A field theoretical model for quarkyonic matter

The possibility that nuclear matter at a density relevant to the interior of massive neutron stars may be a quarkynoic matter has attracted considerable recent interest. In this work, we construct a phenomenological model to describe the quarkyonic matter, that would allow quantitative calculations of its various properties within a well-defined field theoretical framework. This is implemented by synthesizing the Walecka model together with the quark-meson model, where both quark and nucleon degrees of freedom are present based on the quarkyonic scenario. With this model we compute at mean-field level the thermodynamic properties of the symmetric nuclear matter and calibrate model parameters through well-known nuclear physics measurements. We find this model gives a very good description of the symmetric nuclear matter from moderate to high baryon density and demonstrates a continuous transition from nucleon-dominance to quark-dominance for the system.

Neutron star matter equation of state including d*-hexaquark degrees of freedom

We present the extension of a previous study where, assuming a simple free bosonic gas supplemented with a relativistic mean-field model to describe the pure nucleonic part of the equation of state, we studied the consequences that the first non-trivial hexaquark d*(2380) could have on the properties of neutron stars. Compared to that exploratory work, we employ a standard non-linear Walecka model including additional terms that describe the interaction of the d*(2380) di-baryon with the other particles of the system through the exchange of σ- and ω-meson fields. Our results show that the presence of the d*(2380) leads to maximum masses compatible with recent observations of ∼2 M⊙ millisecond pulsars if the interaction of the d*(2380) is slightly repulsive or the d*(2380) does not interact at all. An attractive interaction makes the equation of state too soft to be able to support a 2 M⊙ neutron star whereas an extremely repulsive one induces the collapse of the neutron star into a black hole as soon as the d*(2380) appears.

Particle Ratios from Strongly Interacting Hadronic Matter

We calculate the particle ratios K+/π+, K-/π-, and Λ/π- for a strongly interacting hadronic matter using nonlinear Walecka model (NLWM) in relativistic mean field (RMF) approximation. It is found that interactions among hadrons modify K+/π+ and Λ/π- particle ratios, while K-/π- is found to be insensitive to these interactions.

Cold pasta phase in the extended Thomas–Fermi approximation

In this paper, we aim to obtain more accurate values for the transition density to the homogenous phase in the nuclear pasta that occurs in the inner crust of neutron stars. To that end, we use the nonlinear Walecka model at zero temperature and an approach based on the extended Thomas–Fermi (ETF) approximation.

ON THE CONSISTENCY OF QUANTUM HADRO-DYNAMICS

We explore the consistency of the Quantum Hadro-Dynamics (QHD), namely the Serot and Walecka model, paying attention to its renormalizabilty, the stability of the vacuum and the possible occurrence of a σ-ω condensate. We find that the QHD is not renormalizable as it is usually described, but the true way of formulate it, via the Stueckelberg Lagrangian, alters the formulation of the model in the vacuum but leaves the results in the medium unchanged. Further, we find that the stability of the vacuum imposes a constrain over the parameters of the σ self-interaction while stability against σ condensation at the mean field level imposes a constraint on the coupling constant, namely gσ<8.828 that is kF = 207.2 MeV/c, significantly below the standard value of QHD.