Vacuum Condensate Picture of Quantum Gravity

In quantum gravity perturbation theory in Newton's constant G is known to be badly divergent, and as a result not very useful. Nevertheless some of the most interesting phenomena in physics are often associated with non-analytic behavior in the coupling constant and the existence of nontrivial quantum condensates. It is therefore possible that pathologies encountered in the case of gravity are more likely the result of inadequate analytical treatment, and not necessarily a reflection of some intrinsic insurmountable problem. The nonperturbative treatment of quantum gravity via the Regge-Wheeler lattice path integral formulation reveals the existence of a new phase involving a nontrivial gravitational vacuum condensate, and a new set of scaling exponents characterizing both the running of G and the long-distance behavior of invariant correlation functions. The appearance of such a gravitational condensate is viewed as analogous to the (equally nonperturbative) gluon and chiral condensates known to describe the physical vacuum of QCD. The resulting quantum theory of gravity is highly constrained, and its physical predictions are found to depend only on one adjustable parameter, a genuinely nonperturbative scale xi in many ways analogous to the scaling violation parameter Lambda MSbar of QCD. Recent results point to significant deviations from classical gravity on distance scales approaching the effective infrared cutoff set by the observed cosmological constant. Such subtle quantum effects are expected to be initially small on current cosmological scales, but could become detectable in future high precision satellite experiments.Comment: 72 pages, 7 figures. Typos fixed, references added. Conforms to published version. arXiv admin note: text overlap with arXiv:1506.0779

Renormalization Group Running of Newton's G: The Static Isotropic Case

Corrections are computed to the classical static isotropic solution of general relativity, arising from non-perturbative quantum gravity effects. A slow rise of the effective gravitational coupling with distance is shown to involve a genuinely non-perturbative scale, closely connected with the gravitational vacuum condensate, and thereby, it is argued, related to the observed effective cosmological constant. Several analogies between the proposed vacuum condensate picture of quantum gravitation, and non-perturbative aspects of vacuum condensation in strongly coupled non-abelian gauge theories are developed. In contrast to phenomenological approaches, the underlying functional integral formulation of the theory severely constrains possible scenarios for the renormalization group evolution of couplings. The expected running of Newton's constant $G$ is compared to known vacuum polarization induced effects in QED and QCD. The general analysis is then extended to a set of covariant non-local effective field equations, intended to incorporate the full scale dependence of $G$, and examined in the case of the static isotropic metric. The existence of vacuum solutions to the effective field equations in general severely restricts the possible values of the scaling exponent $\nu$.Comment: 61 pages, 3 figure

Cosmic Inflation from Emergent Spacetime Picture

We argue that the emergent spacetime picture admits a background-independent formulation of cosmic inflation. The inflation in this picture corresponds to the dynamical emergence of spacetime while the conventional inflation is simply an (exponential) expansion of a preexisting spacetime owing to the vacuum energy carried by an inflaton field. We show that the cosmic inflation arises as a time-dependent solution of the matrix quantum mechanics describing the dynamical process of Planck energy condensate in vacuum without introducing any inflaton field as well as an {\it ad hoc} inflation potential. Thus the emergent spacetime picture realizes a background-independent description of the inflationary universe which has a sufficiently elegant and explanatory power to defend the integrity of physics against the multiverse hypothesis.Comment: 6 pages, 1 figure; Contribution to the Proceedings of the Second LeCosPA Symposium "Everything about Gravity", Taipei, 14-18 December, 201

A weak, attractive, long-range force in Higgs condensates

Due to the peculiar nature of the underlying medium, density fluctuations in a `Higgs condensate' are predicted to propagate for infinitely long wavelengths with a group velocity $c_s\to \infty$. On the other hand, for any large but finite $c_s$ there is a weak, attractive $1/r$ potential of strength ${{1}\over{c^2_s}}$ and the energy spectrum deviates from the purely massive form \sqrt{p}^2 + M^2_h} at momenta smaller than $\delta\sim {{M_h}\over{c_s}}$. Physically, the length scale $\delta^{-1}$ corresponds to the mean free-path for the elementary constituents in the condensate and would naturally be placed in the millimeter range.Comment: 12 pages, LaTe