Fluctuation-dissipation theorem and the Unruh effect of scalar and Dirac fields

We present a simple and systematic method to calculate the Rindler noise, which is relevant to the analysis of the Unruh effect, by using the fluctuation-dissipative theorem. To do this, we calculate the dissipative coefficient explicitly from the equations of motion of the detector and the field. This method gives not only the correct answer but also a hint as to the origin of the apparent statistics inversion effect. Moreover, this method is generalized to the Dirac field, by using the fermionic fluctuation-dissipation theorem. We can thus confirm that the fermionic fluctuation-dissipation theorem is working properly.Comment: 26 page

Instability of a plane conducting free surface submitted to an alternating magnetic field

This paper considers the stability of a horizontal liquid-metal free surface in the presence of a horizontal alternating magnetic field. A weak formulation is used to derive a generalized Mathieu–Hill equation for the evolution of surface perturbations. Previous studies which rely on time-averaging the electromagnetic force over one field cycle have predicted a generally weak instability, but we find much larger growth rates near the resonances, where the surface wave frequency is an integral multiple of the field frequency. The method can be extended to include viscous and ohmic damping; the former has little effect, while the latter damps all waves except those whose frequency is close to the field frequency. Growth rates can be closely approximated by simple algebraic formulae, as can the critical magnetic field strength for the onset of instability

Coherent population trapping in quantized light field

A full quantum treatment of coherent population trapping (CPT) is given for a system of resonantly coupled atoms and electromagnetic field. We develop a regular analytical method of the construction of generalized dark states (GDS). It turns out that GDS do exist for all optical transitions $F_g\to F_e$, including bright transitions $F\to F+1$ and $F''\to F''$ with $F''$ a half-integer, for which the CPT effect is absent in a classical field. We propose an idea to use an optically thick medium with a transition $F''\to F''$ with $F'' \ge 3/2$ a half-integer as a ''quantum filter'', which transmits only a quantum light.Comment: revtex4, twocolumn, 6 pages, including 1 figur

The Inverse Scattering Method, Lie-Backlund Transformations and Solitons for Low-energy Effective Field Equations of 5D String Theory

In the framework of the 5D low-energy effective field theory of the heterotic string with no vector fields excited, we combine two non-linear methods in order to construct a solitonic field configuration. We first apply the inverse scattering method on a trivial vacuum solution and obtain an stationary axisymmetric two-soliton configuration consisting of a massless gravitational field coupled to a non-trivial chargeless dilaton and to an axion field endowed with charge. The implementation of this method was done following a scheme previously proposed by Yurova. We also show that within this scheme, is not possible to get massive gravitational solitons at all. We then apply a non-linear Lie-Backlund matrix transformation of Ehlers type on this massless solution and get a massive rotating axisymmetric gravitational soliton coupled to axion and dilaton fields endowed with charges. We study as well some physical properties of the constructed massless and massive solitons and discuss on the effect of the generalized solution generating technique on the seed solution and its further generalizations.Comment: 17 pages in latex, changed title, improved text, added reference