arXiv subjects

Francisco S. Guzmán

Publications and source records attributed to Francisco S. Guzmán.

11 recordsLinked to original sources

arXiv2026

Granular Structure and Local de Broglie Wavelength in Fuzzy Dark Matter Halos

We study the granular structure that emerges in a Fuzzy Dark Matter (FDM) halo formed through kinetic relaxation. After the system reaches a virialized core-halo structure, we separate the density field into a smooth spherical component and a residual density that contains the interference pattern characteristic of FDM halos. The power spectrum of this residual field shows a well defined dominant scale, different from the characteristic scale of the total density and of the smooth core-halo model. We compare this granular scale with a local de Broglie wave-lenght calculated from the velocity field obtained from the density current of the system. We find that both scales remain of the same order of magnitude, with the granular scale systematically smaller than the de Broglie wavelength. The radial behavior of the de Broglie wavelength also reveals a non-uniform internal structure, it decreases from the core and reaches its minimum near the transition between the solitonic core and the outer halo. These results provide a quantitative connection between density fluctuations, the local velocity field, and the core-halo morphology of FDM halos.

gr-qc↗

arXiv2026

Schwarzschild black holes as low-pass filters of fuzzy dark matter granularity

We study the relaxation of a complex massive scalar field around a supermassive black hole, modeling the near-horizon dynamics of Fuzzy Dark Matter (FDM) with spatial granularity. The field is initialized as a broadband, anisotropic multi-mode random field in momentum space with various spectral widths $σ$, decomposed into spherical harmonics up to $\ell_{\max}=100$, and numerically evolved on a finite domain using a specialized radial basis adapted to the background spatial geometry. We track the evolution of each multipole and calculate its Noether flux across both the event horizon and the outer boundary. Since angular momentum barriers suppress the horizon absorption of high-$\ell$ modes, while high-frequency radial components and fine-scale angular structures dissipate via outward radiation and horizon accretion, the Schwarzschild spacetime acts as an effective low-pass filter. Regardless of the initial spectral width, all configurations converge toward a universal late-time relaxation state dominated almost exclusively by low multipoles ($\ell \le 2$) and small radial wavenumbers, with the initial bandwidth $σ$ determining the timescale of global charge depletion. For concrete physical estimates, we set the boson mass to $m_b=10^{-22}\,\mathrm{eV}/c^2$ and the black hole mass to $M_{\mathrm{BH}}=6.5\times10^9 M_\odot$.

gr-qc↗

arXiv2025

Kinematic Imprints of vortex-lines of BEC Dark Matter on Baryonic Matter

Our results demonstrate that vortex lines in Bose-Einstein Condensate Dark Matter (BECDM) can act as gravitational seeds that induce the condensation of baryonic matter, leading to localized gas accumulation even in the absence of imposed symmetries or rotation. Our analysis is based on the numerical solution of the system of equations for the BECDM gravitationally coupled to Euler equations for a compressible ideal gas (IG) that we use as a model of baryonic matter. Numerical simulations are constructed for various scenarios that start with a vortex solution for the BECDM and a randomly distributed ideal gas, with the aim of investigating whether the matter distribution and dynamics of the vortex influences the dynamics and distribution of the gas. We find that the gas condensation process is most efficient when the IG mass dominates over the BECDM, and when the IG has low initial velocity dispersion. We also find that strong bosonic self-interaction does not guarantee the vortex stability, instead, it can trigger dynamical instabilities that disrupt both the vortex structure and the surrounding gas. An interesting finding is that the vortex drives a persistent morphological signature on the gas, often in the form of ring-like features visible in projected density maps. These patterns survive nonlinear evolution and may serve as indirect tracers of vortex structures in BECDM halos, potentially offering a novel and testable observational probe of the model.

