scholarly journals Reconstructing the graviton

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Alfio Bonanno ◽  
Tobias Denz ◽  
Jan M. Pawlowski ◽  
Manuel Reichert
Keyword(s):  
Quantum Gravity ◽  
Spectral Function ◽  
Cross Sections ◽  
Graviton Propagator ◽  
Dynamical Fluctuation

We reconstruct the Lorentzian graviton propagator in asymptotically safe quantum gravity from Euclidean data. The reconstruction is applied to both the dynamical fluctuation graviton and the background graviton propagator. We prove that the spectral function of the latter necessarily has negative parts similar to, and for the same reasons, as the gluon spectral function. In turn, the spectral function of the dynamical graviton is positive. We argue that the latter enters cross sections and other observables in asymptotically safe quantum gravity. Hence, its positivity may hint at the unitarity of asymptotically safe quantum gravity.

scholarly journals Renormalizable and Unitary Model of Quantum Gravity

Symmetry ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1334
Author(s):  
S. A. Larin
Keyword(s):  
Quantum Theory ◽  
Quantum Gravity ◽  
Curvature Tensor ◽  
Relativistic Quantum ◽  
Dimensional Regularization ◽  
Graviton Propagator ◽  
Unitary Model ◽  
Theory Of Gravity ◽  
Made In

We consider R + R 2 relativistic quantum gravity with the action where all possible terms quadratic in the curvature tensor are added to the Einstein-Hilbert term. This model was shown to be renormalizable in the work by K.S. Stelle. In this paper, we demonstrate that the R + R 2 model is also unitary contrary to the statements made in the literature, in particular in the work by Stelle. New expressions for the R + R 2 Lagrangian within dimensional regularization and the graviton propagator are derived. We demonstrate that the R + R 2 model is a good candidate for the fundamental quantum theory of gravity.

Gravity Quantized In Dimension 4

2014 ◽  
Vol 4 (1) ◽  
pp. 298-391
Author(s):  
Beyram Torbrand
Keyword(s):  
Quantum Gravity ◽  
Cross Sections ◽  
Particle Physics ◽  
Critical Dimension ◽  
Einstein Gravity ◽  
Theoretical Physics ◽  
Simple Quantum

This is a sequel to the article 'A More or Less Well-Behaved Quantum Gravity Lagrangean in Dimension 4?' in Advanced Studies in Theoretical Physics, Torbrand Dhrif[6]. We give a simple Quantum Gravity Lagrangean that behaves well, up to the standards of particle physics. Feynman calculus for cross-sections, and the diagrams involved, should behave good. The action is naively renormalizable, has critical dimension and is invariant under scalings in dimension 4. It implies standard Einstein gravity for a massless graviton.

scholarly journals TENSORIAL STRUCTURE OF THE LQG GRAVITON PROPAGATOR

2008 ◽  
Vol 23 (08) ◽  
pp. 1209-1213 ◽  
Author(s):  
EMANUELE ALESCI
Keyword(s):  
Asymptotic Behavior ◽  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Long Distance ◽  
Graviton Propagator ◽  
Distance Limit

We review the construction of the tensorial structure of the graviton propagator in the context of loop quantum gravity and spinfoam formalism. The main result of this analysis is that applying the same strategy used to compute the diagonal terms, the Barrett-Crane vertex is unable to yield the correct propagator in the long distance limit. The problem is in the intertwiner-independence of the Barrett-Crane vertex. We also review the asymptotic behavior of an alternative vertex that is able to give the correct propagator.

scholarly journals Fourth-derivative relativistic quantum gravity

2018 ◽  
Vol 191 ◽  
pp. 07002 ◽  
Author(s):  
S.A. Larin
Keyword(s):  
Quantum Theory ◽  
Quantum Gravity ◽  
Curvature Tensor ◽  
Relativistic Quantum ◽  
Dimensional Regularization ◽  
Quantum Theory Of Gravitation ◽  
Graviton Propagator ◽  
Fourth Derivative ◽  
Theory Of Gravitation

