56,233 research outputs found
Orbiton-mediated multi-phonon scattering in LaSrMnO
We report on Raman scattering measurements of single crystalline
LaSrMnO (=0, 0.06, 0.09 and 0.125), focusing on the high
frequency regime. We observe multi-phonon scattering processes up to
fourth-order which show distinct features: (i) anomalies in peak energy and its
relative intensity and (ii) a pronounced temperature-, polarization-, and
doping-dependence. These features suggest a mixed orbiton-phonon nature of the
observed multi-phonon Raman spectra.Comment: 6pages, 6figures, submitted to PR
Effect of surface roughness on rate-dependent slip in simple fluids
Molecular dynamics simulations are used to investigate the influence of
molecular-scale surface roughness on the slip behavior in thin liquid films.
The slip length increases almost linearly with the shear rate for atomically
smooth rigid walls and incommensurate structures of the liquid/solid interface.
The thermal fluctuations of the wall atoms lead to an effective surface
roughness, which makes the slip length weakly dependent on the shear rate. With
increasing the elastic stiffness of the wall, the surface roughness smoothes
out and the strong rate dependence is restored again. Both periodically and
randomly corrugated rigid surfaces reduce the slip length and its shear rate
dependence.Comment: 15 pages, 5 figures; submitted to J. Chem. Phy
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Independence at Risk: Older Californians With Disabilities Struggle to Remain at Home as Public Supports Shrink
Presents findings about aging Californians with disabilities who depend on paid public programs and unpaid help to live at home. Makes policy recommendations, including consolidating long-term care programs and enhancing support for caregivers
Dynamical solution to the problem at TeV scale
We introduce a new confining force (\mu-color) at TeV scale to dynamically
generate a supersymmetry preserving mass scale which would replace the \mu
parameter in the minimal supersymmetric standard model (MSSM). We discuss the
Higgs phenomenology and also the pattern of soft supersymmetry breaking
parameters allowing the correct electroweak symmetry breaking within the
\mu-color model, which have quite distinctive features from the MSSM and also
from other generalizations of the MSSM.Comment: 12 pages, REVte
Study of CP Property of the Higgs at a Photon Collider using
We study possible effects of CP violation in the Higgs sector on
production at a -collider. These studies are performed in a
model-independent way in terms of six form-factors which
parametrize the CP mixing in the Higgs sector, and a strategy for their
determination is developed. We observe that the angular distribution of the
decay lepton from produced in this process is independent of any CP
violation in the vertex and hence best suited for studying CP mixing in
the Higgs sector. Analytical expressions are obtained for the angular
distribution of leptons in the c.m. frame of the two colliding photons for a
general polarization state of the incoming photons. We construct combined
asymmetries in the initial state lepton (photon) polarization and the final
state lepton charge. They involve CP even ('s) and odd ('s) combinations
of the mixing parameters. We study limits up to which the values of and
, with only two of them allowed to vary at a time, can be probed by
measurements of these asymmetries, using circularly polarized photons. We use
the numerical values of the asymmetries predicted by various models to
discriminate among them. We show that this method can be sensitive to the
loop-induced CP violation in the Higgs sector in the MSSM.Comment: 15 pages, 9 figures added one referenc
Relic density of neutralino dark matter in the MSSM with CP violation
We calculate the relic density of dark matter in the MSSM with CP violation.
We analyse various scenarios of neutralino annihilation: the cases of a bino,
bino-wino and bino-Higgsino LSP, annihilation through Higgs, as well as
sfermion coannihilation scenarios. Large phase effects are found, on the one
hand due to shifts in the masses, on the other hand due to modifications of the
couplings. Taking special care to disentangle the effects in masses and
couplings, we demonstrate that the presence of CP phases can have a significant
influence on the neutralino relic abundance. Typical variations in \Omega h^2
solely from modifications in the couplings are O(10%-100%), but can reach an
order of magnitude in some cases.Comment: 36 pages, 21 figures (low resolution). A version with high-resolution
figures can be downloaded from http://cern.ch/kraml/papers/omc
String or M theory axion as a quintessence
A slow-rolling scalar field ( Quintessence) with potential energy
has been proposed as the origin of
accelerating universe at present. We investigate the effective potential of
in the framework of supergravity model including the quantum corrections
induced by generic (nonrenormalizable) couplings of to the gauge and
charged matter multiplets. It is argued that the K\"ahler potential,
superpotential and gauge kinetic functions of the underlying supergravity model
are required to be invariant under the variation of with an extremely fine
accuracy in order to provide a working quintessence potential. Applying these
results for string or -theory, we point out that the heterotic -theory or
Type I string axion can be a plausible candidate for quintessence if (i) it
does not couple to the instanton number of gauge interactions not weaker than
those of the standard model and (ii) the modulus partner of the
periodic quintessence axion has a large VEV:
. It is stressed
that such a large gives the gauge unification scale at around the
phenomenologically favored value GeV. To provide an
accelerating universe, the quintessence axion should be at near the top of its
effective potential at present, which requires a severe fine tuning of the
initial condition of and in the early universe. We discuss a late
time inflation scenario based on the modular and CP invariance of the moduli
effective potential, yielding the required initial condition in a natural
manner if the K\"ahler metric of the quintessence axion superfield receives a
sizable nonperturbative contribution.Comment: 23 pages, 3 figures, version to be published at Phys. Rev.
Se and Cu NMR studies of the electronic correlations in CuTiSe ()
We report Se and Cu nuclear magnetic resonance (NMR)
investigation on the charge-density-wave (CDW) superconductor CuTiSe
( and 0.07). At high magnetic fields where superconductivity is
suppressed, the temperature dependence of Se and Cu spin-lattice
relaxation rates 1/T_{1}^{77}1/T_{1}$
vs \emph{T} increases with the Cu doping. This can be described by a modified
Korringa relation which suggests the significance of electronic correlations
and the Se 4\emph{p}- and Ti 3\emph{d}-band contribution to the density of
states at the Fermi level in the studied compounds.Comment: Revised manuscript. Submitted to Journal of Physics: Condensed Matte
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