Dynamics of money

We present a dynamical many-body theory of money in which the value of mone y is a time dependent "strategic variable" that is chosen by the individual agents. The value of money in equilibrium is not fixed by the equations, a nd thus represents a continuous symmetry. The dynamics breaks this continuo us symmetry by fixating the value of money at a level which depends on init ial conditions. The fluctuations around the equilibrium, for instance in th e presence of noise, are governed by the "Goldstone modes" associated with the broken symmetry. The idea is illustrated by a simple network model of m onopolistic vendors and buyers. [S1063-651X(99)12308-0].