Results 31 to 40 of about 20,416 (75)

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

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

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

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

On the Chern-Simons State in General Relativity and Modified Gravity Theories

, 2014
The Chern-Simons state is one solution to quantum constraints of gravity in the context of general relativity (GR) theory if we use Ashtekar's variables and if one orders the constraints with the triads to the left.
R. Rosas-Rodríguez
semanticscholar   +1 more source

Quantum Gravity and Inflation [PDF]

, 2004
Using the Ashtekar-Sen variables of loop quantum gravity, a new class of exact solutions to the equations of quantum cosmology is found for gravity coupled to a scalar field, that corresponds to inflating universes.
A. D. Linde, A. D. Linde, A. Perez, A. Vilenkin, Carlo Rovelli, Chopin Soo, Chopin Soo, D. Oriti, G. A. M. Marugan, G. F. Mazenko, H. Kodama, H. Kodama, J. B. Hartle, J. Martin, Justin Malecki, L. Smolin, Lee Smolin, Stephon Alexander, T. Thiemann, T. Vachaspati, Takashi Sano, William H. Kinney   +21 more
core   +4 more sources

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
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Isotropic Loop Quantum Cosmology [PDF]

, 2002
Isotropic models in loop quantum cosmology allow explicit calculations, thanks largely to a completely known volume spectrum, which is exploited in order to write down the evolution equation in a discrete internal time.
, Ames W F, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Baez J C, Bahcall J N, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Bojowald M, Gurovich V Ts, Hawking S W, Immirzi G, Kuchar K V, Martin Bojowald, Rovelli C, Thiemann T, Thiemann T, Thiemann T, Veneziano G, Witten E   +25 more
core   +3 more sources

Coherent states for FLRW space-times in loop quantum gravity

, 2011
We construct a class of coherent spin-network states that capture proprieties of curved space-times of the Friedmann-Lama\^itre-Robertson-Walker type on which they are peaked.
Abhay Ashtekar, Abhay Ashtekar, Antonino Marcianò, Carlo Rovelli, Claudio Perini, Elena Magliaro, Robert M. Wald, Thomas Thiemann   +7 more
core   +2 more sources

Nonmetricity formulation of general relativity and its scalar-tensor extension

, 2018
Einstein's celebrated theory of gravitation can be presented in three forms: general relativity, teleparallel gravity, and the rarely considered before symmetric teleparallel gravity.
Järv, Laur, Rünkla, Mihkel, Saal, Margus, Vilson, Ott   +3 more
core   +1 more source