49 research outputs found
Laser Interferometers as Dark Matter Detectors
While the global cosmological and local galactic abundance of dark matter is well established, its identity, physical size, and composition remain a mystery. In this paper, we analyze an important question of dark matter detectability through its gravitational interaction, using current and next generation gravitational-wave observatories to look for macroscopic (kilogram-scale or larger) objects. Keeping the size of the dark matter objects to be smaller than the physical dimensions of the detectors, and keeping their mass as a free parameter, we derive the expected event rates. For favorable choice of mass, we find that dark matter interactions could be detected in space-based detectors such as LISA at a rate of one per ten years. We then assume the existence of an additional Yukawa force between dark matter and regular matter. By choosing the range of the force to be comparable to the size of the detectors, we derive the levels of sensitivity to such a new force, which exceeds the sensitivity of other probes in a wide range of parameters. For sufficiently large Yukawa coupling strength, the rate of dark matter events can then exceed 10 per year for both ground- and space-based detectors. Thus, gravitational-wave observatories can make an important contribution to a global effort of searching for nongravitational interactions of dark matter
In-situ characterization of the thermal state of resonant optical interferometers via tracking of their higher-order mode resonances
Thermal lensing in resonant optical interferometers such as those used for
gravitational wave detection is a concern due to the negative impact on control
signals and instrument sensitivity. In this paper we describe a method for
monitoring the thermal state of such interferometers by probing the
higher-order spatial mode resonances of the cavities within them. We
demonstrate the use of this technique to measure changes in the Advanced LIGO
input mode cleaner cavity geometry as a function of input power, and
subsequently infer the optical absorption at the mirror surfaces at the level
of 1 ppm per mirror. We also demonstrate the generation of a useful error
signal for thermal state of the Advanced LIGO power recycling cavity by
continuously tracking the first order spatial mode resonance frequency. Such an
error signal could be used as an input to thermal compensation systems to
maintain the interferometer cavity geometries in the presence of transients in
circulating light power levels, thereby maintaining optimal sensitivity and
maximizing the duty-cycle of the detectors
Proof of the Generalized Second Law for Quasistationary Semiclassical Black Holes
A simple direct explicit proof of the generalized second law of black hole
thermodynamics is given for a quasistationary semiclassical black hole.Comment: 12 pages, LaTeX, report Alberta-Thy-10-93 (revision of paper in
response to Phys. Rev. Lett. referees' comments, which suffered a series of
long delays
Effect of Immunomodulating Adjuvant Dzherelo (Immunoxel) in HIV Infected Patients Receiving Standard Antiretroviral Therapy
Open-label, matched-case, comparative trial was conducted in 40 HIV-infected patients to evaluate the adjunct effect of Dzherelo (Immunoxel) on immune and viral parameters. Arm A (n=20) received anti-retroviral therapy (ART) consisting of zidovudine, lamivudine, and efavirenz and arm B (n=20) received ART with Dzherelo. After 2 months total T-lymphocytes increased in ART recipients from 664 to 819 cells/μl (P=0.06), whereas in Dzherelo recipients they rose from 595 to 785(P=0.03). The CD4 T-cells expanded by 57.3% (218 to 343; P=0.002) in the ART arm and by 93.5% (184 to 356; P=0.004) in the Dzherelo arm. The accrual in absolute and relative number of CD8+ lymphocytes in ART and in the Dzherelo recipients was 43.2% (2.7%) and 50.4% (-0.5%) respectively. The CD4/CD8 ratio in Dzherelo recipients increased from 1.495 to 1.940 (P=0.03) but insignificant in the control: 1.418 to 1.613 (P=0.14). Activated CD3+ HLADR+ T-cells increased from 209 to 264 (P=0.02) and from 161 to 348 (P=0.0007) in ART and Dzherelo recipients respectively. No changes in CD20+ B-lymphocytes were seen in the control, but in Dzherelo patients they declined from 509 to 333 (P=0.00008). The proportion of CD3- CD16+CD56+ NK cells was not affected by ART but addition of Dzherelo raised NK cells from 11.2% to 17.1% (P=0.0001). About three-quarters (14/19) of patients on ART displayed decrease in viral load (1718 to 1419 copies/ml; P=0.008), while 95% of patients on Dzherelo had a decrease (1793 to 1368; P=0.001). Dzherelo has a favorable effect on the immune status and viral burden when given as an immunomodulating adjunct to ART
Imaging spontaneous currents in superconducting arrays of pi-junctions
Superconductors separated by a thin tunneling barrier exhibit the Josephson
effect that allows charge transport at zero voltage, typically with no phase
