arXiv subjects

Piero Rettegno

Publications and source records attributed to Piero Rettegno.

At least 19 recordsLinked to original sources

arXiv2026

High-order effective-one-body tidal interactions and gravitational scattering

Using state-of-the-art scattering results in post-Minkowskian (PM) gravity, we improve the tidal sector of four different flavors of the effective-one-body (EOB) formalism. We notably explore both adiabatic and post-adiabatic gravitoelectric and gravitomagnetic quadrupolar tidal effects at the next-to-next-to-leading PM-order. When comparing the predictions of the so-constructed Lagrange-PM-tidal version of EOB to recent numerical-relativity data on the scattering of neutron stars, we find improved agreement with respect to existing EOB models and PM expansions. Our work lays the foundation for the development of an accurate tidal sector of the PM EOB models, and points out the need to explore improved resummation schemes in PN EOB for bound and circularized orbits.

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arXiv2026

A novel Lagrange-multiplier approach to the effective-one-body dynamics of binary systems in post-Minkowskian gravity

We present a new approach to the conservative dynamics of binary systems, within the effective one-body (EOB) framework, based on the use of a Lagrange multiplier to impose the mass-shell constraint. When applied to the post-Minkowskian (PM) description of the two-body problem in Einsteinian gravity, this Lagrange-EOB (LEOB) approach allows for a new formulation of the conservative dynamics that avoids the drawbacks of the recursive definition of EOB-PM Hamiltonians. Using state-of-the-art expressions of the resummed waveform and radiation reaction, we apply our new formalism to the construction of an aligned-spin, quasi-circular, inspiraling EOB waveform model, called {\tt LEOB-PM}, that incorporates analytical information up to the 4PM level, completed by 4PN contributions up to the sixth order in eccentricity, in the orbital sector, and by 4.5PN contributions, in the spin-orbit sector. In the nonspinning case, we find that an uncalibrated LEOB-PM model delivers maximum EOB/NR unfaithfulness ${\bar{F}}_{\rm EOBNR}$ (with the Advanced LIGO noise in the total mass range $10-200M_\odot$) varying between $0.2\%$ and $1\%$ over all the nonspinning dataset of the Simulating eXtreme Spacetime (SXS) Numerical Relativity (NR) catalog up to mass ratio $q=15$. It also delivers excellent phasing agreement with the $q=32$ configuration of the RIT catalog. We also found consistency between binding energies within a few percent at the NR merger location. Then, when NR-informing the dynamics of the model (both orbital and spinning sectors) by using 17 SXS dataset, we find that the EOB/NR unfaithfulness (compared to 530 spin-aligned SXS waveforms) has a median value of $5.39\times 10^{-4}$, or $6.13\times 10^{-4}$ (depending on the spin-spin interactions), reaching at most $\sim 1\%$ in some of the high-spin corners.

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arXiv2025

Gravitational scattering of two neutron stars

We present the first numerical relativity simulations of the gravitational scattering of two neutron stars. Constraint-satisfying initial data for two equal-mass nonspinning sequences are constructed at fixed energy and various initial angular momenta (impact parameter) and evolved with Einstein equations through the scattering process. The strong-field scattering dynamics are explored up to scattering angles of $220^\circ$ and the threshold of dynamical captures. The transition to bound orbits is aided by significant mass ejecta up to baryon mass ${\sim}0.1M_\odot$. A quantitative comparison with predictions of the scattering angle from state-of-the-art effective-one-body and post-Minkowskian calculations indicates quantitative agreement for large initial angular momenta although significant discrepancies in the tidal contribution emerge toward the capture threshold. Gravitational waveforms and radiated energy are in qualitative agreement with the analogous black hole problem and state-of-the-art effective-one-body predictions. Toward the capture threshold waveforms from scattering dynamics carry a strong imprint of matter effects, including the stars' $f$-mode excitations during the close encounter. Overall, our simulations open a new avenue to study tidal interactions in the relativistic two-body problem.

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arXiv2025

Radiation reaction force for scalar-tensor theories in effective-one-body formalism

Whilst most of the binary configurations in modified theories of gravity are studied under quasi-circular orbit limit, eccentricity effects could play a significant role in future gravitational wave detections. We derive the gravitational radiation-reaction force for nonspinning eccentric orbits within the effective-one-body (EOB) description for the massless scalar-tensor theories up to 1.5 post-Newtonian (PN) order. The effects in such theories start at $1/c^3$ and interestingly, the 1.5PN order effect is due to the radiation reaction square effects which is a conservative effect. The results derived here can be implemented in the quasi-circular EOB-based waveform models to construct waveform templates for generic orbit binaries within massless scalar-tensor theories of gravity.

