10,720 research outputs found
Gauge singlet scalar as inflaton and thermal relic dark matter
We show that, by adding a gauge singlet scalar S to the standard model which
is nonminimally coupled to gravity, S can act both as the inflaton and as
thermal relic dark matter. We obtain the allowed region of the (m_s, m_h)
parameter space which gives a spectral index in agreement with observational
bounds and also produces the observed dark matter density while not violating
vacuum stability or nonperturbativity constraints. We show that, in contrast to
the case of Higgs inflation, once quantum corrections are included the spectral
index is significantly larger than the classical value (n = 0.966 for N = 60)
for all allowed values of the Higgs mass m_h. The range of Higgs mass
compatible with the constraints is 145 GeV < m_h < 170 GeV. The S mass lies in
the range 45 GeV < ms < 1 TeV for the case of a real S scalar with large
quartic self-coupling lambdas, with a smaller upper bound for smaller lambdas.
A region of the parameter space is accessible to direct searches at the LHC via
h-->SS, while future direct dark matter searches should be able to
significantly constrain the model.Comment: 13 pages, 7 figures. Published versio
Pseudo diamagnetism of four component exciton condensates
We analyze the spin structure of the ground state of four-component exciton
condensates in coupled quantum wells as a function of spin-dependent
interactions and applied magnetic field. The four components correspond to the
degenerate exciton states characterized by and spin projections
to the axis of the structure. We show that in a wide range of parameters, the
chemical potential of the system increases as a function of magnetic field,
which manifests a pseudo-diamagnetism of the system. The transitions to
polarized two- and one-component condensates can be of the first-order in this
case. The predicted effects are caused by energy conserving mixing of
and excitons.Comment: 4 pages, 2 figure
Spectral statistics in disordered metals: a trajectories approach
We show that the perturbative expansion of the two-level correlation
function, , in disordered conductors can be understood
semiclassically in terms of self-intersecting particle trajectories. This
requires the extension of the standard diagonal approximation to include pairs
of paths which are non-identical but have almost identical action. The number
of diagrams thus produced is much smaller than in a standard field-theoretical
approach. We show that such a simplification occurs because has a
natural representation as the second derivative of free energy . We
calculate to 3-loop order, and verify a one-parameter scaling
hypothesis for it in 2d. We discuss the possibility of applying our ``weak
diagonal approximation'' to generic chaotic systems.Comment: 9 pages in REVTeX two-column format including 4 figures; submitted to
Phys.Rev.
Impurity Scattering in Luttinger Liquid with Electron-Phonon Coupling
We study the influence of electron-phonon coupling on electron transport
through a Luttinger liquid with an embedded weak scatterer or weak link. We
derive the renormalization group (RG) equations which indicate that the
directions of RG flows can change upon varying either the relative strength of
the electron-electron and electron-phonon coupling or the ratio of Fermi to
sound velocities. This results in the rich phase diagram with up to three fixed
points: an unstable one with a finite value of conductance and two stable ones,
corresponding to an ideal metal or insulator.Comment: 4 pages, 2 figure
Superfluidity of "dirty" indirect excitons and magnetoexcitons in two-dimensional trap
The superfluid phase transition of bosons in a two-dimensional (2D) system
with disorder and an external parabolic potential is studied. The theory is
applied to experiments on indirect excitons in coupled quantum wells. The
random field is allowed to be large compared to the dipole-dipole repulsion
between excitons. The slope of the external parabolic trap is assumed to change
slowly enough to apply the local density approximation (LDA) for the superfluid
density, which allows us to calculate the Kosterlitz-Thouless temperature
at each local point of the trap. The superfluid phase occurs
around the center of the trap () with the normal phase outside
this area. As temperature increases, the superfluid area shrinks and disappears
at temperature . Disorder acts to deplete the condensate; the
minimal total number of excitons for which superfluidity exists increases with
disorder at fixed temperature. If the disorder is large enough, it can destroy
the superfluid entirely. The effect of magnetic field is also calculated for
the case of indirect excitons. In a strong magnetic field , the superfluid
component decreases, primarily due to the change of the exciton effective mass.Comment: 13 pages, 3 figure
Boundedness of Pseudodifferential Operators on Banach Function Spaces
We show that if the Hardy-Littlewood maximal operator is bounded on a
separable Banach function space and on its associate space
, then a pseudodifferential operator
is bounded on whenever the symbol belongs to the
H\"ormander class with ,
or to the the Miyachi class
with ,
. This result is applied to the case of
variable Lebesgue spaces .Comment: To appear in a special volume of Operator Theory: Advances and
Applications dedicated to Ant\'onio Ferreira dos Santo
Fictitious Level Dynamics: A Novel Approach to Spectral Statistics in Disordered Conductors
We establish a new approach to calculating spectral statistics in disordered
conductors, by considering how energy levels move in response to changes in the
impurity potential. We use this fictitious dynamics to calculate the spectral
form factor in two ways. First, describing the dynamics using a Fokker-Planck
equation, we make a physically motivated decoupling, obtaining the spectral
correlations in terms of the quantum return probability. Second, from an
identity which we derive between two- and three-particle correlation functions,
we make a mathematically controlled decoupling to obtain the same result. We
also calculate weak localization corrections to this result, and show for two
dimensional systems (which are of most interest) that corrections vanish to
three-loop order.Comment: 35 pages in REVTeX format including 10 postscript figures; to be
published in a special issue (on Topics in Mesoscopic Physics) of the Journal
of Mathematical Physics, October 199
Local community leaders on social resilience to environmental disasters:The case of El Niño in Lurigancho-Chosica in Perú
This study aims to investigate how community leaders of Lurigancho-Chosica, in Lima-Perú, perceive environmental (im)mobility in their community, because of El Niño-Southern Oscillation [ENSO]. ENSO is a recurrent climate event that will likely worsen with rising world temperatures. Lurigancho-Chosica is a highly vulnerable area and one of the most affected by ENSO in the country because of landslides. Using a qualitative approach, interviews were conducted with ten community leaders as key informants from Lurigancho-Chosica to explore their perspectives on the effects of ENSO on their communities and to understand the social resilience of their communities to deal with similar disasters and changes. Findings indicate that, although knowledgeable about the impacts of ENSO, community leaders emphasized that most community inhabitants used multiple coping strategies to deal with the structural limitations of their communities to deal with ENSO. Community leaders themselves opted to strengthen the adaptive capacities of their communities to be more socially resilient, preferring community organization over migration or relocation strategies
Theory of non-equilibrium electronic Mach-Zehnder interferometer
We develop a theoretical description of interaction-induced phenomena in an
electronic Mach-Zehnder interferometer formed by integer quantum Hall edge
states (with \nu =1 and 2 channels) out of equilibrium. Using the
non-equilibrium functional bosonization framework, we derive an effective
action which contains all the physics of the problem. We apply the theory to
the model of a short-range interaction and to a more realistic case of
long-range Coulomb interaction. The theory takes into account
interaction-induced effects of dispersion of plasmons, charging, and
decoherence. In the case of long-range interaction we find a good agreement
between our theoretical results for the visibility of Aharonov-Bohm
oscillations and experimental data.Comment: 19 pages, 10 figure
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