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One of the biggest challenges to theoretical physics of our time is to find a background-independent quantum theory of gravity. Today one encounters a profusion of different attempts at quantization, but no fully accepted - or acceptable,…

General Relativity and Quantum Cosmology · Physics 2008-01-29 M. D. Iftime

We shall present here the causal interpretation of canonical quantum gravity in terms of new variables. Then we shall apply it to the minisuperspace of cosmology. A vacuum solution of quantum cosmology is obtained and the Bohmian trajectory…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Ali Shojai , Fatimah Shojai

The problem of time emerging in the canonical quantization procedure of gravity signals a necessity to properly define a relational time parameter. Previous approaches, which are here briefly discussed, make use of the dependence of the…

General Relativity and Quantum Cosmology · Physics 2023-02-01 Giulia Maniccia , Giovanni Montani

A "quantum-first" approach to gravity is described, where rather than quantizing general relativity, one seeks to formulate the physics of gravity within a quantum-mechanical framework with suitably general postulates. Important guides are…

High Energy Physics - Theory · Physics 2018-05-23 Steven B. Giddings

We present a brief description of the ``consistent discretization'' approach to classical and quantum general relativity. We exhibit a classical simple example to illustrate the approach and summarize current classical and quantum…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Rodolfo Gambini , Jorge Pullin

The recently introduced manifestly covariant canonical quantization scheme is applied to gravity. New diffeomorphism anomalies generating a multi-dimensional generalization of the Virasoro algebra arise. This does not contradict theorems…

High Energy Physics - Theory · Physics 2007-05-23 T. A. Larsson

We present a new approach to quantum gravity starting from Feynman's formulation for the simplest example, that of a scalar field as the representative matter. We show that we extend his treatment to a calculable framework using resummation…

High Energy Physics - Phenomenology · Physics 2009-11-07 B. F. L. Ward

A new formulation of quantum mechanics based on differential commutator brackets is developed. We have found a wave equation representing the fermionic particle. In this formalism, the continuity equation mixes the Klein-Gordon and…

General Physics · Physics 2012-03-21 Arbab I. Arbab , Faisal A. Yassein

The relativistic conception of space and time is challenged by the quantum nature of physical observables. It has been known for a long time that Poincar\'e symmetry of field theory can be extended to the larger conformal symmetry. We use…

Quantum Physics · Physics 2013-02-27 Marc-Thierry Jaekel , Serge Reynaud

In this paper canonical quantum gravity on noncommutative space-time is considered. The corresponding generalized classical theory is formulated by using the moyal star product, which enables the representation of the field quantities…

General Relativity and Quantum Cosmology · Physics 2016-09-02 Martin Kober

On the basis of a manifestly covariant formalism of non-relativistic quantum mechanics in general coordinate systems, proposed by us recently, we derive general expressions for inertial forces. The results enable us further to discuss, and…

Quantum Physics · Physics 2007-05-23 Minoru Omote , Susumu Kamefuchi

I give a pedagogical explanation of what it is about quantization that makes general relativity go from being a nearly perfect classical theory to a very problematic quantum one. I also explain why some quantization of gravity is…

General Relativity and Quantum Cosmology · Physics 2015-05-13 R. P. Woodard

A quantum hamiltonian which evolves the gravitational field according to time as measured by constant surfaces of a scalar field is defined through a regularization procedure based on the loop representation, and is shown to be finite and…

General Relativity and Quantum Cosmology · Physics 2011-09-30 Carlo Rovelli , Lee Smolin

It is common practice to describe elementary particles by irreducible unitary representations of the Poincar\'e group. In the same way, multi-particle systems can be described by irreducible unitary representations of the Poincar\'e group.…

General Physics · Physics 2023-07-18 Walter Smilga

An inconsistency of quantum field theory, regarding the signs of vacuum energy and vacuum pressure of elementary fields versus non-elementary fields (like e.g. phonon fields), is pointed out. An improved law for the canonical quantization…

General Physics · Physics 2016-12-08 Gerold Gründler

General relativity is a background-independent theory of a dynamical classical spacetime geometry. Quantum theory is formulated in a classical spacetime, as an intrinsically probabilistic, contextual theory of non-classical, interfering…

General Relativity and Quantum Cosmology · Physics 2026-04-22 Tristan Hübsch , Djordje Minic

The status of multifractional theories is reviewed using comparative tables. Theoretical foundations, classical matter and gravity dynamics, cosmology and experimental constraints are summarized and the application of the multifractional…

High Energy Physics - Theory · Physics 2021-08-16 Gianluca Calcagni

Canonical vacuum gravity is expressed in generally-covariant form in order that spacetime diffeomorphisms be represented within its equal-time phase space. In accordance with the principle of general covariance, the time mapping ${\T}:…

General Relativity and Quantum Cosmology · Physics 2009-02-20 Ioannis Kouletsis

Geometric quantization is an attempt at using the differential-geometric ingredients of classical phase spaces regarded as symplectic manifolds in order to define a corresponding quantum theory. Generally, the process of geometric…

Mathematical Physics · Physics 2018-01-09 Andrea Carosso

`How do our ideas about quantum mechanics affect our understanding of spacetime?' This familiar question leads to quantum gravity. The complementary question is also important: `How do our ideas about spacetime affect our understanding of…

General Relativity and Quantum Cosmology · Physics 2009-11-11 James B. Hartle