Results 21 to 30 of about 20,706 (73)

Unimodular Loop Quantum Cosmology

, 2010
Unimodular gravity is based on a modification of the usual Einstein-Hilbert action that allows one to recover general relativity with a dynamical cosmological constant.
A. Ashtekar, A. Ashtekar, A. Einstein, C. Rovelli, C. J. Isham, D. Marolf, Dah-Wei Chiou, M. Bojowald, Marc Geiller, P. A. M. Dirac, R. M. Wald, S. Hawking, T. Thiemann   +12 more
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Loop quantum gravity: the first twenty five years

, 2011
This is a review paper invited by the journal "Classical ad Quantum Gravity" for a "Cluster Issue" on approaches to quantum gravity. I give a synthetic presentation of loop gravity. I spell-out the aims of the theory and compare the results obtained with
Amelino-Camelia G, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Atiyah M, Baez J, Barrau A, Barrau A, Barrett J W Dowdall R J Fairbairn W J Hellmann F Pereira R, Bianchi E, Bianchi E, Bianchi E, Bianchi E Donà P Speziale S, Bianchi E Han M Magliaro E Perini C Rovelli C Wieland W, Bianchi E Han M Magliaro E Perini C Rovelli C Wieland W, Bianchi E Krajewski T Rovelli C Vidotto F, Bilson-Thompson S Markopoulou F Smolin L, Bojowald M, Calcagni G Gielen S Oriti D, Calmet X, Campiglia M Henderson A Nelson W, Carlo Rovelli, Ding Y, Ding Y Han M Rovelli C, Dittrich B, Dittrich B, Dittrich B, Dittrich B, Domagala M Giesel K Kaminski W Lewandowski J, Fairbairn W J Meusburger C, Fleischhack C, Freidel L, Freidel L Speziale S, Freidel L Speziale S, Geloun J B Gurau R Rivasseau V, Giesel K, Giesel K, Giesel K, Giesel K, Giesel K Tambornino J Thiemann T, Grain J Barrau A Cailleteau T Mielczarek J, Gurau R, Han M, Han M Rovelli C, Henderson A Rovelli C Vidotto F Wilson-Ewing E, Immirzi G, Immirzi G, Jacobson T, Kaminski W, Kaminski W, Krajewski T Magnen J Rivasseau V Tanasa A Vitale P, Livine E R, Livine E R, Major S, Major S A, Major S A, Martin-Benito M Garay L J Mena Marugan G A, Meissner K A, Mielczarek J, Minkowski H, Modesto L Premont-Schwarz I, Noui K, Oeckl R, Oriti D, Penrose R, Perez A, Ponzano G, Rivasseau V Wang Z, Rovelli C, Rovelli C, Rovelli C, Rovelli C, Rovelli C, Rovelli C, Rovelli C Smerlak M, Rovelli C Speziale S, Singh P, Singh P Vidotto F, Smolin L, Smolin L, Thiemann T, Thiemann T, Thiemann T, Thiemann T, Wieland W   +89 more
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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
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The cosmological implications of a fundamental length: a DSR inspired de-Sitter spacetime

, 2008
We study a de-Sitter model in the framework of a Deformed Special Relativity (DSR) inspired structure. The effects of this framework appear as the existence of a fundamental length which influences the behavior of the scale factor.
Amelino-Camelia G, Amelino-Camelia G, Ashtekar A, Brandenberger R H, Carmona J M, Cheng T-P, Connes A, Green M, H R Sepangi, Khosravi N, Khosravi N Sepangi H R, Kowalski-Glikman J, Liddle A R, Magueijo J, Majid S, N Khosravi, Nascimento J R, Perkins D, Polchinski J, Rovelli C, Rovelli C, Seiberg N, Susskind L, Zachos C K   +23 more
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Planck-scale structure of spacetime and some implications for astrophysics and cosmology

, 2003
I briefly review some scenarios for the role of the Planck length in quantum gravity. In particular, I examine the differences between the schemes in which quantum gravity is expected to introduce a maximum acceleration and the schemes in which the ...
Amelino-Camelia, Giovanni
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The present moment in quantum cosmology: challenges to the arguments for the elimination of time [PDF]

, 2000
Barbour, Hawking, Misner and others have argued that time cannot play an essential role in the formulation of a quantum theory of cosmology. Here we present three challenges to their arguments, taken from works and remarks by Kauffman, Markopoulou and ...
Smolin, Lee
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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
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Observational Exclusion of a Consistent Quantum Cosmology Scenario

, 2015
It is often argued that inflation erases all the information about what took place before it started. Quantum gravity, relevant in the Planck era, seems therefore mostly impossible to probe with cosmological observations.
Barrau, Aurelien, Bolliet, Boris, Grain, Julien, Schander, Susanne   +3 more
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Loop Quantum Cosmology, Boundary Proposals, and Inflation

, 2003
Loop quantum cosmology of the closed isotropic model is studied with a special emphasis on a comparison with traditional results obtained in the Wheeler-DeWitt approach.
A. Ashtekar, A. Vilenkin, A. Vilenkin, B.S. DeWitt, C. Rovelli, C.W. Misner, G. Immirzi, H.D. Conradi, J.B. Hartle, J.F. Barbero G., Kevin Vandersloot, 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, N. Kontoleon, T. Thiemann, T. Thiemann   +26 more
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Spherically Symmetric Quantum Geometry: Hamiltonian Constraint

, 2005
Variables adapted to the quantum dynamics of spherically symmetric models are introduced, which further simplify the spherically symmetric volume operator and allow an explicit computation of all matrix elements of the Euclidean and Lorentzian ...
Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A, Ashtekar A Bojowald M Willis J, Ashtekar A Pawlowski T Singh P, Banerjee K, 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 M, Bojowald M, Bojowald M, Bojowald M, Bojowald M Hernández H H Morales-Técotl H A, Bojowald M Morales-Técotl H A, Bojowald M Skirzewski A, Brunnemann J, Cartin D, Date G, Fleischhack C, Giesel K Thiemann T, Hofmann S Winkler O, Hossain G M, Husain V, Husain V, Immirzi G, Lewandowski J Okołów A Sahlmann H Thiemann T, Martin Bojowald, Neville D E, Neville D E, Nicolai H, Perez A, Rafal Swiderski, Rovelli C, Rovelli C, Singh P, Smolin L, Thiemann T, Thiemann T, Thiemann T, Thiemann T, Tsujikawa S, Vereshchagin G V, Willis J   +61 more
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