Narrow Results

We use the Foldy-Wouthuysen representation to construct Lorentz-invariant interactions of heavy fields, building the interactions starting from non-relativistic heavy particle fields. We show that the couplings obtained feature a straightforward 1/m, where m is the mass of the heavy particle, expansion, which ensures Lorentz invariance order by order in effective field theories. We illustrate possible applications on the examples of pion-nucleon and pion-nucleon-delta couplings in chiral effective field theory. For instance, we show that one of the terms usually considered to be a part of chiral index-1 πNΔ vertex is redundant. We discuss the implications of this fact.

In the present work we study the equation of state for asymmetric hadronic matter, to be applied in neutron star structure calculation. The delta-rich hadronic stellar matter condensate is studied in the context of mean-field approximation in an extended Walecka's theory version, including the Rarita–Schwinger 3/2-spinor to the hadronic sector. The leptonic sector is also incorporated in beta-equilibrium to the dense stelar medium composition. The role of neutrino trapping for the the formed photo-neutron structure including delta matter in its composition is discussed.

Lattice QCD results can be extrapolated to physical quark masses using Chiral Perturbation Theory. Here, treatment of statistical and systematic errors is discussed. One way of estimating the theoretical uncertainty is to perform a matching of the theory to a framework with an additional degree of freedom. This is illustrated for the nucleon axial vector coupling constant g_A by effectively integrating out the leading Δ(1232) contribution.