Strangeness and $Δ$ resonance in compact stars with relativistic-mean-field models
We explore the effects of strangeness and $Δ$ resonance in baryonic matter and compact stars within the relativistic-mean-field (RMF) models. The covariant density functional PKDD is adopted for $N$-$N$ interaction, parameters fixed based on finite hypernuclei and neutron stars are taken for the hyperon-meson couplings, and the universal baryon-meson coupling scheme is adopted for the $Δ$-meson couplings. In light of the recent observations of GW170817 with the dimensionless combined tidal deformability $197 \leq \barΛ\leq 720$, we find it is essential to include the $Δ$ resonances in compact stars, and small $Δ$-$ρ$ coupling $g_{ρΔ}$ is favored if the mass $2.27{}_{-0.15}^{+0.17}\ M_\odot$ of PSR J2215+5135 is confirmed.
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