arXiv subjects

Haroldo C. D. Lima

Publications and source records attributed to Haroldo C. D. Lima.

3 recordsLinked to original sources

arXiv2026

Inspirals into bosonic dark matter stars and chirp mimickers

We investigate extreme--mass--ratio inspirals in which a stellar-mass compact object orbits a supermassive bosonic dark matter star, modeled as a boson star, using fully relativistic perturbative methods. Unlike inspirals around electro-vacuum black holes, these systems can shed scalar matter through dynamical friction which significantly alters the inspiral dynamics. We show that this additional dissipation can induce a chirp-like gravitational-wave signal closely resembling that of black hole binaries, allowing boson stars to act as gravitational-wave chirp mimickers even when they are not ultracompact. The inspiral evolution and resulting waveform depend sensitively on the compactness of the central boson star: highly compact configurations trigger dipolar scalar radiation, leading to a rapid plunge, whereas less compact stars yield smoother inspirals dominated by gravitational and quadrupolar scalar waves. To support waveform modeling, we derive semi-analytical prescriptions for the gravitational and scalar energy fluxes that remain accurate deep into the relativistic regime. Our findings indicate that future space-based detectors such as LISA could distinguish these mimicker signals from true black hole inspirals through measurable phase dephasings induced by scalar dissipation.

gr-qc↗

arXiv2026

Two shadows of a single black hole: Vacuum birefringence phenomena within Einstein-nonlinear-electrodynamics

One of the main features of nonlinear electrodynamics is the existence of an effective geometry that describes the geodesic motion of photons. A detailed analysis of the properties of effective geometry is of utmost importance for a better understanding of nonlinear electrodynamics theories and their possible imprints on physics, especially in the context of black holes. We consider a nonlinear electrodynamics model that depends on the two electromagnetic scalar invariants and obtain that the motion of photons in nonlinear electrodynamics exhibits \textit{vacuum birefringence}, i.e., photons can propagate along two distinct paths, depending on their polarization. As a consequence of this phenomenon, we show that static black hole solutions sourced by nonlinear electrodynamics can admit two distinct unstable light rings, leading to the formation of two distinct shadows. Moreover, to explore the potential astrophysical relevance of our results, we also compare them with the astrophysical observations for the shadow radius of Sagittarius A*. We place upper limits on the charge-to-mass ratio of the nonlinear electrodynamics-sourced black hole. We also show that the motion of photons in this context can be interpreted as nongeodesic curves subjected to a four-force term from the perspective of an observer in the spacetime metric, generalizing previous results in the literature for nonlinear electrodynamics models that depend on a single electromagnetic scalar invariant.

gr-qc↗

arXiv2025

Spherical Einstein-Friedberg-Lee-Sirlin boson stars: Self-interacting solutions and their astrophysical appearance

We investigate boson stars within the framework of the self-interacting Einstein-Friedberg-Lee-Sirlin (E-FLS) model, constituted by a complex scalar field with a quartic self-interaction and a real scalar field. Our analysis explores the family of static solutions across a broad range of parameters, including the self-interaction of the complex scalar field. We obtain that positive self-interaction terms increase the maximum mass and compactness of E-FLS stars, allowing them to reach masses comparable to the Chandrasekhar limit without the need of ultralight bosonic masses. Moreover, in the limit where the real scalar field becomes massless, the solutions present larger effective radii and allow a broader range of stable solutions. Astrophysical images, generated via backward ray-tracing, show that these compact, self-interacting E-FLS stars produce strong gravitational lensing, yielding shadows that could visually mimic black holes, thus providing potential observational signatures detectable in ongoing electromagnetic surveys.

gr-qc↗