scholarly journals Low energy description of quantum gravity and complementarity

2014 ◽  
Vol 733 ◽  
pp. 126-133 ◽  
Author(s):  
Yasunori Nomura ◽  
Jaime Varela ◽  
Sean J. Weinberg
Keyword(s):  
Quantum Gravity ◽  
Low Energy

scholarly journals The Swampland Conjectures: A Bridge from Quantum Gravity to Particle Physics

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 273
Author(s):  
Mariana Graña ◽  
Alvaro Herráez
Keyword(s):  
Effective Field Theories ◽  
Quantum Gravity ◽  
Particle Physics ◽  
Effective Field ◽  
Low Energy ◽  
Field Theories ◽  
Neutrino Masses ◽  
Higgs Potential ◽  
Photon Mass ◽  
Effective Theories

The swampland is the set of seemingly consistent low-energy effective field theories that cannot be consistently coupled to quantum gravity. In this review we cover some of the conjectural properties that effective theories should possess in order not to fall in the swampland, and we give an overview of their main applications to particle physics. The latter include predictions on neutrino masses, bounds on the cosmological constant, the electroweak and QCD scales, the photon mass, the Higgs potential and some insights about supersymmetry.

scholarly journals The UV fate of anomalous U(1)s and the Swampland

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Nathaniel Craig ◽  
Isabel Garcia Garcia ◽  
Graham D. Kribs
Keyword(s):  
Quantum Gravity ◽  
Gauge Theories ◽  
Critical Size ◽  
Gauge Coupling ◽  
Low Energy ◽  
Gravitational Anomaly ◽  
Light Vector ◽  
Energy Theory ◽  
The Cost ◽  
Weak Gravity

Abstract Massive U(1) gauge theories featuring parametrically light vectors are suspected to belong in the Swampland of consistent EFTs that cannot be embedded into a theory of quantum gravity. We study four-dimensional, chiral U(1) gauge theories that appear anomalous over a range of energies up to the scale of anomaly-cancelling massive chiral fermions. We show that such theories must be UV-completed at a finite cutoff below which a radial mode must appear, and cannot be decoupled — a Stückelberg limit does not exist. When the infrared fermion spectrum contains a mixed U(1)-gravitational anomaly, this class of theories provides a toy model of a boundary into the Swampland, for sufficiently small values of the vector mass. In this context, we show that the limit of a parametrically light vector comes at the cost of a quantum gravity scale that lies parametrically below MP1, and our result provides field theoretic evidence for the existence of a Swampland of EFTs that is disconnected from the subset of theories compatible with a gravitational UV-completion. Moreover, when the low energy theory also contains a U(1)3 anomaly, the Weak Gravity Conjecture scale makes an appearance in the form of a quantum gravity cutoff for values of the gauge coupling above a certain critical size.

scholarly journals Limits on quantum gravity effects from Swift short gamma-ray bursts

2017 ◽  
Vol 607 ◽  
pp. A121 ◽  
Author(s):  
M. G. Bernardini ◽  
G. Ghirlanda ◽  
S. Campana ◽  
P. D’Avanzo ◽  
J.-L. Atteia ◽  
...  
Keyword(s):  
Quantum Gravity ◽  
Gamma Ray ◽  
Lorentz Invariance ◽  
Spectral Energy Distribution ◽  
Gamma Ray Bursts ◽  
Low Energy ◽  
Energy Separation ◽  
Spectral Energy ◽  
Spectral Evolution ◽  
Short Grbs

The delay in arrival times between high and low energy photons from cosmic sources can be used to test the violation of the Lorentz invariance (LIV), predicted by some quantum gravity theories, and to constrain its characteristic energy scale EQG that is of the order of the Planck energy. Gamma-ray bursts (GRBs) and blazars are ideal for this purpose thanks to their broad spectral energy distribution and cosmological distances: at first order approximation, the constraints on EQG are proportional to the photon energy separation and the distance of the source. However, the LIV tiny contribution to the total time delay can be dominated by intrinsic delays related to the physics of the sources: long GRBs typically show a delay between high and low energy photons related to their spectral evolution (spectral lag). Short GRBs have null intrinsic spectral lags and are therefore an ideal tool to measure any LIV effect. We considered a sample of 15 short GRBs with known redshift observed by Swift and we estimate a limit on EQG ≳ 1.5 × 1016 GeV. Our estimate represents an improvement with respect to the limit obtained with a larger (double) sample of long GRBs and is more robust than the estimates on single events because it accounts for the intrinsic delay in a statistical sense.

