[Aspuru-Guzik Group List] ITAMP seminar - Martin Schaden, Rutgers University (Mon, 04/11, 3pm, Pratt seminar room)

*ITAMP Seminar * *Speaker:* Prof. Martin Schaden (Rutgers University) *Title:* Causal Space-Times on a Null Lattice (based on arXiv:1509.03095v2) *Abstract: *I propose a discrete model of Quantum Gravity based on the same principle as the Global Positioning System: the intersection of forward light-cones from four spatially separate events (with certain restrictions) determines another event. I show that causal manifold can thus be triangulated by a topologically hypercubic lattice with light-like links; the length of the spatial diagonal of each plaquette being determined by spinors describing its light-like edges. This lattice model has an SL(2,C) x U^4(1) structure group and is geometric. The description foliates in a causal and physically transparent manner. The observables, the most general local action and the integration measure of this model are all derived from this stucture group and for smooth configurations have well-known continuum limits. Consistency constraints on a configuration to describe the triangulation of a causal manifold are derived and a one-parameter ambiguity of the invariant integration measure is exploited to regularize the model. Finally its SL(2,C) structure group is uniquely (without Gribov ambiguity) localized and the integration measure expressed in terms of geometrical invariants. Should time and interest permit, I will discuss global issues and show numerical results on a small lattice describing the vicinity of the Big Bang in the (unphysical) limit where the cosmological term dominates the dynamics. *Date:* Monday, April 11th *Time:* 3pm-4pm *Location:* Pratt Seminar Room (P-G03,4) @ Center for Astrophysics (60 Garden Street) -- Dr. Igor Pikovski Institute for Theoretical Atomic, Molecular and Optical Physics (ITAMP) Harvard-Smithsonian Center for Astrophysics 60 Garden St, MS-14; Cambridge, MA 02138, USA Tel.: +1 (617) 496-7613 e-mail: igor.pikovski(a)cfa.harvard.edu www.cfa.harvard.edu/~igor.pikovski/