Speaker: Yasaman Yazdi (Alberta U., Imperial Coll., London)
Title: The SJ Vacuum in de Sitter Spacetime
I present results from a study of the Sorkin-Johnston (SJ) vacuum in de Sitter spacetime for a free scalar field theory. We find evidence for a new vacuum state in de Sitter spacetime which is de Sitter invariant in 4d. Using a causal set discretisation of a slab of 2d and 4d de Sitter spacetime, we find the causal set SJ vacuum for a range of masses m≥0 of the free scalar field. While our simulations are limited to a finite volume slab of global de Sitter spacetime, they show good convergence as the volume is increased. We find that the 4d causal set SJ vacuum, while de Sitter invariant, shows a significant departure from the continuum Mottola-Allen α-vacua. Moreover, the causal set SJ vacuum is well-defined for all masses, including the minimally coupled massless m=0 case which is ill-defined in other de Sitter invariant vacuum state definitions.
Room: Sala de Reuniões e Seminários (2nd Floor of physics building)