scholarly journals A microscopic model for an emergent cosmological constant

2018 ◽  
Vol 27 (14) ◽  
pp. 1846002 ◽  
Author(s):  
Alejandro Perez ◽  
Daniel Sudarsky ◽  
James D. Bjorken
Keyword(s):  
Quantum Gravity ◽  
Cosmological Constant ◽  
Phenomenological Model ◽  
Particle Physics ◽  
Degrees Of Freedom ◽  
Low Energy ◽  
Microscopic Model ◽  
Energy Particle

The value of the cosmological constant is explained in terms of a noisy diffusion of energy from the low energy particle physics degrees of freedom to the fundamental Planckian granularity which is expected from general arguments in quantum gravity. The quantitative success of our phenomenological model is encouraging and provides possibly useful insights about physics at the scale of quantum gravity.

scholarly journals Phenomenology of theories of gravity without Lorentz invariance: The preferred frame case

2014 ◽  
Vol 23 (13) ◽  
pp. 1443009 ◽  
Author(s):  
Diego Blas ◽  
Eugene Lim
Keyword(s):  
Quantum Gravity ◽  
Lorentz Invariance ◽  
Low Energy ◽  
Time Direction ◽  
Preferred Frame ◽  
Theories Of Gravity ◽  
Theories Of Gravitation

Theories of gravitation without Lorentz invariance are candidates of low-energy descriptions of quantum gravity. In this paper, we will describe the phenomenological consequences of the candidates associated to the existence of a preferred time direction.

scholarly journals Low energy quantum gravity from the effective average action

2010 ◽  
Vol 82 (8) ◽  
Author(s):  
A. Satz ◽  
A. Codello ◽  
F. D. Mazzitelli
Keyword(s):  
Quantum Gravity ◽  
Low Energy ◽  
Average Action ◽  
Energy Quantum

scholarly journals Spacetime has a “thickness”

2017 ◽  
Vol 26 (12) ◽  
pp. 1742002 ◽  
Author(s):  
Samir D. Mathur
Keyword(s):  
Black Hole ◽  
Quantum Gravity ◽  
Gravity Wave ◽  
Hawking Radiation ◽  
Finite Thickness ◽  
Low Energy ◽  
Leading Order ◽  
Curved Spacetime ◽  
Thickness Parameter

Suppose we assume that (a) information about a black hole is encoded in its Hawking radiation and (b) causality is not violated to leading order in gently curved spacetime. Then, we argue that spacetime cannot just be described as a manifold with a shape; it must be given an additional attribute which we call “thickness.” This thickness characterizes the spread of the quantum gravity wave functional in superspace — the space of all three-geometries. Low energy particles travel on spacetime without noticing the thickness parameter, so they just see an effective manifold. Objects with energy large enough to create a horizon do note the finite thickness; this modifies the semiclassical evolution in such a way that we avoid horizon formation and the consequent violation of causality.

scholarly journals The equivalence principle in a quantum world

2015 ◽  
Vol 24 (12) ◽  
pp. 1544013 ◽  
Author(s):  
N. E. J. Bjerrum-Bohr ◽  
John F. Donoghue ◽  
Basem Kamal El-Menoufi ◽  
Barry R. Holstein ◽  
Ludovic Planté ◽  
...  
Keyword(s):  
Quantum Gravity ◽  
Effective Field Theory ◽  
Equivalence Principle ◽  
Quantum Physics ◽  
Effective Field ◽  
Low Energy ◽  
Quantum Corrections ◽  
The Core ◽  
Modern Methods ◽  
Coordinate Invariance

We show how modern methods can be applied to quantum gravity at low energy. We test how quantum corrections challenge the classical framework behind the equivalence principle (EP), for instance through introduction of nonlocality from quantum physics, embodied in the uncertainty principle. When the energy is small, we now have the tools to address this conflict explicitly. Despite the violation of some classical concepts, the EP continues to provide the core of the quantum gravity framework through the symmetry — general coordinate invariance — that is used to organize the effective field theory (EFT).

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