Forks in the road, on the way to quantum gravity

@article{Sorkin1997ForksIT,
  title={Forks in the road, on the way to quantum gravity},
  author={Rafael D. Sorkin},
  journal={International Journal of Theoretical Physics},
  year={1997},
  volume={36},
  pages={2759-2781}
}
  • R. Sorkin
  • Published 1 June 1997
  • Physics
  • International Journal of Theoretical Physics
In seeking to arrive at a theory of “quantum gravity,” one faces several choices among alternative approaches. I list some of these “forks in the road” and offer reasons for taking one alternative over the other. In particular, I advocate the following: the sum-over-histories framework for quantum dynamics over the “observable and state-vector” framework; relative probabilities over absolute ones; spacetime over space as the gravitational “substance” (4 over 3+1); a Lorentzian metric over a… 

A Spacetime Approach to Defining Vacuum States and Entropy

We apply a recent proposal for a distinguished ground state of a quantum field in a globally hyperbolic spacetime to the free massless scalar field in a causal diamond in two-dimensional Minkowski

Decoherence in Quantum Gravity: Issues and Critiques

An increasing number of papers have appeared in recent years on decoherence in quantum gravity at the Planck energy. We discuss the meaning of decoherence in quantum gravity starting from the common

The Construction Interpretation: Conceptual Roads to Quantum Gravity

In the first part of this paper I propose the Construction Interpretation of the Quantum. The main point of this interpretation is that (unlike previous interpretations) it is not actually an

Discrete Approaches Towards the Definition of a Quantum Theory of Gravity

We study the elongated phase of 4-D Dynamical Triangulations. In the case of the sphere topology by using the Walkup's theorem we show that the dominating configurations are stacked spheres. These

The Role of Time in Relational Quantum Theories

We propose a solution to the problem of time for systems with a single global Hamiltonian constraint. Our solution stems from the observation that, for these theories, conventional gauge theory

Quantum-Level Background Independence and the Problem of Time

Here we finally introduce Background Independence and the Problem of Time at the level of Quantum Gravity itself, outlining each of its Isham–Kuchař type facets enumerated below. 1) The

Discrete quantum gravity and causal sets

This paper provides a thorough introduction to the physical and conceptual need for a theory of quantum gravity; some knowledge of general relativity and nonrelativistic quantum mechanics is assumed.

Entanglement Entropy of Scalar Fields in Causal Set Theory

Entanglement entropy is now widely accepted as having deep connections with quantum gravity. It is therefore desirable to understand it in the context of causal sets, especially since they provide

Large Fluctuations in the Horizon Area and What They Can Tell Us about Entropy and Quantum Gravity

We evoke situations where large fluctuations in the entropy are induced, our main example being a spacetime containing a potential black hole whose formation depends on the outcome of a quantum
...

References

SHOWING 1-10 OF 91 REFERENCES

Impossible Measurements on Quantum Fields

It is shown that the attempt to extend the notion of ideal measurement to quantum field theory leads to a conflict with locality, because (for most observables) the state vector reduction associated

Spacetime Quantum Mechanics and the Quantum Mechanics of Spacetime

These are the author's lectures at the 1992 Les Houches Summer School, "Gravitation and Quantizations". They develop a generalized sum-over-histories quantum mechanics for quantum cosmology that does

Space-Time Approach to Non-Relativistic Quantum Mechanics

Non-relativistic quantum mechanics is formulated here in a different way. It is, however, mathematically equivalent to the familiar formulation. In quantum mechanics the probability of an event which

Failure of unitarity for interacting fields on spacetimes with closed timelike curves.

TLDR
It is shown that the unitarity relations are not satisfied for interacting fields, and this work considers the {lambda}{phi}{sup 4} theory in detail, but the results appear to hold for a wide class of fields.

Canonical Quantum Gravity

This is a review of the aspirations and disappointments of the canonical quantization of geometry. I compare the two chief ways of looking at canonical gravity, geometrodynamics and connection

QUANTUM THEORY OF GRAVITY. II. THE MANIFESTLY COVARIANT THEORY.

Contrary to the situation which holds for the canonical theory described in the first paper of this series, there exists at present no tractable pure operator language on which to base a manifestly

Proposal for solving the "problem of time" in canonical quantum gravity.

  • Wald
  • Physics, Philosophy
    Physical review. D, Particles and fields
  • 1993
TLDR
This work describes an approach to defining states and local observables in quantum gravity which exploits the analogy between the Hamiltonian formulation of general relativity and that of a relativistic particle.

An Introduction to General Topology and Quantum Topology

The aim of this course is to give a short introduction to the classical theory of general topology and to consider some ways in which one might attempt to formulate a genuine theory of ‘quantum

ASPECTS OF SPIN AND STATISTICS IN GENERALLY COVARIANT THEORIES

In this paper, we explore the consequences of diffeomorphism invariance in generally covariant theories. Such theories in two and three dimensions are known to admit topological excitations called

AN ANALYSIS OF THE REPRESENTATIONS OF THE MAPPING CLASS GROUP OF A MULTIGEON THREE-MANIFOLD

It is known that the distinct unitary irreducible representations (UIR's) of the mapping class group G of a three-manifold ℳ give rise to distinct quantum sectors ("θ sectors") in quantum theories of
...