The emergence of space-time gravitational physics as an effective theory from the c=1 matrix model

Abstract

We discuss further a recent space-time interpretation of the $c=1$ matrix model which retains both sides of the inverted harmonic oscillator potential in the underlying free fermion theory and reproduces the physics of the discrete state moduli of two-dimensional string theory. We show that within this framework the linear tachyon background in flat space arises from the fermi vacuum. We argue that this framework does not suffer from any obvious nonperturbative inconsistency. We also identify and discuss a class of nearly static configurations in the free fermion theory which are interpreted as static metric backgrounds in space-time. These backgrounds are classically absorbing --- a beam of tachyons thrown at such a background is only partly reflected back --- and are tentatively identified with the eternal back-hole of 2-dimensional string theory.