title: New perspective on cosmic coincidence problems
abstract: Cosmological data suggest that we live in an interesting period in the history of the universe when rho(Lambda) approximately rho(M) approximately rho(R). The occurrence of any epoch with such a "triple coincidence" is puzzling, while the question of why we happen to live during this special epoch is the "Why now?" problem. We introduce a framework which makes the triple coincidence inevitable; furthermore, the "Why now?" problem is transformed and greatly ameliorated. The framework assumes that the only relevant mass scales are the electroweak scale M(EW), and the Planck scale M(Pl) and requires rho(1/4)(Lambda) approximately M(2)(EW)/M(Pl) parametrically. Assuming that the true vacuum energy vanishes, we present a simple model, where a false vacuum energy yields a cosmological constant of this form.
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720 Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.initials: N
authors.lastname: Arkani-Hamed
authors.initials: LJ
authors.lastname: Hall
authors.initials: C
authors.lastname: Kolda
authors.initials: H
authors.lastname: Murayama