Modern Physics Letters A

The Pierre Auger Southern Observatory, a hybrid detector for the study of ultra-high energy cosmic rays (UHECRs), is now operating for more than three years and approaching completion. This paper describes the present status and the performance of the Observatory, with an emphasis on the advantages provided by the combined use of two different detection techniques. A panorama of the most recent results related to the spectrum, composition and arrival directions of the UHECR is then presented, along with a brief discussion of their impact on our knowledge of the UHECRs' origin and composition.

A novel mechanism of baryogenesis is proposed on the basis of the phase transition from the conformal invariant spacetime to the Einstein spacetime in quantum gravity. Strong-coupling gravitational excitations with dynamical mass about 10¹⁷ GeV are generated at the transition. They eventually decay into ordinary matters. We show that the low energy effective interactions between the gravitational potential describing the excitation and the non-conserving matter currents by the axial anomalies can explain matter asymmetry out of thermal equilibrium.

We study the propagation of a linearly polarized laser beam in the external transverse magnetic field taking into consideration the vacuum polarization by arbitrary spin particles. Induced ellipticity of the beam is evaluated using the effective Lagrangian. With the help of the PVLAS experimental data, we obtain bounds on masses of charged higher spin particles contributed to ellipticity.

It is well known that, in the five-dimensional scenario of braneworld and space–time-mass theories, geodesic motion in 5D is observed to be non-geodesic in 4D. Usually, the discussion is purely geometric and based on the dimensional reduction of the geodesic equation in 5D, without any reference to the test particle whatsoever. In this work we obtain the equation of motion in 4D directly from the principle of least action. So our main thrust is not the geometry but the particle observed in 4D. A clear physical picture emerges from our work. Specifically, that the deviation from the geodesic motion in 4D is due to the variation of the rest mass of a particle, which is induced by the scalar field in the 5D metric and the explicit dependence of the space–time metric on the extra coordinate. Thus, the principle of least action not only leads to the correct equations of motion, but also provides a concrete physical meaning for a number of algebraic quantities appearing in the geometrical reduction of the geodesic equation.

In a previous paper (J. Phys. A36, 11807 (2003)), the "asymptotic iteration method" was introduced and developed for solving second-order homogeneous linear differential equations. In this paper we use the method to study the quantum quartic anharmonic oscillator problem. We obtain accurate eigenvalues for both small and large coupling parameters.

We study the statefinder parameter in the five-dimensional big bounce model, and apply it to differentiate the attractor solutions of quintessence and phantom field. It is found that the evolving trajectories of these two attractor solutions in the statefinder parameters plane are quite different, and that are different from the statefinder trajectories of other dark energy models.

Hawking radiation from a general Kerr–Newman black hole is investigated using Damour–Ruffini's method. Considering the back-reaction of particle's energy, charge and angular momentum to the spacetime, we obtain a modified nonthermal spectrum. Maybe the information loss paradox can be explained, furthermore, the result is also consistent with the result obtained using Parikh and Wilczek's method.