arXiv subjects

H. Perez Rojas

Publications and source records attributed to H. Perez Rojas.

31 records · Page 2Linked to original sources

arXiv2005

Quantum instability of magnetized stellar objects

The equations of state for degenerate electron and neutron gases are studied in the presence of magnetic fields. After including quantum effects to study the structural properties of these systems, it is found that some hypermagnetized stars can be unstable based on the criterium of stability of pressures. Highly magnetized white dwarfs should collapse producing a supernova type Ia, whilst superstrongly magnetized neutron stars cannot stand their own magnetic field and must implode, too. A comparison of our results with a set of the available observational data of some compact stars is also presented, and the agreement between this theory and observations is verified.

astro-ph↗

arXiv2004

Effect of a Magnetic Field on the Electroweak Symmetry

We discuss the effect of a strong magnetic field in the behavior of the symmetry of an electrically neutral electroweak plasma. We analyze the case of a strong field and low temperatures as compared with the W rest energy. If the magnetic field is large enough, it is self-consistently maintained. Charged vector bosons play the most important role, leading only to a decrease of the symmetry breaking parameter, the symmetry restoration not being possible.

hep-ph↗

arXiv2004

Vacuum pressures and energy in a strong magnetic field

We study vacuum in a strong magnetic field. It shows a nonlinear response, as a ferromagnetic medium. Anisotropic pressures arise, and a negative pressure is exerted in the direction perpendicular to the field. The analogy of this effect with the Casimir effect is analyzed. The vacuum transverse pressure is found to be of the same order of the statistical pressure for $B\sim10^{15}G$ and $N\sim10^{33}electrons/cm^{3}$. Vacuum interaction with the field is studied also for $B\sim10^{16}G$ and larger, including the electron anomalous magnetic moment. We estimate quark contribution to vacuum behavior.

hep-ph↗

arXiv2004

Negative Pressures and Energies in Magnetized and Casimir Vacua

We study the electron-positron vacuum in a strong magnetic field $B$ in parallel with Casimir effect. Use is made of the energy-momentum tensor, taken as the zero temperature and zero density limit of the relativistic quantum statistical tensor. In both magnetic field and Casimir cases it is shown the arising of anisotropic pressures. In the first case the pressure transversal to the field $B$ is negative, whereas along $B$ an usual positive pressure arises. Similarly, in addition to the usual negative Casimir pressure perpendicular to the plates, the existence of a positive pressure along the plates is predicted. The anisotropic pressures suggests a flow of the virtual particles in both cases. By assuming regions of the universe having random orientation of the lines of force, cosmological consequences are discussed in the magnetic field case.

hep-ph↗

arXiv2004

Self-Magnetization of charged particles and Bose-Einstein Condensation

We discuss the Bose-Einstein condensation of relativistic vector charged particles in a strong external magnetic field in very dense matter, as may be paired spin-up electrons. We show that for electrons such systems may maintain self-consistently magnetic fields of order in between the interval $10^{10}-10^{13}$ Gauss. This could be the origin of large magnetic fields in some white dwarfs, but may also impose bounds due to the arising of strong anisotropy in the pressures, which may produce a transverse collapse of the star.

astro-ph↗

arXiv2003

Magnetic collapse of a neutron gas: Can magnetars indeed be formed

A relativistic degenerate neutron gas in equilibrium with a background of electrons and protons in a magnetic field exerts its pressure anisotropically, having a smaller value perpendicular than along the magnetic field. For critical fields the magnetic pressure may produce the vanishing of the equatorial pressure of the neutron gas. Taking it as a model for neutron stars, the outcome could be a transverse collapse of the star. This fixes a limit to the fields to be observable in stable neutron star pulsars as a function of their density. The final structure left over after the implosion might be a mixed phase of nucleons and meson condensate, a strange star, or a highly distorted black hole or black "cigar", but no any magnetar, if viewed as a super strongly magnetized neutron star. However, we do not exclude the possibility of a supersotrong magnetic fields arising in supernova explosions which lead directly to strange stars. In other words, if any magnetars exist, they cannot be neutron stars.

astro-ph↗

arXiv2000

Quantum Magnetic Collapse

We study the thermodynamics of degenerate electron and charged vector boson gases in very intense magnetic fields. In degenerate conditions of the electron gas, the pressure transverse to the magnetic field $B$ may vanish, leading to a transverse collapse. For W-bosons an instability arises because the magnetization diverges at the critical field B_c = M_W^2/e. If the magnetic field is self-consistently maintained, the maximum value it can take is of the order of $2B_c/3$, but in any case the system becomes unstable and collapses.

hep-ph↗

arXiv1999

Effective Magnetic Moment of Neutrinos in Strong Magnetic Fields

We compute the effective magnetic moment of neutrino in the highly dense and strongly magnetized media. It is shown that this magnetic moment is generated due to the effective mass of neutrino and gives sufficiently high value of the magnetic moment in the core of neutron stars.

hep-ph↗

arXiv1997

$λ$-Type phase transition for a weakly interacting bose gas

A mechanism generating a $λ$-type behavior in the specific heat of a Bose gas near the critical temperature $T_c$ is discussed. It is shown to work for a general class of quasiparticle spectra, and especially, for the Bogoliubov's model of a weakly interacting Bose gas, where a temperature-dependent quasi-particle spectrum is obtained.

cond-mat↗

arXiv1996

On Bose-Einstein Condensation in any Dimension

Arbitrarily large ground state population is a general property of any ideal bose gas when conditions of degeneracy are satisfied; it occurs at any dimension D. For $D = 1$, the condensation is diffuse, at $D = 2$ it is a sort of quasi-condensate. The discussion is made by following a microscopic approach and for finite systems. Some astrophysical consequences are discussed, as well as the temperature-dependent mass case.

cond-mat↗

arXiv1995

Bose-Einstein condensation may occur in a constant magnetic field

Bose-Einstein condensation of charged scalar and vector particles may actually occur in presence of a constant homogeneous magnetic field, but there is no critical temperature at which condensation starts. The condensate is described by the statistical distribution. The Meissner effect is possible in the scalar, but not in the vector field case, which exhibits a ferromagnetic behavior.

hep-th↗

arXiv1994

Conserved Quantities and Electroweak Phase Transitions

Some cosmological consequences of including the adequate conserved quantities in the density matrix of the electroweak theory are investigated. Several arguments against including the charges associated to the spontaneously broken symmetry are presented. Special attention is focused on the phenomenon of $W$-boson condensation and its interplay with the phase transition for the symmetry restoration is considered. The emerging cosmological implications, such as on the baryon and lepton number densities, are of interest.

hep-th↗

arXiv1993

Renormalization in Quantum Statistics of Systems with Spontaneous Symmetry Breaking

Renormalization in quantum statistics in the presence of a charge associated to a spontaneously broken symmetry is discussed for the scalar field model. In contrast to the case of non-broken symmetry, the renormalization mass counterterm depends on the chemical potential. We argue that this is connected to the ill-defined character of the charge operator.

hep-th↗