Many body effects in nuclear matter QCD sum rules

TL;DR

This paper investigates the effects of three- and four-nucleon interactions on nucleon properties in symmetric nuclear matter using QCD sum rules, emphasizing the role of nonlocal condensates and pion-nucleon sigma term dependence.

Contribution

It extends previous work by including four-nucleon forces in QCD sum rule calculations of nuclear matter, providing a detailed analysis of their impact on nucleon characteristics.

Findings

Four-nucleon forces significantly affect nucleon self energies.

Nucleon effective mass and potential energy depend on the pion-nucleon sigma term.

Hierarchy of many-body forces is confirmed through the analysis.

Abstract

We calculate the single-particle nucleon characteristics in symmetric nuclear matter with inclusion of the 3N and 4N interactions. We calculated the contribution of the 3N interactions earlier, now we add that of the 4N ones. The contribution of the 4N forces to nucleon self energies is expressed in terms of the nonlocal scalar condensate (d=3) and of the configurations of the vector-scalar and the scalar-scalar quark condensates (d=6) in which two diquark operators act on two different nucleons of the matter.These four-quark condensates are obtained in the model-independent way. The density dependence of the nucleon effective mass, of the vector self energy and of the single-particle potential energy are obtained. We traced the dependence of the nucleon characteristics on the actual value of the pion-nucleon sigma term. We obtained also the nucleon characteristics in terms of the quasifree nucleons, with the noninteracting nucleons surrounded by their pion clouds as the starting point. This approach leads to strict hierarchy of the many body forces.