Backreaction I: The torus

We use wrapped D-brane probes to measure position dependent perturbations o f compactification moduli. Due to the backreaction of the D-branes on the l ocal geometry, we suspect that measuring the fluctuations of one modulus to high precision will generically affect the others. These considerations le ad us to conjecture a novel uncertainty principle on the Calabi-Yau moduli space. We begin our investigation with a gedanken experiment on a torus. (C ) 2001 Elsevier Science B.V. All rights reserved.