shift between the superconductors in the lowest energy state. Recently,
Josephson junctions with ground state phase shifts of pi proposed by theory
three decades ago have been demonstrated. In superconducting loops,
pi-junctions cause spontaneous circulation of persistent currents in zero
magnetic field, analogous to spin-1/2 systems. Here we image the spontaneous
zero-field currents in superconducting networks of temperature-controlled
pi-junctions with weakly ferromagnetic barriers using a scanning SQUID
microscope. We find an onset of spontaneous supercurrents at the 0-pi
transition temperature of the junctions Tpi = 3 K. We image the currents in
non-uniformly frustrated arrays consisting of cells with even and odd numbers
of pi-junctions. Such arrays are attractive model systems for studying the
exotic phases of the 2D XY-model and achieving scalable adiabatic quantum
computers.Comment: Pre-referee version. Accepted to Nature Physic
The advanced LIGO input optics
The advanced LIGO gravitational wave detectors are nearing their design sensitivity and should begin taking meaningful astrophysical data in the fall of 2015. These resonant optical interferometers will have unprecedented sensitivity to the strains caused by passing gravitational waves. The input optics play a significant part in allowing these devices to reach such sensitivities. Residing between the pre-stabilized laser and the main interferometer, the input optics subsystem is tasked with preparing the laser beam for interferometry at the sub-attometer level while operating at continuous wave input power levels ranging from 100 mW to 150 W. These extreme operating conditions required every major component to be custom designed. These designs draw heavily on the experience and understanding gained during the operation of Initial LIGO and Enhanced LIGO. In this article, we report on how the components of the input optics were designed to meet their stringent requirements and present measurements showing how well they have lived up to their design
The Advanced LIGO Input Optics
The advanced LIGO gravitational wave detectors are nearing their design sensitivity and should begin taking meaningful astrophysical data in the fall of 2015. These resonant optical interferometers will have unprecedented sensitivity to the strains caused by passing gravitational waves. The input optics play a significant part in allowing these devices to reach such sensitivities. Residing between the pre-stabilized laser and the main interferometer, the input optics subsystem is tasked with preparing the laser beam for interferometry at the sub-attometer level while operating at continuous wave input power levels ranging from 100 mW to 150 W. These extreme operating conditions required every major component to be custom designed. These designs draw heavily on the experience and understanding gained during the operation of Initial LIGO and Enhanced LIGO. In this article, we report on how the components of the input optics were designed to meet their stringent requirements and present measurements showing how well they have lived up to their design
Thermal effects in the Input Optics of the Enhanced Laser Interferometer Gravitational-Wave Observatory interferometers
We present the design and performance of the LIGO Input Optics subsystem as implemented for the sixth science run of the LIGO interferometers. The Initial LIGO Input Optics experienced thermal side effects when operating with 7 W input power. We designed, built, and implemented improved versions of the Input Optics for Enhanced LIGO, an incremental upgrade to the Initial LIGO interferometers, designed to run with 30 W input power. At four times the power of Initial LIGO, the Enhanced LIGO Input Optics demonstrated improved performance including better optical isolation, less thermal drift, minimal thermal lensing, and higher optical efficiency. The success of the Input Optics design fosters confidence for its ability to perform well in Advanced LIGO
DC readout experiment in Enhanced LIGO
The two 4 km long gravitational wave detectors operated by the Laser
Interferometer Gravitational-wave Observatory (LIGO) were modified in 2008 to
read out the gravitational wave channel using the DC readout form of homodyne
detection and to include an optical filter cavity at the output of the
detector. As part of the upgrade to Enhanced LIGO, these modifications replaced
the radio-frequency (RF) heterodyne system used previously. We describe the
motivations for and the implementation of DC readout and the output mode
cleaner in Enhanced LIGO. We present characterizations of the system, including
measurements and models of the couplings of the noises from the laser source to
the gravitational wave readout channel. We show that noise couplings using DC
readout are improved over those for RF readout, and we find that the achieved
shot-noise-limited sensitivity is consistent with modeled results