Nuclear matter

About: Nuclear matter is a research topic. Over the lifetime, 10180 publications have been published within this topic receiving 248261 citations.

Variations on the excluded-volume mechanism

Abstract: The conventional excluded-volume mechanism in the theoretical description of matter properties is generalized by introducing more general functional dependencies of the available volume fraction. The requirement of thermodynamic consistency governs the appearance of rearrangement contributions to thermodynamic quantities and to particle potentials. The main features of the method are studied in three examples: the dissolution of deuterons in warm and dense nuclear matter, the stiffening or softening of the nuclear matter equation of state in a relativistic mean-field model, and the effects of medium-dependent effective degeneracy factors in a Fermi gas model for quark matter.

Level Structure of Nuclear Matter and Liquid He 3

Abstract: Using the $K$ matrix as computed in the study of nuclear matter and liquid ${\mathrm{He}}^{3}$ as the effective interaction at the Fermi surface, the possible superfluidity of these systems has been investigated. A theory of the cooperative phenomenon valid for particle-particle interaction in states of arbitrary angular momentum has been developed following the methods of Bardeen, Cooper, and Schrieffer. It is found for states of relative angular momentum other than $l=0$ that the particle pairs must be correlated with respect to an arbitrary direction in the medium. As a result the change of structure of the Fermi surface is angularly dependent. An energy gap does not occur other than for $l=0$, the particle excitation energy vanishing for certain orientations of the momentum. It is also shown that the specific heat shows a discontinuity at the transition temperature, but somewhat different from the case of $l=0$.Application of these results to liquid ${\mathrm{He}}^{3}$ shows that the cooperative effects arise from the interaction in the state with $l=2$, and that the transition temperature is at about 0.1\ifmmode^\circ\else\textdegree\fi{}K. In nuclear matter the $^{1}S_{0}$ interaction is very weak and probably repulsive at the Fermi surface, and the attractive $^{1}D_{2}$ interaction gives a negligible energy shift. The $^{3}S_{1}$ interaction is attractive and in nuclear matter gives a few-tenths of an Mev energy gap. These results suggest that in finite nuclei, with pairing of identical nucleons in the same shell, the cooperative effects are not strictly analogous to those in nuclear matter but instead are closely associated with the finite level spacing.