Results 21 to 30 of about 20,270 (72)

Covariant action for bouncing cosmologies in modified Gauss-Bonnet gravity

, 2019
Cyclic universes with bouncing solutions are candidates for solving the big bang initial singularity problem. Here we seek bouncing solutions in a modified Gauss-Bonnet gravity theory, of the type $R+f(G)$, where $R$ is the Ricci scalar, $G$ is the Gauss-
Lemos, José P. S., Terrucha, Inês, Vernieri, Daniele   +2 more
core   +1 more source

Loop quantum gravity corrections to gravitational wave dispersion [PDF]

, 1997
Cosmological tensor perturbations equations are derived for Hamiltonian cosmology based on Ashtekar's formulation of general relativity, including typical quantum gravity effects in the Hamiltonian constraint as they are expected from loop quantum ...
Bojowald, Martin, Hossain, Golam Mortuza
core   +3 more sources

Switching internal times and a new perspective on the 'wave function of the universe'

, 2019
Despite its importance in general relativity, a quantum notion of general covariance has not yet been established in quantum gravity and cosmology, where, given the a priori absence of coordinates, it is necessary to replace classical frames with ...
Hoehn, Philipp A
core   +1 more source

The Semiclassical Limit of Loop Quantum Cosmology [PDF]

, 2001
The continuum and semiclassical limits of isotropic, spatially flat loop quantum cosmology are discussed, with an emphasis on the role played by the Barbero-Immirzi parameter \gamma in controlling space-time discreteness.
Ashtekar A, Ashtekar A, Ashtekar A, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bombelli L, Bombelli L, Corichi A, Karasev M V, Martin Bojowald, Rovelli C, Sahlmann H, Thiemann T, Thiemann T, Varadarajan M   +20 more
core   +3 more sources

Loop Quantum Cosmology: Recent Progress

, 2004
Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like cosmological ones. This leads to several applications where loop effects play a significant role when one is sensitive to the ...
A Ashtekar, A Ashtekar, A Ashtekar, A Ashtekar, A Ashtekar, A Ashtekar, A Okolow, C Rovelli, C Rovelli, C Rovelli, C Rovelli, G M Hossain, G W Gibbons, J F Barbero, J Z Simon, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, M Bojowald, Martin Bojowald, P Singh, T Thiemann, T Thiemann, V A Belinskii, V Husain   +35 more
core   +1 more source

Brane-world gravity [PDF]

, 2003
The observable universe could be a 1+3-surface (the "brane") embedded in a 1+3+d-dimensional spacetime (the "bulk"), with standard-model particles and fields trapped on the brane while gravity is free to access the bulk.
Maartens, Roy
core   +3 more sources

A no-singularity scenario in loop quantum gravity

, 2012
Canonical methods allow the derivation of effective gravitational actions from the behavior of space-time deformations reflecting general covariance.
Ashtekar A, Ashtekar A, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Cailleteau T Mielczarek J Barrau A Grain J, Date G, George M Paily, Henderson A Laddha A Tomlin C, Kreienbuehl A, Martin Bojowald, Perez A, Rendall A D, Reyes J D, Rovelli C, Rovelli C, Thiemann T, Thiemann T   +23 more
core   +1 more source

Hubble operator in isotropic loop quantum cosmology

, 2003
We present a construction of the Hubble operator for the spatially flat isotropic loop quantum cosmology. This operator is a Dirac observable on a subspace of the space of physical solutions.
Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M Vandersloot K, Date G, Dirac P A M, Fernando J, Gaul M, Golam Mortuza Hossain, Immirzi G, Kodama H, Misner C W, Perez A Rovelli C, Rovelli C, Rovelli C, Smolin L, Thiemann T, Thiemann T, Thiemann T   +26 more
core   +1 more source

Loop Quantum Gravity: Four Recent Advances and a Dozen Frequently Asked Questions

, 2007
As per organizers' request, my talk at the 11th Marcel Grossmann Conference consisted of two parts. In the first, I illustrated recent advances in loop quantum gravity through examples.
Ashtekar, Abhay
core   +1 more source

Relational Motivation for Conformal Operator Ordering in Quantum Cosmology

, 2009
Operator-ordering in quantum cosmology is a major as-yet unsettled ambiguity with not only formal but also physical consequences. We determine the Lagrangian origin of the conformal invariance that underlies the conformal operator-ordering choice in ...
Anderson, Edward
core   +1 more source