Mixed boundary states from 1-loop bosonic closed strings

We analyze in a simple calculation the way 2-dimensional moduli induce a noise-like mixing between the right and left sectors of the 1-loop partition function of bosonic closed strings. As it is a direct consequence of string interactions, we argue it must be taken as a renormalization to the tree-level dynamics as far as the Wilsonian view on renormalization group is kept. We also highlight the way this noise effect brings a thermodynamical meaning to space-filling D -branes.