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@cfa.harvard.edu
www.cfa.harvard.edu/~igor.pikovski/