Monopole decay in the external electric field

The possibility of the magnetic monopole decay in the constant electric field is investigated and the exponential factor in the probability is obtained. Corrections due to Coulomb interaction are calculated. The relation between masses of particles for the process to exist is obtained.Comment: 13 pages, 8 figure

A near-infrared variability campaign of TMR-1: New light on the nature of the candidate protoplanet TMR-1C

(abridged) We present a near-infrared (NIR) photometric variability study of the candidate protoplanet, TMR-1C, located at a separation of about 10" (~1000 AU) from the Class I protobinary TMR-1AB in the Taurus molecular cloud. Our campaign was conducted between October, 2011, and January, 2012. We were able to obtain 44 epochs of observations in each of the H and Ks filters. Based on the final accuracy of our observations, we do not find any strong evidence of short-term NIR variability at amplitudes of >0.15-0.2 mag for TMR-1C or TMR-1AB. Our present observations, however, have reconfirmed the large-amplitude long-term variations in the NIR emission for TMR-1C, which were earlier observed between 1998 and 2002, and have also shown that no particular correlation exists between the brightness and the color changes. TMR-1C became brighter in the H-band by ~1.8 mag between 1998 and 2002, and then fainter again by ~0.7 mag between 2002 and 2011. In contrast, it has persistently become brighter in the Ks-band in the period between 1998 and 2011. The (H-Ks) color for TMR-1C shows large variations, from a red value of 1.3+/-0.07 and 1.6+/-0.05 mag in 1998 and 2000, to a much bluer color of -0.1+/-0.5 mag in 2002, and then again a red color of 1.1+/-0.08 mag in 2011. The observed variability from 1998 to 2011 suggests that TMR-1C becomes fainter when it gets redder, as expected from variable extinction, while the brightening observed in the Ks-band could be due to physical variations in its inner disk structure. The NIR colors for TMR-1C obtained using the high precision photometry from 1998, 2000, and 2011 observations are similar to the protostars in Taurus, suggesting that it could be a faint dusty Class I source. Our study has also revealed two new variable sources in the vicinity of TMR-1AB, which show long-term variations of ~1-2 mag in the NIR colors between 2002 and 2011.Comment: Accepted in A&

Semiclassical Calculation of Photon-Stimulated Schwinger Pair Creation

We consider the electron-positron pair creation by a photon in an external constant electric field. The presented treatment is based on a purely quasiclassical calculation of the imaginary part of the on-shell photon polarization operator. By using this approach we find the pair production rate for photons with polarization parallel as well as orthogonal to the external electric field in the leading order in the parameter $eE / m ^ 2$, which has been recently found by other methods. For the orthogonal polarization we also find a new contribution to the rate, which is leading in the ratio of the photon energy to the electron mass $\omega/m$. We also reproduce by a purely geometrical calculation the exponential factor in the probability of the stimulated pair creation at arbitrary energy of the photon.Comment: 16 pages, 4 figure

Fluctuations of temperature gradients in turbulent thermal convection

Broad theoretical arguments are proposed to show, formally, that the magnitude G of the temperature gradients in turbulent thermal convection at high Rayleigh numbers obeys the same advection-diffusion equation that governs the temperature fluctuation T, except that the velocity field in the new equation is substantially smoothed. This smoothed field leads to a -1 scaling of the spectrum of G in the same range of scales for which the spectral exponent of T lies between -7/5 and -5/3. This result is confirmed by measurements in a confined container with cryogenic helium gas as the working fluid for Rayleigh number Ra=1.5x10^{11}. Also confirmed is the logarithmic form of the autocorrelation function of G. The anomalous scaling of dissipation-like quantities of T and G are identical in the inertial range, showing that the analogy between the two fields is quite deep

Destruction of a metastable string by particle collisions

We calculate the probability of destruction of a metastable string by collisions of the Goldstone bosons, corresponding to the transverse waves on the string. We find a general formula that allows to determine the probability of the string breakup by a collision of arbitrary number of the bosons. We find that the destruction of a metastable string takes place only in collisions of even number of the bosons, and we explicitly calculate the energy dependence of such process in a two-particle collision for an arbitrary relation between the energy and the largest infrared scale in the problem, the length of the critical gap in the string.Comment: 15 pages, 1 figur

On the Detection of Magnetic Helicity

Magnetic fields in various astrophysical settings may be helical and, in the cosmological context, may provide a measure of primordial CP violation during baryogenesis. Yet it is difficult, even in principle, to devise a scheme by which magnetic helicity may be detected, except in some very special systems. We propose that charged cosmic rays originating from known sources may be useful for this purpose. We show that the correlator of the arrival momenta of the cosmic rays is sensitive to the helicity of an intervening magnetic field. If the sources themselves are not known, the method may still be useful provided we have some knowledge of their spatial distribution.Comment: 5 pages, 1 figure, discussions and references added, submited to Phys. Rev.