arXiv subjects

Marcos Silva

Publications and source records attributed to Marcos Silva.

5 recordsLinked to original sources

arXiv2026

Optical properties of gravitating strings

We study the optical properties of gravitating Abelian-Higgs cosmic strings and compare them with those of the idealized infinitely thin string. We analyze the structure of the corresponding vortex solutions, characterizing their width, curvature profile, and approach to the ideal string limit. By investigating photon propagation in the string spacetime, we show that the finite core of the vortex gives rise to distinctive observational signatures absent in the ideal string approximation, including a characteristic triple-imaging configuration, strong demagnification of the central image, and a nontrivial Shapiro time delay between external and internal images. We determine how these effects depend on the parameters of the Abelian-Higgs model and show that the sign of the time delay is controlled by the ratio of the gauge boson mass to the Higgs boson mass, causing the string core to behave as either a temporal shortcut or a temporal barrier. Our results demonstrate that lensing effects can reveal information about the vortex formation and internal structure.

hep-th↗

arXiv2025

Scalar and spinor fields in gravitating cosmic string spacetimes

We study the scattering behavior of scalar and spinor fields in the background of a gravitating cosmic string spacetime. The model explored here for the background vortex is non-abelian, becoming abelian in an appropriate limiting case. We adopted the formalism we developed in \cite{silva2021scattering}, modifying the standard partial wave approach. We apply the method for a scalar and also a fermion field interacting with the background spacetime with a nontrivial asymptotic structure. The spacetime metric, obtained numerically in \cite{de2015gravitating}, forms the basis of our state-of-the-art numerical study. We make an exhaustive analysis and compare all the results in the non-abelian model with the corresponding abelian one for both massless and massive fields. We analyze the field configuration's total cross-section and angular profile at small and large distances from the core. We show that the total cross-section oscillates with the incident momentum of the wave, as anticipated in \cite{silva2021scattering}, and also, the angular profile can be explained reasonably well with a Fraunhofer diffraction pattern, especially for the scalar field scattering.

hep-th↗

arXiv2025

Toward Integrated Solutions: A Systematic Interdisciplinary Review of Cybergrooming Research

Cybergrooming exploits minors through online trust-building, yet research remains fragmented, limiting holistic prevention. Social sciences focus on behavioral insights, while computational methods emphasize detection, but their integration remains insufficient. This review systematically synthesizes both fields using the PRISMA framework to enhance clarity, reproducibility, and cross-disciplinary collaboration. Findings show that qualitative methods offer deep insights but are resource-intensive, machine learning models depend on data quality, and standard metrics struggle with imbalance and cultural nuances. By bridging these gaps, this review advances interdisciplinary cybergrooming research, guiding future efforts toward more effective prevention and detection strategies.

cs.CY↗

arXiv2021

Cosmic adventures in stringland: Scattering of bosonic and fermionic fields in gravitating cosmic string spacetimes

We show that when considering a scalar field scattering in a gravitating cosmic string spacetime, the standard partial-wave approach's scattering amplitude is singular. In order to avoid the divergence caused by the spacetime asymptotically conical structure, we propose a modification of the asymptotic ansatz in the partial-wave formalism and find the corrections in the phase-shift and total scattering cross-section. We also developed a toy model for the spacetime metric of a cosmic string and showed how local interaction with the vortex gauge field affects the scalar field total cross-section. Then we apply this formalism to a Dirac field and show the explicit formula for the fermionic total cross-section. Finally, we study the scattering of bosonic and fermionic fields in the spacetime of an abelian and a nonabelian gravitating cosmic strings and show that the cross-sections have damped oscillations. In order to understand the origin of this behavior, we used the aforementioned toy model to show that the spacetime particular asymptotical structure causes the observed oscillations.

hep-th↗

arXiv2021

Scattering cross-section in gravitating cosmic string spacetimes

We propose a modification of the partial wave approach to deal with the relativistic quantum scattering of bosonic and fermionic particles in a class of models concerning gravitating cosmic string spacetimes. These spacetimes are characterized by the Minkowski line element at the center of the vortex, non-vanishing curvature at a finite distance from the center but with a conical structure far from the core. We find the correction in the partial wave expansion and the phase shift. Consequently, we show the explicit form of the scattering amplitude and the correction to the differential cross-section for a massive scalar field. We also implement our formalism in a toy model mimicking this class of gravitating cosmic string spacetime. Moreover, we discuss the procedure to apply this formalism to a massive Dirac field.

hep-th↗