Wormholes and Child Universes

Abstract

Evidence to the case that classical gravitation provides the clue to make sense out of quantum gravity is presented. The key observation is the existence in classical gravitation of child universe solutions or "almost" solutions , "almost" because of some singularity problems. The difficulties of these child universe solutions due to their generic singularity problems will be very likely be cured by quantum effects, just like for example "almost" instanton solutions are made relevant in gauge theories with breaking of conformal invariance. Some well motivated modifcations of General Relativity where these singularity problems are absent even at the classical level are discussed. High energy density excitations, responsible for UV divergences in quantum field theories, including quantum gravity, are likely to be the source of child universes which carry them out of the original space time. This decoupling could prevent these high UV excitations from having any influence on physical amplitudes. Child universe production could therefore be responsible for UV regularization in quantum field theories which take into account semiclassically gravitational effects. Child universe production in the last stages of black hole evaporation, the prediction of absence of tranplanckian primordial perturbations, connection to the minimum length hypothesis and in particular the connection to the maximal curvature hypothesis are discussed. Some discussion of superexcited states in the case these states are Kaluza Klein excitations is carried out. Finally, the posibility of obtaining "string like" effects from the wormholes associated with the child universes is discussed.

The null energy condition and its violation

“…According to eqs. (12) and (13), this leads to NEC-violation, and at the same time to the gradient instability. However, with the higher derivative terms present, the latter instability occurs at low momenta p only, and can be made harmless [61] by careful choice of parameters and of the form of the higher derivative corrections.…”

“…Since we cannot create an appropriate singularity (and control the evolution through any singularity), we cannot create a universe "like ours". Widely discussed ways out are to invoke tunneling [8,9,10,11] or other quantum effects [12,13,14] and modify gravity [15,16,17], but it is certainly of interest to stay within General Relativity and invoke NEC-violation instead. There were several attempts in the latter direction [18], but many of them are problematic because of instabilities.…”

Consistent null-energy-condition violation: Towards creating a universe in the laboratory

“…[5,6]). Widely discussed ways out are to invoke tunneling [7,8,9,10,11,12,13,14,15,16] or other quantum effects [17,18,19], modify gravity [20,21,22] and violate NEC [23,24,25,26]. The latter option, however, has been problematic, since most of the NEC-violating theories are plagued by pathologies like ghosts, gradient instability and/or superluminality.…”

Instability of static semiclosed worlds in generalized Galileon theories

“…The condition (15) under the assumption (10) requires ′ to be negative, meaning that is monotonous by decreasing, which leads to the contradiction between (17) and (14). Thus, the arguments above prove that < 0 near = 0.…”