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arXiv2025

Effective-one-body waveform model for noncircularized, planar, coalescing black hole binaries II:high accuracy by improving logarithmic terms in resummations

Effective-one-body (EOB) models are based on analytical building blocks that, mathematically, are truncated Taylor series with logarithms. These functions are usually resummed using Padé approximants obtained first assuming that the logarithms are constant, and then replacing them back into the resulting rational functions. A recent study pointed out that this procedure introduces spurious logarithmic terms when the resummed functions are reexpanded. Here we update the TEOBResumS-Dalí waveform model for spin-aligned, noncircularized coalescing black hole binaries by systematically implementing new (still Padé based) resummations for all EOB functions (that is, the metric potentials $A, D$ and the residual waveform amplitude corrections $ρ_{\ell m}$ up to $\ell=8$). Once the model is informed by 50 Numerical Relativity simulations, this new approach proves key in lowering the maximum EOB/NR unfaithfulness $\bar{F}_{\rm EOBNR}^{\rm max}$ for the $\ell=m=2$ mode (with the Advanced LIGO noise in the total mass range $10-200M_{\odot}$) over 530 spin-aligned waveforms of the Simulating eXtreme Spacetimes catalog. A median unfaithfulness equal to $3.09\times 10^{-4}$ is achieved, which is a marked improvement over the previous value, $1.06\times 10^{-3}$. The largest value, ${\rm Max}[\bar{F}^{\rm max}_{\rm EOBNR}]= 6.80\times 10^{-3}$, is found for an equal-mass, equal-spin simulation with dimensionless spins $\sim +0.998$; only five configurations have $\bar{F}^{\rm max}_{\rm EOBNR} > 5\times 10^{-3}$ (four of which equal-mass and with equal spins larger than $\sim +0.98$). Results for eccentric binaries are similarly excellent (well below $10^{-2}$ and mostly around $10^{-3}$).

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arXiv2024

Effective-one-body waveform model for non-circularized, planar, coalescing black hole binaries: the importance of radiation reaction

We present an updated version of the TEOBResumS-Dali effective-one-body (EOB) waveform model for spin aligned binaries on non-circularized orbits. Recently computed 4PN (nonspinning) terms are incorporated in the waveform and radiation reaction. The model is informed by a restricted sample ($\sim60$) of spin-aligned, quasi-circular, Numerical Relativity (NR) simulations. In the quasi-circular limit, the model displays EOB/NR unfaithfulness ${\bar{F}}^{\rm max}_{\rm EOBNR}\lesssim 10^{-2}$ (with median~ $1.06\times 10^{-3}$) (with Advanced LIGO noise and in the total mass range $10-200M_\odot$) for the dominant $\ell=m=2$ mode all over the 534 spin-aligned configurations available through the Simulating eXtreme Spacetime catalog of NR waveforms. Similar figures are also obtained with the 28 public eccentric SXS simulations and good compatibility between EOB and NR scattering angles is found. The quasi-circular limit of TEOBResumS-Dali is also found to be highly consistent with the TEOBResumS-GIOTTO quasi-circular model. We then systematically explore the importance of NR-tuning {\it also} the radiation reaction of the system. When this is done, the median of the distribution of quasi-circular ${\bar{F}}^{\rm max}_{\rm EOBNR}$ is lowered to $3.92\times 10^{-4}$, though balanced by a tail up to $\sim 0.1$ for large, positive spins. The same is true for the eccentric-inspiral datasets. We conclude that an improvement of the analytical description of the spin-dependent flux (and its interplay with the conservative part) is likely to be the cornerstone to lower the EOB/NR unfaithfulness below the $10^{-4}$ level all over the parameter space, thus grazing the current NR uncertainties as well as the expected needs for next generation of GW detector like Einstein Telescope.

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arXiv2024

Angular Momentum Flux in Scalar-Tensor Theories up to 1.5 post-Newtonian Order

We compute the angular momentum flux from a non-circular nonspinning binary system of compact objects in massless scalar-tensor theories up to one and a half post-Newtonian (1.5PN) order using multipole moments. The angular momentum flux in scalar-tensor theories involves both a tensorial and a scalar contribution which can be further decomposed as instantaneous, tail and non-linear memory effects up to 1.5PN order. We compute the explicit expressions of tail effects using the Fourier decomposition of tensorial and scalar multipole moments, and non-linear memory effects using the Newtonian order quasi-Keplerian representation of elliptic orbits in scalar-tensor theories. This work is important to construct the radiation-reaction force and hence the waveform templates for eccentric binaries in scalar-tensor theories of gravity.

