Andrea Antonelli

Andrea Antonelli

Gravitational-wave astrophysicist: interested in gravity, astrophysics of black holes, and statistical analysis.

Publications

  1. "The impact of confusion noise on golden binary neutron-star events in next-generation terrestrial observatories", Reali, Antonelli, et al. [Paper]
    Abstract Next-generation terrestrial gravitational-wave observatories will detect O(10^5) signals from compact binary coalescences every year. These signals can last for several hours in the detectors’ sensitivity band and they will be affected by multiple unresolved sources contributing to a confusion-noise background in the data. Using an information-matrix formalism, we estimate the impact of the confusion noise power spectral density in broadening the parameter estimates of a GW170817-like event. If our estimate of the confusion noise power spectral density is neglected, we find that masses, spins, and distance are biased in about half of our simulations under realistic circumstances. The sky localization, while still precise, can be biased in up to 80 percent of our simulations, potentially posing a problem in follow-up searches for electromagnetic counterparts.
  2. "Constraining the evolution of Newton's constant with slow inspirals observed from spaceborne gravitational-wave detectors", Barbieri et al. (including Antonelli). [Paper]
    Abstract Spaceborne gravitational-wave (GW) detectors observing at milli-Hz and deci-Hz frequencies are expected to detect large numbers of quasi-monochromatic signals. The first and second time-derivative of the GW frequency can be measured for the most favourable sources and used to look for negative post-Newtonian corrections, which can be induced by the source's environment or modifications of general relativity. We present an analytical, Fisher-matrix-based approach to estimate how precisely such corrections can be constrained. We use this method to estimate the bounds attainable on the time evolution of the gravitational constant G(t) with different classes of quasi-monochromatic sources observable with LISA and DECIGO, two representative spaceborne detectors for milli-Hz and deci-Hz GW frequencies. We find that the most constraining source among a simulated population of LISA galactic binaries could yield Gdot/G_0 < 10^-6 yr^-1, while the best currently known verification binary will reach Gdot/G_0 < 10^-4 yr^-1. We also perform Monte-Carlo simulations using quasi-monochromatic waveforms to check the validity of our Fisher-matrix approach, as well as inspiralling waveforms to analyse binaries that do not satisfy the quasi-monochromatic assumption. We find that our analytical Fisher matrix produces good order-of-magnitude constraints even for sources well beyond its regime of validity. Monte-Carlo investigations also show that chirping stellar-mass compact binaries detected by DECIGO-like detectors at cosmological distances of tens of Mpc can yield constraints as tight as Gdot/G_0 < 10^-11 yr^-1.
  3. "Measuring accretion-disk effects with gravitational waves from extreme mass ratio inspirals" , Speri, Antonelli, et al. [Paper]
    Abstract Gravitational wave observations of extreme mass-ratio inspirals (EMRIs) offer the opportunity to probe the environments of active galactic nuclei (AGN) through the torques that accretion disks induce on the binary. Within a Bayesian framework, we study how well such environmental effects can be measured using gravitational wave observations from the Laser Interferometer Space Antenna(LISA). We focus on the torque induced by planetary-type migration on quasi-circular inspirals, and use different prescriptions for geometrically-thin and radiatively-efficient disks. We find that LISA could detect migration for a wide range of disk viscosities and accretion rates, for both α and β disk prescriptions. For a typical EMRI with masses 50M⊙ + 10^6M⊙, we find that LISA could distinguish between migration in α and β disks and measure the torque amplitude with 20 percent relative precision. Provided an accurate torque model, we also show how to turn gravitational-wave measurements of the torque into constraints on the disk properties. Furthermore, if an electromagnetic counterpart is identified, the multimessenger observations of the AGN-EMRI system could yield direct measurements of the disk viscosity. Finally, we investigate the impact of neglecting environmental effects in the analysis of the gravitational-wave signal of our reference system, finding 3-sigma biases in the primary mass and spin. Our analysis can be easily generalized to any environmental effect, provided that the torque has a simple power law-like dependence on the orbital separation.
  4. "A Fisher matrix for gravitational-wave population inference", Gair, Antonelli, Barbieri. [Paper] [Code]
    Abstract We derive a Fisher matrix for the parameters characterising a population of gravitational-wave events. This provides a guide to the precision with which population parameters can be estimated with multiple observations, which becomes increasingly accurate as the number of events and the signal-to-noise ratio of the sampled events increases. The formalism takes into account individual event measurement uncertainties and selection effects, and can be applied to arbitrary population models. We illustrate the framework with two examples: an analytical calculation of the Fisher matrix for the mean and variance of a Gaussian model describing a population affected by selection effects, and an estimation of the precision with which the slope of a power law distribution of supermassive black-hole masses can be measured using extreme-mass-ratio inspiral observations. We compare the Fisher predictions to results from Monte Carlo analyses, finding very good agreement.
  5. "The impact of relativistic corrections on the detectability of dark-matter spikes with gravitational waves", Speeney, Antonelli, Baibhav, Berti. arXiv: 2204.12508 [gr-qc]. Phys.Rev.D. 106 (2022) 4, 044027. [Paper].
    Abstract Black holes located within a dark matter cloud can create overdensity regions known as dark matter spikes. The presence of spikes modifies the gravitational-wave signals from binary systems through changes in the gravitational potential or dynamical friction effects. We assess the importance of including relativistic effects in both the dark matter distribution and the dynamical friction. As a first step we numerically calculate the particle dark matter spike distribution in full general relativity, using both Hernquist and Navarro-Frenk-White profiles in a Schwarzschild background, and we produce analytical fits to the spike profiles for a large range of scale parameters. Then we use a post-Newtonian prescription for the gravitational-wave dephasing to estimate the effect of relativistic corrections to the spike profile and to the dynamical friction. Finally we include the torques generated by dynamical friction in fast-to-generate relativistic models for circular extreme mass-ratio inspirals around a nonspinning black hole. We find that both types of relativistic corrections positively impact the detectability of dark matter effects, leading to higher dephasings and mismatches between gravitational-wave signals with and without dark matter spikes.
