Dark energy from quantum fluctuations

We have derived the quantum vacuum pressure P_vac as a primary entity, removing a trivial and a gauge terms from the cosmological constant-like part (the zeroth term) of the effective action for a free matter field. The quantum vacuum energy density G_vac appears a secondary entity, but both are of expected order. Moreover P_vac and G_vac are dynamical, and therefore they can be used in the Einstein equations. In particular, they could dynamically support holographic dark energy model as well as the `thermodynamic' one.Comment: 4 pages (in AdP style), 2 references added, prepared for the proceedings of the Grassmannian Conference in Fundamental Cosmology (Grasscosmofun'09), 14-19 September 2009, Szczecin, Polan

Chern-Simons approach to three-manifold invariants

% A new, formal, non-combinatorial approach to invariants of % three-dimensional manifolds of Reshetikhin, Turaev and % Witten in the framework of non-perturbative topological % quantum Chern-Simons theory, corresponding to an arbitrary % compact simple Lie group, is presented. A direct % implementation of surgery instructions in the context of % quantum field theory is proposed. An explicit form of the % specialization of the invariant to the group SU(2) is % derived, and shown to agree with the result of Lickorish. % % AMS subject classifications (1991): 57M25, 57N10, 57R65, 81T13.Comment: 10 page

One-loop contribution to the matter-driven expansion of the Universe

Standard perturbative quantum gravity formalism is applied to compute the lowest order corrections to the spatially flat cosmological FLRW solution governed by ordinary matter. The presented approach is analogous to the one used to compute quantum corrections to the Coulomb potential in electrodynamics, or to the approach applied in computation of quantum corrections to the Schwarzschild solution in gravity. In this framework, it is shown that the corrections to the classical metric coming from the one-loop graviton vacuum polarization (self-energy) have (UV cutoff dependent) repulsive properties, which could be not negligible in the very early Universe.Comment: 6 pages. arXiv admin note: substantial text overlap with arXiv:1011.625