arXiv subjects

D. Suárez-Fontanella

Publications and source records attributed to D. Suárez-Fontanella.

4 recordsLinked to original sources

arXiv2026

Resonant Axion-Photon Conversion in the Early Inspiral of Neutron Star Binaries

We consider the early binary neutron star inspiral phase as a scenario to probe environmental axion--photon resonant conversion. For this we approximately model the merger site electromagnetic fields as the superposition of two rotating dipolar stellar magnetic fields at the thousand--km scale when both magnetospheres are not largely distorted. We capture the time-sliced near-zone magnetospheric geometry relevant for axion--photon mixing. Plasma effects are incorporated through an effective Goldreich--Julian charge density, used to determine the effective plasma frequency and the location of resonant conversion surfaces. Our results show that axion--photon resonant conversion in binary magnetospheres mostly occurs on extended peanut-shaped surfaces whose global geometry evolves as the binary inspiral evolves. As a consequence, the total electromagnetic power emitted through axion--photon conversion exhibits a characteristic dependence on axion mass and a slow temporal modulation correlated with the gravitational wave frequency emission. This feature is potentially detectable for $m_a \in [50,170] \,\rm μeV$ and set $g_{a γ} \lesssim 10^{-11}\rm \,GeV^{-1}$ as it lies within the sensitivity limits of current or planned radio observation missions. In light of our results we discuss the opportunity of binary neutron star inspirals as time-dependent, multimessenger probes of axion physics, and motivate coordinated searches combining gravitational wave observations with radio and millimeter wavelength electromagnetic measurements.

astro-ph.HE↗

arXiv2025

Probing ALP-photon couplings in Neutron Stars: Scalar versus pseudoscalar cases

We investigate the distribution of an interacting axion-like massive field within a magnetized Neutron Star. For this we consider the effect of an intense density-dependent axially symmetric stellar magnetic field ${\bf B}(r,θ)$ adding another much weaker, but non-vanishing, electric field. We particularize the latter for the case when a finite chiral charge density is present. The axion field is thus coupled to a generic function $Q(F_0,G_0)$ depending on Lorentz invariants $F_0, G_0$ which can be constructed from these electromagnetic fields. From this, the static axion field equations are solved as function of stellar radial coordinate and angular direction, $a(r,θ)$, using a prescribed linear form for $Q$. In addition, we use a semi-analytical approach to calculate the stellar structure in this hybrid system where pressure components are treated under a perturbative scheme, provided induced deformations with respect to spherical symmetry are tiny. Our results show that the axion couplings to magnetic and electric fields along with its mass, critically determine the axion spatial distribution. Furthermore, we focus on the possibility that the axion field might accumulate in specific outer regions of the star, particularly within the crust, where it could form a condensate. We explore the possible presence of magnetic flux tubes from superconductor phases in this outer layers and qualitatively show they may enhance local conversion into photons. We explore prospects of detectability through indirect methods.

astro-ph.HE↗

arXiv2025

About the Upstream Contamination

This study investigates the upward transport of waterborne pollutants from a lower container to an upper container through vertically falling water streams. While previous analyses have primarily focused on inclined channels, we extend the theoretical framework to consider vertical configurations. Two distinct cases are examined: (i) a vertical flow within a cylindrical tube, and (ii) a free-falling water jet. For the first case, we derive an analytical expression for the critical water flux required to prevent the upward migration of particles. In the second case, we establish a relationship among water flux, particle size, and vertical position along the stream, which determines the feasibility of upward particle transport. Our findings reveal a fundamental difference between the two configurations. In the tubular flow case, surface tension has negligible influence on particle motion. In contrast, in the free-fall scenario, upward particle transport is only possible in the presence of surface tension. Moreover, we demonstrate that for any given water flux, there exists a threshold height difference beyond which contamination of the upper container is not possible. Increasing the water flux further inhibits any upward transport of pollutants

physics.flu-dyn↗

arXiv2024

Gravitational Wave emission in Binary Neutron Star early post-merger within a dark environment

Using an effective Lagrangian model inspired by Takami et al. 2015 we qualitatively study the early post-merger of a nearly symmetric binary Neutron Star (BNS) merger event with a non-vanishing ambient fraction of dark matter. For this we first mimic the dynamics of two oscillating Neutron Star (NS) masses in the gravitational potential well as they merge. We parametrize the dynamics and ejecta properties in the coalescence event allowing the formation of a surrounding debris disk that may be containing a non-vanishing dark matter fraction. In order to analyze the possible novel dark contribution, we start from a dark-matter free modellization as a benchmark. Using Monte Carlo Markov Chain (MCMC) techniques we approximately recover the gravitational waveforms, restricted to early post-merger time interval from existing simulations in the CoRe database. Later, we explore the impact of an additional dark viscous fluid under a prescribed velocity dependent force in the Lagrangian and obtain the resulting waveforms and some spectral features originating in the first few ms in the BNS post-merger. Finally we discuss our qualitative findings and its range of validity in light of the prospects of detectability in present or future experimental settings.

gr-qc↗