Title:	Generalized causal set d'Alembertians
Authors:	Aslanbeigi, Siavash Saravani, Mehdi Sorkin, Rafael D.
Keywords:	Models of Quantum Gravity Stochastic Processes Lattice Models of Gravity
Issue Date:	4-Jun-2014
Publisher:	Springer for SISSA (International School for Advanced Studies)
Citation:	Journal of High Energy Physics, 2014, Vol. 06, p. 24,
Abstract:	We introduce a family of generalized d’Alembertian operators in D-dimensional Minkowski spacetimes M D which are manifestly Lorentz-invariant, retarded, and non-local, the extent of the nonlocality being governed by a single parameter ρ. The prototypes of these operators arose in earlier work as averages of matrix operators meant to describe the propagation of a scalar field in a causal set. We generalize the original definitions to produce an infinite family of “Generalized Causet Box (GCB) operators” parametrized by certain coefficients {a, b n }, and we derive the conditions on the latter needed for the usual d’Alembertian to be recovered in the infrared limit. The continuum average of a GCB operator is an integral operator in M D , and it is these continuum operators that we mainly study. To that end, we compute their action on plane waves, or equivalently their Fourier transforms g(p) [p being the momentum-vector]. For timelike p, g(p) has an imaginary part whose sign depends on whether p is past or future-directed. For small p, g(p) is necessarily proportional to p · p, but for large p it becomes constant, raising the possibility of a genuinely Lorentzian perturbative regulator for quantum field theory in M D . We also address the question of whether or not the evolution defined by the GCB operators is stable, finding evidence that the original 4D causal set d’Alembertian is unstable, while its 2D counterpart is stable.
Description:	Open Access
URI:	http://hdl.handle.net/2289/5975
ISSN:	1029-8479
Alternative Location:	http://arxiv.org/abs/1403.1622 http://dx.doi.org/10.1007/JHEP06(2014)024
Copyright:	2014 The Authors & SCOAP3
Appears in Collections:	Research Papers (TP)

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