1,202 research outputs found
Non-analytical power law correction to the Einstein-Hilbert action: gravitational wave propagation
We analyze the features of the Minkowskian limit of a particular
non-analytical f(R) model, whose Taylor expansion in the weak field limit does
not hold, as far as gravitational waves (GWs) are concerned. We solve the
corresponding Einstein equations and we find an explicit expression of the
modified GWs as the sum of two terms, i.e. the standard one and a modified
part. As a result, GWs in this model are not transverse, and their polarization
is different from that of General Relativity. The velocity of the GW modified
part depends crucially on the parameters characterizing the model, and it
mostly results much smaller than the speed of light. Moreover, this
investigation allows one to further test the viability of this particular f(R)
gravity theory as far as interferometric observations of GWs are concerned.Comment: 18 pages, 3 figure
EBEX: A balloon-borne CMB polarization experiment
EBEX is a NASA-funded balloon-borne experiment designed to measure the
polarization of the cosmic microwave background (CMB). Observations will be
made using 1432 transition edge sensor (TES) bolometric detectors read out with
frequency multiplexed SQuIDs. EBEX will observe in three frequency bands
centered at 150, 250, and 410 GHz, with 768, 384, and 280 detectors in each
band, respectively. This broad frequency coverage is designed to provide
valuable information about polarized foreground signals from dust. The
polarized sky signals will be modulated with an achromatic half wave plate
(AHWP) rotating on a superconducting magnetic bearing (SMB) and analyzed with a
fixed wire grid polarizer. EBEX will observe a patch covering ~1% of the sky
with 8' resolution, allowing for observation of the angular power spectrum from
\ell = 20 to 1000. This will allow EBEX to search for both the primordial
B-mode signal predicted by inflation and the anticipated lensing B-mode signal.
Calculations to predict EBEX constraints on r using expected noise levels show
that, for a likelihood centered around zero and with negligible foregrounds,
99% of the area falls below r = 0.035. This value increases by a factor of 1.6
after a process of foreground subtraction. This estimate does not include
systematic uncertainties. An engineering flight was launched in June, 2009,
from Ft. Sumner, NM, and the long duration science flight in Antarctica is
planned for 2011. These proceedings describe the EBEX instrument and the North
American engineering flight.Comment: 12 pages, 9 figures, Conference proceedings for SPIE Millimeter,
Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy V
(2010
Utilizing weak pump depletion to stabilize squeezed vacuum states
We propose and demonstrate a pump-phase locking technique that makes use of
weak pump depletion (WPD) - an unavoidable effect that is usually neglected -
in a sub-threshold optical parametric oscillator (OPO). We show that the phase
difference between seed and pump beam is imprinted on both light fields by the
non-linear interaction in the crystal and can be read out without disturbing
the squeezed output. Our new locking technique allows for the first
experimental realization of a pump-phase lock by reading out the pre-existing
phase information in the pump field. There is no degradation of the detected
squeezed states required to implement this scheme.Comment: 11 pages, 7 figure
Gravitational waves, diffusion and decoherence
The quite different behaviors exhibited by microscopic and macroscopic
systems with respect to quantum interferences suggest that there may exist a
naturally frontier between quantum and classical worlds. The value of the
Planck mass (22g) may lead to the idea of a connection between this
borderline and intrinsic fluctuations of spacetime. We show that it is possible
to obtain quantitative answers to these questions by studying the diffusion and
decoherence mechanisms induced on quantum systems by gravitational waves
generated at the galactic or cosmic scales. We prove that this universal
fluctuating environment strongly affects quantum interferences on macroscopic
systems, while leaving essentially untouched those on microscopic systems. We
obtain the relevant parameters which, besides the ratio of the system's mass to
Planck mass, characterize the diffusion constant and decoherence time. We
discuss the feasibility of experiments aiming at observing these effects in the
context of ongoing progress towards more and more sensitive matter-wave
interferometry.Comment: Notes for two lectures given at the International School of Physics
Enrico Fermi on Atom Optics and Space Physics (Varenna, July 2007
Newtonian and relativistic theory of orbits and emission of gravitational waves
This review paper is devoted to the theory of orbits. We start with the
discussion of the Newtonian problem of motion then we consider the relativistic
problem of motion, in particular the PN approximation and the further
gravitomagnetic corrections. Finally by a classification of orbits in
accordance with the conditions of motion, we calculate the gravitational waves
luminosity for different types of stellar encounters and orbits.Comment: 44 pages, 22 figures. arXiv admin note: substantial text overlap with
arXiv:gr-qc/0501041 by other authors without attributio
Gravitational waves: search results, data analysis and parameter estimation
The Amaldi 10 Parallel Session C2 on gravitational wave (GW) search results, data analysis and parameter estimation included three lively sessions of lectures by 13 presenters, and 34 posters. The talks and posters covered a huge range of material, including results and analysis techniques for ground-based GW detectors, targeting anticipated signals from different astrophysical sources: compact binary inspiral, merger and ringdown; GW bursts from intermediate mass binary black hole mergers, cosmic string cusps, core-collapse supernovae, and other unmodeled sources; continuous waves from spinning neutron stars; and a stochastic GW background. There was considerable emphasis on Bayesian techniques for estimating the parameters of coalescing compact binary systems from the gravitational waveforms extracted from the data from the advanced detector network. This included methods to distinguish deviations of the signals from what is expected in the context of General Relativity
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