5,244 research outputs found
Quantum Nondemolition Squeezing of a Nanomechanical Resonator
We show that the nanoresonator position can be squeezed significantly below
the ground state level by measuring the nanoresonator with a quantum point
contact or a single-electron transistor and applying a periodic voltage across
the detector. The mechanism of squeezing is basically a generalization of
quantum nondemolition measurement of an oscillator to the case of continuous
measurement by a weakly coupled detector. The quantum feedback is necessary to
prevent the ``heating'' due to measurement back-action. We also discuss a
procedure of experimental verification of the squeezed state.Comment: 9 pages, 3 figure
Mesoscopic Mechanical Resonators as Quantum Non-Inertial Reference Frames
An atom attached to a micrometer-scale wire that is vibrating at a frequency
of 100 MHz and with displacement amplitude 1 nm experiences an acceleration
magnitude 10^9 ms^-2, approaching the surface gravity of a neutron star. As one
application of such extreme non-inertial forces in a mesoscopic setting, we
consider a model two-path atom interferometer with one path consisting of the
100 MHz vibrating wire atom guide. The vibrating wire guide serves as a
non-inertial reference frame and induces an in principle measurable phase shift
in the wave function of an atom traversing the wire frame. We furthermore
consider the effect on the two-path atom wave interference when the vibrating
wire is modeled as a quantum object, hence functioning as a quantum
non-inertial reference frame. We outline a possible realization of the
vibrating wire, atom interferometer using a superfluid helium quantum
interference setup.Comment: Published versio
Multilevel Monte Carlo for Random Degenerate Scalar Convection Diffusion Equation
We consider the numerical solution of scalar, nonlinear degenerate
convection-diffusion problems with random diffusion coefficient and with random
flux functions. Building on recent results on the existence, uniqueness and
continuous dependence of weak solutions on data in the deterministic case, we
develop a definition of random entropy solution. We establish existence,
uniqueness, measurability and integrability results for these random entropy
solutions, generalizing \cite{Mishr478,MishSch10a} to possibly degenerate
hyperbolic-parabolic problems with random data. We next address the numerical
approximation of random entropy solutions, specifically the approximation of
the deterministic first and second order statistics. To this end, we consider
explicit and implicit time discretization and Finite Difference methods in
space, and single as well as Multi-Level Monte-Carlo methods to sample the
statistics. We establish convergence rate estimates with respect to the
discretization parameters, as well as with respect to the overall work,
indicating substantial gains in efficiency are afforded under realistic
regularity assumptions by the use of the Multi-Level Monte-Carlo method.
Numerical experiments are presented which confirm the theoretical convergence
estimates.Comment: 24 Page
Flavor Changing Neutral Current Effects and CP Violation in the Minimal 3-3-1 Model
We investigate in detail the flavor structure of the minimal 331 model and
its implications for several flavor changing neutral current (FCNC) processes.
In this model, where the weak SU(2)_L gauge group of the Standard Model is
extended to a SU(3)_L, the by far dominant new contributions come from an
additional neutral Z' gauge boson, that can transmit FCNCs at tree-level. At
the same time, electroweak precision observables receive new contributions only
at the loop level and do not constrain the model very strongly. In our
analysis, we take into account new CP violating effects that have been
neglected in earlier analyses, and account for a general flavor structure
without reference to a certain parameterization of the new mixing matrix. We
begin by studying the bounds obtained from quantities such as Delta M_K,
epsilon_K, Delta M_{d/s} as well as sin 2 beta|_{J/psi K_S}, and go on to
explore the implications for several clean rare decay channels, namely the
decays K+->pi+ nu nu, K_L -> pi0 nu nu, B_{d/s} -> mu+ mu- and K_L -> pi0 l+l-.
We find sizeable effects in all these decays, but the most interesting quantity
turns out to be the B_s - bar B_s mixing phase beta_s, as measured in the
mixing induced CP asymmetry of B_s -> J/psi phi, which can be large. In
general, we find effects in purely hadronic channels to be larger than in
(semi-)leptonic ones, due to a suppression of the Z'-lepton couplings.Comment: 29 pages, 11 figures, Some Comments and References added, version to
appear in Phys Rev
Recommended from our members
Palaeolimnology of Lake Sapanca and identification of historic earthquake signals, Northern Anatolian Fault Zone (Turkey)
Lake Sapanca is located on a strand of the Northern Anatolian Fault Zone (NAFZ, Turkey), where a series of strong earthquakes (Ms >6.0) have occurred over the past hundred years. Identifying prehistoric
earthquakes in and around Lake Sapanca is key to a better understanding of plate movements along the
NAFZ. This study contributes to the development of palaeolimnological tools to identify past earthquakes
in Lake Sapanca. To this end several promising proxies were investigated, specifically lithology, magnetic
susceptibility, grain size (thin-section and laser analysis), geochemistry, pollen concentration, diatom
assemblages, 137Cs and 210Pb. Sedimentological indicators provided evidence for reworked, turbidite-like
or homogeneous facies (event layers) in several short cores (<45 cm). Other indicators of sediment input
and the historical chronicles available for the area suggest that three of these event layers likely originated
from the AD 1957, 1967 and 1999 earthquakes. Recent changes in sediment deposition and nutrient
levels have also been identified, but are probably not related to earthquakes. This study demonstrates
that a combination of indicators can be used to recognize earthquake-related event layers in cores that encompass a longer period of time
Numerical methods for Lévy processes
We survey the use and limitations of some numerical methods for pricing derivative contracts in multidimensional geometric Lévy model
On Kolmogorov equations for anisotropic multivariate Lévy processes
For d-dimensional exponential Lévy models, variational formulations of the Kolmogorov equations arising in asset pricing are derived. Well-posedness of these equations is verified. Particular attention is paid to pure jump, d-variate Lévy processes built from parametric, copula dependence models in their jump structure. The domains of the associated Dirichlet forms are shown to be certain anisotropic Sobolev spaces. Singularity-free representations of the Dirichlet forms are given which remain bounded for piecewise polynomial, continuous functions of finite element type. We prove that the variational problem can be localized to a bounded domain with explicit localization error bounds. Furthermore, we collect several analytical tools for further numerical analysi
Antibody response to streptococcal cell wall antigens associated with experimental arthritis in rats.
The antibody response to group A streptococcal cell wall components was measured in rats during the development of chronic, remittent experimental arthritis. The arthritis was induced by a single intraperitoneal injection of an aqueous suspension of group A streptococcal cell wall fragments and antibodies were measured by a radioactive antigen-binding assay. Antibodies in serum against both peptidoglycan and A polysaccharide reached maximum levels at 1 or 2 weeks and declined to preimmunization levels by day 63. The kinetics and magnitude of the antibody responses were similar in neonatally thymectomized and non-thymectomized rats. A relationship between chronic joint lesions and anti-peptidoglycan concentration in serum was indicated, since all rats which produced high levels of antibody developed severe chronic arthritis. However, 46% of the rats which produced very low levels of antibody also developed moderate to severe arthritis. There was no correlation between anti-A polysaccharide antibodies and joint disease, although the concentration of this antibody was 10- to 100-fold greater than the anti-peptidoglycan. We conclude that antibody can be a component in the pathogenesis of this experimental model of arthritis, but its role requires further elucidation
- …