arXiv subjects

Saulo Albuquerque

Publications and source records attributed to Saulo Albuquerque.

8 recordsLinked to original sources

arXiv2026

Optimal frequency scales for probing black-hole geometries

Can gravitational waves probe the near-horizon geometry of black holes, and if yes, which frequency scale is optimal? Although shorter wavelengths usually resolve smaller scales, we show that black-hole scattering may impose an information-theoretic optimum. We study a controlled scattering Gedankenexperiment in which Gaussian pulses of scalar test fields are sent toward a black- hole potential and the reflected waveform is used to infer the geometry. Near-horizon deviations are parametrized with the Rezzolla-Zhidenko metric, and information recovery is quantified by the Fisher matrix in the high-signal-to-noise limit. Narrow, high-frequency pulses resolve short scales but are mostly transmitted through the barrier, while wide pulses are efficiently reflected but poorly resolve the potential. Their competition selects an optimal pulse width, numerically found to be set by about the inverse square root of the potential peak. Using the P\"oschl-Teller analytical solutions, we further model the correct excitation of quasinormal modes and separate the information in the fundamental mode from that in the full waveform, including the prompt response. The optimal probe is therefore not the highest-frequency pulse, but the waveform that balances spatial resolution against reflected information, linking black-hole spectroscopy, semiclassical barrier scattering, and information theory.

gr-qc↗

arXiv2026

The Sequential Monte Carlo goes NUTS: Boosting Gravitational-Wave Inference

Sequential Monte Carlo (SMC) methods have recently been applied to gravitational-wave inference as a powerful alternative to standard sampling techniques, such as Nested Sampling. At the same time, gradient-based Markov Chain Monte Carlo algorithms, most notably the No-U-Turn Sampler (NUTS), provide an efficient way to explore high-dimensional parameter spaces. In this work we present SHARPy, a Bayesian inference framework that combines the parallelism and evidence-estimation capabilities of SMC with the state-of-the-art sampling performance of NUTS. Moreover, SHARPy exploits the local geometric structure of the posterior to further improve efficiency. Built on JAX, a high-performance computing framework that enables automatic differentiation and hardware acceleration, SHARPy performs gravitational-wave inference on binary black-hole events in around ten minutes, yielding posterior samples and Bayesian evidence estimates that are consistent with those obtained through Nested Sampling. This work sets a new milestone in Gravitational-Wave inference with likelihood-based methods and paves the way for model comparison tasks to be accomplished in minutes.

gr-qc↗

arXiv2025

Bayesian analysis of analog gravity systems with the Rezzolla-Zhidenko metric

Analog gravity systems have the unique opportunity to probe theoretical aspects of black hole physics in a controlled laboratory environment that one cannot easily observe for astrophysical black holes. In this work, we address the question of whether one could use controlled initial perturbations to excite the black hole ringdown and infer the effective black hole metric. Using a theory-agnostic ansatz for the effective metric described by the Rezzolla-Zhidenko metric and evolving perturbations on that background, we quantify with Bayesian analysis what regions of the effective spacetime could be constrained in experiments. In contrast to standard ringdown analyses based on quasi-normal mode extraction, a laboratory-controlled setup, in combination with our framework, allows one to model the entire signal, including the prompt response and possible effects of late-time tails. Therefore, it has the intriguing advantage of not relying on start and end times when the superposition of quasi-normal modes is a good signal approximation. It also avoids the non-trivial question of how many modes are present. We demonstrate that this approach is feasible in principle and discuss opportunities beyond this study.

gr-qc↗

arXiv2024

Inverse problem of analog gravity systems II: Rotation and energy-dependent boundary conditions

