Modern Physics Letters A

Large-scale spatial variations of the guide magnetic field of interplanetary and interstellar plasmas give rise to the adiabatic focusing term in the Fokker–Planck transport equation of cosmic rays. As a consequence of the adiabatic focusing term, the diffusion approximation to cosmic ray transport in the weak focusing limit gives rise to first-order Fermi acceleration of energetic particles if the product HL of the cross helicity state of Alfvenic turbulence H and the focusing length L is negative. The basic physical mechanisms for this new acceleration process are clarified and the astrophysical conditions for efficient acceleration are investigated. It is shown that in the interstellar medium this mechanism preferentially accelerates cosmic ray hadrons over 10 orders of magnitude in momentum. Due to heavy Coulomb and ionization losses at low momenta, injection or preacceleration of particles above the threshold momentum p_c≃0.17Z^2/3GeV/c is required.

In the framework of conformal field theory, the mapping from (unbounded) wedge regions of Minkowski spacetime to (bounded) double-cone regions is extended to the Unruh temperature associated to a uniformly accelerated observer. The link between a previous result, the diamond's temperature, and the conformal factor (Weyl rescaling of the metric) is worked out. One thus explains from a mathematical point of view why an observer with finite lifetime experiences the vacuum as a thermal state whatever his acceleration, even vanishing.

We study the entropy of extremal warped black hole obtained from the topologically massive gravity with a negative cosmological constant of Λ = -1/l². We compare the entropy S_e = πα/3G from the Wald formalism with S_w = πl u /3G from the entropy function approach. These are the same if α = l u. Also we obtain the same Cardy formula when J_e = l³ q with J_e the angular momentum and q the conserved quantity.

One of the challenges in connecting higher dimensional theories to cosmology is stabilization of the moduli fields. We investigate the role of a Lorentz violating vector field in the context of stabilization. Specifically, we compute the one-loop Casimir energy in Randall–Sundrum five-dimensional (non-supersymmetric) S¹/ Z₂ orbifolds resulting from the interaction of a real scalar field with periodic boundary conditions with a Lorentz violating vector field. We find that the result is an enhanced attractive Casimir force. Hence, for stability, positive contributions to the Casimir force from branes and additional fields would be required to counter the destabilizing, attractive effect of Lorentz violating fields.

We describe a kinematical analogy for the marginal decay of ¼-BPS dyons in four-dimensional string compactifications. In this analogy, the electric and magnetic charges play the role of spatial momenta, the BPS mass plays the role of energy, and ½BPS dyons correspond to massless particles. Using SO(12, 1) "Lorentz" invariance and standard kinematical formulas in particle physics, we provide simple derivations of the curves of marginal stability. We also show how these curves map into the momentum ellipsoid, and propose some applications of this analogy.

Motivated by the chiral suppression in the mixing between a scalar glueball and quarkonia, we have investigated the mixing of three important candidates of glueballs: f₀(1370), f₀(1500) and f₀(1710), with their latest two-body pseudoscalar meson decay data in a simple decay model. In our work, we utilize a general mass matrix, in which the chiral suppression parameter a and the direct mixing r between |S〉 and |N〉 are introduced as free parameters. The most hopeful result in our fits suggests that the f₀(1710) is mainly the mixing of |G〉 and |S〉, the f₀(1370) has almost equal |G〉, |S〉 and |N〉 components, and the f₀(1500) is mainly the mixing of |S> and |N> with sizable glueball component. We find that r is reasonably small as expected, the chiral suppression parameter a can be small which suggests the chiral suppression in the mixing between glueball and quarkonia is necessary to be considered, and the SU(3) symmetry is respected in decay processes.

In this paper, we discuss gravitational collapse of spherically symmetric spacetimes. We derive a general formalism by taking two arbitrary spherically symmetric spacetimes with g₀₀ = 1. Israel's junction conditions are used to develop this formalism. The formulas for extrinsic curvature tensor are obtained. The general form of the surface energy–momentum tensor depending on extrinsic curvature tensor components is derived. This leads us to the surface energy density and the tangential pressure. The formalism is applied to two known spherically symmetric spacetimes. The results obtained show the regions for the collapse and expansion of the shell.