Course  Materials  

Cyclic Homology Theory
This course on cyclic homology is split into 3 parts. The first and the third one will be taught by JeanLouis Loday, and the second one by Mariusz Wodzicki. Part I is devoted to the very foundations. Part II reveals connections between advanced homological calculations regarding pseudodifferential symbols and operators, noncommutative residue and the Virasoro cocycle. Part III deals with topics ranging from Lie algebras to graphcomplexes. As a prerequisite for this course, the knowledge of basic notions of homological algebra is expected, and the knowledge of very basic differential geometry (familiarity with differential forms and connections) is encouraged. Part I:
One way of discovering the cyclic (co)homology theory is to unravel completely the most simple simplicial model of the circle. Comparing its simplicial structure with the nstratum (identified with the cyclic group of order n+1) gives right away the construction of the cyclic category. Then follows the definition of a cyclic module and all its (co)homology theories: simplicial, cyclic, negative cyclic, periodic. Then, one can apply them to different kinds of cyclic modules: among the most important ones are those which come from an associative algebra and those which come from a Hopf algebra. On the topological side, cyclic spaces give rise to topological spaces equipped with an action of the circle. The Chern character, which, historically, was the motivation for Alain Connes to set up the cyclic cohomology theory, permits us to compare algebraic Ktheory to cyclic homology. Part II:
This part is concerned with some more advanced computations. A detailed calculation of symbols, and of the algebra of pseudodifferential operators (of unbounded order as well as of order zero) will be presented. Connections with the noncommutative residue, the higher noncommutative residue, and the Virasoro cocycle will be described. Part III:
An important relationship with Lie algebras is given by the computation of the Lie algebra homology of matrices in terms of cyclic homology (LodayQuillenTsygan theorem). A variation involving Hochschild homology needs the notion of Leibniz algebras. It turns out that Leibniz algebras are strongly related to the SchoutenNijenhuis bracket. The same technique applied to Lie algebras of derivations of algebraic operads leads to different kinds of graphcomplexes (a la Kontsevich). Thus a graphcomplex can be interpreted as an operadic version of the cyclic complex. Their importance is due to the relationship with Teichmuller spaces and the outer automorphisms group of a free group. The Leibniz version leads to noncommutative graphcomplexes, yet to be fully explored. Course Summary:

Part I
JeanLouis Loday
Notes by P. Witkowski


Download  Last update  
27.11.2006 

Table of contents  


Part II
Mariusz Wodzicki
Notes by P. Witkowski


Download  Last update  
22.12.2006 

Table of contents  


Part III
JeanLouis Loday
Notes by P. Witkowski


Download  Last update  
16.04.2007 

Table of contents  

Exam  Exam questions  

The exam was on 30th January 2007. It consisted of the written part (five exercises) and oral part. In the oral part each student had to answer two questions: easy one and difficult one (chosen from the two difficult questions). Four students (on the graduate and undergraduate level) passed the exam. 
Exam, written and oral 