In this work, we study the inverse problem of analog gravity systems which admit rotation and energy-dependent boundary conditions. By extending two recent results, we provide a recipe that allows one to relate resonant transmission spectra with effective potentials and even reconstruct the boundary condition at the core. Our methodology is based on the WKB method and the identification of universal features in the transmission. One of the main advantages of this method is that it is parameter-free, and relies only on general properties of the underlying potential, instead of specific models. While the reconstruction of underlying potentials is generally not uniquely possible, the inverse method provides effective potentials with similar spectral properties to the original one. To demonstrate the accuracy and scope of our method, we apply it to a rotating imperfect draining vortex, which has been proposed as an analog system to astrophysical extreme compact objects. We conclude that the capability to explore energy-dependent boundary conditions could be of interest for experimental studies of such systems.

gr-qc↗

arXiv2024

Inverse problem in energy-dependent potentials using semiclassical methods

Wave equations with energy-dependent potentials appear in many areas of physics, ranging from nuclear physics to black hole perturbation theory. In this work, we use the semi-classical WKB method to first revisit the computation of bound states of potential wells and reflection/transmission coefficients in terms of the Bohr-Sommerfeld rule and the Gamow formula. We then discuss the inverse problem, in which the latter observables are used as a starting point to reconstruct the properties of the potentials. By extending known inversion techniques to energy-dependent potentials, we demonstrate that so-called width-equivalent or WKB-equivalent potentials are not isospectral anymore. Instead, we explicitly demonstrate that constructing quasi-isospectral potentials with the inverse techniques is still possible. Those reconstructed, energy-independent potentials share key properties with the width-equivalent potentials. We report that including energy-dependent terms allows for a rich phenomenology, particularly for the energy-independent equivalent potentials.

hep-ph↗

arXiv2024

Inverse problem of analog gravity systems

Analog gravity models of black holes and exotic compact objects provide a unique opportunity to study key properties of such systems in controlled laboratory environments. In contrast to astrophysical systems, analog gravity systems can be prepared carefully and their dynamical aspects thus investigated in unprecedented ways. While gravitational wave scattering properties of astrophysical compact objects are more connected to quasinormal modes, laboratory experiments can also access the transmission and reflection coefficients, which are otherwise mostly relevant for Hawking radiation related phenomena. In this work, we report two distinct results. First, we outline a semiclassical, nonparametric method that allows for the reconstruction of the effective perturbation potential from the knowledge of transmission and reflection coefficients for certain types of potentials in the Schrödinger wave equation admitting resonant tunneling. Second, we show how to use our method by applying it to an imperfect draining vortex, which has been suggested as an analog of extreme compact objects. Although the inverse problem is, in general, not unique, choosing physically motivated assumptions and requiring the validity of semiclassical theory, we demonstrate that the method provides efficient and accurate results.

gr-qc↗

arXiv2023

Massless Dirac Perturbations in a Consistent Model of Loop Quantum Gravity Black Hole: Quasinormal Modes and Particle Emission Rates

We consider perturbations of the massless Dirac field in the background of a black hole solution found by Bodendorfer, Mele, and Münch (BMM), using a polymerization technique that furnishes contributions inspired by Loop Quantum Gravity (LQG) Theory. Using the sixth order WKB method, we analyzed its quasinormal modes for several modes, multipole numbers and the two classes of BMM black holes. We also considered the potential that governs these perturbations to analyze the bound on the Greybody Factor (GF) due the emission rates of particles. As results, we found that the Loop Quantum Gravity parameters are responsible for raising the potential and the real and imaginary parts of the quasinormal frequencies and decrease the bound on the Greybody Factor for the two classes of black holes (with more prominent effects for the de-amplification case, which is compatible with previous analyses done for other fields).

gr-qc↗

arXiv2023

Quantum Configuration and Phase Spaces: Finsler and Hamilton Geometries

In this paper, we review two approaches that can describe, in a geometrical way, the kinematics of particles that are affected by Planck-scale departures, named Finsler and Hamilton geometries. By relying on maps that connect the spaces of velocities and momenta, we discuss the properties of configuration and phase spaces induced by these two distinct geometries. In particular, we exemplify this approach by considering the so-called $q$-de Sitter-inspired modified dispersion relation as a laboratory for this study. We finalize with some points that we consider as positive and negative ones of each approach for the description of quantum configuration and phases spaces.

gr-qc↗