14,803 research outputs found
Superconducting re-entrant cavity transducer for a resonant bar gravitational radiation antenna
Copyright @ American Institute of PhysicsA 10‐GHz superconducting niobium re‐entrant cavity parametric transducer was developed for use in a cryogenic 1.5‐tonne Nb resonant bar gravitational radiation antenna. The transducer has a very high electrical Q (6×105 at 4.2 K), and was operated at high cavity fields without degrading the Q. A very high electromechanical coupling between the antenna and the transducer was therefore achieved. The highest coupling attained, constrained by the available pump power, was 0.11. If the transducer were to be operated in conjunction with a wideband impedance matching element, an antenna bandwidth comparable to the frequency of the antenna would be attained. The temperature dependence of the Q of the transducer was in good agreement with theory. At temperatures above about 6 K the Q was degraded by the increase in the BCS surface resistance, while at lower temperatures the Q was limited by radiative losses
Strichartz estimates for the Schr\"odinger equation on polygonal domains
We prove Strichartz estimates with a loss of derivatives for the
Schr\"odinger equation on polygonal domains with either Dirichlet or Neumann
homogeneous boundary conditions. Using a standard doubling procedure, estimates
the on polygon follow from those on Euclidean surfaces with conical
singularities. We develop a Littlewood-Paley squarefunction estimate with
respect to the spectrum of the Laplacian on these spaces. This allows us to
reduce matters to proving estimates at each frequency scale. The problem can be
localized in space provided the time intervals are sufficiently small.
Strichartz estimates then follow from a result of the second author regarding
the Schr\"odinger equation on the Euclidean cone.Comment: 12 page
Sparticle Mass Spectrum in Grand Unified Theories
We carry out a detailed analysis of sparticle mass spectrum in supersymmetric
grand unified theories. We consider the spectroscopy of the squarks and
sleptons in SU(5) and SO(10) grand unified theories, and show how the
underlying supersymmetry breaking parameters of these theories can be
determined from a measurement of different sparticle masses. This analysis is
done analytically by integrating the one-loop renormalization group equations
with appropriate boundary conditions implied by the underlying grand unified
gauge group. We also consider the impact of non-universal gaugino masses on the
sparticle spectrum, especially the neutralino and chargino masses which arise
in supersymmetric grand unified theories with non-minimal gauge kinetic
function. In particular, we study the interrelationships between the squark and
slepton masses which arise in grand unified theories at the one-loop level,
which can be used to distinguish between the different underlying gauge groups
and their breaking pattern to the Standard Model gauge group. We also comment
on the corrections that can affect these one-loop results.Comment: 19 pages, 6 figure
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
On the gravitational wave background from compact binary coalescences in the band of ground-based interferometers
This paper reports a comprehensive study on the gravitational wave (GW)
background from compact binary coalescences. We consider in our calculations
newly available observation-based neutron star and black hole mass
distributions and complete analytical waveforms that include post-Newtonian
amplitude corrections. Our results show that: (i) post-Newtonian effects cause
a small reduction in the GW background signal; (ii) below 100 Hz the background
depends primarily on the local coalescence rate and the average chirp
mass and is independent of the chirp mass distribution; (iii) the effects of
cosmic star formation rates and delay times between the formation and merger of
binaries are linear below 100 Hz and can be represented by a single parameter
within a factor of ~ 2; (iv) a simple power law model of the energy density
parameter up to 50-100 Hz is sufficient to be used
as a search template for ground-based interferometers. In terms of the
detection prospects of the background signal, we show that: (i) detection (a
signal-to-noise ratio of 3) within one year of observation by the Advanced LIGO
detectors (H1-L1) requires a coalescence rate of for binary neutron stars (binary black holes); (ii) this limit on
could be reduced 3-fold for two co-located detectors, whereas the
currently proposed worldwide network of advanced instruments gives only ~ 30%
improvement in detectability; (iii) the improved sensitivity of the planned
Einstein Telescope allows not only confident detection of the background but
also the high frequency components of the spectrum to be measured. Finally we
show that sub-threshold binary neutron star merger events produce a strong
foreground, which could be an issue for future terrestrial stochastic searches
of primordial GWs.Comment: A few typos corrected to match the published version in MNRA
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