Tests Of Quantum Gravity Research Articles

Logarithmic corrections to $$ \mathcal{N} = {4} $$ and $$ \mathcal{N} = {8} $$ black hole entropy: a one loop test of quantum gravity

We compute logarithmic corrections to the entropy of supersymmetric extremal black holes in $$ \mathcal{N} = {4} $$ and $$ \mathcal{N} = {8} $$ supersymmetric string theories and find results in perfect agreement with the microscopic results. In particular these logarithmic corrections vanish for quarter BPS black holes in $$ \mathcal{N} = {4} $$ supersymmetric theories, but has a finite coefficient for 1/8 BPS black holes in the $$ \mathcal{N} = {8} $$ supersymmetric theory. On the macroscopic side these computations require evaluating the one loop determinant of massless fields around the near horizon geometry, and include, in particular, contributions from dynamical four dimensional gravitons propagating in the loop. Thus our analysis provides a test of one loop quantum gravity corrections to the black hole entropy, or equivalently of the AdS 2/CF T 1 correspondence. We also extend our analysis to $$ \mathcal{N} = {2} $$ supersymmetric STU model and make a prediction for the logarithmic correction to the black hole entropy in that theory.

Gravitationally induced inhibitions of dispersion according to the Schrödinger–Newton equation

We reconsider the time-dependent Schrödinger–Newton equation as a model for the self-gravitational interaction of a quantum system. We numerically locate the onset of gravitationally induced inhibitions of dispersion of Gaussian wave packets and find them to occur at mass values more than six orders of magnitude higher than reported by Salzman and Carlip (Salzman and Carlip 2006, arXiv:gr-qc/0606120, Carlip 2008 Class. Quantum Grav. 25 107–44), namely at about 1010 u. This fits much better to simple analytical estimates but unfortunately also questions the experimental realizability of the proposed laboratory test of quantum gravity in the foreseeable future, not just because of large masses, but also because of the need to provide sufficiently long coherence times.

Cosmological Footprints of Loop Quantum Gravity

The primordial spectrum of cosmological tensor perturbations is considered as a possible probe of quantum gravity effects. Together with string theory, loop quantum gravity is one of the most promising frameworks to study quantum effects in the early universe. We show that the associated corrections should modify the potential seen by gravitational waves during the inflationary amplification. The resulting power spectrum should exhibit a characteristic tilt. This opens a new window for cosmological tests of quantum gravity.

Tests of quantum gravity and large extra dimensions models using high energy γ-ray observations

Observations of the multi-TeV spectra of the nearby BL objects Mkn 421 and Mkn 501 exhibit the high energy cutoffs predicted to be the result of intergalactic annihilation interactions, primarily with infrared photons having a flux level as determined by various astronomical observations. After correction for this absorption effect, the derived intrinsic spectra of these multi-TeV sources can be explained within the framework of simple synchrotron self-Compton emission models. Stecker and Glashow have shown that the existence of such annihilations via electron–positron pair production interactions up to an energy of 20 TeV puts strong constraints on Lorentz invariance violation. Such constraints have important implications for quantum gravity models as well as models involving large extra dimensions. We also discuss the implications of observations of high energy γ-rays from the Crab Nebula on constraining quantum gravity models.

Tests of quantum gravity from observations of γ-ray bursts

Tests of quantum gravity from observations of γ-ray bursts

Tests of quantum gravity from observations of γ-ray bursts

The recent confirmation that at least some γ-ray bursts originate at cosmological distances1,2,3,4 suggests that the radiation from them could be used to probe some of the fundamental laws of physics. Here we show that γ-ray bursts will be sensitive to an energy dispersion predicted by some approaches to quantum gravity. Many of the bursts have structure on relatively rapid timescales5, which means that in principle it is possible to look for energy-dependent dispersion of the radiation, manifested in the arrival times of the photons, if several different energy bands are observed simultaneously. A simple estimate indicates that, because of their high energies and distant origin, observations of these bursts should be sensitive to a dispersion scale that is comparable to the Planck energy scale (∼1019 GeV), which is sufficient to test theories of quantum gravity. Such observations are already possible using existing γ-ray burst detectors.