H. Perez Rojas

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(2)(W)/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.

Magnetized strange quark matter and magnetized strange quark stars

Strange quark matter could be found in the core of neutron stars or forming strange quark stars. As is well known, these astrophysical objects are endowed with strong magnetic fields that affect the microscopic properties of matter and modify the macroscopic properties of the system. In this article we study the role of a strong magnetic field in the thermodynamical properties of a magnetized degenerate strange quark gas, taking into account {beta}-equilibrium and charge neutrality. Quarks and electrons interact with the magnetic field via their electric charges and anomalous magnetic moments. In contrast to the magnetic field value of 10{sup 19} G, obtained when anomalous magnetic moments are not taken into account, we find the upper bound B < or approx. 8.6x10{sup 17} G, for the stability of the system. A phase transition could be hidden for fields greater than this value.

Bose-Einstein condensation may occur in a constant magnetic field

Abstract It is argued that Bose-Einstein condensation of charged scalar and vector particles may actually occur in the presence of a constant homogeneous magnetic field, but there is no critical temperature at which condensation starts, the phase transition being diffuse. The condensate is described by the statistical distribution. The scalar is diamagnetic whereas the vector exhibits a ferromagnetic behavior. Astrophysical and cosmological consequences are considered.

ANISOTROPIC PRESSURES IN VERY DENSE MAGNETIZED MATTER

The problem of anisotropic pressures arising from the spatial symmetry breaking introduced by an external magnetic field in quantum systems is discussed. The role of the conservation of energy and momentum of external fields as well as of systems providing boundary conditions in quantum statistics is considered. The vanishing of the average transverse momentum for an electron–positron system in its Landau ground state, i.e. the vanishing of its transverse pressure, is shown. The situation for the neutron case and strange quark matter (SQM) in β equilibrium is briefly discussed. Thermodynamical relations in external fields as well as the form of the stress tensor in a quantum relativistic medium are obtained. The ferromagnetic symmetry breaking is briefly discussed for very dense matter. It is concluded that stable matter cannot exist for fields greater than B = 1018 G.

Quark stars and quantum-magnetically induced collapse

Quark matter is expected to exist in the interior of compact stellar objects as neutron stars or even the more exotic strange stars, based on the Bodmer–Witten conjecture. Bare strange quark stars and (normal) strange quark-matter stars, those possessing a baryon (electron-supported) crust, are hypothesized as good candidates to explain the properties of a set of peculiar stellar sources such as the enigmatic X-ray source RX J1856.5-3754, some pulsars such as PSR B1828-11 and PSR B1642-03, and the anomalous X-ray pulsars and soft γ-ray repeaters. In the MIT bag model, quarks are treated as a degenerate Fermi gas confined to a region of space having a vacuum energy density Bbag (the Bag constant). In this note, we modify the MIT bag model by including the electromagnetic interaction. We also show that this version of the MIT model implies the anisotropy of the bag pressure due to the presence of the magnetic field. The equations of state of the degenerate quarks gases are studied in the presence of ultra strong magnetic fields. The behavior of a system made up of quarks having (or not) anomalous magnetic moment is reviewed. A structural instability is found, which is related to the anisotropic nature of the pressures in this highly magnetized matter. The conditions for the collapse of this system are obtained and compared to a previous model of neutron stars that is built on a neutron gas having anomalous magnetic moment.

Negative pressures in QED vacuum in an external magnetic field

Our aim is to study the electron–positron vacuum pressures in the presence of a strong magnetic field B. To that end, we obtain a general energy–momentum tensor, depending on external parameters, which in the zero temperature and zero density limit leads to vacuum expressions which are approximation-independent. Anisotropic pressures arise, and in the tree approximation of the magnetic field case, the pressure along B is positive, whereas perpendicular to B it is negative. Due to the common axial symmetry, the formal analogy with the Casimir effect is discussed, which in addition to the usual negative pressure perpendicular to the plates, there is a positive pressure along the plates. The formal correspondence between the Casimir and blackbody energy–momentum tensors is also discussed. The fermion hot vacuum behavior in a magnetic field is also briefly discussed.

Is the photon paramagnetic

A photon exhibits a tiny anomalous magnetic moment {mu}{sub {gamma}} due to its interaction with an external constant magnetic field in vacuum through the virtual electron-positron background. It is paramagnetic ({mu}{sub {gamma}}>0) in the whole region of transparency, i.e., below the first threshold energy for pair creation, and has a maximum near this threshold. The photon magnetic moment is different for eigenmodes polarized along and perpendicular to the magnetic field. Explicit expressions are given for {mu}{sub {gamma}} for the cases of photon energies smaller than and closer to the first pair creation threshold. The region beyond the first threshold is briefly discussed.

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 in the investigation of the structural properties of these systems, it is found that some hypermagnetized stars can be unstable according to the criterion of stability of pressures. Highly magnetized white dwarfs should collapse producing a supernova type Ia, while superstrong 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.

Quantized Faraday effect in (3+1)-dimensional and (2+1)-dimensional systems

We study Faraday rotation in the quantum relativistic limit. Starting from the photon self-energy in the presence of a constant magnetic field the rotation of the polarization vector of a plane electromagnetic wave which travel along the fermion-antifermion gas is studied. The connection between Faraday Effect and Quantum Hall Effect (QHE) is discussed. The Faraday Effect is also investigated for a massless relativistic (2D+1)-dimensional fermion system which is derived by using the compactification along the dimension parallel to the magnetic field. The Faraday angle shows a quantized behavior as Hall conductivity in two and three dimensions.

A reciprocal of Coleman's theorem and the quantum statistics of systems with spontaneous symmetry breaking

Abstract The completely different conservation properties of charges associated to unbroken and broken symmetries are discussed. The impossibility of establishing a conservation law for nondegenerate Hilbert space representations in the broken case leads to a reciprocal of Colemans theorem. The quantum statistical implication is that these charges cannot be introduced as conserved operators in the density matrix.