  6. "Noisy neighbours: inference biases from overlapping gravitational-wave signals", Antonelli, Burke, Gair. Mon.Not.Roy.Astron.Soc. 507 (2021) 4, 5069-5086. [Paper] [Code].
    Abstract Understanding and dealing with inference biases in gravitational-wave (GW) parameter estimation when a plethora of signals are present in the data is one of the key challenges for the analysis of data from future GW detectors. Working within the linear signal approximation, we describe generic metrics to predict inference biases on GW source parameters in the presence of confusion noise from unfitted foregrounds, from overlapping signals that coalesce close in time to one another, and from residuals of other signals that have been incorrectly fitted out. We illustrate the formalism with simplified, yet realistic, scenarios appropriate to third-generation ground-based (Einstein Telescope) and space-based (LISA) detectors, and demonstrate its validity against Monte Carlo simulations. We find it to be a reliable tool to cheaply predict the extent and direction of the biases. Finally, we show how this formalism can be used to correct for biases that arise in the sequential characterization of multiple sources in a single data set, which could be a valuable tool to use within a global-fit analysis pipeline.
  7. "Gravitational spin-orbit and aligned spin1-spin2 couplings through third-subleading post-Newtonian orders", Antonelli, Kavanagh, Khalil, Steinhoff, Vines. Phys.Rev.D. 102 (2020) 124024. [Paper].
    Abstract The study of scattering encounters continues to provide new insights into the general relativistic two-body problem. The local-in-time conservative dynamics of an aligned-spin binary, for both unbound and bound orbits, is fully encoded in the gauge-invariant scattering-angle function, which is most naturally expressed in a post-Minkowskian (PM) expansion, and which exhibits a remarkably simple dependence on the masses of the two bodies (in terms of appropriate geometric variables). This dependence links the PM and small-mass-ratio approximations, allowing gravitational self-force results to determine new post-Newtonian (PN) information to all orders in the mass ratio. In this paper, we exploit this interplay between relativistic scattering and self-force theory to obtain the third-subleading (4.5PN) spin-orbit dynamics for generic spins, and the third-subleading (5PN) spin1 -spin2 dynamics for aligned spins. We further implement these novel PN results in an effective-one-body framework, and demonstrate the improvement in accuracy by comparing against numerical-relativity simulations.
  8. "Gravitational spin-orbit coupling through third-subleading post-Newtonian order: from first-order self-force to arbitrary mass ratios", Antonelli, Kavanagh, Khalil, Steinhoff, Vines. Phys.Rev.Lett. 125 (2020) 1, 011103. [Paper].
    Abstract Exploiting simple yet remarkable properties of relativistic gravitational scattering, we use first-order self-force (linear-in-mass-ratio) results to obtain arbitrary-mass-ratio results for the complete third-subleading post-Newtonian (4.5PN) corrections to the spin-orbit sector of spinning-binary conservative dynamics, for generic (bound or unbound) orbits and spin orientations. We thereby improve important ingredients of models of gravitational waves from spinning binaries, and we demonstrate the improvement in accuracy by comparing against aligned-spin numerical simulations of binary black holes.
  9. "Quasicircular inspirals and plunges from nonspinning effective-one-body Hamiltonians with gravitational self-force information", Antonelli, van de Meent, Buonanno, Steinhoff, Vines. Phys.Rev.D 101 (2020) 2, 024024. [Paper].
    Abstract The self-force program aims at accurately modeling relativistic two-body systems with a small mass ratio (SMR). In the context of the effective-one-body (EOB) framework, current results from this program can be used to determine the effective metric components at linear order in the mass ratio, resumming post-Newtonian (PN) dynamics around the test-particle limit in the process. It was shown in [Akcay et al., Phys. Rev. D 86, 104041 (2012).PRVDAQ1550-799810.1103/PhysRevD.86.104041] that, in the original (standard) EOB gauge, the SMR contribution to the metric component gtteff exhibits a coordinate singularity at the light-ring (LR) radius. In this paper, we adopt a different gauge for the EOB dynamics and obtain a Hamiltonian that is free of poles at the LR, with complete circular-orbit information at linear order in the mass ratio and non-circular-orbit and higher-order-in-mass-ratio terms up to 3PN order. We confirm the absence of the LR divergence in such an EOB Hamiltonian via plunging trajectories through the LR radius. Moreover, we compare the binding energies and inspiral waveforms of EOB models with SMR, PN and mixed SMR-3PN information on a quasicircular inspiral against numerical-relativity predictions. We find good agreement between numerical-relativity simulations and EOB models with SMR-3PN information for both equal- and unequal-mass ratios. In particular, when compared to EOB inspiral waveforms with only 3PN information, EOB Hamiltonians with SMR-3PN information improves the modeling of binary systems with small mass ratios q≲1/3, with a dephasing accumulated in ∼30 gravitational-wave (GW) cycles being of the order of few hundredths of a radian up to 4 GW cycles before merger.
  10. "Energetics of two-body Hamiltonians in post-Minkowskian gravity", Antonelli, et al. . Phys.Rev.D 99 (2019) 10, 104004. [Paper]
    Abstract Advanced methods for computing perturbative, quantum-gravitational scattering amplitudes show great promise for improving our knowledge of classical gravitational dynamics. This is especially true in the weak-field and arbitrary-speed (post-Minkowskian, PM) regime, where the conservative dynamics at 3PM order has been recently determined for the first time, via an amplitude calculation. Such PM results are most relevantly applicable to relativistic scattering (unbound orbits), while bound/inspiraling binary systems, the most frequent sources of gravitational waves for the LIGO and Virgo detectors, are most suitably modeled by the weak-field and slow-motion (post-Newtonian, PN) approximation. Nonetheless, it has been suggested that PM results can independently lead to improved modeling of bound binary dynamics, especially when taken as inputs for effective-one-body (EOB) models of inspiraling binaries. Here, we initiate a quantitative study of this possibility, by comparing PM, EOB and PN predictions for the binding energy of a two-body system on a quasicircular inspiraling orbit against results of numerical relativity (NR) simulations. The binding energy is one of the two central ingredients (the other being the gravitational-wave energy flux) that enters the computation of gravitational waveforms employed by LIGO and Virgo detectors, and for (quasi)circular orbits it provides an accurate diagnostic of the conservative sector of a model. We find that, whereas 3PM results do improve the agreement with NR with respect to 2PM (especially when used in the EOB framework), it is crucial to push PM calculations at higher orders if one wants to achieve better performances than current waveform models used for LIGO/Virgo data analysis.

