Electromagnetic field with constraints and Papapetrou equation

It is shown that geometric optical description of electromagnetic wave with account of its polarization in curved space-time can be obtained straightforwardly from the classical variational principle for electromagnetic field. For this end the entire functional space of electromagnetic fields must be reduced to its subspace of locally plane monochromatic waves. We have formulated the constraints under which the entire functional space of electromagnetic fields reduces to its subspace of locally plane monochromatic waves. These constraints introduce variables of another kind which specify a field of local frames associated to the wave and contain some congruence of null-curves. The Lagrangian for constrained electromagnetic field contains variables of two kinds, namely, a congruence of null-curves and the field itself. This yields two kinds of Euler-Lagrange equations. Equations of first kind are trivial due to the constraints imposed. Variation of the curves yields the Papapetrou equations for a classical massless particle with helicity 1.Comment: 11 pages, PDF fil

Motion of a Vector Particle in a Curved Space-time. IV. Asymptotical shape of caustic

The studies of influence of spin on a photon motion in a Schwartzschild spacetime is continued. In the previous paper [2] the first order correction to the geodesic motion is reduced to a non-uniform linear ordinary differential equation and the equation obtained has been solved by the standard method of integration of the Green function. If each photon draws a world line specified by this solution then light rays from infinitely distant source form a caustic which does not appear without the spin-gravity interaction. The goal of the present work is to obtain explicit form of caustic.Comment: 6 page

Dirac equations in curved space-time versus Papapetrou spinning particles

We find out classical particles, starting from Dirac quantum fields on a curved space-time, by an eikonal approximation and a localization hypothesis for amplitudes. We recover the results by Mathisson-Papapetrou, hence establishing a fundamental correspondence between the coupling of classical and quantum spinning particles with the gravitational field.Comment: 6 pages, 1 figure, accepted for publication in Europhysics Letter

Does One Size Fit All? Drug Resistance and Standard Treatments: Results of Six Tuberculosis Programmes in Former Soviet Countries.

SETTING: After the collapse of the Soviet Union, countries in the region faced a dramatic increase in tuberculosis cases and the emergence of drug resistance. OBJECTIVE: To discuss the relevance of the DOTS strategy in settings with a high prevalence of drug resistance. DESIGN: Retrospective analysis of one-year treatment outcomes of short-course chemotherapy (SCC) and results of drug susceptibility testing (DST) surveys of six programmes located in the former Soviet Union: Kemerovo prison, Russia; Abkhasia, Georgia; Nagorno-Karabagh, Azerbaijan; Karakalpakstan, Uzbekistan; Dashoguz Velayat, Turkmenistan; and South Kazakhstan Oblast, Kazakhstan. Results are reported for new and previously treated smear-positive patients. RESULTS: Treatment outcomes of 3090 patients and DST results of 1383 patients were collected. Treatment success rates ranged between 87% and 61%, in Nagorno-Karabagh and Kemerovo, respectively, and failure rates between 7% and 23%. Any drug resistance ranged between 66% and 31% in the same programmes. MDR rates ranged between 28% in Karakalpakstan and Kemerovo prison and 4% in Nagorno-Karabagh. CONCLUSION: These results show the limits of SCC in settings with a high prevalence of drug resistance. They demonstrate that adapting treatment according to resistance patterns, access to reliable culture, DST and good quality second-line drugs are necessary