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arXiv2024

Gravitational spin-orbit coupling through the third-subleading post-Newtonian order: exploring spin-gauge flexibility

We build upon recent work by Antonelli et al. [Phys. Rev. Lett. 125 (2020) 1, 011103] to obtain, within the effective-one-body (EOB) formalism, and for an arbitrary choice of gauge, the third-subleading post-Newtonian (4.5PN) corrections to the spin-orbit conservative dynamics of spin-aligned binaries. This is then specialized to: (i) the well-known Damour-Jaranowski-Schäfer ($\rm DJS$) gauge, where the dependence on the angular momentum of the gyro-gravitomagnetic functions $(G_S,G_{S_*})$ is removed and (ii) to an alternative gauge (called anti-$\rm DJS$ gauge, $\overline{\rm DJS}$) that is chosen so as to precisely reproduce the Hamiltonian of a spinning test-particle at linear order in the particle spin and keep the full dependence on the radial and angular momentum in $(G_S,G_{S_*})$. We use these results to extend by one perturbative order, in PN sense, the analytical knowledge of the periastron advance. After performing a suitable factorization and resummation of $(G_S,G_{S_*})$, the $\rm DJS$ and $\overline{\rm DJS}$ performances are compared via various gauge-invariant quantities at the EOB last stable circular orbit. We eventually find some indications that the $\overline{\rm DJS}$ gauge might be advantageous in the description of the inspiral dynamics of circularized binaries.

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arXiv2023

Analytic systematics in next-generation of effective-one-body gravitational waveform models for future observations

The success of analytic waveform modeling within the effective-one-body (EOB) approach relies on the precise understanding of the physical importance of each technical element included in the model. The urgency of constructing progressively more sophisticated and complete waveform models (e.g. including spin precession and eccentricity) partly defocused the research from a careful comprehension of each building block (e.g. Hamiltonian, radiation reaction, ringdown attachment). Here we go back to the spirit of the first EOB works. We focus first on nonspinning, quasi-circular, black hole binaries and analyze systematically the mutual synergy between numerical relativity (NR) informed functions and the high post-Newtonian corrections (up to 5PN) to the EOB potentials. Our main finding is that it is essential to correctly control the noncircular part of the dynamics during the late plunge up to merger. We then improve the {\tt TEOBResumS-GIOTTO} waveform model for quasi-circular, spin-aligned black hole binaries. We obtain maximal EOB/NR unfaithfulness ${\bar{F}}^{\rm max}_{\rm EOBNR}\sim 10^{-3}$ (with Advanced LIGO noise and in the total mass range $10-200M_\odot$) for the dominant $\ell=m=2$ mode all over the 534 spin-aligned configurations available through the Simulating eXtreme Spacetime catalog. The model performance, also including higher modes, is then explored using the NR surrogates \nrsurqeight{} and \nrsurqfifteen, to validate it up to mass ratio $m_1/m_2=15$. We find that, over the set of configurations considered, more than $98\%$ of the total-mass-maximized unfaithfulness lie below the $3\%$ threshold when comparing to the surrogate models.

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arXiv2023

Double copy, Kerr-Schild gauges and the Effective-One-Body formalism

We look for a classical double copy structure between gravity and electrodynamics by connecting the descriptions of the scattering of two point masses, and of two point charges, in terms of perturbative (post-Minkowskian or post-Lorentzian) expansions. We do so by recasting available analytical information within the effective-one-body formalism using Kerr-Schild gauges in both cases. Working at the third perturbative level, we find that the usual linear relation (holding in the probe limit) between the dimensionless electric potential, $\tildeϕ= \frac{G M}{e_1 e_2} ϕ^{\rm el}$, and the Schwarzschildlike gravitational one, $Φ^{\rm grav}$, is deformed, in the comparable-mass, comparable-charge, case, into a nonlinear relation which becomes universal in the high energy limit: $Φ^{\rm grav}= 2\tildeϕ-5\tildeϕ^2 + 18\tildeϕ^3$.

