Common Signatures of Statistical Coulomb Fragmentation of Highly Excited Nuclei and Phase Transitions in Confined Microcanonical Systems

TL;DR

This paper explores how signatures of Coulomb fragmentation in highly excited nuclei can mimic phase transition signals in confined systems, highlighting potential misinterpretations in experimental data due to phase space truncation effects.

Contribution

It demonstrates that observed phase transition signatures in nuclear fragmentation may be artifacts of microcanonical phase space truncation, not true phase transitions.

Findings

Heat capacity can appear negative due to phase space truncation.

Bimodality in experimental data may result from pseudo-microcanonical effects.

Signatures of phase transitions can be mimicked by Coulomb fragmentation phenomena.

Abstract

Characteristic signatures of statistical Coulomb fragmentation of highly excited nuclear systems were analyzed. It was found that in some important aspects, they coincide with perceived signatures of phase transitions in confined hypothetical pseudo-microcanonical systems, thus potentially giving rise to a false interpretation of experimental observations in terms of phase transitions. It is demonstrated that the heat capacity as derived based on experimental observations may show domains of faux negative heat capacity for the same fundamental reason a faux negative heat capacity appears in constrained numerical modeling of phase transitions in excited nuclear matter, the reason being an effective truncation of the microcanonical phase space. Similarly, selected experimental data may exhibit bimodality apparently in accordance with the truncated pseudo-microcanonical (but not the true microcanonical) calculations for confined systems.