Brillouin scattering and the CMB

Brillouin scattering of photons off the density fluctuations in a fluid is potentially important for cosmology. We derive the Brillouin spectral distortion of blackbody radiation, and discuss the possible implications for the cosmic microwave background. The thermal Sunyaev-Zeldovich effect is slightly modified by Brillouin distortion, but only at very long wavelengths.Comment: 4 pages Revtex, 2 figs. Minor changes to improve clarity; version to appear in GR

Kaluza's theory in generalized coordinates

Maxwell's equations can be obtained in generalized coordinates by considering the electromagnetic field as an external agent. The work here presented shows how to obtain the electrodynamics for a charged particle in generalized coordinates eliminating the concept of external force. Based on Kaluza's formalism, the one here presented extends the 5x5 metric into a 6x6 space-time giving enough room to include magnetic monopoles in a very natural way.Comment: 11 pages, RevTex. Accepted for publication in the Journal of Matematical Physic

A structure factor approach to the Sunyaev-Zel'dovich effect

Structure factor theory (SFT) is applied to analyze distortions to the Cosmic Microwave Background Radiation (CMBR) due the Sunyaev-Zel'dovich Effect (SZE) in typical clusters of galaxies. It is shown that a suitable structure factor associated to a collisionless (Knudsen) gas is able to reproduce the SZE distortion of the CMBR . Physical arguments suggest that SFT yields an approximate solution to the Kompaneets equation and sets plausible values for the two ``free'' parameters involved in the calculation of the spectral distortion. Finally, further applications of the SFT to other standard cosmological problems are briefly discussed.Comment: 6 pages, 3 figures. RevTex. Submitted to Physica

Rotational Viscosity in Linear Irreversible Thermodynamics and its Application to Neutron Stars

A generalized analysis of the local entropy production of a simple fluid is used to show that, if intrinsic angular momentum is taken into account, rotational viscosity must arise in the linear non-equilibrium regime. As a consequence, the stress tensor of dense rotating matter, such as the one present in neutron stars, posseses a significant non-vansishing antisymmetrical part. A simple argument suggests that, due to the extreme magnetic fields present in neutron stars, the relaxation time associated to rotational viscosity is large (approx 10^{21} s). The formalism leads to generalized Navier-Stokes equations useful in neutron star physics which involve vorticity in the linear regime.Comment: 6 pages Revtex; to appear J. Nonequilibrium Therm

On the gravitational instability of a dissipative medium

This paper shows that the ordinary Jeans wave number can be obtained as a limiting case of a more general approach that includes dissipative effects. Corrections to the Jeans critical mass associated to viscosity are established. Some possible implications of the results are finally discussed.Comment: 5 pages, RevTe

On the nature of the so-called generic instabilities in dissipative relativistic hydrodynamics

It is shown that the so-called generic instabilities that appear in the framework of relativistic linear irreversible thermodynamics, describing the fluctuations of a simple fluid close to equilibrium, arise due to the coupling of heat with hydrodynamic acceleration which appears in Eckart's formalism of relativistic irreversible thermodynamics. Further, we emphasize that such behavior should be interpreted as a contradiction to the postulates of linear irreversible thermodynamics (LIT), namely a violation of Onsager's hypothesis on the regression of fluctuations, and not as fluid instabilities. Such contradictions can be avoided within a relativistic linear framework if a Meixner-like approach to the phenomenological equations is employed.Comment: 13 pages, no figures. Accepted for publication in GR

Memorias del Séptimo Foro de la Enseñanza de las Matemáticas

En el Séptimo Foro de Enseñanza de las Matemática Ibero 2017 se abordaron temas relacionados con el uso de la historia de las matemáticas en el aula, las transformaciones en las habilidades, destrezas y conocimientos en los alumnos universitarios en la primera década del 2000, el uso de plataformas digitales en la enseñanza de las matemáticas; se expuso sobre situaciones problema en la vida cotidiana relacionados con las matemáticas escolares y la modelación matemática, sobre la historia de la enseñanza de las matermáticas, entre otros temas.ITESO, A.C.Universidad Iberoamericana, Campus Santa F