astro-ph.GA↗

arXiv2023

Spherical solutions of the Schrödinger-Poisson system with core-tail structure

We construct spherically symmetric equilibrium solutions of the Schrödinger-Poisson (SP) system of equations with a core-tail structure that could serve as models of Fuzzy Dark Matter (FDM) halos. The core is assumed to be a solitonic ground state equilibrium configuration of the SP equations, and the tail is integrated from a transition radius onwards. The total mass of the system parametrizes the family of solutions and constrains the tail density profile. The tail has a radial velocity profile, whereas the core is stationary. We investigate the evolution of these equilibrium configurations and find that the tail initially perturbs the core, and consequently, the whole solution oscillates around a virialized solution that we call 'relaxed', whose average also has a core-tail structure. We measure the departure of the relaxed configuration from the equilibrium solution in order to estimate the utility of the latter. We also find that the core-halo scaling relation of equilibrium configurations has an exponent $α=1/3$, whereas relaxed configurations exhibit a scaling with $α=0.54$.

astro-ph.GA↗

arXiv2023

CAFE-AMR: A computational MHD Solar Physics simulation tool that uses AMR

The study of our Sun holds significant importance in Space Weather research, encompassing a diverse range of phenomena characterized by distinct temporal and spatial scales. To address these complexities, we developed CAFE-AMR, an implementation of an Adaptive Mesh Refinement (AMR) strategy coupled with a Magnetohydrodynamics (MHD) equation solver, aiming to tackle Solar Physics-related problems. CAFE-AMR employs standard fluid dynamics methods, including Finite Volume discretization, HLL and Roe class flux formulas, linear order reconstructors, second-order Runge-Kutta, and Corner Transport Upwind time stepping. In this paper, we present the core structure of CAFE-AMR, discuss and evaluate mesh refinement criteria strategies, and conduct various tests, including simulations of idealized Solar Wind models, relevant for Space Weather applications.

astro-ph.IM↗

arXiv2023

The Effect of Boundary Conditions on Structure Formation in Fuzzy Dark Matter

We illustrate the effect of boundary conditions on the evolution of structure in Fuzzy Dark Matter. Scenarios explored include the evolution of single, ground-state equilibrium solutions of the Schrödinger-Poisson system, the relaxation of a Gaussian density fluctuation, mergers of two equilibrium configurations, and the random merger of many solitons. For comparison, each scenario is evolved twice, with isolation boundary conditions and periodic boundary conditions, the two commonly used to simulate isolated systems and structure formation, respectively. Replacing isolation boundary conditions by periodic boundary conditions changes the domain topology and dynamics of each scenario, by affecting the outcome of gravitational cooling. With periodic boundary conditions, the ground-state equilibrium solution and Gaussian fluctuation each evolve toward the single equilibrium solitonic core of the isolated case, but surrounded by a tail, unlike the isolated versions. The case of head-on, binary mergers illustrates additional effects, caused by the pull suffered by the system due to the infinite network of periodic images along each direction of the domain. Binary merger with angular momentum is the first scenario we found in which the tail has a polynomial profile when using a periodic domain. Finally, the 3D merger of many, randomly-placed solitonic cores of different mass makes a solitonic core surrounded by a tail with power-law-like density profile, for periodic boundary conditions, while producing a core with a much sharper fall-off in the isolated case. This suggests that the conclusion of earlier work that the ground-state equilibrium solution is an attractor for the asymptotic state is true even in 3D and for general circumstances, but only if gravitational cooling is able to carry mass and energy off to infinity, which isolation boundary conditions allow, but periodic ones do not.

astro-ph.CO↗

arXiv2023

Stationary solutions of the Schrödinger-Poisson-Euler system and their stability

We present the construction of stationary boson-fermion spherically symmetric configurations governed by Newtonian gravity. Bosons are described in the Gross-Pitaevskii regime and fermions are assumed to obey Euler equations for an inviscid fluid with polytropic equation of state. The two components are coupled through the gravitational potential. The families of solutions are parametrized by the central value of the wave function describing the bosons and the central denisty of the fluid. We explore the stability of the solutions using numerical evolutions that solve the time dependent Schrödinger-Euler-Poisson system, using the truncation error of the numerical methods as the perturbation. We find that all configurations are stable as long as the polytropic equation of state (EoS) is enforced during the evolution. When the configurations are evolved using the ideal gas EoS they all are unstable that decay into a sort of twin solutions that approach a nearly stationary configuration. We expect these solutions and their evolution serve to test numerical codes that are currently being used in the study of Fuzzy Dark Matter plus baryons.

