9,380 research outputs found
Solving Cosmological Problems of Supersymmetric Axion Models in an Inflationary Universe
We revisit inflationary cosmology of axion models in the light of recent
developments on the inflaton decay in supergravity. We find that all the
cosmological difficulties, including gravitino, axino overproduction and
axionic isocurvature fluctuation, can be avoided if the saxion field has large
initial amplitude during inflation and decays before big-bang nucleosynthesis.Comment: 19 pages, 4 figure
Mode coupling theory in the FDR-preserving field theory of interacting Brownian particles
We develop a renormalized perturbation theory for the dynamics of interacting
Brownian particles, which preserves the fluctuation-dissipation relation order
by order. We then show that the resulting one-loop theory gives a closed
equation for the density correlation function, which is identical with that in
the standard mode coupling theory.Comment: version to be published in Fast Track Communication in Journal of
Physics A:Math. Theo
Baryon Asymmetry in a Heavy Moduli Scenario
In some models of supersymmetry breaking, modulus fields are heavy enough to
decay before BBN. But the large entropy produced via moduli decay significantly
dilutes the preexisting baryon asymmetry of the universe. We study whether
Affleck-Dine mechanism can provide enough baryon asymmetry which survives the
dilution, and find several situations in which desirable amount of baryon
number remains after the dilution. The possibility of non-thermal dark matter
is also discussed. This provides the realistic cosmological scenario with heavy
moduli.Comment: 36 pages, 5 figures; added a reference; v3: minor correction
New Superconducting and Magnetic Phases Emerge on the Verge of Antiferromagnetism in CeIn
We report the discovery of new superconducting and novel magnetic phases in
CeIn on the verge of antiferromagnetism (AFM) under pressure () through
the In-nuclear quadrupole resonance (NQR) measurements. We have found a
-induced phase separation of AFM and paramagnetism (PM) without any trace
for a quantum phase transition in CeIn. A new type of superconductivity
(SC) was found in GPa to coexist with AFM that is magnetically
separated from PM where the heavy fermion SC takes place. We propose that the
magnetic excitations such as spin-density fluctuations induced by the
first-order magnetic phase transition might mediate attractive interaction to
form Cooper pairs.Comment: 4 pages, 4 EPS figures, submitted to J. Phys. Soc. Jp
^{115}In-NQR evidence for unconventional superconductivity in CeIn_3 under pressure
We report evidence for unconventional superconductivity in CeIn_3 at a
pressure P = 2.65 GPa above critical pressure (P_c ~ 2.5 GPa) revealed by the
measurements of nuclear-spin-lattice-relaxation time (T_1) and
ac-susceptibility (ac-chi). Both the measurements of T_1 and ac-chi have
pointed to a superconducting transition at T_c = 95 mK, which is much lower
than an onset temperature T_{onset} = 0.15 K at zero resistance. The
temperature dependence of 1/T_1 shows no coherence peak just below T_c,
indicative of an unconventional nature for the superconductivity induced in
CeIn_3.Comment: 4 pages, 4 figures, to be published in Phys.Rev.
Spectrum of Background X-rays from Moduli Dark Matter
We examine the -ray spectrum from the decay of the dark-matter moduli with
mass keV, in particular, paying attention to the line
spectrum from the moduli trapped in the halo of our galaxy. It is found that
with the energy resolution of the current experiments (%) the line
intensity is about twice stronger than that of the continuum spectrum from the
moduli that spread in the whole universe. Therefore, in the future experiments
with higher energy resolutions it may be possible to detect such line photons.
We also investigate the -ray spectrum emitted from the decay of the
multi-GeV moduli. It is shown that the emitted photons may form MeV-bump in the
-ray spectrum. We also find that if the modulus mass is of the order of
10 GeV, the emitted photons at the peak of the continuum spectrum loses their
energy by the scattering and the shape of the spectrum is significantly
changed, which makes the constraint weaker than that obtained in the previous
works.Comment: 14 pages (RevTeX file) including four postscript figures, reviced
version to be published in Physical Review
Inflation from a Supersymmetric Axion Model
We show that a supersymmetric axion model naturally induces a hybrid
inflation with the waterfall field identified as a Peccei-Quinn scalar. The
Peccei-Quinn scale is predicted to be around 10^{15}GeV for reproducing the
large-scale density perturbation of the Universe. After the built-in late-time
entropy-production process, the axion becomes a dark matter candidate. Several
cosmological implications are discussed.Comment: 5 pages; to appear in PR
A Study of Gaussianity in CMB band maps
The detection of non-Gaussianity in the CMB data would rule out a number of
inflationary models. A null detection of non-Gaussianity, instead, would
exclude alternative models for the early universe. Thus, a detection or
non-detection of primordial non-Gaussianity in the CMB data is crucial to
discriminate among inflationary models, and to test alternative scenarios.
However, there are various non-cosmological sources of non-Gaussianity. This
makes important to employ different indicators in order to detect distinct
forms of non-Gaussianity in CMB data. Recently, we proposed two new indicators
to measure deviation from Gaussianity on large angular scales, and used them to
study the Gaussianity of the raw band WMAP maps with and without the KQ75 mask.
Here we extend this work by using these indicators to perform similar analyses
of deviation from Gaussianity of the foreground-reduced Q, V, and W band maps.
We show that there is a significant deviation from Gaussianity in the
considered full-sky maps, which is reduced to a level consistent with
Gaussianity when the KQ75 mask is employed.Comment: 5 pages, 2 PS figures, uses ws-ijmpd.cls ; to be published in the
International Journal of Modern Physics
Statistics of Bubble Rearrangements in a Slowly Sheared Two-dimensional Foam
Many physical systems exhibit plastic flow when subjected to slow steady
shear. A unified picture of plastic flow is still lacking; however, there is an
emerging theoretical understanding of such flows based on irreversible motions
of the constituent ``particles'' of the material. Depending on the specific
system, various irreversible events have been studied, such as T1 events in
foam and shear transformation zones (STZ's) in amorphous solids. This paper
presents an experimental study of the T1 events in a model, two-dimensional
foam: bubble rafts. In particular, I report on the connection between the
distribution of T1 events and the behavior of the average stress and average
velocity profiles during both the initial elastic response of the bubble raft
and the subsequent plastic flow at sufficiently high strains
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