Noncommutative differential geometry of matrix algebras. (English) Zbl 0704.53081

This paper is concerned with a noncommutative generalization of the exterior calculus in the following sense. Let Der(A) denote the Lie algebra of derivations of an associative algebra A with unit. Then the complex C(Der(A),A) of A-valued cochains of Der(A) is a graded differential algebra, and the smallest differential subalgebra \(\Omega_ D(A)\) of this complex which contains A is a natural generalization of the algebra of differential forms, the role of the Lie algebra of vector fields being played by Der(A).
In the paper under review the algebra A is identified with the algebra \(M_ n({\mathbb{C}})\) of complex \(n\times n\) matrices (n\(\geq 2)\). This gives rise to the so-called differential geometry of \(M_ n({\mathbb{C}})\) in which \(\Omega_ D(M_ n({\mathbb{C}})\) assumes the role of the algebra of differential forms. The existence of an invariant canonical symplectic 2- form is demonstrated for which the corresponding Poisson bracket is given by \(\{A,B\}=i[A,B]\). An invariant canonical Riemannian structure for \(M_ n({\mathbb{C}})\) is introduced and the resulting Hodge theory on \(\Omega_ D(M_ n({\mathbb{C}}))\) is developed. A Hermitian connection on the free Hermitian \(M_ n({\mathbb{C}})\) module of rank one is regarded as an analog of an electromagnetic potential. It is found that there is a unique potential with vanishing curvature that is not a pure gauge. This potential is gauge invariant and is related to the symplectic form.
Reviewer: H.Rund


53C80 Applications of global differential geometry to the sciences
15A75 Exterior algebra, Grassmann algebras
81T13 Yang-Mills and other gauge theories in quantum field theory
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[6] DOI: 10.1063/1.528917 · Zbl 0704.53082
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