Cayley 4-form, comass, and triality isomorphisms
Differential Geometry
2008-10-24 v2 Metric Geometry
Representation Theory
Abstract
Following an idea of Dadok, Harvey and Lawson, we apply the triality property of SO(8) to study the comass of certain self-dual 4-forms on R^8. In particular, we prove that the Cayley 4-form has comass 1 and that any self-dual 4-form realizing the maximal Wirtinger ratio is SO(8)-conjugate to the Cayley 4-form. We also use triality to prove that the stabilizer in SO(8) of the Cayley form is Spin(7). The results have applications in systolic geometry, calibrated geometry, and Spin(7) manifolds.
Cite
@article{arxiv.0801.0283,
title = {Cayley 4-form, comass, and triality isomorphisms},
author = {Mikhail G. Katz and Steven Shnider},
journal= {arXiv preprint arXiv:0801.0283},
year = {2008}
}
Comments
20 pages