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Formulating a quantum theory of gravity lies at the heart of fundamental theoretical physics. This collection of lecture notes encompasses a selection of topics that were covered in six mini-courses at the Nordita PhD school "Towards…

High Energy Physics - Theory · Physics 2025-10-10 Ivano Basile , Luca Buoninfante , Francesco Di Filippo , Benjamin Knorr , Alessia Platania , Anna Tokareva

Algebraic quantum field theory provides a general, mathematically precise description of the structure of quantum field theories, and then draws out consequences of this structure by means of various mathematical tools -- the theory of…

Mathematical Physics · Physics 2007-05-23 Hans Halvorson , Michael Mueger

We review the investigations on the quantum structure of spactime, to be found at the Planck scale if one takes into account the operational limitations to localization of events which result from the concurrence of Quantum Mechanics and…

High Energy Physics - Theory · Physics 2015-10-15 Dorothea Bahns , Sergio Doplicher , Gerardo Morsella , Gherardo Piacitelli

We argue that quantum gravity should be a super-quantum theory, that is, a theory whose non-local correlations are stronger than those of canonical quantum theory. As a super-quantum theory, quantum gravity should display distinct…

General Relativity and Quantum Cosmology · Physics 2013-12-09 Lay Nam Chang , Zachary Lewis , Djordje Minic , Tatsu Takeuchi

We present a new model of quantum gravity as a theory of random geometries given explicitly in terms of a multitrace matrix model. This is a generalization of the usual discretized random surfaces of 2D quantum gravity which works away from…

High Energy Physics - Theory · Physics 2017-11-22 Badis Ydri , Cherine Soudani , Ahlam Rouag

In an attempt to re-establish space-time as an essential frame for formulating quantum gravity - rather than an "emergent" one -, we find that exact invariance under scale transformations is an essential new ingredient for such a theory.…

General Relativity and Quantum Cosmology · Physics 2009-09-21 Gerard 't Hooft

Getting signatures of quantum gravity is one of the topical lines of research in modern theoretical physics and cosmology. This short review faces this challenge under a novel perspective. Instead of separating quantum-gravity effects of a…

General Relativity and Quantum Cosmology · Physics 2017-10-24 Gianluca Calcagni

This monograph provides a largely self--contained and broadly accessible exposition of two cosmological applications of algebraic quantum field theory (QFT) in curved spacetime: a fundamental analysis of the cosmological evolution according…

General Relativity and Quantum Cosmology · Physics 2015-06-08 Thomas-Paul Hack

Quantum Field Theory (QFT) represents a vast generalization of Quantum Mechanics (QM), as it deals with systems that have an infinite number of degrees of freedom. The Stone-von Neumann theorem, which establishes the equivalence of…

Mathematical Physics · Physics 2023-07-13 Ahmed Halawani

Quantum gravity is quite elusive at the experimental level; thus a lot of interest has been raised by recent searches for quantum gravity effects in the propagation of light from distant sources, like gamma ray bursters and active galactic…

General Physics · Physics 2010-12-03 Stefano Ansoldi , Edoardo Milotti

It is shown that adopting the \emph{Quantum Field} ---extended entity in space-time build by dynamic appearance propagation and annihilation of virtual particles--- as the primary ontology the astonishing features of quantum mechanics can…

Quantum Physics · Physics 2015-03-03 Alberto C. de la Torre

We study a class of perturbative scalar quantum field theories where dynamics is characterized by Lorentz-invariant or Lorentz-breaking non-local operators of fractional order and the underlying spacetime has a varying spectral dimension.…

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

The search for a quantum theory of gravity has been one of the main aims of theoretical physics for many years by now. However the efforts in this direction have been often hampered by the lack of experimental/observational tests able to…

General Relativity and Quantum Cosmology · Physics 2008-11-26 S. Liberati

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

At the beginning of the previous century, Newtonian mechanics fell victim to two new revolutionary theories, Quantum Mechanics (QM) and General Relativity (GR). Both theories have transformed our view of physical phenomena, with QM…

Quantum Physics · Physics 2018-03-22 Richard Howl , Lucia Hackermuller , David Edward Bruschi , Ivette Fuentes

I briefly review the current status of quantum gravity. After giving some general motivations for the need of such a theory, I discuss the main approaches in quantizing general relativity: Covariant approaches (perturbation theory,…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Claus Kiefer

Non-Abelian Gauss law is interpreted in terms of area bits described in a local frame which fit together into closed surfaces and the Non-Abelian Stokes law in terms of length bits described in a local frame which fit together into closed…

General Relativity and Quantum Cosmology · Physics 2007-05-23 H. S. Sharatchandra , H. Gopalkrishna Gadiyar

Quantum field theory (QFT) on non-stationary spacetimes is well understood from the side of the algebra of observables. The state space, however, is largely unexplored, due to the non-existence of distinguished states (vacuum, scattering…

General Relativity and Quantum Cosmology · Physics 2018-09-25 Klaus Fredenhagen , Thomas-Paul Hack , Nicola Pinamonti

Quantum gravity, as a fundamental theory of space-time, is expected to reveal how the universe may have started, perhaps during or before an inflationary epoch. It may then leave a potentially observable (but probably minuscule) trace in…

General Relativity and Quantum Cosmology · Physics 2015-12-17 Martin Bojowald

We propose a new phenomenological model for quantum gravity. This is based on a new interpretation in which quantum gravity is not an interaction, rather it is just responsible for generation of space-time-matter. Then we show this model is…

High Energy Physics - Phenomenology · Physics 2008-09-16 F. Darabi