arXiv subjects

Ofek Birnholtz

Publications and source records attributed to Ofek Birnholtz.

27 records · Page 2Linked to original sources

arXiv2018

Parameter estimation for black hole echo signals and their statistical significance

Searching for black hole echo signals with gravitational waves provides a means of probing the near-horizon regime of these objects. We demonstrate a pipeline to efficiently search for these signals in gravitational wave data and calculate model selection probabilities between signal and no-signal hypotheses. As an example of its use we calculate Bayes factors for the Abedi-Dykaar-Afshordi (ADA) model on events in LIGO's first observing run and compare to existing results in the literature. We discuss the benefits of using a full likelihood exploration over existing search methods that used template banks and calculated p-values. We use the waveforms of ADA, although the method is easily extendable to other waveforms. With these waveforms we are able to demonstrate a range of echo amplitudes that is already is ruled out by the data.

gr-qc↗

arXiv2017

Testing pseudo-complex general relativity with gravitational waves

We show how the model of pseudo-complex general relativity can be tested using gravitational wave signals from coalescing compact objects. The model, which agrees with Einstein gravity in the weak-field limit, diverges dramatically in the near-horizon regime, with certain parameter ranges excluding the existence of black holes. We show that simple limits can be placed on the model in both the inspiral and ringdown phase of coalescing compact objects. We discuss further how these bounds relate to current observational limits. In particular, for minimal scenarios previously considered in the literature, gravitational wave observations are able to constrain pseudo-complex general relativity parameters to values that require the existence of black hole horizons.

gr-qc↗

arXiv2016

Comments on: "Echoes from the abyss: Evidence for Planck-scale structure at black hole horizons"

Recently, Abedi, Dykaar and Afshordi claimed evidence for a repeating damped echo signal following the binary black hole merger gravitational-wave events recorded in the first observational period of the Advanced LIGO interferometers. We discuss the methods of data analysis and significance estimation leading to this claim, and identify several important shortcomings. We conclude that their analysis does not provide significant observational evidence for the existence of Planck-scale structure at black hole horizons, and suggest renewed analysis correcting for these shortcomings.

gr-qc↗

arXiv2015

Theory of post-Newtonian radiation and reaction

We address issues with extant formulations of dissipative effects in the effective field theory (EFT) which describes the post-Newtonian (PN) inspiral of two gravitating bodies by (re)formulating several parts of the theory. Novel ingredients include gauge invariant spherical fields in the radiation zone; a system zone which preserves time reversal such that its violation arises not from local odd propagation but rather from interaction with the radiation sector in a way which resembles the balayage method; 2-way multipoles to perform zone matching within the EFT action; and a double-field radiation-reaction action which is the non-quantum version of the Closed Time Path formalism and generalizes to any theory with directed propagators including theories which are defined by equations of motion rather than an action. This formulation unifies the treatment of outgoing radiation and its reaction force. We demonstrate the theory in the scalar, electromagnetic and gravitational cases by economizing the following: the expression for the radiation source multipoles; the derivation of the leading outgoing radiation and associated reaction force such that it is maximally reduced to mere multiplication; and the derivation of the gravitational next to leading PN order. In fact we present a novel expression for the +1PN correction to all mass multipoles. We introduce useful definitions for multi-index summation, for the normalization of Bessel functions and for the normalization of the gravito-magnetic vector potential.

hep-th↗

arXiv2015

An action for reaction in general dimension

We present an effective field theory study of radiation and radiation reaction effects for scalar and electromagnetic fields in general spacetime dimensions. Our method unifies the treatment of outgoing radiation and its reaction force within a single action principle. Central ingredients are the field doubling method, which is the classical version of the closed time path formalism and allows a treatment of non-conservative effects within an action, action level matching of system and radiation zones, and the use of fields which are adapted to the enhanced symmetries of each zone. New results include compact expressions for radiative multipoles, radiation, and radiation reaction effective action in any spacetime dimension. We emphasize dimension-dependent features such as the difference between electric and magnetic multipoles in higher dimensions and the temporal non-locality nature of the effective action for odd spacetime dimensions, which is a reflection of indirect propagation ("tail effect") in the full theory. This work generalizes the method and results developed for 4 dimensions in [arXiv:1305.6930], and prepares the way for a treatment of the gravitational case.

hep-th↗

arXiv2015

Gravitational radiation-reaction in arbitrary dimension

We use effective field theory tools to study non-conservative effects in systems of gravitating objects in general spacetime dimension. Using the classical version of the Closed Time Path formalism, we treat both the radiative gravitational field and its dynamical sources within a single action principle. New results include the radiation-reaction effective action in arbitrary dimensions to leading and +1PN orders, as well as the generalized Quadrupole formula to order +1PN.

gr-qc↗

arXiv2014

Comments on initial conditions for the Abraham-Lorentz(-Dirac) equation

An accelerating electric charge coupled to its own electromagnetic (EM) field both emits radiation and experiences the radiation's reaction as a (self-)force. Considering the system from an Effective Field Theory perspective, and using the physical initial conditions of no incoming radiation can help resolve many of the problems associated with the often considered "notorious" Abraham-Lorentz / Abraham-Lorentz-Dirac equations.

physics.class-ph↗

arXiv2014

Radiation reaction at the level of the action

The aim of this paper is to highlight a recently proposed method for the treatment of classical radiative effects, in particular radiation reaction, via effective field theory methods. We emphasize important features of the method, and in particular the doubling of fields. We apply the method to two simple systems: for the mass-rope system in 1+1 dimensions we derive an effective action for the mass which describes a damped harmonic oscillator, while for the electromagnetic charge-field system, i.e. the system of an accelerating electric charge in 3+1 d, we derive the leading Abraham-Lorentz-Dirac force.

hep-th↗

arXiv2013

Gravitational Wave Memory from Gamma Ray Bursts' Jets

While the possible roles of GRBs' progenitors as Gravitational Waves (GW) sources have been extensively studied, little attention has been given to the jet itself as a GW source. We expect the jet's acceleration to produce a GW Memory signal. While all relativistic jet models display anti-beaming of GW radiation away from the jet axis, thus radiating away from directions of GRBs' gamma radiation, this effect is not overwhelming. The decrease of the signal amplitude towards the cone of gamma-ray detectability is weak, and for some models and parameters the GW signal reaches a significant amplitude for much of the gamma-ray cone. Thus both signals may be jointly detected. We find different waveforms and fourier signatures for uniform jets and structured jet models - thus offering a method of using GW signatures to probe the internal structure and acceleration of GRB jets. The GW signal peaks just outside the jet (core) of a uniform (structuted) jet. Within the jet (core) the GW signal displays wiggles, due to a polarization effect; thus for a uniform jet, the peak amplitude accompanies a smoother signal than the peak of a structured jet. For the most probable detection angle and for typical GRB parameters, we expect frequencies < ~600Hz and amplitudes h~10^-25. Our estimates of the expected signals suggest that the signals are not strong enough for a single cluster of DECIGO nor for aLIGO's sensitivities. However, sensitivies of ~10^-25/sqrt(Hz) in the DECIGO band should suffice to detect typical long GRBs at 2Gpc and short GRBs at 200Mpc, implying a monthly event of a long GRB and a detection of a short GRB every decade. In addition, we expect much more frequent detection of GW from GRBs directed away from us, including orphan afterglows. The ultimate DECIGO sensitivy should increase the range and enable detecting these signals in all models even to high cosmological z.

astro-ph.HE↗