Holography, Time and Quantum Mechanics
  In this talk we entertain the possibility that the synthesis of general covariance and quantum mechanics requires an extension of the basic kinematical setup of quantum mechanics. According to the holographic principle, regions of spacetime bounded by a finite area carry finite entropy. When we in addition assume that the origin of the entropy is a finite dimensional Hilbert space, and apply this to cosmological solutions using a suitable notion of complementarity, we find as a consequence that gravitational effects can lead to dynamical variation in the dimensionality of such Hilbert spaces. This happens generally in cosmological settings like our own universe. 
Vijay Balasubramanian, Jan de Boer and Djordje Minic