scholarly journals Perturbative quantum gravity comes of age

2014 ◽  
Vol 23 (09) ◽  
pp. 1430020 ◽  
Author(s):  
R. P. Woodard
Keyword(s):  
Quantum Gravity ◽  
Gravitational Effects ◽  
Hard Science ◽  
The Future ◽  
Cosmological Data ◽  
Perturbative Quantum ◽  
Primordial Inflation

I argue that cosmological data from the epoch of primordial inflation is catalyzing the maturation of quantum gravity from speculation into a hard science. I explain why quantum gravitational effects from primordial inflation are observable. I then review what has been done, both theoretically and observationally, and what the future holds. I also discuss what this tells us about quantum gravity.

Final remarks on Part II

2021 ◽  
pp. 503-503
Author(s):  
Iosif L. Buchbinder ◽  
Ilya L. Shapiro
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Quantum Gravity ◽  
Cosmological Constant ◽  
General Situation ◽  
Quantum Field ◽  
Gravitational Effects ◽  
Higher Derivative ◽  
Perfect Model ◽  
Perturbative Quantum

This brief concluding chapter summarizes the general situation in semiclassical theory and quantum gravity. Even in the framework of the usual perturbative quantum field theory, there are several approaches leading to theoretically satisfactory models of quantum gravitational effects, starting from quantum field theory in curved spacetime. Here, the expression “satisfactory” does not mean perfectness, as there is no theoretically perfect model of quantum gravity. The chapter then goes on to review the main unsolved problems of quantum gravity, such as higher-derivative ghosts and instabilities and the cosmological constant problem. It concludes with the hope that the basic aspects of the models presented in this book will be useful for anyone who intends to start working in this fascinating area.

scholarly journals NONCOMMUTATIVITY AND NON-ANTICOMMUTATIVITY PERTURBATIVE QUANTUM GRAVITY

2012 ◽  
Vol 27 (13) ◽  
pp. 1250075 ◽  
Author(s):  
MIR FAIZAL
Keyword(s):  
Quantum Gravity ◽  
Lagrangian Density ◽  
Background Field ◽  
Field Method ◽  
Gauge Fixing ◽  
Perturbative Quantum ◽  
Background Field Method

In this paper, we will study perturbative quantum gravity on supermanifolds with both noncommutativity and non-anticommutativity of spacetime coordinates. We shall first analyze the BRST and the anti-BRST symmetries of this theory. Then we will also analyze the effect of shifting all the fields of this theory in background field method. We will construct a Lagrangian density which apart from being invariant under the extended BRST transformations is also invariant under on-shell extended anti-BRST transformations. This will be done by using the Batalin–Vilkovisky (BV) formalism. Finally, we will show that the sum of the gauge-fixing term and the ghost term for this theory can be elegantly written down in superspace with a two Grassmann parameter.

scholarly journals Quantum gravity: A brief history of ideas and some prospects

2015 ◽  
Vol 24 (11) ◽  
pp. 1530028 ◽  
Author(s):  
Steven Carlip ◽  
Dah-Wei Chiou ◽  
Wei-Tou Ni ◽  
Richard Woodard
Keyword(s):  
Black Hole ◽  
String Theory ◽  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Black Hole Thermodynamics ◽  
History Of Ideas ◽  
Foreseeable Future ◽  
Gravitational Effects ◽  
History Of

We present a bird's-eye survey on the development of fundamental ideas of quantum gravity, placing emphasis on perturbative approaches, string theory, loop quantum gravity (LQG) and black hole thermodynamics. The early ideas at the dawn of quantum gravity as well as the possible observations of quantum gravitational effects in the foreseeable future are also briefly discussed.

scholarly journals Collinear and soft divergences in perturbative quantum gravity

2011 ◽  
Vol 84 (10) ◽  
Author(s):  
Ratindranath Akhoury ◽  
Ryo Saotome ◽  
George Sterman
Keyword(s):  
Quantum Gravity ◽  
Perturbative Quantum

scholarly journals Discrete Hilbert space, the Born Rule, and quantum gravity

2021 ◽  
Vol 36 (03) ◽  
pp. 2150013
Author(s):  
Stephen D. H. Hsu
Keyword(s):  
Hilbert Space ◽  
Quantum Gravity ◽  
Discrete Models ◽  
Born Rule ◽  
Gravitational Effects ◽  
Spacetime Geometry ◽  
Decoherent Histories ◽  
Lattice Quantum ◽  
Spacetime Interval ◽  
Matter Fields

Quantum gravitational effects suggest a minimal length, or spacetime interval, of order of the Planck length. This in turn suggests that Hilbert space itself may be discrete rather than continuous. One implication is that quantum states with norm below some very small threshold do not exist. The exclusion of what Everett referred to as maverick branches is necessary for the emergence of the Born Rule in no collapse quantum mechanics. We discuss this in the context of quantum gravity, showing that discrete models (such as simplicial or lattice quantum gravity) indeed suggest a discrete Hilbert space with minimum norm. These considerations are related to the ultimate level of fine-graining found in decoherent histories (of spacetime geometry plus matter fields) produced by quantum gravity.

Pulsar–black hole binaries as a window on quantum gravity

2017 ◽  
Vol 26 (12) ◽  
pp. 1743004 ◽  
Author(s):  
John Estes ◽  
Michael Kavic ◽  
Matthew Lippert ◽  
John H. Simonetti
Keyword(s):  
Quantum Gravity ◽  
Laser Interferometer ◽  
Mean Square ◽  
Mean Square Deviation ◽  
Space Antenna ◽  
Gravitational Effects ◽  
Arrival Times ◽  
Black Hole Binaries ◽  
Laser Interferometer Space Antenna ◽  
Square Kilometer Array

Pulsars (PSRs) are some of the most accurate clocks found in nature, while black holes (BHs) offer a unique arena for the study of quantum gravity. As such, PSR–BH binaries provide ideal astrophysical systems for detecting effects of quantum gravity. With the success of aLIGO and the advent of instruments like the Square Kilometer Array (SKA) and Evolved Laser Interferometer Space Antenna (eLISA), the prospects for discovery of such PSR–BH binaries are very promising. We argue that PSR–BH binaries can serve as ready-made testing grounds for proposed resolutions to the BH information paradox. We propose using timing signals from a PSR beam passing through the region near a BH event horizon as a probe of quantum gravitational effects. In particular, we demonstrate that fluctuations of the geometry outside a BH lead to an increase in the measured root-mean-square deviation of arrival times of PSR pulsar traveling near the horizon.

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