Physical and Chemical Models

We present our first attempts to formulate a thermodynamics-like description of explosions. The motivation is partly a fundamental interest in non-equilibrium statistical physics, partly the resemblance of an explosion to the late stages of a heavy-ion collision. We perform numerical simulations on a microscopic model of interacting billiard-ball like particles, and we analyse the results of such simulations trying to identify collective variables describing the degree of equilibrium during the explosion.

           Introduction

The assumption of thermodynamic equilibrium at an intermediate stage of a heavy-ion collision is often incorporated in models of the colliding nuclear mat- ter. These models range from statistical models of nuclear multifragmentation to the fluid dynamical models of the quark gluon plasma. In contrast, mi- croscopic models of molecular dynamics type (e.g. RQMD, FMD and NMD), which are based upon constituent interactions, do not contain this assump- tion. Such models are appropriate for testing to what extent thermodynamic equilibrium is actually achieved. And if it is not, the application of thermo- static concepts such as temperature and entropy becomes questionable. In this study we employ a very simple model, and focus on the thermodynamic or "overall" description of the system.

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