DIFFERENTIAL GEOMETRY SEMINAR

                             Monday, April 24

                            Communications 226
                                 3:45 p.m.


                             Albert Nijenhuis
                    (UW and University of Pennsylvania)

            CONNECTION-FREE STRUCTURES IN DIFFERENTIAL GEOMETRY


According to a commonly-held view, differential geometry is the study of
connections, associated with further structures, whether they be Riemannian
metrics or otherwise.

Notable exceptions are structures defined by tangent vector fields (with
applications to Lie groups, differential equations, etc.) and differential
forms (with applications to de Rham cohomology, for example).

This lecture deals with another kind of pointwise-defined structure, the
vector 1-forms: tensor fields of type (1,1).  (Their best known application
is to almost-complex structures.)

The talk will focus on differential invariants of vector 1-forms, and their
properties.  Some of these are illustrated with graphs, replacing otherwise
seemingly aimless calculations. Derivations (differential operators,
whether formal or real), which appear everywhere in D.G. (whence its name),
play an important part here, as well.


For more information about this seminar, view the Differential Geometry
Seminar World-Wide Web page at 

    https://www.math.washington.edu/~lee/Seminars/dg.html


To request disability accommodations, contact the Office of the ADA
Coordinator, at least ten days in advance of the event: 543-6450 (voice);
543-6452 (TDD); 685-3885 (FAX); access@u.washington.edu (E-mail).