31 research outputs found
Next-to-leading order spin-orbit and spin(a)-spin(b) Hamiltonians for n gravitating spinning compact objects
We derive the post-Newtonian next-to-leading order conservative spin-orbit
and spin(a)-spin(b) gravitational interaction Hamiltonians for arbitrary many
compact objects. The spin-orbit Hamiltonian completes the knowledge of
Hamiltonians up to and including 2.5PN for the general relativistic three-body
problem. The new Hamiltonians include highly nontrivial three-body
interactions, in contrast to the leading order consisting of two-body
interactions only. This may be important for the study of effects like Kozai
resonances in mergers of black holes with binary black holes.Comment: 13 pages, 1 Mathematica source file, v2: submitted version, v3:
published version, some minor correction
Kerr Black Holes are Not Unique to General Relativity
Considerable attention has recently focused on gravity theories obtained by
extending general relativity with additional scalar, vector, or tensor degrees
of freedom. In this paper, we show that the black-hole solutions of these
theories are essentially indistinguishable from those of general relativity.
Thus, we conclude that a potential observational verification of the Kerr
metric around an astrophysical black hole cannot, in and of itself, be used to
distinguish between these theories. On the other hand, it remains true that
detection of deviations from the Kerr metric will signify the need for a major
change in our understanding of gravitational physics.Comment: 4 pages, Physical Review Letters in pres
Performance analysis of the Karhunen–Loève Transform for artificial and astrophysical transmissions: denoizing and detection
In this work, we propose a new method of computing the Karhunen–Loève Transform (KLT) applied to complex voltage data for the detection and noise level reduction in astronomical signals. We compared this method with the standard KLT techniques based on the Toeplitz correlation matrix and we conducted a performance analysis for the detection and extraction of astrophysical and artificial signals via Monte Carlo (MC) simulations. We applied our novel method to a real data study-case: the Voyager 1 telemetry signal. We evaluated the KLT performance in an astrophysical context: our technique provides a remarkable improvement in computation time and MC simulations show significant reconstruction results for signal-to-noise ratio (SNR) down to −10 dB and comparable results with standard signal detection techniques. The application to artificial signals, such as the Voyager 1 data, shows a notable gain in SNR after the KLT
Performance analysis of the Karhunen–Loève Transform for artificial and astrophysical transmissions: denoizing and detection
In this work, we propose a new method of computing the Karhunen–Loève Transform (KLT) applied to complex voltage data for the detection and noise level reduction in astronomical signals. We compared this method with the standard KLT techniques based on the Toeplitz correlation matrix and we conducted a performance analysis for the detection and extraction of astrophysical and artificial signals via Monte Carlo (MC) simulations. We applied our novel method to a real data study-case: the Voyager 1 telemetry signal. We evaluated the KLT performance in an astrophysical context: our technique provides a remarkable improvement in computation time and MC simulations show significant reconstruction results for signal-to-noise ratio (SNR) down to −10 dB and comparable results with standard signal detection techniques. The application to artificial signals, such as the Voyager 1 data, shows a notable gain in SNR after the KLT
FPGA-based digital back-ends for the Sardinia Radio Telescope
The Sardinia Radio Telescope (SRT), located in San Basilio, about 35 km north of Cagliari, is the largest (64-m diameter) radio telescope in Italy. It is a general-purpose, fully-steerable radio telescope designed to operate in the 300 MHz - 116 GHz frequency range, which allows it to perform a wide variety of scientific studies. The advanced electronic digital platforms that are installed at SRT play a key role, in particular those based on FPGAs (Field Programmable Gate Array), both because of their processing capability and their reconfigurability. In this paper, we present an overview of the digital back-ends available at SRT, as well as the ones under development; it is important to underline that, for all of them, FPGAs are the beating heart