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arXiv2023

Strong-field scattering of two spinning black holes: Numerical Relativity versus post-Minkowskian gravity

Highly accurate models of the gravitational-wave signal from coalescing compact binaries are built by completing analytical computations of the binary dynamics with non-perturbative information from numerical relativity (NR) simulations. In this paper we present four sets of NR simulations of equal-mass black hole binaries that undergo strong-field scattering: (i) we reproduce and extend the nonspinning simulations first presented in [Damour \textit{et al.}, Phys.Rev.D 89 (2014) 8, 081503], (ii) we compute two suites of nonspinning simulations at higher energies, probing stronger field interactions, (iii) we present a series of \textit{spinning} simulations including, for the first time, unequal-spin configurations. When comparing the NR scattering angles to analytical predictions based on state-of-the-art post-Minkowskian (PM) calculations, we find that PM-expanded scattering angles show poor convergence towards NR data. By contrast, a resummed computation of scattering angles via a spin-dependent, radiation-reacted, effective-one-body potential shows excellent agreement for both nonspinning and spinning configurations.

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arXiv2023

Spin-orbit contribution to radiative losses for spinning binaries with aligned spins

We compute the leading order contribution to radiative losses in the case of spinning binaries with aligned spins due to their spin-orbit interaction. The orbital average along hyperboliclike orbits is taken through an appropriate spin-orbit modification to the quasi-Keplerian parametrization for nonspinning bodies, which maintains the same functional form, but with spin-dependent orbital elements. We perform consistency checks with existing PN-based and PM-based results. In the former case, we compare our expressions for both radiated energy and angular momentum with those obtained in [JHEP \textbf{04}, 154 (2022)] by applying the boundary-to-bound correspondence to known results for ellipticlike orbits, finding agreement. The linear momentum loss is instead newly computed here. In the latter case, we also find agreement with the low-velocity limit of recent calculations of the total radiated energy, angular momentum and linear momentum in the framework of an extension of the worldline quantum field theory approach to the classical scattering of spinning bodies at the leading post-Minkowskian order [Phys. Rev. Lett. \textbf{128}, no.1, 011101 (2022), Phys. Rev. D \textbf{106}, no.4, 044013 (2022)]. We get exact expressions of the radiative losses in terms of the orbital elements, even if they are at the leading post-Newtonian order, so that their expansion for large values of the eccentricity parameter (or equivalently of the impact parameter) provides higher-order terms in the corresponding post-Minkowskian expansion, which can be useful for future crosschecks of other approaches.

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arXiv2023

Strong-field scattering of two black holes: Numerical Relativity meets Post-Minkowskian gravity

We compare numerical relativity (NR) data on the scattering of equal-mass, non-spinning binary black holes to various analytical predictions based on post-Minkowskian (PM) results. While the usual sequence of PM-expanded scattering angles shows a rather poor convergence towards NR data, we find that a reformulation of PM information in terms of Effective-One-Body radial potentials leads to remarkable agreement with NR data, especially when using the radiation-reacted 4PM information. Using Firsov's inversion formula we directly extract, for the first time, from NR simulations a (radiation-reacted) gravitational potential describing the scattering of equal-mass, non-spinning binary black holes. We urge the NR community to compute more sequences of scattering simulations, so as to extend this knowledge to a wider region of parameter space.

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arXiv2023

Inferring eccentricity evolution from observations of coalescing binary black holes

The origin and formation of stellar-mass binary black holes remains an open question that can be addressed by precise measurements of the binary and orbital parameters from their gravitational-wave signal. Such binaries are expected to circularize due to the emission of gravitational waves as they approach merger. However, depending on their formation channel, some binaries could have a non-negligible eccentricity when entering the frequency band of current gravitational-wave detectors. In order to measure eccentricity in an observed gravitational-wave signal, accurate waveform models that describe binaries in eccentric orbits are necessary. In this work we demonstrate the efficacy of the improved TEOBResumS waveform model for eccentric coalescing binaries with aligned spins. We first validate the model against mock signals of aligned-spin binary black hole mergers and quantify the impact of eccentricity on the estimation of other intrinsic binary parameters. We then perform a fully Bayesian reanalysis of GW150914 with the eccentric waveform model. We find (i) that the model is reliable for aligned-spin binary black holes and (ii) that GW150914 is consistent with a non-eccentric merger although we cannot rule out small values of initial eccentricity at a reference frequency of $20$ Hz. Finally, we present a systematic method to measure the eccentricity and its evolution directly from the gravitational-wave posterior samples. Such an estimator is useful when comparing results from different analyses as the definition of eccentricity may differ between models. Our scheme can be applied even in the case of small eccentricities and can be adopted straightforwardly in post-processing to allow for direct comparison between models.

