Semi-classical Approach to Charged Dilatonic Black Hole in Two Dimensions

We consider exactly solvable semi-classical theory of two dimensional dilatonic gravity with electromagnetic interactions. As was done in the paper by Russo, Susskind and Thorlacius, the term which changes the kinetic term is added to the action. The theory contains massless fermions as matter fields and there appear the quantum corrections including chiral anomaly. The screening effect due to the chiral anomaly has a tendency to cloak the singularity. In a region of the parameter space, the essential behavior of the theory is similar to that of Callan, Giddings, Harvey and Strominger's dilatonic black hole theory modified in the paper by Russo, Susskind and Thorlacius and the singularity formed by the collapsing matter emerges naked. We find, however, another region of the parameter space where the singularity disappears in a finite proper time. Furthermore, in the region of the parameter space, there appears a discontinuity in the metric on the trajectory of the collapsing matter, which would be a signal of topology changeComment: 21pp, NDA-FP-5/92, OCHA-PP-2

Is english our lingua franca or the native speaker's property? The native speaker orientation among middle school students in Japan

This paper reports the first empirical study to date that sought to examine the native speaker orientation among middle school EFL students in Japan. To this end, this preliminary study measured their language attitudes in this respect addressing age-stratified and gender variations. The data was elicited from an attitude survey with 318 eighth and ninth graders at a public middle school. The findings suggest that the students gave the highest evaluations to native than to nonnative varieties of English. Second, they opted for learning English for its currency and utility in the English as a native language setting, rather than for its transnational function as a lingua franca. Lastly, the finding indicated a possible developmental trajectory of their native speaker orientation

Hawking radiation via tachyon condensation and its implications to tachyon cosmology

Hawking radiation can be derived from the collapsing process of matter to form a black hole. In this work, we show in more detail that the freely infalling process of a probe (D-)particle (or point-like object) in a non-extreme black hole background is essentially a tachyon condensation process. That is, a probe D-particle will behave as an unstable D-particle in the near-horizon region of a non-extreme black hole. From this point of view, Hawking radiation can be viewed as the thermal radiation from rolling tachyon on an unstable D-particle (i.e., the infalling probe) at the Hagedorn temperature. The result has interesting implications to tachyon cosmology: the uniform tachyon rolling in cosmology can automatically create particle pairs at late times, via a mechanism just like the Hawking radiation process near a black hole. So this particle creation process can naturally give rise to a hot universe with thermal perturbations beyond tachyon inflation, providing an alternative reheating mechanism.Comment: 22 page

Charged Dilatonic Black Hole and Hawking Radiation in Two Dimensions

We consider Callan, Giddings, Harvey and Strominger's (CGHS) two dimensional dilatonic gravity with electromagnetic interactions. This model can be also solved classically. Among the solutions describing static black holes, there exist extremal solutions which have zero temperatures. In the extremal solutions, the space-time metric is not singular. We also obtain the solutions describing charged matter (chiral fermions) collapsing into black holes. Through the collapsing, not only future horizon but past horizon is also shifted. The quantum corrections including chiral anomaly are also discussed. In a way similar to CGHS model, the curvature singularity also appeared, except extremal case, when the matter collapsing. The screening effects due to the chiral anomaly have a tendency to cloak the singularityComment: 15p

Modeling of Protostellar Clouds and their Observational Properties

A physical model and two-dimensional numerical method for computing the evolution and spectra of protostellar clouds are described. The physical model is based on a system of magneto-gasdynamical equations, including ohmic and ambipolar diffusion, and a scheme for calculating the thermal and ionization structure of a cloud. The dust and gas temperatures are determined during the calculations of the thermal structure of the cloud. The results of computing the dynamical and thermal structure of the cloud are used to model the radiative transfer in continuum and in molecular lines. We presented the results for clouds in hydrostatic and thermal equilibrium. The evolution of a rotating magnetic protostellar cloud starting from a quasi-static state is also considered. Spectral maps for optically thick lines of linear molecules are analyzed. We have shown that the influence of the magnetic field and rotation can lead to a redistribution of angular momentum in the cloud and the formation of a characteristic rotational velocity structure. As a result, the distribution of the velocity centroid of the molecular lines can acquire an hourglass shape. We plan to use the developed program package together with a model for the chemical evolution to interpret and model observed starless and protostellar cores.Comment: Accepted to Astronomy Report