Constraints on discrete global symmetries in quantum gravity

Abstract The question whether global symmetries can be realized in quantum-gravity-matter-systems has far-reaching phenomenological consequences. Here, we collect evidence that within an asymptotically safe context, discrete global symmetries of the form ℤn, n > 4, cannot be realized in a near-perturbative regime. In contrast, an effective-field-theory approach to quantum gravity might feature such symmetries, providing a mechanism to generate mass hierarchies in the infrared without the need for additional fine-tuning.

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Chern-Weil global symmetries and how quantum gravity avoids them

Journal of High Energy Physics ◽

10.1007/jhep11(2021)053 ◽

2021 ◽

Vol 2021 (11) ◽

Author(s):

Ben Heidenreich ◽

Jacob McNamara ◽

Miguel Montero ◽

Matthew Reece ◽

Tom Rudelius ◽

...

Keyword(s):

Field Theory ◽

String Theory ◽

Quantum Gravity ◽

Global Symmetries ◽

Effective Field Theory ◽

Degrees Of Freedom ◽

Effective Field ◽

Global Symmetry ◽

Unified Framework ◽

Particle Phenomenology

Abstract We draw attention to a class of generalized global symmetries, which we call “Chern-Weil global symmetries,” that arise ubiquitously in gauge theories. The Noether currents of these Chern-Weil global symmetries are given by wedge products of gauge field strengths, such as F2 ∧ H3 and tr($$ {F}_2^2 $$ F 2 2 ), and their conservation follows from Bianchi identities. As a result, they are not easy to break. However, it is widely believed that exact global symmetries are not allowed in a consistent theory of quantum gravity. As a result, any Chern-Weil global symmetry in a low-energy effective field theory must be either broken or gauged when the theory is coupled to gravity. In this paper, we explore the processes by which Chern-Weil symmetries may be broken or gauged in effective field theory and string theory. We will see that many familiar phenomena in string theory, such as axions, Chern-Simons terms, worldvolume degrees of freedom, and branes ending on or dissolving in other branes, can be interpreted as consequences of the absence of Chern-Weil symmetries in quantum gravity, suggesting that they might be general features of quantum gravity. We further discuss implications of breaking and gauging Chern-Weil symmetries for particle phenomenology and for boundary CFTs of AdS bulk theories. Chern-Weil global symmetries thus offer a unified framework for understanding many familiar aspects of quantum field theory and quantum gravity.

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Spin effects in the effective field theory approach to Post-Minkowskian conservative dynamics

Journal of High Energy Physics ◽

10.1007/jhep06(2021)012 ◽

2021 ◽

Vol 2021 (6) ◽

Author(s):

Zhengwen Liu ◽

Rafael A. Porto ◽

Zixin Yang

Keyword(s):

Field Theory ◽

Effective Field Theory ◽

Scattering Problem ◽

Finite Size ◽

Effective Field ◽

Compact Objects ◽

Scattering Data ◽

Theory Approach ◽

Spin Effects ◽

Radial Action

Abstract Building upon the worldline effective field theory (EFT) formalism for spinning bodies developed for the Post-Newtonian regime, we generalize the EFT approach to Post-Minkowskian (PM) dynamics to include rotational degrees of freedom in a manifestly covariant framework. We introduce a systematic procedure to compute the total change in momentum and spin in the gravitational scattering of compact objects. For the special case of spins aligned with the orbital angular momentum, we show how to construct the radial action for elliptic-like orbits using the Boundary-to-Bound correspondence. As a paradigmatic example, we solve the scattering problem to next-to-leading PM order with linear and bilinear spin effects and arbitrary initial conditions, incorporating for the first time finite-size corrections. We obtain the aligned-spin radial action from the resulting scattering data, and derive the periastron advance and binding energy for circular orbits. We also provide the (square of the) center-of-mass momentum to $$ \mathcal{O}\left({G}^2\right) $$ O G 2 , which may be used to reconstruct a Hamiltonian. Our results are in perfect agreement with the existent literature, while at the same time extend the knowledge of the PM dynamics of compact binaries at quadratic order in spins.

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Precision Higgs couplings in neutral naturalness models: an effective field theory approach

Journal of High Energy Physics ◽

10.1007/jhep02(2021)234 ◽

2021 ◽

Vol 2021 (2) ◽

Author(s):

Lucien Heurtier ◽

Hao-Lin Li ◽

Huayang Song ◽

Shufang Su ◽

Wei Su ◽

...

Keyword(s):

Field Theory ◽

Effective Field Theory ◽

Goldstone Boson ◽

Higgs Sector ◽

New Physics ◽

Effective Field ◽

Precision Measurements ◽

Global Symmetry ◽

Theory Approach ◽

Decay Channels

AbstractThe Higgs sector in neutral naturalness models provides a portal to the hidden sectors, and thus measurements of Higgs couplings at current and future colliders play a central role in constraining the parameter space of the model. We investigate a class of neutral naturalness models, in which the Higgs boson is a pseudo-Goldstone boson from the universal SO(N)/SO(N −1) coset structure. Integrating out the radial mode from the spontaneous global symmetry breaking, we obtain various dimension-six operators in the Standard Model effective field theory, and calculate the low energy Higgs effective potential with radiative corrections included. We perform aχ2fit to the Higgs coupling precision measurements at current and future colliders and show that the new physics scale could be explored up to 2.3 (2.4) TeV without (with) the Higgs invisible decay channels at future Higgs factories. The limits are comparable to the indirect constraints obtained via electroweak precision measurements.

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Singularity Theorems in the Effective Field Theory for Quantum Gravity at Second Order in Curvature

Universe ◽

10.3390/universe6100171 ◽

2020 ◽

Vol 6 (10) ◽

pp. 171

Author(s):

Folkert Kuipers ◽

Xavier Calmet

Keyword(s):

Field Theory ◽

Quantum Gravity ◽

Effective Field Theory ◽

Energy Condition ◽

Null Energy Condition ◽

Effective Field ◽

Second Order ◽

Jordan Frame ◽

Singularity Theorems ◽

Massive Spin

In this paper, we discuss singularity theorems in quantum gravity using effective field theory methods. To second order in curvature, the effective field theory contains two new degrees of freedom which have important implications for the derivation of these theorems: a massive spin-2 field and a massive spin-0 field. Using an explicit mapping of this theory from the Jordan frame to the Einstein frame, we show that the massive spin-2 field violates the null energy condition, while the massive spin-0 field satisfies the null energy condition, but may violate the strong energy condition. Due to this violation, classical singularity theorems are no longer applicable, indicating that singularities can be avoided, if the leading quantum corrections are taken into account.

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