The anomaly-induced effective action and natural inflation

The anomaly-induced inflation (modified Starobinsky model) is based on the application of the effective quantum field theory approach to the Early Universe. We present a brief general review of the model and show that it does not require a fine-tuning for the parameters of the theory or initial data, gives a real chance to meet a graceful exit to the FRW phase and also has positive features with respect to the metric perturbations.Comment: Invited talk at the International Workshop on Astroparticle and High Energy Physics, October 14 - 18, 2003, Valencia, Spai

The Running of the Cosmological and the Newton Constant controlled by the Cosmological Event Horizon

We study the renormalisation group running of the cosmological and the Newton constant, where the renormalisation scale is given by the inverse of the radius of the cosmological event horizon. In this framework, we discuss the future evolution of the universe, where we find stable de Sitter solutions, but also "big crunch"-like and "big rip"-like events, depending on the choice of the parameters in the model.Comment: 14 pages, 7 figures, minor improvements, references adde

On the Running of the Cosmological Constant in Quantum General Relativity

We present arguments that show what the running of the cosmological constant means when quantum general relativity is formulated following the prescription developed by Feynman.Comment: 5 page

Inhomogeneous vacuum energy

Vacuum energy remains the simplest model of dark energy which could drive the accelerated expansion of the Universe without necessarily introducing any new degrees of freedom. Inhomogeneous vacuum energy is necessarily interacting in general relativity. Although the four-velocity of vacuum energy is undefined, an interacting vacuum has an energy transfer and the vacuum energy defines a particular foliation of spacetime with spatially homogeneous vacuum energy in cosmological solutions. It is possible to give a consistent description of vacuum dynamics and in particular the relativistic equations of motion for inhomogeneous perturbations given a covariant prescription for the vacuum energy, or equivalently the energy transfer four-vector, and we construct gauge-invariant vacuum perturbations. We show that any dark energy cosmology can be decomposed into an interacting vacuum+matter cosmology whose inhomogeneous perturbations obey simple first-order equations.Comment: 8 pages; v2 clarified discussion of Chaplygin gas model, references adde

Vacuum properties of nonsymmetric gravity in de Sitter space

We consider quantum effects of a massive antisymmetric tensor field on the dynamics of de Sitter space-time. Our starting point is the most general, stable, linearized Lagrangian arising in nonsymmetric gravitational theories (NGTs), where part of the antisymmetric field mass is generated by the cosmological term. We construct a renormalization group (RG) improved effective action by integrating out one loop vacuum fluctuations of the antisymmetric tensor field and show that, in the limit when the RG scale goes to zero, the Hubble parameter -- and thus the effective cosmological constant -- relaxes rapidly to zero. We thus conclude that quantum loop effects in de Sitter space can dramatically change the infrared sector of the on-shell gravity, making the expansion rate insensitive to the original (bare) cosmological constant.Comment: 32 pages, 2 eps figure

Kaluza-Klein Higher Derivative Induced Gravity

The existence and stability analysis of an inflationary solution in a $D+4$-dimensional anisotropic induced gravity is presented in this paper. Nontrivial conditions in the field equations are shown to be compatible with a cosmological model in which the 4-dimension external space evolves inflationary, while, the D-dimension internal one is static. In particular, only two additional constraints on the coupling constants are derived from the abundant field equations and perturbation equations. In addition, a compact formula for the non-redundant 4+D dimensional Friedmann equation is also derived for convenience. Possible implications are also discussed in this paper.Comment: 13 pages, typos/errors corrected, three additional appendices adde

Nonsaturated Holographic Dark Energy

It has been well established by today that the concept of holographic dark energy (HDE) does entail a serious candidate for the dark energy of the universe. Here we deal with models where the holographic bound for dark energy is not saturated for a large portion of the history of the universe. This is particularly compelling when the IR cutoff is set by the Hubble scale, since otherwise a transition from a decelerated to an accelerated era cannot be obtained for a spatially flat universe. We demonstrate by three generic but disparate dynamical models, two of them containing a variable Newton constant, that transition between the two eras is always obtained for the IR cutoff in the form of the Hubble scale and the nonsaturated HDE. We also give arguments of why such a choice for the dark energy is more consistent and favored over the widely accepted saturated form.Comment: 9 pages, minor revision, to appear in JCA

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV

Gravitational Theory, Galaxy Rotation Curves and Cosmology without Dark Matter

Einstein gravity coupled to a massive skew symmetric field F_{\mu\nu\lambda} leads to an acceleration law that modifies the Newtonian law of attraction between particles. We use a framework of non-perturbative renormalization group equations as well as observational input to characterize special renormalization group trajectories to allow for the running of the effective gravitational coupling G and the coupling of the skew field to matter. The latter lead to an increase of Newton's constant at large galactic and cosmological distances. For weak fields a fit to the flat rotation curves of galaxies is obtained in terms of the mass (mass-to-light ratio M/L) of galaxies. The fits assume that the galaxies are not dominated by exotic dark matter and that the effective gravitational constant G runs with distance scale. The equations of motion for test particles yield predictions for the solar system and the binary pulsar PSR 1913+16 that agree with the observations. The gravitational lensing of clusters of galaxies can be explained without exotic dark matter. An FLRW cosmological model with an effective G=G(t) running with time can lead to consistent fits to cosmological data without assuming the existence of exotic cold dark matter.Comment: 33 pages, 20 figures, 1 table. Latex file. Additional text and references. Corrections. To be published in Journal of Cosmology and Astroparticle Physics (JCAP