96 research outputs found
Polarized Proton Scattering at 134 MeV from 154-Sm and 166-Er
This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit
Racetrack inflation and assisted moduli stabilisation
We present a model of inflation based on a racetrack model without flux
stabilization. The initial conditions are set automatically through topological
inflation. This ensures that the dilaton is not swept to weak coupling through
either thermal effects or fast roll. Including the effect of non-dilaton fields
we find that moduli provide natural candidates for the inflaton. The resulting
potential generates slow-roll inflation without the need to fine tune
parameters. The energy scale of inflation must be near the GUT scale and the
scalar density perturbation generated has a spectrum consistent with WMAP data.Comment: 17 pages, 6 figures (Latex); Error in v.1 eliminated and improved
example of modular inflation presente
The 13-C(p,d) Reaction at 120 MeV
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
N=1 Supergravity Chaotic Inflation in the Braneworld Scenario
We study a N=1 Supergravity chaotic inflationary model, in the context of the
braneworld scenario. It is shown that successful inflation and reheating
consistent with phenomenological constraints can be achieved via the new terms
in the Friedmann equation arising from brane physics. Interestingly, the model
satisfies observational bounds with sub-Planckian field values, implying that
chaotic inflation on the brane is free from the well known difficulties
associated with the presence of higher order non-renormalizable terms in the
superpotential. A bound on the mass scale of the fifth dimension, M_5 \gsim
1.3 \times 10^{-6} M_P, is obtained from the requirement that the reheating
temperature be higher than the temperature of the electroweak phase transition.Comment: 5 pages, 1 Table, Revtex
Supernovae as a probe of particle physics and cosmology
It has very recently been demonstrated by Csaki, Kaloper and Terning (CKT)
that the faintness of supernovae at high redshift can be accommodated by mixing
of a light axion with the photon in the presence of an intergalactic magnetic
field, as opposed to the usual explanation of an accelerating universe by a
dark energy component. In this paper we analyze further aspects of the CKT
mechanism and its generalizations. The CKT mechanism also passes various
cosmological constraints from the fluctuations of the CMB and the formation of
structure at large scales, without requiring an accelerating phase in the
expansion of the Universe. We investigate the statistical significance of
current supernova data for pinning down the different components of the
cosmological energy-momentum tensor and for probing physics beyond the standard
models.Comment: 17 pages, LaTeX, 4 figures; v2: typos corrected, minor changes,
references added; v3: updated figures, details regarding fits include
D0 Matrix Mechanics: New Fuzzy Solutions at Large N
We wish to consider in this report the large N limit of a particular matrix
model introduced by Myers describing D-brane physics in the presence of an RR
flux background. At finite N, fuzzy spheres appear naturally as non-trivial
solutions to this matrix model and have been extensively studied. In this
report, we wish to demonstrate several new classes of solutions which appear in
the large N limit, corresponding to the fuzzy cylinder,the fuzzy plane and a
warped fuzzy plane. The latter two solutions arise from a possible "central
extension" to our model that arises after we account for non-trivial issues
involved in the large N limit. As is the case for finite N, these new solutions
are to be interpreted as constituent D0-branes forming D2 bound states
describing new fuzzy geometries.Comment: revised version: references added, derivation of "central extensions"
improved upon. To appear in JHE
Supergravity Inflation Free from Harmful Relics
We present a realistic supergravity inflation model which is free from the
overproduction of potentially dangerous relics in cosmology, namely moduli and
gravitinos which can lead to the inconsistencies with the predictions of baryon
asymmetry and nucleosynthesis. The radiative correction turns out to play a
crucial role in our analysis which raises the mass of supersymmetry breaking
field to intermediate scale. We pay a particular attention to the non-thermal
production of gravitinos using the non-minimal Kahler potential we obtained
from loop correction. This non-thermal gravitino production however is
diminished because of the relatively small scale of inflaton mass and small
amplitudes of hidden sector fields.Comment: 10 pages, revtex, 1 eps figure, references added, conclusion section
expande
A Circulating Hydrogen Ultra-High Purification System for the MuCap Experiment
The MuCap experiment is a high-precision measurement of the rate for the
basic electroweak process of muon capture, mu- + p -> n + nu . The experimental
approach is based on an active target consisting of a time projection chamber
(TPC) operating with pure hydrogen gas. The hydrogen has to be kept extremely
pure and at a stable pressure. A Circulating Hydrogen Ultrahigh Purification
System was designed at the Petersburg Nuclear Physics Institute (PNPI) to
continuously clean the hydrogen from impurities. The system is based on an
adsorption cryopump to stimulate the hydrogen flow and on a cold adsorbent for
the hydrogen cleaning. It was installed at the Paul Scherrer Institute (PSI) in
2004 and performed reliably during three experiment runs. During several months
long operating periods the system maintained the hydrogen purity in the
detector on the level of 20 ppb for moisture, which is the main contaminant,
and of better than 7 ppb and 5 ppb for nitrogen and oxygen, respectively. The
pressure inside the TPC was stabilized to within 0.024% of 10 bar at a hydrogen
flow rate of 3 standard liters per minute.Comment: submitted to Nucl. Instr. Methods Phys. Res.
Soft Masses in Strong Unification
We examine the infra-red structure of soft supersymmetry breaking masses of
the squarks and sleptons in supersymmetric (SUSY) strong unification schemes
where . We show that combinations of soft masses
approach fixed points which leads to very simple predictions for soft masses at
the intermediate scale. The assumption that the high energy gaugino mass
dominates over the soft scalar masses leads to a strong suppression
of flavour changing neutral currents, and a low energy SUSY spectrum which is
simply predicted in terms of two parameters, namely and
. Due to the quickly falling gauge couplings beneath the high energy
scale, the low energy spectrum has a characteristic ``scalar dominated''
signature quite unlike the standard gaugino dominated MSSM where the
right-handed sleptons are predicted to be rather light. We also examine the new
sources of flavour changing expected in such models, and in particular show
that the flavour violation coming from the D-term of a gauged family
symmetry may be reduced to an acceptable level.Comment: 49 pages, Late
Path Integral Monte Carlo Approach to the U(1) Lattice Gauge Theory in (2+1) Dimensions
Path Integral Monte Carlo simulations have been performed for U(1) lattice
gauge theory in (2+1) dimensions on anisotropic lattices. We extractthe static
quark potential, the string tension and the low-lying "glueball" spectrum.The
Euclidean string tension and mass gap decrease exponentially at weakcoupling in
excellent agreement with the predictions of Polyakov and G{\" o}pfert and Mack,
but their magnitudes are five times bigger than predicted. Extrapolations are
made to the extreme anisotropic or Hamiltonian limit, and comparisons are made
with previous estimates obtained in the Hamiltonian formulation.Comment: 12 pages, 16 figure
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