arXiv subjects

H

Publications and source records attributed to H.

3 recordsLinked to original sources

arXiv2014

ASTRO-H White Paper - Stars -- Accretion, Shocks, Charge Exchanges and Magnetic Phenomena

X-ray emission from stars has origins as diverse as the stars themselves: accretion shocks, shocks generated in wind-wind collisions, or release of magnetic energy. Although the scenarios responsible for X-ray emission are thought to be known, the physical mechanisms operating are in many cases not yet fully understood. Full testing of many of these mechanisms requires high energy resolution, large effective area, and coverage of broad energy bands. The loss of the X-ray calorimeter spectrometer on board ASTRO-E2 was a huge blow to the field; it would have provided a large sample of high resolution spectra of stars with high signal-to-noise ratio. Now, with the advent of the ASTRO-H Soft X-ray Spectrometer and Hard X-ray Imager, we will be able to examine some of the hot topics in stellar astrophysics and solve outstanding mysteries.

astro-ph.HE↗

arXiv1999

Massive-Scalar Absorption by Extremal p-branes

We study the absorption probability of minimally-coupled massive scalars by extremal p-branes. In particular, we find that the massive scalar wave equation under the self-dual string background has the same form as the massless scalar wave equation under the dyonic string background. Thus it can be cast into the form of a modified Mathieu equation and solved exactly. Another example that we can solve exactly is that of the D=4 two-charge black hole with equal charges, for which we obtain the closed-form absorption probability. We also obtain the leading-order absorption probabilities for D3-, M2- and M5-branes.

hep-th↗

arXiv1995

Topological Charge Distribution and $CP^1$ Model with $θ$ Term

The two dimensional $CP^1$ model with $θ$ term is simulated. We compute the topological charge distribution $P(Q)$ by employing the ``set method" and ``trial function method", which are effective in the calculations for very wide range of $Q$ and large volume. The distribution $P(Q)$ shows the Gaussian behavior in the small $β$ (inverse coupling constant) region and deviates from it in the large $β$ region. The free energy and its moment are calculated as a function of $θ$. For small $β$, the partition function is given by the elliptic theta function, and the distribution of its zeros on the complex $θ$ plane leads to the first order phase transition at $θ=π$. In the large $β$ region, on the other hand, this first order phase transition disappears, but definite conclusion concerning the transition is not reached due to large errors.

hep-lat↗