Every Poincaré gauge theory is conformal: A compelling case for dynamical vector torsion

The Poincaré gauge theory (PGT) of gravity provides a viable formulation of general relativity (Einstein–Cartan theory), and a popular model-building framework for modified gravity with torsion. Notoriously, however, the PGT terms which propagate vector torsion lead to strongly-coupled ghosts: the m...

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Main Authors: Will Barker, Michael Hobson, Anthony Lasenby, Yun-Cherng Lin, Zhiyuan Wei
Format: Article
Language:English
Published: Elsevier 2025-04-01
Series:Physics Letters B
Online Access:http://www.sciencedirect.com/science/article/pii/S0370269325000760
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author Will Barker
Michael Hobson
Anthony Lasenby
Yun-Cherng Lin
Zhiyuan Wei
author_facet Will Barker
Michael Hobson
Anthony Lasenby
Yun-Cherng Lin
Zhiyuan Wei
author_sort Will Barker
collection DOAJ
description The Poincaré gauge theory (PGT) of gravity provides a viable formulation of general relativity (Einstein–Cartan theory), and a popular model-building framework for modified gravity with torsion. Notoriously, however, the PGT terms which propagate vector torsion lead to strongly-coupled ghosts: the modern view is that only scalar torsion can propagate. To fix this, we revisit the concept of embedding explicit mass scales in scale-invariant theories, showing how the Klein–Gordon theory naturally leads to a slowly-rolling inflaton. We then show that the unique scale-invariant embedding of PGT leads to two new terms, one of which is the Maxwell term for vector torsion. We provide the full spectrum of quantum particles in the resulting theory. Our result means that every PGT is conformal and – after a two-decade hiatus – vector torsion is back on the menu.
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series Physics Letters B
spelling doaj-art-08fa385b4a3d41d6b207ee1f5546f5ad2025-08-20T02:50:45ZengElsevierPhysics Letters B0370-26932025-04-0186313931610.1016/j.physletb.2025.139316Every Poincaré gauge theory is conformal: A compelling case for dynamical vector torsionWill Barker0Michael Hobson1Anthony Lasenby2Yun-Cherng Lin3Zhiyuan Wei4Astrophysics Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK; Kavli Institute for Cosmology, Madingley Road, Cambridge CB3 0HA, UK; Corresponding author.Astrophysics Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UKAstrophysics Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK; Kavli Institute for Cosmology, Madingley Road, Cambridge CB3 0HA, UKAstrophysics Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK; Kavli Institute for Cosmology, Madingley Road, Cambridge CB3 0HA, UKAstrophysics Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK; Institute for Complex Quantum Systems, Ulm University, Albert-Einstein-Allee, 89069 Ulm, GermanyThe Poincaré gauge theory (PGT) of gravity provides a viable formulation of general relativity (Einstein–Cartan theory), and a popular model-building framework for modified gravity with torsion. Notoriously, however, the PGT terms which propagate vector torsion lead to strongly-coupled ghosts: the modern view is that only scalar torsion can propagate. To fix this, we revisit the concept of embedding explicit mass scales in scale-invariant theories, showing how the Klein–Gordon theory naturally leads to a slowly-rolling inflaton. We then show that the unique scale-invariant embedding of PGT leads to two new terms, one of which is the Maxwell term for vector torsion. We provide the full spectrum of quantum particles in the resulting theory. Our result means that every PGT is conformal and – after a two-decade hiatus – vector torsion is back on the menu.http://www.sciencedirect.com/science/article/pii/S0370269325000760
spellingShingle Will Barker
Michael Hobson
Anthony Lasenby
Yun-Cherng Lin
Zhiyuan Wei
Every Poincaré gauge theory is conformal: A compelling case for dynamical vector torsion
Physics Letters B
title Every Poincaré gauge theory is conformal: A compelling case for dynamical vector torsion
title_full Every Poincaré gauge theory is conformal: A compelling case for dynamical vector torsion
title_fullStr Every Poincaré gauge theory is conformal: A compelling case for dynamical vector torsion
title_full_unstemmed Every Poincaré gauge theory is conformal: A compelling case for dynamical vector torsion
title_short Every Poincaré gauge theory is conformal: A compelling case for dynamical vector torsion
title_sort every poincare gauge theory is conformal a compelling case for dynamical vector torsion
url http://www.sciencedirect.com/science/article/pii/S0370269325000760
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AT yunchernglin everypoincaregaugetheoryisconformalacompellingcasefordynamicalvectortorsion
AT zhiyuanwei everypoincaregaugetheoryisconformalacompellingcasefordynamicalvectortorsion