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arXiv 1205.6902nucl-thastro-ph.SR
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冷中子物质的响应函数:密度、自旋和电流涨落

Response functions of cold neutron matter: density, spin and current fluctuations

Jochen Keller, Armen Sedrakian

摘要:

本文研究了单组分对关联重子费米液体对密度、自旋及其电流扰动的响应。一套完整的响应函数是在低温制度内的有效理论的基础上,一个小的动量传递膨胀和任意的动量传递有效的数值方案。这两种方法的比较验证了其收敛域内的摄动近似。我们推导了与密度、密度流、自旋和自旋流微扰相关的集体激发的谱函数。导出了密度和自旋涨落的色散关系,结果表明,密度涨落导致类激子无阻尼束缚态,而自旋激发对应于高于破偶阈值的扩散模.集体对破坏模式的中子物质在亚核密度的比热的贡献进行了计算,并示出在不太低的温度下的简并电子气相媲美。

英文摘要:

We study the response of a single-component pair-correlated baryonic Fermi-liquid to density, spin, and their current perturbations. A complete set of response functions is derived in the low-temperature regime both within an effective theory based on a small momentum transfer expansion and within a numerical scheme valid for arbitrary momentum transfers. A comparison of these two approaches validates the perturbative approximation within the domain of its convergence. We derive the spectral functions of collective excitations associated with the density, density-current, spin, and spin-current perturbations. The dispersion relations of density and spin fluctuations are derived and it is shown that the density fluctuations lead to exciton-like undamped bound states, whereas the spin excitations correspond to diffusive modes above the pair-breaking threshold. The contribution of the collective pair-breaking modes to the specific heat of neutron matter at subnuclear densities is computed and is shown to be comparable to that of the degenerate electron gas at not too low temperatures.

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