We consider relativistic quantum gravity with the action including terms quadratic in the curvature tensor. This model is known to be renormalizable. We demonstrate that the model is also unitary. New expressions for the corresponding Lagrangian and the graviton propagator within dimensional regularization are derived. We argue that the considered model is the proper candidate for the fundamental quantum theory of gravitation.

scholarly journals GRAVITON-PHOTON CONVERSION ON SPIN 0 AND 1/2 PARTICLES

2002 ◽  
Vol 17 (27) ◽  
pp. 3963-3973 ◽  
Author(s):  
FINN RAVNDAL ◽  
MATS SUNDBERG
Keyword(s):  
Quantum Gravity ◽  
Cross Sections ◽  
Differential Cross ◽  
Forward Direction ◽  
Differential Cross Sections ◽  
High Energies ◽  
Photon Conversion

The differential cross-sections for scattering of gravitons into photons on bosons and fermions are calculated in linearized quantum gravity. They are found to be strongly peaked in the forward direction and become constant at high energies. Numerically, they are very small as expected for such gravitational interactions.

scholarly journals Higher-derivative relativistic quantum gravity

2018 ◽  
Vol 33 (05) ◽  
pp. 1850028 ◽  
Author(s):  
S. A. Larin
Keyword(s):  
Quantum Theory ◽  
Quantum Gravity ◽  
Curvature Tensor ◽  
Relativistic Quantum ◽  
Dimensional Regularization ◽  
Quantum Theory Of Gravitation ◽  
Higher Derivative ◽  
Graviton Propagator ◽  
Theory Of Gravitation

Relativistic quantum gravity with the action including terms quadratic in the curvature tensor is analyzed. We derive new expressions for the corresponding Lagrangian and the graviton propagator within dimensional regularization. We argue that the considered model is a good candidate for the fundamental quantum theory of gravitation.

scholarly journals BLACK HOLES AND ASYMPTOTICALLY SAFE GRAVITY

2012 ◽  
Vol 27 (05) ◽  
pp. 1250019 ◽  
Author(s):  
KEVIN FALLS ◽  
DANIEL F. LITIM ◽  
AARTI RAGHURAMAN
Keyword(s):  
Black Holes ◽  
Quantum Gravity ◽  
Cross Sections ◽  
Production Cross ◽  
Hadron Collider ◽  
Conformal Structure ◽  
Gravity Models ◽  
Particle Collisions ◽  
Penrose Diagram ◽  
Black Hole Remnant

Quantum gravitational corrections to black holes are studied in four and higher dimensions using a renormalisation group improvement of the metric. The quantum effects are worked out in detail for asymptotically safe gravity, where the short-distance physics is characterized by a nontrivial fixed point of the gravitational coupling. We find that a weakening of gravity implies a decrease of the event horizon, and the existence of a Planck-size black hole remnant with vanishing temperature and vanishing heat capacity. The absence of curvature singularities is generic and discussed together with the conformal structure and the Penrose diagram of asymptotically safe black holes. The production cross-section of mini-black holes in energetic particle collisions, such as those at the Large Hadron Collider, is analysed within low-scale quantum gravity models. Quantum gravity corrections imply that cross-sections display a threshold, are suppressed in the Planckian, and reproduce the semiclassical result in the deep trans-Planckian region. Further implications are discussed.

scholarly journals Isoscalar and isovector kaon form factors from e+e− and τ data

2019 ◽  
Vol 212 ◽  
pp. 03006
Author(s):  
Konstantin Beloborodov ◽  
Vladimir Druzhinin ◽  
Sergey Serednyakov
Keyword(s):  
Vector Meson ◽  
Spectral Function ◽  
Cross Sections ◽  
Relative Phase ◽  
Form Factors ◽  
Experimental Results ◽  
Vector Meson Dominance ◽  
Dominance Model ◽  
Vector Meson Dominance Model ◽  
Model Independent

The recent precise measurements of the e+e−→ KS KL and e+e−→ K+K− cross sections and the hadronic spectral function of the τ−→ K−KS ντ decay are used to extract the isoscalar and isovector electromagnetic kaon form factors and their relative phase in a model independent way. The experimental results are compared with a fit based on the vector-meson-dominance model.

Sign in / Sign up

Export Citation Format

Share Document