12,714 research outputs found
Interacting Dipoles in Type-I Clathrates: Why Glass-like though Crystal?
Almost identical thermal properties of type-I clathrate compounds to those of
glasses follow naturally from the consideration that off-centered guest ions
possess electric dipole moments. Local fields from neighbor dipoles create many
potential minima in the configuration space. A theoretical analysis based on
two-level tunneling states demonstrates that interacting dipoles are a key to
quantitatively explain the glass-like behaviors of low-temperature thermal
properties of type-I clathrate compounds with off-centered guest ions.From this
analysis, we predict the existence of a glass transition
Stability of the Accretion Flows with Stalled Shocks in Core-Collapse Supernovae
Bearing in mind the application to the theory of core-collapse supernovae, we
performed a global linear analysis on the stability of spherically symmetric
accretion flows through a standing shock wave onto a proto neutron star. As
unperturbed flows, we adopted the spherically symmetric steady solutions to the
Euler equations obtained with realistic equation of state and formulae for
neutrino reaction rates taken into account. Then we solved the equations for
linear perturbations numerically, and obtained the eigen frequencies and eigen
functions. We found (1) the flows are stable for all modes if the neutrino
luminosity is lower than ergs/s for
. (2) For larger luminosities, the non-radial
instabilities are induced, probably via the advection-acoustic cycles.
Interestingly, the modes with and 3 become unstable at first for
relatively low neutrino luminosities, e.g. ergs/s
for the same accretion rate, whereas the mode is the most unstable for
higher luminosities, ergs/s. These are all oscillatory
modes. (3) For still larger luminosities, ergs/s for
, non-oscillatory modes, both radial and
non-radial, become unstable. These non-radial modes were identified as
convection. We confirmed the results obtained by numerical simulations that the
instabilities induced by the advection-acoustic cycles are more important than
the convection for lower neutrino luminosities.Comment: 46 pages, 19 figures, Accepted by Ap
Localization-delocalization transition in one-dimensional electron systems with long-range correlated disorder
We investigate localization properties of electron eigenstates in
one-dimensional (1d) systems with long-range correlated diagonal disorder.
Numerical studies on the localization length of eigenstates demonstrate
the existence of the localization-delocalization transition in 1d systems and
elucidate non-trivial behavior of as a function of the disorder strength.
The critical exponent for localization length is extracted for various
values of parameters characterizing the disorder, revealing that every
disobeys the Harris criterion .Comment: 6 pages, 6 figuers, to be published in Phys. Rev.
Low-scale Supersymmetry from Inflation
We investigate an inflation model with the inflaton being identified with a
Higgs boson responsible for the breaking of U(1)B-L symmetry. We show that
supersymmetry must remain a good symmetry at scales one order of magnitude
below the inflation scale, in order for the inflation model to solve the
horizon and flatness problems, as well as to account for the observed density
perturbation. The upper bound on the soft supersymmetry breaking mass lies
between 1TeV and 10^3TeV. Interestingly, our finding opens up a possibility
that universes with the low-scale supersymmetry are realized by the
inflationary selection. Our inflation model has rich implications; non-thermal
leptogenesis naturally works, and the gravitino and moduli problems as well as
the moduli destabilization problem can be solved or ameliorated; the
standard-model higgs boson receives a sizable radiative correction if the
supersymmertry breaking takes a value on the high side ~10^3TeV.Comment: 23pages, 3 figures. v2: references adde
Gravitino Problem in Supergravity Chaotic Inflation and SUSY Breaking Scale after BICEP2
Gravitinos are generically produced by inflaton decays, which place tight
constraints on inflation models as well as supersymmetry breaking scale. We
revisit the gravitino production from decays of the inflaton and the
supersymmetry breaking field, based on a chaotic inflation model suggested by
the recent BICEP2 result. We study cosmological constraints on thermally and
non-thermally produced gravitinos for a wide range of the gravitino mass, and
show that there are only three allowed regions of the gravitino mass:
eV, --TeV and GeV.Comment: 18 pages, 1 figur
Kinetic Term Anarchy for Polynomial Chaotic Inflation
We argue that there may arise a relatively flat inflaton potential over
super-Planckian field values with an approximate shift symmetry, if the
coefficients of the kinetic terms for many singlet scalars are subject to a
certain random distribution. The inflaton potential generically contains
various shift-symmetry breaking terms, leading to a possibly large deviation of
the predicted values of the spectral index and tensor-to-scalar ratio from
those of the simple quadratic chaotic inflation. We revisit a polynomial
chaotic inflation in supergravity as such.Comment: 16 page
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