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symmetric monoidal (∞,1)-category of spectra
The Pfaffian of a skew-symmetric matrix is a square root of its determinant.
Let be a skew-symmetric -matrix with entries in some field (or ring) .
The Pfaffian is the element
where
runs over all permutations of elements;
is the signature of a permutation.
Expressed equivalently in terms of the Levi-Civita symbol and using the Einstein summation convention the Pfaffian is
(Pfaffian is square root of determinant)
Let be a skew-symmetric -matrix with entries in some field (or ring) .
Then the Pfaffian of (1) is a square root of the determinant of :
Proofs are spelled out for instance in Haber 15, Sections 2 and 3
Let be the Grassmann algebra on generators , which we think of as a vector
Then the Pfaffian is the Berezinian integral
Compare this to the Berezinian integral representation of the determinant, which is
Pfaffians appear in the expression of certain multiparticle wave functions. Most notable is the pfaffian state of spinless electrons
where denotes the Pfaffian of the matrix whose labels are and is the filling fraction, which is an even integer. For Pfaffian state see
Basics:
See also
J.-G. Luque, J.-Y. Thibon, Pfaffian and hafnian identities in shuffle algebras, math.CO/0204026
Claudiu Raicu, Jerzy Weyman, Local cohomology with support in ideals of symmetric minors and Pfaffians, arxiv/1509.03954
Haber, Notes on antisymmetric matrices and the pfaffian, pdf
There is also a deformed noncommutative version of Pfaffian related to quantum linear groups:
Pfaffian variety is subject of 4.4 in
Relation to -functions is discussed in
Other articles:
A combinatorial construction proves an identity for the product of the Pfaffian of a skew-symmetric matrix by the Pfaffian of one of its submatrices. Several applications of this identity are followed by a brief history of Pfaffians.
Discussion of Euler forms (differential form-representatives of Euler classes in de Rham cohomology) as Pfaffians of curvature forms:
Shiing-Shen Chern, A simple intrinsic proof of the Gauss-Bonnet formula for closed Riemannian manifolds, Annals of Mathematics Second Series 45:4 (1944) 747-752 (jstor:1969302)
Varghese Mathai, Daniel Quillen, below (7.3) of Superconnections, Thom classes, and equivariant differential forms, Topology Volume 25, Issue 1, 1986 (10.1016/0040-9383(86)90007-8)
Siye Wu, Section 2.2 of Mathai-Quillen formalism, pages 390-399 in Encyclopedia of Mathematical Physics 2006 (arXiv:hep-th/0505003)
Gerard Walschap, ch. 6.3 of Metric structures in differential deometry, Graduate Texts in Mathematics, Springer 2004
Hiro Lee Tanaka, Pfaffians and the Euler class, 2014 (pdf)
Liviu Nicolaescu, Section 8.3.2 of Lectures on the Geometry of Manifolds, 2018 (pdf, MO comment)
Last revised on June 12, 2024 at 16:35:01. See the history of this page for a list of all contributions to it.