We study the superfluid dynamics of the outer core of neutron stars by means of a generalized hydrodynamic model made of a neutronic superfluid and a protonic superconductor, coupled by both the dynamic entrainment and the Skyrme SLy4 nucleon-nucleon interactions. The resulting nonlinear equations of motion are probed in the search for dynamical instabilities triggered by the relative motion of the superfluids that could be of potential relevance to observational features of neutron stars. Through linear analysis, the origin and expected growth of the instabilities is explored for varying nuclear-matter density. Differently from previous findings, the dispersion of linear excitations in our model shows rotonic structures below the pair-breaking energy threshold, which lies at the origin of the dynamical instabilities and could eventually lead to emergent vorticity along with modulations of the superfluid density.

中文翻译：

---

中子星超流体外核的旋转不稳定性

我们通过由中子超流体和质子超导体组成的广义流体动力学模型研究中子星外核的超流体动力学，通过动态夹带和 Skyrme SLy4 核子-核子相互作用耦合。在寻找可能与中子星观测特征潜在相关的超流体的相对运动引发的动力学不稳定性的过程中，对由此产生的非线性运动方程进行了探索。通过线性分析，探索了不同核物质密度的不稳定性的起源和预期增长。与之前的发现不同，我们模型中线性激发的色散显示出低于破对能量阈值的旋转结构，