Hyperonic Direct-Urca Neutrino Emission with Lattice-QCD-Informed Form Factors

We investigate the sensitivity of direct-Urca neutrino emission in hyperonic neutron-star matter to the structure and momentum dependence of baryonic transition form factors. Using the zero-temperature FSU2H relativistic mean-field equation of state, we derive the relativistic emissivity for general spin- 1/2 baryon transitions with the complete six form-factor contribution. We compare conventional static flavor-SU(3) couplings with vacuum lattice-QCD-informed form factors, using direct lattice vacuum input for n to p and Λ to p and a hybrid construction for the remaining hyperonic channels. Evaluating the latter both at q 2=0 and at the kinetic momentum transfer sampled at the Fermi surfaces separates changes in the zero-momentum couplings from momentum-transfer effects. The sensitivity is strongly channel dependent. The nucleonic transition probes q 2 0 and is only weakly affected, whereas hyperonic channels can sample substantially larger momentum transfers and receive correspondingly larger corrections. These modifications propagate to the integrated neutrino luminosity of stellar configurations. Our results estimate the possible scale of the sensitivity coming from momentum transfer dependence, absent from static-coupling treatments and motivate future first-principles studies of baryonic weak currents in dense matter.