4 research outputs found
Radiative Origin of Mass Scales and Cosmic Inflation in Scale-Invariant Models
In this work we analyze the radiative generation of mass scales in high-energy physics in classically scale-invariant models of particle physics and gravity. Radiative generation in this context is based on the Coleman-Weinberg mechanism which anomalously breaks scale-invariance. This approach is used to dynamically generate the Planck mass, Majorana masses for right-handed neutrinos and the Higgs mass from a common origin, and it also presents a convenient approach for reanalyzing the hierarchy problem. Within this framework, globally scale-invariant quadratic gravity allows to also describe cosmic inflation with a radiatively generated inflaton potential and the computed predictions for inflationary observables are within the strongest experimental constraints. The ensuing discussion with respect to the dynamical generation of the Planck mass and inflation is deepened by the inclusion of radiative effects due to gravitational degrees of freedom into the picture. In particular, we find that the quantum corrections of the massive spin-2 ghost, which is necessarily present in quadratic gravity, plays a decisive role in generating the Planck mass while simultaneously providing inflationary predictions which are consistent with the strongest experimental constraint
Probing alternative cosmologies through the inverse distance ladder
We study the implications of a combined analysis of cosmic standard candles
and standard rulers on the viability of cosmological models beyond the
cosmological concordance model. To this end, we employ data in the form of the
joint light-curve analysis supernova compilation, baryon acoustic oscillations,
cosmic microwave background data, and a recently proposed set of Quasars as
objects of known brightness. The advantage of including the latter is that they
extend the local distance measures to redshifts which have previously been out
of reach and we investigate how this allows one to test cosmologies beyond
CDM. We focus on two particular modifications: One is the theory of a
massive tensor field interacting with the standard metric of gravity, so-called
bigravity, and the other conformal gravity, a theory of gravity that has no
knowledge of fundamental length scales. The former of the two constitutes a
veritable extension of General Relativity, given that it adds to the metric
tensor of gravity a second dynamical tensor field. The resulting dynamics have
been proposed as a self-accelerating cosmology. Conformal gravity on the other
hand is a much more drastic change of the underlying gravitational theory. Its
ignorance towards fundamental length scales offers a completely different
approach to late time acceleration and the so-called cosmological constant
problem. In this sense, both models offer - in one way or another - an
explanation for the cosmological constant problem. We perform a combined
cosmological fit which provides strong constraints on some of these extensions,
while some alternative cosmologies are in fact favoured by the data. We also
briefly comment on the implications of the long-standing -tension.Comment: 36 pages, 15 figure
Unified Emergence of Energy Scales and Cosmic Inflation
In the quest for unification of the Standard Model with gravity, classical
scale invariance can be utilized to dynamically generate the Planck mass
. Then, the relation of Planck scale physics to the scale of
electroweak symmetry breaking requires further explanation. In this
paper, we propose a model that uses the spontaneous breaking of scale
invariance in the scalar sector as a unified origin for dynamical generation of
both scales. Using the Gildener-Weinberg approximation, only one scalar
acquires a vacuum expectation value of ,
thus radiatively generating and
via the neutrino option with right handed neutrino masses . Consequently, active SM neutrinos are given a
mass with the inclusion of a type-I seesaw mechanism. Furthermore, we adopt an
unbroken symmetry and a -odd set of right-handed Majorana neutrinos
that do not take part in the neutrino option and are able to produce the
correct dark matter relic abundance (dominantly) via inflaton decay. The model
also describes cosmic inflation and the inflationary CMB observables are
predicted to interpolate between those of and linear chaotic inflationary
model and are thus well within the strongest experimental constraints.Comment: 21+10 pages, 11 figures, 1 table, v2: matches published versio