# Zero-parameter extension of general relativity with a varying cosmological constant

@article{Alexander2019ZeroparameterEO, title={Zero-parameter extension of general relativity with a varying cosmological constant}, author={Stephon H. S. Alexander and Marina Cort{\^e}s and Andrew R. Liddle and Jo{\~a}o Magueijo and Robert Sims and Lee Smolin}, journal={Physical Review D}, year={2019} }

We provide a new extension of general relativity (GR) which has the remarkable property of being more constrained than GR plus a cosmological constant, having one less free parameter. This is implemented by allowing the cosmological constant to have a consistent space-time variation, through coding its dynamics in the torsion tensor. We demonstrate this mechanism by adding a `quasi-topological' term to the Einstein action, which naturally realizes a dynamical torsion with an automatic…

## 17 Citations

### Canonical structure of minimal varying Λ theories

- Mathematics
- 2021

Minimal varying Λ theories are defined by an action built from the Einstein–Cartan–Holst first order action for gravity with the cosmological constant Λ as an independent scalar field, and…

### Varying Λ Theory Revisited

- Physics
- 2021

— We revisit the variable Λ theory recently developed by Alexander et al. [1, 2]. We implement it to explain the current expansion of the Universe. The varying Λ theory reduces one degree of freedom.…

### The cosmological constant from conformal transformations: Möbius invariance and Schwarzian action

- Mathematics, PhysicsClassical and Quantum Gravity
- 2020

The homogeneous Friedman–Lemaî tre-Robertson–Walker (FLRW) cosmology of a free scalar field with vanishing cosmological constant was recently shown to be invariant under the one-dimensional conformal…

### Losing the trace to find dynamical Newton or Planck constants

- Physics, Mathematics
- 2020

We show that promoting the trace part of the Einstein equations to a trivial identity results in the Newton constant being an integration constant. Thus, in this formulation the Newton constant is a…

### Quantum cosmology of a dynamical Lambda

- Mathematics
- 2020

By allowing torsion into the gravitational dynamics one can promote the cosmological constant, $\Lambda$, to a dynamical variable in a class of quasi-topological theories. In this paper we perform a…

### Generating the cosmological constant from a conformal transformation

- Mathematics, Physics
- 2020

The homogeneous Friedman-Lema\^itre-Robertson-Walker (FLRW) cosmology of a free scalar field with vanishing cosmological constant was recently shown to be invariant under the one-dimensional…

### Gravity waves in parity-violating Copernican universes

- PhysicsPhysical Review D
- 2020

In recent work minimal theories allowing the variation of the cosmological constant, $\mathrm{\ensuremath{\Lambda}}$, by means of a balancing torsion, have been proposed. It was found that such…

### Linking the Baum-Hawking-Coleman mechanism with unimodular gravity and Vilenkin's probability flux

- Physics
- 2021

We revisit a mechanism proposed by Hawking to resolve the cosmological constant problem (and the controversy it generated) to identify possibly more palatable alternatives and explore new connections…

### Torsion and the probability of inflation

- PhysicsJournal of Cosmology and Astroparticle Physics
- 2022

We revisit the problem of the “probability of inflation” from the point of view of the Einstein-Cartan theory, where torsion can be present off-shell even in the absence of spinorial currents. An…

### Limitations on Standard Sirens tests of gravity from screening

- PhysicsJournal of Cosmology and Astroparticle Physics
- 2019

Modified gravity theories with an effective Newton constant that varies over cosmological timescales generally predict a different gravitational wave luminosity distance than General Relativity.…

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