The entropy puzzle and the quark combination model

TL;DR

This paper investigates how entropy changes during quark-hadron transition using two methods, revealing that entropy can increase or decrease depending on temperature and expansion factors, thus addressing a key puzzle in the model.

Contribution

It demonstrates how entropy variation during hadronization depends on temperature and volume expansion, providing insights into the entropy puzzle in quark combination models.

Findings

Entropy increases if the hadronic phase temperature is lower than the quark phase.

Entropy increase is confirmed if the hadronic volume exceeds 2.5-3 times that of the quark phase.

Entropy change depends on temperature differences and system expansion during hadronization.

Abstract

We use two available methods, the Duhem-Gibbs relation and the entropy formula in terms of particle phase space distributions, to calculate the entropy in a quark combination model. The entropy of the system extracted from the Duhem-Gibbs relation is found to increase in hadronization if the average temperature of the hadronic phase is lower than that of the quark phase. The increase of the entropy can also be confirmed from the entropy formula if the volume of the hadronic phase is larger than 2.5-3.0 times that of the quark phase. So whether the entropy increases or decreases during combination depends on the temperature before and after combination and on how much expansion the system undergoes during combination. The current study provides an example to shed light on the entropy issue in the quark combination model.