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arXiv 2201.07536nucl-thhep-ph
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对称核物质中的S波π介子凝聚

S-wave pion condensation in symmetric nuclear matter

D. N. Voskresensky

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15 pages, 2 figures
发表信息：
Phys.Rev.D105 (2022)116007
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摘要：

本文综述了线性西格玛模型、拉氏量有限项的Manohar-Georgi和Gasser-Sainio-Svarc模型以及唯象方法中的S波π介子-核子相互作用。与当前的代数定理和领域的重新定义的微妙之处进行了讨论。在第一个和第三个模型中，同位旋对称物质中的s波π介子凝聚很可能至少在高密度下不会发生，而在第二个模型中，它可能在中等密度下已经出现。在唯象方法中，考虑了文献中所用的s波π介子-核子散射振幅和π介子极化算符的两种参数化。第一个参数化采用了离质量壳振幅，并允许满足当前的代数定理。利用它在气体近似下重建了同位旋对称物质中的s波π介子极化算符。有了这个π极化算符，同位旋对称物质中的s波π凝聚至少在高密度时不会发生。第二种参数化采用质量壳层上的π介子-核子散射振幅，不满足Adler和Weinberg条件。在这样的参数化下，同位旋对称物质中的s波π介子凝聚很可能已经在核子密度$n\simeq (1.4-2.5) n_0$下发生，其中$n_0$是原子核的密度，这应该会导致可观察到的效应。这两个参数化允许成功地描述π原子的数据。

英文摘要：

S-wave pion-nucleon interactions in the linear sigma model, and in Manohar-Georgi and Gasser-Sainio-Svarc models with finite number of terms in Lagrangians, as well as in a general phenomenological approach are reviewed. Subtleties associated with the current algebra theorems and field redefinitions are discussed. In the first and third models most likely the s-wave pion condensation in the isospin-symmetric matter does not occur at least up to high densities, whereas within the second model it may appear already at moderate densities. In the phenomenological approach two parameterizations of the s-wave pion-nucleon scattering amplitude and the pion polarization operator used in the literature are considered. The first parameterization employs the off-mass-shell amplitude and allows to fulfil the current algebra theorems. Using it the s-wave pion polarization operator in the isospin-symmetric matter is reconstructed within the gas approximation. With this pion polarization operator the s-wave pion condensation in the isospin-symmetric matter does not occur at least up to high densities. Second parameterization uses the on-mass-shell pion-nucleon scattering amplitude and does not satisfy the Adler and Weinberg conditions. With such a parameterization most likely the s-wave pion condensation in the isospin-symmetric matter may occur already at the nucleon density $n\simeq (1.4-2.5) n_0$, where $n_0$ is the density of the atomic nucleus, that should result in observable effects. Both parameterizations allow to successfully describe the pion atom data.

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