119233128
Accessibility of the gravitational-wave background due to binary coalescences to second and third generation gravitational-wave detectors
Compact binary coalescences, such as binary neutron stars or black holes, are among the most promising candidate sources for the current and future terrestrial gravitational-wave detectors. While such sources are best searched using matched template techniques and chirp template banks, integrating chirp signals from binaries over the entire universe also leads to a gravitational-wave background (GWB). In this paper we systematically scan the parameter space for the binary coalescence GWB models, taking into account uncertainties in the star formation rate and in the delay time between the formation and coalescence of the binary, and we compare the computed GWB to the expected sensitivities of the second and third generation gravitational-wave detector networks. We find that second generation detectors are likely to detect the binary coalescence GWB, while the third generation detectors will probe most of the available parameter space. The binary coalescence GWB will, in fact, be a foreground for the third generation detectors, potentially masking the GWB background due to cosmological sources. Accessing the cosmological GWB with third generation detectors will therefore require identification and subtraction of all inspiral signals from all binaries in the detectors’ frequency band.
120491282
Accessibility of the stochastic gravitational wave background from magnetars to the interferometric gravitational wave detectors
119279483
Gravity Waves from Quantum Stress Tensor Fluctuations in Inflation
We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a non-scale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of transplanckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation.
14403021
Fluctuations of the Hawking flux
The fluctuations of the flux radiated by an evaporating black hole will be discussed. Two approaches to this problem will be adopted. In the first, the squared flux operator is defined by normal ordering. In this case, both the mean flux and the mean squared flux are well defined local quantites. It is shown that the flux undergoes large fluctuations on a time scale of the order of the black hole's mass. Thus the semiclassical theory of gravity, in which a classical gravitational field is coupled to the expectation value of the stress tensor, breaks down below this time scale. In the second approach, one does not attempt to give meaning to the squared flux as a local quantity, but only as a time-averaged quantity. In both approaches, the mean squared mass minus the square of the mean mass grows linearly in time, but four times as fast in the second approach as in the first.
124998001
Nonequilibrium backreaction on a moving charge and mirror in quantum fields
119162976
Smearing effect due to the spread of a probe particle on the Brownian motion near a perfectly reflecting boundary
Quantum fluctuations of electromagnetic vacuum are investigated in a half-space bounded by a perfectly reflecting plate by introducing a probe described by a charged wave-packet distribution in time-direction. The wave-packet distribution of the probe enables one to investigate the smearing effect upon the measured vacuum fluctuations caused by the quantum nature of the probe particle. It is shown that the wave-packet spread of the probe particle significantly influences the measured velocity dispersion of the probe. In particular, the asymptotic late-time behavior of its $z$-component, $ $, for the wave-packet case is quite different from the test point-particle case ($z$ is the coordinate normal to the plate). The result for the wave-packet is $ \sim 1/\t^2$ in the late time ($\t$ is the measuring time), in stead of the reported late-time behavior $ \sim 1/z^2$ for a point-particle probe. This result can be quite significant for further investigations on the measurement of vacuum fluctuations.
13893354
Fluctuations of the retarded Van der Waals force
The retarded van der Waals force between a polarizable particle and a perfectly conducting plate is reexamined. The expression for this force given by Casimir and Polder represents a mean force, but there are large fluctuations around this mean value on short time scales that are of the same order of magnitude as the mean force itself. However, these fluctuations occur on time scales which are typically of the order of the light travel time between the atom and the plate. As a consequence, they will not be observed in an experiment that measures the force averaged over a much longer time. In the large time limit, the magnitude of the mean-squared velocity of a test particle due to this fluctuating van der Waals force approaches a constant, and is similar to a Brownian motion of a test particle in a thermal bath with an effective temperature. However, the fluctuations are not isotropic in this case, and the shift in the mean-square velocity components can even be negative. We interpret this negative shift to correspond to a reduction in the velocity spread of a wave packet. The force fluctuations discussed in this paper are a special case of the more general problem of stress tensor fluctuations. These are of interest in a variety of areas of physics, including gravity theory. Thus the effects of van der Waals force fluctuations serve as a useful model for better understanding quantum effects in gravity theory.