14,160 research outputs found
Observation of enhanced optical spring damping in a macroscopic mechanical resonator and application for parametric instability control in advanced gravitational-wave detectors
We show that optical spring damping in an optomechanical resonator can be enhanced by injecting a phase delay in the laser frequency-locking servo to rotate the real and imaginary components of the optical spring constant. This enhances damping at the expense of optical rigidity. We demonstrate enhanced parametric damping which reduces the Q factor of a 0.1-kg-scale resonator from 1.3×10^5 to 6.5×10^3. By using this technique adequate optical spring damping can be obtained to damp parametric instability predicted for advanced laser interferometer gravitational-wave detectors
Fluxon Dynamics of a Long Josephson Junction with Two-gap Superconductors
We investigate the phase dynamics of a long Josephson junction (LJJ) with
two-gap superconductors. In this junction, two channels for tunneling between
the adjacent superconductor (S) layers as well as one interband channel within
each S layer are available for a Cooper pair. Due to the interplay between the
conventional and interband Josephson effects, the LJJ can exhibit unusual phase
dynamics. Accounting for excitation of a stable 2-phase texture arising
from the interband Josephson effect, we find that the critical current between
the S layers may become both spatially and temporally modulated. The spatial
critical current modulation behaves as either a potential well or barrier,
depending on the symmetry of superconducting order parameter, and modifies the
Josephson vortex trajectories. We find that these changes in phase dynamics
result in emission of electromagnetic waves as the Josephson vortex passes
through the region of the 2-phase texture. We discuss the effects of this
radiation emission on the current-voltage characteristics of the junction.Comment: 14 pages, 6 figure
Boundedness and Stability of Impulsively Perturbed Systems in a Banach Space
Consider a linear impulsive equation in a Banach space
with . Suppose each solution of
the corresponding semi-homogeneous equation
(2) is bounded for any bounded sequence .
The conditions are determined ensuring
(a) the solution of the corresponding homogeneous equation has an exponential
estimate;
(b) each solution of (1),(2) is bounded on the half-line for any bounded
and bounded sequence ;
(c) for any tending to
zero;
(d) exponential estimate of implies a similar estimate for .Comment: 19 pages, LaTex-fil
A General Approach to Optomechanical Parametric Instabilities
We present a simple feedback description of parametric instabilities which
can be applied to a variety of optical systems. Parametric instabilities are of
particular interest to the field of gravitational-wave interferometry where
high mechanical quality factors and a large amount of stored optical power have
the potential for instability. In our use of Advanced LIGO as an example
application, we find that parametric instabilities, if left unaddressed,
present a potential threat to the stability of high-power operation
Decay of weak solutions to the 2D dissipative quasi-geostrophic equation
We address the decay of the norm of weak solutions to the 2D dissipative
quasi-geostrophic equation. When the initial data is in only, we prove
that the norm tends to zero but with no uniform rate, that is, there are
solutions with arbitrarily slow decay. For the initial data in ,
with , we are able to obtain a uniform decay rate in . We
also prove that when the norm of the initial data
is small enough, the norms, for have uniform
decay rates. This result allows us to prove decay for the norms, for , when the initial data is in .Comment: A paragraph describing work by Carrillo and Ferreira proving results
directly related to the ones in this paper is added in the Introduction. Rest
of the article remains unchange
Critical Behaviour of integrable mixed spins chains
We construct a mixed spin 1/2 and integrable model and investigate its
finite size properties. For a certain conformal invariant mixed spin system the
central charge can be decomposed in terms of the conformal anomaly of two
single integrable models of spin 1/2 and spin . We also compute the
ground state energy and the sound velocity in the thermodynamic limit.Comment: This was the first correct calculation of the central charge in mixed
integrable spin chains. For effects of a magnetic field see
J.Phys.A:Math.Gen. 26 (1993) 730
Isoscalar Hamiltonians for light atomic nuclei
The charge-dependent realistic nuclear Hamiltonian for a nucleus, composed of
neutrons and protons, can be successfully approximated by a charge-independent
one. The parameters of such a Hamiltonian, i.e., the nucleon mass and the NN
potential, depend upon the mass number A, charge Z and isospin quantum number T
of state of the studied nucleus.Comment: REVTeX, 22 pages, 3 eps figures, to appear in PR
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