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arXiv2022

Effective one body Hamiltonian in scalar-tensor gravity at third post-Newtonian order

We determine the general local-in-time effective-one-body (EOB) Hamiltonian for massless Scalar-Tensor (ST) theories at third post-Newtonian (PN) order. Starting from the Lagrangian derived in [Phys. Rev. D 99, 044047 (2019)], we map it to the corresponding ordinary Hamiltonian describing the two-body interaction in ST theories at 3PN level. Using a canonical transformation, we then map this onto an EOB Hamiltonian so as to determine the ST corrections to the 3PN-accurate EOB potentials $(A,B,Q_e)$ at 3PN. We then focus on circular orbits and compare the effect of the newly computed 3PN terms, also completed with finite-size and nonlocal-in-time contributions, on predictions for the frequency at the innermost stable circular orbit. Our results will be useful to build high-accuracy waveform models in ST theory, which could be used to perform precise tests against General Relativity using gravitational wave data from coalescing compact binaries.

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arXiv2022

GW190521 as a dynamical capture of two nonspinning black holes

Gravitational waves from $\sim 90$ black holes binary systems have currently been detected by the LIGO and Virgo experiments, and their progenitors' properties inferred. This allowed the scientific community to draw conclusions on the formation channels of black holes in binaries, informing population models and -- at times -- defying our understanding of black hole astrophysics. The most challenging event detected so far is the short duration gravitational-wave transient GW190521. We analyze this signal under the hypothesis that it was generated by the merger of two nonspinning black holes on hyperbolic orbits. The best configuration matching the data corresponds to two black holes of source frame masses of $81^{+62}_{-25}M_\odot$ and $52^{+32}_{-32}M_\odot$ undergoing two encounters and then merging into an intermediate-mass black hole. We find that the hyperbolic merger hypothesis is favored with respect to a quasi-circular merger with precessing spins with Bayes' factors larger than 4300 to 1, although this number will be reduced by the currently uncertain prior odds. Our results suggest that GW190521 might be the first gravitational-wave detection from the dynamical capture of two stellar-mass nonspinning black holes.

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arXiv2022

Strong-field scattering of two spinning black holes: Numerics versus Analytics

We present new Numerical Relativity calculations of the scattering angle $χ$ between two, equal-mass, black holes on hyperbolic-like orbits. We build upon previous work considering, for the first time, spinning black holes, with equal spins either aligned or antialigned with the orbital angular momentum. We detail the numerical techniques used in the computation of $χ$. Special care is taken in estimating error uncertainties on the quantities computed. The numerical values are compared with analytical predictions obtained using a new, state-of-the-art, effective one body model valid on generic orbits that incorporates post-Newtonian analytic information up to 5PN in the nonspinning, conservative sector and that has been additionally informed by Numerical Relativity simulations of quasi-circular coalescing black hole binaries. Our results indicate that the spin sector of the analytic model should be improved further in order to achieve satisfactory consistency with the most relativistic spinning configurations.

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arXiv2021

Waveforms and fluxes: Towards a self-consistent effective one body waveform model for nonprecessing, coalescing black-hole binaries for third generation detectors

We present a comprehensive comparison between numerical relativity (NR) angular momentum fluxes at infinity and the corresponding quantity entering the radiation reaction in TEOBResumS, an Effective-One-Body (EOB) waveform model for nonprecessing coalescing black hole binaries on quasi-circular orbits. This comparison prompted us to implement two changes in the model: (i) including Next-to-Quasi-Circular corrections in the $\ell=m$, $\ell\leq 5$ multipoles entering the radiation reaction and (ii) consequently updating the NR-informed spin-orbital sector of the model. This yields a new waveform model that presents a higher self-consistency between waveform and dynamics and an improved agreement with NR simulations. We test the model computing the EOB/NR unfaithfulness $\bar{F}_{\rm EOB/NR}$ over all 534 spin-aligned configurations available through the Simulating eXtreme Spacetime catalog, notably using the noise spectral density of Advanced LIGO, Einstein Telescope and Cosmic Explorer, for total mass up to $500M_\odot$. We find that the maximum unfaithfulness $\bar{F}^{\rm max}_{\rm EOB/NR}$ is mostly between $10^{-4}$ and $10^{-3}$, and the performance progressively worsens up to $\sim 5\times 10^{-3}$ as the effective spin of the system is increased. We perform similar analyses on the \SEOB{} model, that delivers $\bar{F}^{\rm max}_{\rm EOB/NR}$ values uniformly distributed versus effective spin and mostly between $10^{-3}$ and $10^{-2}$. We conclude that the improved TEOBResumS model already represents a reliable and robust first step towards the development of highly accurate waveform templates for third generation detectors.

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