Can bimodality exist without phase transition?

TL;DR

This paper presents an exactly solvable statistical model showing that bimodal distributions can occur without phase transitions, challenging the common belief that bimodality signals a first-order phase transition.

Contribution

It provides a counterexample demonstrating bimodality can exist independently of phase transitions using a generalized statistical multifragmentation model.

Findings

Bimodal nuclear fragment distributions can occur without phase transitions.

Negative surface tension at supercritical temperatures causes bimodality.

The model describes a compressible nuclear liquid with a tricritical point.

Abstract

Here we present an explicit counterexample to the widely spread beliefs about an exclusive role of bimodality as the first order phase transition signal. On the basis of an exactly solvable statistical model generalizing the statistical multifragmentation model of nuclei we demonstrate that the bimodal nuclear fragment size distributions can naturally appear in infinite system without a phase transition. It appears at the supercritical temperatures due to the negative values of the surface tension coefficient. The developed statistical model corresponds to the compressible nuclear liquid with the tricritical endpoint located at one third of the normal nuclear density.