Nuclear matter properties in relativistic mean field model with nucleon volume extensions

In relativistic field models nucleons and mesons are all regarded as point-like particles. These models can be used to describe main properties of nuclear matter. In fact, however, a nucleon has a definite size. It is wellknown that in standard state of nuclear matter, the total volume occupied by all nucleons is about ten percent of the volume of nuclear matter. In the conditions of extreme high densities, e.g., the internal of neutron stars and high energy heavy-ion collides, the rate of nucleon occupied volume is several times larger. It is interesting to study the effect of nucleon volume extension in Walecka model [1–3]. Zhang et. al. studied effect of the nucleon extension of MIT bag model [4]. In this paper we do the similar calculation but not breaking relativistic Lorentz invariance to exclude the definite nucleon volume. As an initial proper approximation, we assume that the nucleon volume τ is fixed. Suppose N nucleons existing still in the nuclear matter of volume V , the effective existing space of nucleons is V − τN , i.e., simply regarding the nucleon as a hard shell and subtracting the nucleon volume. In the direction of relativistically moving of a nucleon, the radius will be abstracted. Therefore, the effective moving space is then V (1 − τρs), where ρs is the nuclear scalar density before considering the extraction of the nucleon volume. In other words, the nuclear scalar density ρs in the effective moving space is transformed as