The shear construction

  • Marco Freibert
  • Andrew Swann
Original Paper


The twist construction is a method to build new interesting examples of geometric structures with torus symmetry from well-known ones. In fact it can be used to construct arbitrary nilmanifolds from tori. In our previous paper, we presented a generalization of the twist, a shear construction of rank one, which allowed us to build certain solvable Lie algebras from \({\mathbb R}^n\) via several shears. Here, we define the higher rank version of this shear construction using vector bundles with flat connections instead of group actions. We show that this produces any solvable Lie algebra from \({\mathbb R}^n\) by a succession of shears. We give examples of the shear and discuss in detail how one can obtain certain geometric structures (calibrated \( G _2\), co-calibrated \( G _2\) and almost semi-Kähler) on three-step solvable Lie algebras by shearing almost Abelian Lie algebras. This discussion yields a classification of calibrated \( G _2\)-structures on Lie algebras of the form \((\mathfrak {h}_3\oplus {\mathbb R}^3)\rtimes {\mathbb R}\).


Generalization of twist construction Solvable Lie groups Calibrated and cocalibrated G2-structures 

Mathematics Subject Classification

Primary 53C15 Secondary 53C12 22E25 32C37 



Funding was provided by Det Frie Forskningsråd (Grant Nos. DFF - 4002-00125, DFF - 6108-00358).


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Authors and Affiliations

  1. 1.Mathematisches SeminarChristian-Albrechts-Universität zu KielKielGermany
  2. 2.Department of MathematicsAarhus UniversityAarhusDenmark

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