Chemical and mechanical instability in warm and dense nuclear matter

Abstract

We investigate the possible thermodynamic instability in a warm and dense nuclear medium (T<50 MeV and \rho_0<\rho_B< 3\rho_0) where a phase transition from nucleonic matter to resonance-dominated Delta-matter can take place. The analysis is performed by requiring the global conservation of baryon and electric charge numbers in the framework of a relativistic equation of state. Similarly to the liquid-gas phase transition, we show that the nucleon-Delta matter phase transition is characterized by both mechanical instability (fluctuations on the baryon density) and by chemical-diffusive instability (fluctuations on the charge concentration) in asymmetric nuclear matter. We then perform an investigation and a comparative study on the different nature of such instabilities and phase transitions.Comment: 12 pages, 15 figure

Nuclear phase transition and thermodynamic instabilities in dense nuclear matter

“…An important feature of this conditions is that, unlike the case of a single conserved charge, the pressure in the mixed phase is not constant and, although the total ρ B and ρ C are fixed, baryon and charge densities can be different in the two phases. For such a system in thermal equilibrium, the possible phase transition can be characterized by mechanical (fluctuations in the baryon density) and chemical instabilities (fluctuations in the electric charge density) [11,19]. As usual the condition of the mechanical stability implies…”

“…By introducing the notation µ i, j = (∂µ i /∂ρ j ) T,P (with i, j = B, C), the chemical stability for a process at constant P and T can be expressed with the following conditions [11] …”

“…In analogy with the liquid-gas case, we are going to investigate the existence of a possible phase transition in the nuclear medium by studying the presence of instabilities (mechanical and/or chemical) in the system. The chemical stability condition is satisfied if [11] ∂µ C ∂y T,P > 0 or…”

“…In regime of finite values of density and temperature, a state of high density resonance matter may be formed and the ∆(1232)-isobar degrees of freedom are expected to play a central role in relativistic heavy ion collisions and in the physics of compact stars [7,8] Alternating Gradient Synchrotron (AGS) to RHIC [9,10]. Moreover, in the framework of the nonlinear Walecka model, it has been predicted that a phase transition from nucleonic matter to ∆-excited nuclear matter can take place and the occurrence of this transition sensibly depends on the ∆-meson coupling constants [11,12].…”

Thermodynamic instabilities in hot and dense nuclear matter

“…In particular, the formation of resonances matter contributes essentially to baryon stopping, hadronic flow effects and enhanced strangeness. Following Ref.s [2,7], we take into account of the Δ-isobar degree of freedoms.We are dealing with the study of a multi-component system at finite temperature and density with two conserved charges: baryon (B) number and zero net strangeness (S) number (r S = ρ S /ρ B = 0). For what concern the electric charge (Q), we work in symmetric nuclear matter with a fixed value of Z/A = 0.5 and we do not consider fluctuations in the electric charge fraction, due to the high temperature regime considered in the present investigation.…”