About some formalisms of interaction Phase transition models in economics?*

The aim of the present work is to scrutinise the economic use of phase transitions formalisms and to assess their relevance. The formal correspondence between the issue of micro-macro passage when agents are interacting and the physics problem of phase transition is first set out. The second section presents two formal tools likely to be associated with these problems and to exhibit the typical phenomena of phase transition. It is then possible to highlight the key points upon which the phase transition phenomena in these formal representations rely, and then to assess the relevance of their economic "counterparts" associated with these crucial characteristics. A more general appraisal of these formalisms for economics is finally sketched.