A matrix model for Misner universe and closed string tachyons

We use D-instantons to probe the geometry of Misner universe, and calculatethe world volume field theory action, which is of the 1+0 dimensional form andhighly non-local. Turning on closed string tachyons, we see from the deformedmoduli space of the D-instantons that the spacelike singularity is removed andthe region near the singularity becomes a fuzzy cone, where space and time donot commute. When realized cosmologically there can be controllabletrans-planckian effects. And the infinite past is now causally connected withthe infinite future, thus also providing a model for big crunch/big bangtransition. In the spirit of IKKT matrix theory, we propose that theD-instanton action here provides a holographic description for Misner universeand time is generated dynamically. In addition we show that winding stringproduction from the vacua and instability of D-branes have simple uniforminterpretations in this second quantized formalism.Comment: 15 pages, no figures, harvmac; added discussion on space-time noncommutativity and consequences in cosmology; some conclusions better clarified, added comparison with McGreevy & Silverstein's work, added footnotes and reference