Cosmological signatures of time-asymmetric gravity

  title={Cosmological signatures of time-asymmetric gravity},
  author={Marina Cort{\^e}s and Andrew R. Liddle and Lee Smolin},
  journal={Physical Review D},
We develop the model proposed by Cort\^es, Gomes & Smolin, to predict cosmological signatures of time-asymmetric extensions of general relativity they proposed recently. Within this class of models the equation of motion of chiral fermions is modified by a torsion term. This term leads to a dispersion law for neutrinos that associates a new time-varying energy with each particle. We find a new neutrino contribution to the Friedmann equation resulting from the torsion term in the Ashtekar… 

MOND as a regime of quantum gravity

We propose that there is a regime of quantum gravity phenomena, for the case that the cosmological constant is small and positive, which concerns phenomena at temperatures below the deSitter

Minimally modified theories of gravity: a playground for testing the uniqueness of general relativity

In a recent paper [1], it was introduced a new class of gravitational theories with two local degrees of freedom. The existence of these theories apparently challenges the distinctive role of general

A democratic Cosmos

Despite the success of our best models in Theoretical Physics, especially concerning Cosmology and Particle Physics, we still face persistent challenges. Among them we have the cosmological

The Dynamics of Difference

A proposal is made for a fundamental theory, in which the history of the universe is constituted of diverse views of itself. Views are attributes of events, and the theory’s only be-ables; they

Temporal Relationalism

  • L. Smolin
  • Physics, Philosophy
    Beyond Spacetime
  • 2020
Because of the non-locality of quantum entanglement, realist approaches to completing quantum mechanics have implications for our conception of space. Quantum gravity also is expected to predict

Reversing the irreversible: From limit cycles to emergent time symmetry

In 1979 Penrose hypothesized that the arrows of time are explained by the hypothesis that the fundamental laws are time irreversible. That is, our reversible laws, such as the standard model and

Realism and causality. I. Pilot wave and retrocausal models as possible facilitators

Of all basic principles of classical physics, realism should arguably be the last to be given up when seeking a better interpretation of quantum mechanics. We examine the de Broglie-Bohm pilot wave

Realism and causality. II. Retrocausality in energetic causal sets

We describe a new form of retrocausality, which is found in the behaviour of a class of causal set theories, called energetic causal sets (ECS). These are discrete sets of events, connected by causal

What Are We Missing in Our Search for Quantum Gravity

Some reflections are presented on the state of the search for a quantum theory of gravity. I discuss diverse regimes of possible quantum gravitational phenomenon, some well explored, some novel.

Four principles for quantum gravity

Four principles are proposed to underlie the quantum theory of gravity. We show that these suffice to recover the Einstein equations. We also suggest that MOND results from a modification of the



Time asymmetric extensions of general relativity

We describe a class of modified gravity theories that deform general relativity in a way that breaks time reversal invariance and, very mildly, locality. The algebra of constraints, local physical

Torsion cosmology and the accelerating universe

Investigations of the dynamic modes of the Poincare gauge theory of gravity found only two good propagating torsion modes; they are effectively a scalar and a pseudoscalar. Cosmology affords a

Einstein gravity as a 3D conformally invariant theory

We give an alternative description of the physical content of general relativity that does not require a Lorentz invariant spacetime. Instead, we find that gravity admits a dual description in terms

A shape dynamical approach to holographic renormalization

We provide a bottom-up argument to derive some known results from holographic renormalization using the classical bulk–bulk equivalence of General Relativity and Shape Dynamics, a theory with spatial

The gravity/CFT correspondence

General Relativity can be formulated in terms of a spatially Weyl invariant gauge theory called Shape Dynamics. Using this formulation, we establish a “bulk/bulk” duality between gravity and a Weyl

The universe as a process of unique events

This work introduces a new kind of deterministic dynamics for a causal set in which new events are generated from pairs of progenitor events by a rule which is based on extremizing the distinctions between causal past sets of events.

The link between general relativity and shape dynamics

We define the concept of a linking theory and show how two equivalent gauge theories possessing different gauge symmetries generically arise from a linking theory. We show that under special

A Gravitational Origin of the Arrows of Time

The only widely accepted explanation for the various arrows of time that everywhere and at all epochs point in the same direction is the ‘past hypothesis’: the Universe had a very special low-entropy