33,326 research outputs found
Thermal distortions of non-Gaussian beams in Fabry–Perot cavities
Thermal effects are already important in currently operating interferometric gravitational wave detectors. Planned upgrades of these detectors involve increasing optical power to combat quantum shot noise. We consider the ramifications of this increased power for one particular class of laser beams—wide, flat-topped, mesa beams. In particular we model a single mesa beam Fabry–Perot cavity having thermoelastically deformed mirrors. We calculate the intensity profile of the fundamental cavity eigenmode in the presence of thermal perturbations, and the associated changes in thermal noise. We also outline an idealized method of correcting for such effects. At each stage we contrast our results with those of a comparable Gaussian beam cavity. Although we focus on mesa beams the techniques described are applicable to any azimuthally symmetric system
Path-integral virial estimator for reaction rate calculation based on the quantum instanton approximation
The quantum instanton approximation is a type of quantum transition state
theory that calculates the chemical reaction rate using the reactive flux
correlation function and its low order derivatives at time zero. Here we
present several path-integral estimators for the latter quantities, which
characterize the initial decay profile of the flux correlation function. As
with the internal energy or heat capacity calculation, different estimators
yield different variances (and therefore different convergence properties) in a
Monte Carlo calculation. Here we obtain a virial-type estimator by using a
coordinate scaling procedure rather than integration by parts, which allows
more computational benefits. We also consider two different methods for
treating the flux operator, i.e., local-path and global-path approaches, in
which the latter achieves a smaller variance at the cost of using second-order
potential derivatives. Numerical tests are performed for a one-dimensional
Eckart barrier and a model proton transfer reaction in a polar solvent, which
illustrates the reduced variance of the virial estimator over the corresponding
thermodynamic estimator.Comment: 23 pages, 5 figures, 1 tabl
Lattice analysis for the energy scale of QCD phenomena
We formulate a new framework in lattice QCD to study the relevant energy
scale of QCD phenomena. By considering the Fourier transformation of link
variable, we can investigate the intrinsic energy scale of a physical quantity
nonperturbatively. This framework is broadly available for all lattice QCD
calculations. We apply this framework for the quark-antiquark potential and
meson masses in quenched lattice QCD. The gluonic energy scale relevant for the
confinement is found to be less than 1 GeV in the Landau or Coulomb gauge.Comment: 4 pages, 4 figure
Competing Ground States of the New Class of Halogen-Bridged Metal Complexes
Based on a symmetry argument, we study the ground-state properties of
halogen-bridged binuclear metal chain complexes. We systematically derive
commensurate density-wave solutions from a relevant two-band Peierls-Hubbard
model and numerically draw the the ground-state phase diagram as a function of
electron-electron correlations, electron-phonon interactions, and doping
concentration within the Hartree-Fock approximation. The competition between
two types of charge-density-wave states, which has recently been reported
experimentally, is indeed demonstrated.Comment: 4 pages, 5 figures embedded, to appear in J. Phys. Soc. Jp
Dissipation-induced pure Gaussian state
This paper provides some necessary and sufficient conditions for a
generalMarkovian Gaussian master equation to have a unique pure steady state.
The conditions are described by simple matrix equations; thus the so-called
environment engineering problem for pure-Gaussian-state preparation can be
straightforwardly dealt with in the linear algebraic framework. In fact, based
on one of those conditions, for an arbitrary given pure Gaussian state,we
obtain a complete parametrization of the Gaussian master equation having that
state as a unique steady state; this leads to a systematic procedure for
engineering a desired dissipative system.We demonstrate some examples including
Gaussian cluster states.Comment: 8 page
Modified spin-wave theory of nuclear magnetic relaxation in one-dimensional quantum ferrimagnets: Three-magnon versus Raman processes
Nuclear spin-lattice relaxation in one-dimensional Heisenberg ferrimagnets is
studied by means of a modified spin-wave theory. Calculating beyond the
first-order mechanism, where a nuclear spin directly interacts with spin waves
through the hyperfine coupling, we demonstrate that the
exchange-scattering-enhanced three-magnon nuclear relaxation may generally
predominate over the Raman one with increasing temperature and decreasing
field. Recent proton spin-lattice relaxation-time (T_1_) measurements on the
ferrimagnetic chain compound NiCu(C_7_H_6_N_2_O_6_)(H_2_O)_3_2H_2_O suggest
that the major contribution to 1/T_1_ be made by the three-magnon scattering.Comment: 8 pages, 5 figure
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