astro-ph.GA↗

arXiv2023

Accretion of supersonic magnetized winds onto black holes

We present the accretion of magnetized supersonic winds onto a rotating black hole in three dimensions. We select representative spin-wind orientations in order to illustrate its effects on the evolution and morphology of the shock cone. The most important finding in the magnetized case, unlike the purely hydrodynamical scenario, is the formation of rarified spots where the magnetic field pressure dominates over the gas pressure. In these rarified spots we find the formation of eddies within the shock cone.

astro-ph.HE↗

arXiv2022

Exploration of simple scenarios involving Fuzzy Dark Matter cores and gas at local scales

We introduce a tool that solves the Schrödinger-Euler-Poisson system of equations and allows the study of the interaction between ultralight bosonic dark matter, whose dynamics is described with the Schrödinger-Poisson system and luminous matter which, as a first approximation, is modeled with a single component compressible ideal fluid. The two matter fields are coupled through the Poisson equation, whose source is the addition of both, dark matter and fluid densities. We describe the numerical methods used to solve the system of equations and present tests for each of the two components, that show the accuracy and convergence properties of the code. As simple possible applications we present some toy scenarios: i) the merger between a core of dark matter with a cloud of gas, ii) the merger of bosonic dark matter plus fluid configurations, and iii) the post merger properties, including the dark-matter offset from gas and the correlation between oscillations of the bosonic core and those of the gas.

astro-ph.GA↗

arXiv2022

Construction and evolution of equilibrium configurations of the Schrödinger-Poisson system in the Madelung frame

We present the construction of ground state equilibrium configurations of the Schrödinger-Poisson (SP) system in the Madelung frame and evolve such configuration using finite volume methods. We compare the behavior of these configurations when evolved within the SP and Madelung frames, in terms of conservation of mass and energy. We also discuss the issues of the equations in the Madelung frame and others inherent to the numerical methods used to solve them.

gr-qc↗

arXiv2021

Scalar field dark matter as an alternative explanation for the anisotropic distribution of satellite galaxies

In recent years, the scalar field dark matter (SFDM), also called ultralight bosonic dark matter, has received considerable attention due to the number of problems it might help to solve. Among these are the cusp-core problem and the abundance of small structures of the standard cold dark matter (CDM) model. In this paper we show that multi-state solutions of the low energy and weak gravitational field limit of field equations, interpreted as galactic halo density profiles, can provide a possible explanation to the anisotropic distribution of satellite galaxies observed in the Milky Way, M31 and Centaurus A, where satellites trajectories seem to concentrate on planes close to the poles of the galaxies instead of following homogeneously distributed trajectories. The core hypothesis is that multi-state solutions of the equations describing the dynamics of this dark matter candidate, namely, the Gross-Pitaevskii-Poisson equations, with monopolar and dipolar contributions, can possibly explain the anisotropy of satellite trajectories. In order to construct a proof of concept, we study the trajectories of a number of test particles traveling on top of the gravitational potential due to a multi-state halo with modes (1,0,0)+(2,1,0). The result is that particles accumulate asymptotically in time on planes passing close to the poles. Satellite galaxies are not test particles but interpreted as such, our results indicate that in the asymptotic time their trajectories do not distribute isotropically, instead they prefer to have orbital poles accumulating near the equatorial plane of the multistate halo. The concentration of orbital poles depends on whether the potential is monopolar or dipolar dominated.

astro-ph.GA↗