Corpus ID: 235390555

# Causality and gravity

@inproceedings{Donoghue2021CausalityAG,
title={Causality and gravity},
author={J. Donoghue and G. Menezes},
year={2021}
}
• Published 2021
• Physics
In our classical world, causality is taken to mean that there is no effect before its cause. Technically, we therefore use retarded propagators, which vanish for propagation backwards-in-time, to describe classical physics. Quantum physics is a bit different. Using Feynman boundary conditions, propagators do have a backwards-in-time propagation for so-called negative energy modes. Indeed this is required [1] in order to obtain a more general definition of causality that field operators commute… Expand
1 Citations

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#### References

SHOWING 1-10 OF 51 REFERENCES
Arrow of Causality and Quantum Gravity.
• Physics, Medicine
• Physical review letters
• 2019
In some quantum gravity theories, such as quadratic gravity and possibly asymptotic safety, such a mixed causality condition occurs and this paper discusses some of the implications. Expand
Causality, analyticity and an IR obstruction to UV completion
• Physics
• 2006
We argue that certain apparently consistent low-energy effective field theories described by local, Lorentzinvariant Lagrangians, secretly exhibit macroscopic non-locality and cannot be embedded inExpand
Light-like scattering in quantum gravity
• Physics
• 2016
A bstractWe consider scattering in quantum gravity and derive long-range classical and quantum contributions to the scattering of light-like bosons and fermions (spin-0, spin-12$$\frac{1}{2}$$,Expand
Use of Causality Conditions in Quantum Theory
The limitations on scattering amplitudes imposed by causality requirements are deduced from the demand that the commutator of field operators vanish if the operators are taken at points withExpand
Adding terms quadratic in the curvature to the Einstein-Hilbert action renders gravity renormalizable. This property is preserved in the presence of the most general renormalizable couplings withExpand
Causality constraints on corrections to the graviton three-point coupling
• Physics
• 2014
A bstractWe consider higher derivative corrections to the graviton three-point coupling within a weakly coupled theory of gravity. Lorentz invariance allows further structures beyond the one presentExpand
Gauge Assisted Quadratic Gravity: A Framework for UV Complete Quantum Gravity
• Physics
• 2018
We discuss a variation of quadratic gravity in which the gravitational interaction remains weakly coupled at all energies, but is assisted by a Yang-Mills gauge theory which becomes strong at theExpand
Negative Metric and the Unitarity of the S Matrix
• Physics
• 1969
Abstract It is shown that the introduction of a negative metric in quantum mechanics can lead to a unitary S-matrix, provided that all stable particle states are of positive square length. Such aExpand
Quantum gravity from causal dynamical triangulations: a review
This topical review gives a comprehensive overview and assessment of recent results in Causal Dynamical Triangulations (CDT), a modern formulation of lattice gravity, whose aim is to obtain a theoryExpand
Unitarity, stability, and loops of unstable ghosts
• Physics
• Physical Review D
• 2019
We present a new understanding of the unstable ghost-like resonance which appears in theories such as quadratic gravity and Lee-Wick type theories. Quantum corrections make this resonance unstable,Expand