be driven
primarily by interactions involving third generation leptons and their
superpartners.Comment: 4 pages, 1 figur
- …