Connecting the Quenched $g_A$ in Nuclear Matter To Dense Compact-Star Matter

Abstract: An argument is developed that the long-standing mystery in nuclear physics of the effective axial-current coupling constant in nuclei, $g_A^{\rm eff}\approx 1$, could be understood in terms of the mechanism referred to as pseudo-conformal sound speed" in dense compact-star matter, $v_{\rm pcs}^2/c^2\approx 1/3$. Both pros and cons are presented using an effective field theory anchored on renormalization-group approach to interacting baryons on the Fermi surface that enables one to go beyond Weinberg's highly successful EFT $\chi$EFT$_\pi$ with the pion field only (in nuclear medium) by implementing heavy-meson degrees of freedom. Both hidden local symmetry and hidden scale symmetry, the former involving the vector mesons $\rho$ and $\omega$ and the latter involving the hidden scalar meson, a dilaton $\hat{\sigma}$ ($f_0(500)$), play the crucial role. Going beyond the density regime applicable to normal nuclear matter $n_0$, the notion ofhadron-quark continuity" is brought in via the topological structure of the nucleon, i.e., skyrmion considered to be valid in QCD at large $N_c$ limit. The new inputs for the argumentation are the large N limit of the Grassmanian model for hidden local symmetry and the IR fixed point in QCD for $N_f \leq 3$ involving ``genuine/QCD-conformal dilaton" for hidden scale symmetry.