arXiv subjects

Victor Munoz

Publications and source records attributed to Victor Munoz.

5 recordsLinked to original sources

arXiv2024

A prediction for 25th solar cycle using visibility graph and Hathaway function

We apply a complex network approach to analyse the time series of five solar parameters, and propose an strategy to predict the number of sunspots for the next solar maximum, and when will this maximum will occur. The approach is based on the Visibility Graph (VG) algorithm, and a slightly modified version of it, the Horizontal Visibility Graph (HVG), which map a time series into a complex network. Various network metrics exhibit either an exponential or a scale-free behavior, and we find that the evolution of the characteristic decay exponents is consistent with variations of the sunspots number along solar cycles. During solar minimum, the sunspots number and the solar index time series have characteristic decay exponents that correlate well with the next maximum sunspots number, suggesting that they may be good precursors of the intensity of the next solar maximum. Based on this observation, we find that, based on current data, the algorithm predicts a number of 179 sunspots for cycle 25. Combining this with the Hathaway function, adjusted to yield such maximum sunspots number, we find that the maximum for solar cycle 25 will occur in December 2024/January 2025.

astro-ph.SR↗

arXiv2021

Exploring the Origin of Supermassive Black Holes with Coherent Neutrino Scattering

Collapsing supermassive stars ($M \gtrsim 3 \times 10^4 M_{\odot}$) at high redshifts can naturally provide seeds and explain the origin of the supermassive black holes observed in the centers of nearly all galaxies. During the collapse of supermassive stars, a burst of non-thermal neutrinos is generated with a luminosity that could greatly exceed that of a conventional core collapse supernova explosion. In this work, we investigate the extent to which the neutrinos produced in these explosions can be observed via coherent elastic neutrino-nucleus scattering (CE$ν$NS). Large scale direct dark matter detection experiments provide particularly favorable targets. We find that upcoming $\mathcal{O}(100)$ tonne-scale experiments will be sensitive to the collapse of individual supermassive stars at distances as large as $\mathcal{O}(10)$ Mpc.

astro-ph.HE↗

arXiv2010

Scale-free and small-world properties of earthquake network in Chile

The properties of earthquake networks have been studied so far mainly for the seismic data sets taken from California, Japan and Iran, and features common in these regions have been reported in the literature. Here, an earthquake network is constructed and analyzed for the Chilean data to examine if the scale-free and small-world properties of the earthquake networks constructed in the other geographical regions can also be found in seismicity in Chile. It is shown that the result is affirmative: in all the regions both the exponent "gamma" of the power-law connectivity distribution and the clustering coefficient C take the universal invariant values "gamma ~1" and "C~0.85", respectively, as the cell size becomes larger than a certain value, which is the scale of coarse graining needed for constructing earthquake network. An interpretation for this remarkable result is presented based on physical considerations.

physics.geo-ph↗

arXiv2004

Disperson relation of finite amplitude Alfven wave in a relativistic electron- positron plasma

The linear dispersion relation of a finite amplitude, parallel, circularly polarized Alfvén wave in a relativistic electron-positron plasma is derived. In the nonrelativistic regime, the dispersion relation has two branches, one electromagnetic wave, with a low frequency cutoff at $\sqrt{1+2ω_p^2/Ω_p^2}$ (where $ω_p=(4πn e^2/m)^{1/2}$ is the electron/positron plasma frequency), and an Alfvén wave, with high frequency cutoff at the positron gyrofrequency $Ω_p$. There is only one forward propagating mode for a given frequency. However, due to relativistic effects, there is no low frequency cutoff for the electromagnetic branch, and there appears a critical wave number above which the Alfvén wave ceases to exist. This critical wave number is given by $ck_c/Ω_p=a/η$, where $a=ω_p^2/Ω_p^2$ and $η$ is the ratio between the Alfvén wave magnetic field amplitude and the background magnetic field. In this case, for each frequency in the Alfvén branch, two additional forward propagating modes exist with equal frequency. A simple numerical example is studied: by numerically solving the coupled system of fluid and Maxwell equations, normal incidence of a finite amplitude Alfvén wave on an interface between two electron-positron plasmas of different densities is considered.

physics.plasm-ph↗

arXiv2004

Longitudinal oscillations in a nonextensive relativistic plasma

The dispersion relation of longitudinal electrostatic oscillations in a relativistic plasma is studied in the context of the nonextensive statistics formalism proposed by Tsallis [C. Tsallis, J. Stat. Phys. {\bf 52}, 479 (1988)], where nonextensivity is characterized by a parameter $q$ in Tsallis's entropy. $q=1$ corresponds to the usual Boltzmann-Gibbs, extensive statistics formalism. In the nonrelativistic regime, normalizability of the equilibrium distribution function implies that $-1\leq q\leq\infty$. We show that in the relativistic regime much tighter constraints must be satisfied, namely $0\leq q \leq 1+ k_B T/mc^2$, where $k_B$ is the Boltzmann constant, $T$ is the temperature of the plasma, and $m$ is the particle mass. Then we study longitudinal oscillations in a proton-electron plasma, assuming immobile protons, and electrons whose distribution function maximizes Tsallis's entropy. The dispersion relation of these oscillations is written in integral form for the long wavelength limit. Explicit expressions in terms of generalized hypergeometric functions can be found for all possibles values of $q$ in the ultra-relativistic regime.

physics.plasm-ph↗