Nuclear Incompressibility at Finite Temperature and Entropy

Features of the nuclear isothermal incompressibility $\kappa$ and adiabatic incompressibility $\kappa_Q$ are investigated. The calculations are done at zero and finite temperatures and non zero entropy and for several equations of state. It is shown that $\kappa_Q$ decreases with increasing entropy while the isothermal $\kappa$ increases with increasing $T$. A duality is found between the adiabatic $\kappa_Q$ and the T=0 isothermal $\kappa$. Our isothermal results are compared with a recent lattice Monte Carlo calculation done at finite $T$. The necessity of including correlations is shown if $\kappa$ is to have a peak with increasing $T$ as seen in the Monte Carlo calculations. A peak in $\kappa$ is linked to attractive scattering correlations in two nucleons channel in the virial expansion in our approach which are Pauli blocked at low $T$.Comment: 5 page

Liquid-Gas Phase Transition in Nuclear Equation of State

A canonical ensemble model is used to describe a caloric curve of nuclear liquid-gas phase transition. Allowing a discontinuity in the freeze out density from one spinodal density to another for a given initial temperature, the nuclear liquid-gas phase transition can be described as first order. Averaging over various freeze out densities of all the possible initial temperatures for a given total reaction energy, the first order characteristics of liquid-gas phase transition is smeared out to a smooth transition. Two experiments, one at low beam energy and one at high beam energy show different caloric behaviors and are discussed.Comment: 12 pages in Revtex including two Postscript figure

Low-Latitude Coronal Holes at the Minimum of the 23rd Solar Cycle

Low and mid-latitude coronal holes (CHs) observed on the Sun during the current solar activity minimum (from September 21, 2006, Carrington rotation (CR) 2048, until June 26, 2009 (CR 2084)) were analyzed using {\it SOHO}/EIT and STEREO-A SECCHI EUVI data. From both the observations and Potential Field Source Surface (PFSS) modeling, we find that the area occupied by CHs inside a belt of $\pm 40^\circ$ around the solar equator is larger in the current 2007 solar minimum relative to the similar phase of the previous 1996 solar minimum. The enhanced CH area is related to a recurrent appearance of five persistent CHs, which survived during 7-27 solar rotations. Three of the CHs are of positive magnetic polarity and two are negative. The most long-lived CH was being formed during 2 days and existed for 27 rotations. This CH was associated with fast solar wind at 1 AU of approximately 620$\pm 40$ km s$^{-1}$. The 3D MHD modeling for this time period shows an open field structure above this CH. We conclude that the global magnetic field of the Sun possessed a multi-pole structure during this time period. Calculation of the harmonic power spectrum of the solar magnetic field demonstrates a greater prevalence of multi-pole components over the dipole component in the 2007 solar minimum compared to the 1996 solar minimum. The unusual large separation between the dipole and multi-pole components is due to the very low magnitude of the dipole component, which is three times lower than that in the previous 1996 solar minimum.Comment: 14 pages, 7 figure