Spinor_bundle Knowpia

In differential geometry, given a spin structure on an $n$ -dimensional orientable Riemannian manifold $(M,g),\,$ one defines the spinor bundle to be the complex vector bundle $\pi _{\mathbf {S} }\colon {\mathbf {S} }\to M\,$ associated to the corresponding principal bundle $\pi _{\mathbf {P} }\colon {\mathbf {P} }\to M\,$ of spin frames over $M$ and the spin representation of its structure group ${\mathrm {Spin} }(n)\,$ on the space of spinors $\Delta _{n}$ .

A section of the spinor bundle ${\mathbf {S} }\,$ is called a spinor field.

Formal definition edit

Let $({\mathbf {P} },F_{\mathbf {P} })$ be a spin structure on a Riemannian manifold $(M,g),\,$ that is, an equivariant lift of the oriented orthonormal frame bundle $\mathrm {F} _{SO}(M)\to M$ with respect to the double covering $\rho \colon {\mathrm {Spin} }(n)\to {\mathrm {SO} }(n)$ of the special orthogonal group by the spin group.

The spinor bundle ${\mathbf {S} }\,$ is defined ^[1] to be the complex vector bundle

{\mathbf {S} }={\mathbf {P} }\times _{\kappa }\Delta _{n}\,

associated to the spin structure

{\mathbf {P} }

via the spin representation

\kappa \colon {\mathrm {Spin} }(n)\to {\mathrm {U} }(\Delta _{n}),\,

where

{\mathrm {U} }({\mathbf {W} })\,

denotes the group of unitary operators acting on a Hilbert space

{\mathbf {W} }.\,

It is worth noting that the spin representation

\kappa

is a faithful and unitary representation of the group

{\mathrm {Spin} }(n).

^[2]

Notes edit

^ Friedrich, Thomas (2000), Dirac Operators in Riemannian Geometry, American Mathematical Society, ISBN 978-0-8218-2055-1 page 53
^ Friedrich, Thomas (2000), Dirac Operators in Riemannian Geometry, American Mathematical Society, ISBN 978-0-8218-2055-1 pages 20 and 24

Summary

Formal definition edit

See also edit

Notes edit

Further reading edit