Quantum Gravity

  title={Quantum Gravity},
  author={Enrique {\'A}lvarez},
General lectures on quantum gravity. 1 General Questions on Quantum Gravity It is not clear at all what is the problem in quantum gravity (cf. [3] or [8] for general reviews, written in the same spirit as the present one). The answers to the following questions are not known, and I believe it can do no harm to think about them before embarking in a more technical discussion. To begin, it has been proposed that gravity should not be quantized, owing to its special properties as determining the… 

Notes on “Quantum Gravity” and Noncommutative Geometry

I hesitated for a long time before giving shape to these notes, originally intended for preliminary reading by the attendees to the Summer School “New paths towards quantum gravity” (Holbaek Bay,

Background independent quantum gravity: A Status report

The goal of this review is to present an introduction to loop quantum gravity—a background-independent, non-perturbative approach to the problem of unification of general relativity and quantum

Quantum Gravity: A Primer for Philosophers

‘Quantum Gravity’ does not denote any existing theory: the field of quantum gravity is very much a ‘work in progress’. As you will see in this chapter, there are multiple lines of attack each with

Se p 20 05 Fundamental Structure of Loop Quantum Gravity

In recent twenty years, loop quantum gravity, a background independent approach to unify general relativity and quantum mechanics, has been widely investigated. The aim of loop quantum gravity is to

Canonical Gravity and Applications: Cosmology, Black Holes, and Quantum Gravity

Research on quantum gravity from a non-perturbative 'quantization of geometry' perspective has been the focus of much research in the past two decades, due to the Ashtekar–Barbero Hamiltonian

Quantum gravity as a metaphysical problem

The problem with quantum gravity is usually presented as if it would be difficult to construct even a single quantum theory of relativistic gravity. This is shown to be wrong. A straightforward

Quantum Gravity in 30 Questions

Quantum gravity is the missing piece in our understanding of the fundamental interactions today. Given recent observational breakthroughs in gravity, providing a quantum theory for what lies beyond

Aspects of quantum gravity

For more than 80 years theoretical physicists have been trying to develop a theory of quantum gravity which would successfully combine the tenets of Einstein's theory of general relativity (GR)

Making a Quantum Universe: Symmetry and Gravity

So far, none of attempts to quantize gravity has led to a satisfactory model that not only describe gravity in the realm of a quantum world, but also its relation to elementary particles and other

Approaching the Planck Scale from a Generally Relativistic Point of View: A Philosophical Appraisal of Loop Quantum Gravity

My dissertation studies the foundations of loop quantum gravity (LQG), a candidate for a quantum theory of gravity based on classical general relativity. At the outset, I discuss two---and I claim



How far are we from the quantum theory of gravity

An assessment is offered of the progress that the major approaches to quantum gravity have made towards the goal of constructing a complete and satisfactory theory. The emphasis is on loop quantum

Topics in String Theory and Quantum Gravity

These are the lecture notes for the Les Houches Summer School on Quantum Gravity held in July 1992. The notes present some general critical assessment of other (non-string) approaches to quantum

Introduction to Modern Canonical Quantum General Relativity

This is an introduction to the by now fifteen years old research field of canonical quantum general relativity, sometimes called "loop quantum gravity". The term "modern" in the title refers to the


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

Quantum gravity with a positive cosmological constant

A quantum theory of gravity is described in the case of a positive cosmological constant in 3 + 1 dimensions. Both old and new results are described, which support the case that loop quantum gravity

Perturbative Quantum Gravity and its Relation to Gauge Theory

  • Z. Bern
  • Physics
    Living reviews in relativity
  • 2002
A non-trivial relationship between perturbative gauge theory and gravity scattering amplitudes is described and the unitarity method provides a means for perturbatively quantizing massless gravity theories without the usual formal apparatus associated with the quantization of constrained systems.

BF Description of Higher-Dimensional Gravity Theories

It is well known that, in the first-order formalism, pure three-dimensional gravity is just the BF theory. Similarly, four-dimensional general relativity can be formulated as BF theory with an

Gauge field theory coherent states (GCS): I. General properties

In this paper we outline a rather general construction of diffeomorphism covariant coherent states for quantum gauge theories. By this we mean states ψ(A,E), labelled by a point (A,E) in the


The general problems of three-dimensional quantum gravity are recapitulated here, with emphasis on the mathematical problems of defining the measure of the path integral over all three-dimensional

The world as a hologram

According to ’t Hooft the combination of quantum mechanics and gravity requires the three‐dimensional world to be an image of data that can be stored on a two‐dimensional projection much like a