Publications de Georgios Karananas

Scale invariant Einstein-Cartan gravity and flat space conformal symmetry

Mikhail Chapochnikov, Georgios Karananas, Sebastian Zell

We find the conditions under which scale-invariant Einstein-Cartan gravity with scalar matter fields leads to an approximate conformal invariance of the flat space particle theory up to energies of the order of the Planck mass. In the minimal setup, these ...

Springer Nature2023

Matter matters in Einstein-Cartan gravity

Mikhail Chapochnikov, Georgios Karananas, Andrey Shkerin, Sebastian Zell

We study scalar, fermionic and gauge fields coupled nonminimally to gravity in the Einstein-Cartan formulation. We construct a wide class of models with nondynamical torsion whose gravitational spectra comprise only themassless graviton. Eliminating nonpro ...

American Physical Society2021

Spontaneous conformal symmetry breaking in fishnet CFT

Mikhail Chapochnikov, Georgios Karananas

Quantum field theories with exact but spontaneously broken conformal invariance have an intriguing feature: their vacuum energy (cosmological constant) is equal to zero. Up to now, the only known ultraviolet complete theories where conformal symmetry can b ...

2020

CFT data and spontaneously broken conformal invariance

Georgios Karananas

American Physical Society2018

Gauge coupling unification without leptoquarks

Mikhail Chapochnikov, Georgios Karananas

We propose an interpretation of the gauge coupling unification scale which is not related to any new particle threshold. We revisit Grand Unified Theories and show that it is possible to completely eliminate the scalar as well as vector leptoquarks from th ...

2017

Scale-invariant alternatives to general relativity. II. Dilaton properties

Mikhail Chapochnikov, Georgios Karananas

In the present paper, we revisit gravitational theories which are invariant under TDiffs-transverse (volume-preserving) diffeomorphisms and global scale transformations. It is known that these theories can be rewritten in an equivalent diffeomorphism-invar ...

American Physical Society2016

On the geometrical interpretation of scale-invariant models of inflation

Javier Rubio, Georgios Karananas

We study the geometrical properties of scale-invariant two-field models of inflation. In particular, we show that when the field-derivative space in the Einstein frame is maximally symmetric during inflation, the inflationary predictions can be universal a ...

Elsevier2016

Gauging nonrelativistic field theories using the coset construction

Alexander Monin, Georgios Karananas

We discuss how nonrelativistic spacetime symmetries can be gauged in the context of the coset construction. We consider theories invariant under the centrally extended Galilei algebra as well as the Lifshitz one, and we investigate under what conditions th ...

American Physical Society2016

Weyl vs. conformal

Alexander Monin, Georgios Karananas

In this note we show that given a conformally invariant theory in flat space-time, it is not always possible to couple it to gravity in a Weyl invariant way. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY li ...

Elsevier2016

Poincaré, Scale and Conformal Symmetries : Gauge Perspective and Cosmological Ramifications

Georgios Karananas

Symmetries are omnipresent and play a fundamental role in the description of Nature. Thanks to them, we have at our disposal nontrivial selection rules that dictate how a theory should be constructed. This thesis, which is naturally divided into two parts, ...

EPFL2016

Weyl and Ricci gauging from the coset construction

Alexander Monin, Georgios Karananas

In this paper we demonstrate how, using the coset construction, a theory can be systematically made Weyl invariant by gauging the scale symmetry. We show that an analog of the inverse Higgs constraint allows the elimination of the Weyl vector (gauge) field ...

American Physical Society2016

The particle spectrum of parity-violating Poincare gravitational theory (vol 32, 055012, 2015)

Georgios Karananas

Institute of Physics2015

The particle spectrum of parity-violating Poincare gravitational theory

Georgios Karananas

In this paper we investigate the physical spectrum of the gravitational theory based on the Poincare group with terms that are at most quadratic in tetrad and spin connection, allowing for the presence of parity-even as well as parity-odd invariants. We de ...

Iop Publishing Ltd2015

Higgs-dilaton cosmology: An effective field theory approach

Mikhail Chapochnikov, Javier Rubio, Georgios Karananas

The Higgs-dilaton cosmological model is able to describe simultaneously an inflationary expansion in the early Universe and a dark energy dominated stage responsible for the present day acceleration. It also leads to a nontrivial relation between the spect ...

American Physical Society2013