Other works

  1. "Accurate waveform models for gravitational-wave astrophysics: synergetic approaches from analytical relativity" Antonelli. PhD thesis. [Link]
    Abstract Gravitational-wave (GW) astrophysics is a field in full blossom. Since the landmark detection of GWs from a binary black hole on September 14th 2015, several compact-object binaries have been reported by the LIGO-Virgo collaboration. Such events carry astrophysical and cosmological information ranging from an understanding of how black holes and neutron stars are formed, what neutron stars are composed of, how the Universe expands, and allow testing general relativity in the highly-dynamical strong-field regime. It is the goal of GW astrophysics to extract such information as accurately as possible. Yet, this is only possible if the tools and technology used to detect and analyze GWs are advanced enough. A key aspect of GW searches are waveform models, which encapsulate our best predictions for the gravitational radiation under a certain set of parameters, and that need to be cross-correlated with data to extract GW signals. Waveforms must be very accurate to avoid missing important physics in the data, which might be the key to answer the fundamental questions of GW astrophysics. The continuous improvements of the current LIGO-Virgo detectors, the development of next-generation ground-based detectors such as the Einstein Telescope or the Cosmic Explorer, as well as the development of the Laser Interferometer Space Antenna (LISA), demand accurate waveform models. [Abridged.]
  2. "An Analysis of Anomaly Cancellation for Theories in D=10" Antonelli. Report for the UTRIP Fellowship. [Link]
    Abstract We prove that the swampland for D=10 N=1 SUGRA coupled to D=10 N= 1 SYM is only populated by U(1)^496 and E8 X U(1)^248. With this goal in mind, we review the anomalies for classical and exceptional groups, retrieving trace identities up to the sixth power of the curvature for each class of groups. We expand this idea for low‐dimensional groups, for which the trace of the sixth power is known to factorize, and we retrieve such factorization. We obtain the total anomaly polynomials for individual low dimensional groups and combinations of them and finally we investigate their non‐factorization, in such a way that U(1)^496 and E8 X U(1)^248 are non‐trivially shown to be the only anomaly‐free theories allowed in D=10. Using the method developed for checking the factorization of gauge theories, we retrieve the Green‐Schwarz terms for the two theories populating the swampland.