Effective field theory calculation of conservative binary dynamics at third post-Newtonian order

We reproduce the two-body gravitational conservative dynamics at third post-Newtonian order for spin-less sources by using the effective field theory methods for the gravitationally bound two-body system, proposed by Goldberger and Rothstein. This result has been obtained by automatizing the computation of Feynman amplitudes within a Mathematica algorithm, paving the way for higher-order computations not yet performed by traditional methods.Comment: 24 pages, 6 figures. Typos corrected and references added in v2. Typos corrected in v

Symmetry breaking aspects of the effective Lagrangian for quantum black holes

The physical excitations entering the effective Lagrangian for quantum black holes are related to a Goldstone boson which is present in the Rindler limit and is due to the spontaneous breaking of the translation symmetry of the underlying Minkowski space. This physical interpretation, which closely parallels similar well-known results for the effective stringlike description of flux tubes in QCD, gives a physical insight into the problem of describing the quantum degrees of freedom of black holes. It also suggests that the recently suggested concept of 'black hole complementarity' emerges at the effective Lagrangian level rather than at the fundamental level.Comment: 11 pages, Latex,1 figur

Multichannel matched filtering for spherical gravitational wave antennas

We study the performance of a multidimensional matched filter as a follow-up module of the coherent method recently developed by two of us for the detection of gravitational wave bursts by spherical resonant detectors. We have tested this strategy on the same set of injections used for the coherent method and found that the matched filter sensibly improves the determination of relevant parameters as the arrival time, amplitude, central frequency and arrival direction of the signal. The matched filter also improves the false alarm rate, reducing it roughly by a factor of 3. The hierarchical structure of the whole analysis pipeline allows to obtain these results without a significant increase of the computation time.Comment: 11 pages, 4 figures, final version to be published on Classical and Quantum Gravity as part of the Proceedings of GWDAW1

Bouncing pre-big bang on the brane

A regular bouncing universe is obtained in the context of a dilaton-gravity brane world scenario. The scale factor starts in a contracting inflationary phase both in the Einstein and in the string frame, it then undergoes a bounce (due to interaction with the bulk Weyl tensor), and subsequently enters into a decelerated expanding era. This graceful exit is obtained at low curvature and low coupling, and without violating the Null Energy Condition.Comment: 16 pages, 3 figures; final version to be published on PRD. General improvement of section II (better specification of the matter content on the brane and discussion about the late time behavior), main results unchanged; 2 references adde

Events trigger generator for resonant spherical detectors of gravitational waves

We have set up and tested a pipeline for processing the data from a spherical gravitational wave detector with six transducers. The algorithm exploits the multichannel capability of the system and provides a list of candidate events with their arrival direction. The analysis starts with the conversion of the six detector outputs into the scalar and the five quadrupolar modes of the sphere, which are proportional to the corresponding gravitational wave spherical components. Event triggers are then generated by an adaptation of the WaveBurst algorithm. Event validation and direction reconstruction are made by cross-checking two methods of different inspiration: geometrical (lowest eigenvalue) and probabilistic (maximum likelihood). The combination of the two methods is able to keep substantially unaltered the efficiency and can reduce drastically the detections of fake events (to less than ten per cent). We show a quantitative test of these ideas by simulating the operation of the resonant spherical detector miniGRAIL, whose planned sensitivity in its frequency band (few hundred Hertz's around 3 kHz) is comparable with the present LIGO one.Comment: 14 pages, 8 figures. Version accepted for publication on CQG. Proceedings of the 12th Gravitational Wave Data Analysis Worksho

On the "Causality Argument" in Bouncing Cosmologies

We exhibit a situation in which cosmological perturbations of astrophysical relevance propagating through a bounce are affected in a scale-dependent way. Involving only the evolution of a scalar field in a closed universe described by general relativity, the model is consistent with causality. Such a specific counter-example leads to the conclusion that imposing causality is not sufficient to determine the spectrum of perturbations after a bounce provided it is known before. We discuss consequences of this result for string motivated scenarios.Comment: 4 pages, 1 figure, ReVTeX, to appear in Phys. Rev. Let

Combining chirp mass, luminosity distance and sky localisation from gravitational wave events to detect the cosmic dipole

A key test of the isotropy of the Universe on large scales consists in comparing the dipole in the Cosmic Microwave Background (CMB) temperature with the dipole in the distribution of sources at low redshift. Current analyses find a dipole in the number counts of quasars and radio sources that is 2-5 times larger than expected from the CMB, leading to a tension reaching 5$\sigma$. In this paper, we derive a consistent framework to measure the dipole independently from gravitational wave (GW) detections. We exploit the fact that the observer velocity does not only change the distribution of events in the sky, but also the luminosity distance and redshifted chirp mass, that can be extracted from the GW waveform. We show that the estimator with higher signal-to-noise ratio is the dipole in the chirp mass measured from a population of binary neutron stars. Combining all estimators (accounting for their covariance) improves the detectability of the dipole by 30-50 percent compared to number counting of binary black holes alone. We find that a few $10^6$ events are necessary to detect a dipole consistent with the CMB one, whereas if the dipole is as large as predicted by radio sources, it will already be detectable with $10^5$ events, which would correspond to a single year of observation with next generation GW detectors. GW sources provide therefore a robust and independent way of testing the isotropy of the Universe.Comment: 17 pages, 11 figues, submitted to MNRA

Aligned Spins: Orbital Elements, Decaying Orbits, and Last Stable Circular Orbit to high post-Newtonian Orders

In this article the quasi-Keplerian parameterisation for the case that spins and orbital angular momentum in a compact binary system are aligned or anti-aligned with the orbital angular momentum vector is extended to 3PN point-mass, next-to-next-to-leading order spin-orbit, next-to-next-to-leading order spin(1)-spin(2), and next-to-leading order spin-squared dynamics in the conservative regime. In a further step, we use the expressions for the radiative multipole moments with spin to leading order linear and quadratic in both spins to compute radiation losses of the orbital binding energy and angular momentum. Orbital averaged expressions for the decay of energy and eccentricity are provided. An expression for the last stable circular orbit is given in terms of the angular velocity type variable $x$.Comment: 30 pages, 2 figures, v2: update to match published versio

A Solution to the Graceful Exit Problem in Pre-Big Bang Cosmology

We examine the string cosmology equations with a dilaton potential in the context of the Pre-Big Bang Scenario with the desired scale factor duality, and give a generic algorithm for obtaining solutions with appropriate evolutionary properties. This enables us to find pre-big bang type solutions with suitable dilaton behaviour that are regular at $t=0$, thereby solving the graceful exit problem. However to avoid fine tuning of initial data, an `exotic' equation of state is needed that relates the fluid properties to the dilaton field. We discuss why such an equation of state should be required for reliable dilaton behaviour at late times.Comment: 16 pages LaTeX, 5 figures. To appear in Physical Review

Big-headed marine crocodyliforms and why we must be cautious when using extant species as body length proxies for long-extinct relatives

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