Gravity quantum

Quantum Gravity, Generalized Theory of Gravitation and Superstring... 

Note that string theory says little about the space in which strings move and vibrate. A relatively new mathematical model known as loop quantum gravity represents an alternate approach in which the rules of quantum mechanics are applied directly to Einstein s description of space and time. In this model, space itself comes packaged in... 

Tegmark, M. (1997) On the dimensionality of spacetime. Classical and Quantum Gravity. 14 L69-L75. 

Wikipedia, org, an on-line encyclopedia, offers a very detailed six-part entry on loop quantum gravity written by a loop quantum gravity advocate. A seventh part, written by a string theory advocate, discusses numerous objections to the validity of the loop quantum gravity theory. 

Zicliichi, A. From Quarks and Gluons to Quantum Gravity Proceedings of the International School ofSubnuclear Physics, World Scientific Publishing Company, Inc., Riveredge, NJ, 2003. 

Waldrop, MM Mewing the Universe as a Coat of Chain Mail New Calculations Have Pointed the Way to Quantum Gravity and Suggested a Novel Structure for the Sub sub Microscopic World, Science, 1510 (December 14. 1990). 

The main idea behind the abovementioned proposals is that quantum-gravitational fluctuations in the vacuum must in general be modified by the passage of an energetic particle and that this recoil will be reflected in the backreaction effects on the propagating particle itself. Three possible optical effects of quantum gravity have been identified ... 

It is clear from the preceding analysis of astrophysical sources that it is necessary to analyze the data from other sources such as AGN and/or pulsars to confirm the signature of quantum gravity effects. An alternate possibilty would... 

Here, we shall discuss the implications of cosmological expansion for the searches of a quantum-gravity-induced refractive index and a stochastic effect. We will consider Friedman-Robertson-Walker (FRW) metrics as an appropriate candidate for standard homogeneous and isotropic cosmology. Let R be the FRW scale factor, and a subscript 0 will denote the value at the present era. Ho is the present Hubble expansion parameter, and the deceleration parameter qo is defined in terms of the curvature k of the FRW metric by k ( 2[Pg.588]

In the context of quantum-gravity-induced refractive-index phenomena, we face the same situation. Let the two photons travel with velocities very close to c, whose present energies are E and E2, respectively. At earlier epochs, their energies would have been blueshifted by a common factor 1 + z. Let AEo = E — E2, then... 

The energy-dependent speed of light is associated with the effect of the medium on the propagation of photon. The fluctuating refractive index of the medium induces this kind of the energy dependence. This kind of the medium has been considered, such as quantum gravity and the Maxwell vacuum with nonzero conductivity. So, it to make distinction between the contributions from standard model predictions as well as from other theories is needed. 

C. J. Isham, Structural issues in quantum gravity, gr-qc/9510063 (lecture given at the GR14... 

J. Stachel, Einstein and quantum mechanics, in A. Asthekar and J. Stachel (Eds.), Conceptual Problems of Quantum Gravity, Einstein Studies, Vol. 2, Birkhauser, Boston, 1999. 

M. Requardt and Sisir Roy, (Quantum)Space-Time as a Statistical Geometry of Fuzzy Lumps and the Connection with Random Metric Spaces - to be published in Classical Quantum Gravity (2001). 

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