Math 582, Fall 2017


Course Title:  Introduction to C*-algebra theory

Instructor:  Nigel Higson

Class Meeting Times:  Mondays, Wednesdays and Fridays, 9:05-9:55 in 106 McAllister

Office Hours:  By appointment in 228 McAllister (contact me in class or by email)

Overview:  C*-algebra theory is (or at least began as) the study of  relations among  operators on Hilbert space, and especially the study of  the different ways in which specific relations may be realized on Hilbert space.  There are obvious relations with group theory (via unitary group representations) and quantum theory (via the canonical commutation and anticommutation relations, among other things).   I will try to develop the basic theory of C*-algebras in the class, roughly as follows:

Hilbert spaces and projection operators. Adjoint and norm. Unitary operators, isometries and partial isometries.  Spectrum of bounded and unbounded operators.

Commutative Banach algebras.   Spectrum and spectral radius formula. Gelfand transform. Definition and characterization of commutative C*-algebras. Functional calculus.

C*-Algebra fundamentals.   Basic definitions. Morphisms between C*-algebras, ideals and quotients. States, representations and  the GNS construction.

The C*-algebra of compact operators. Definitions. Representations.  Applications.

Approximately finite-dimensional  algebras.    Bratteli diagrams.  Dimension groups. Classification theory for AF algebras.

Group C*-algebras. C*-algebras of locally compact groups.  Crossed product algebras.  Amenability.  Irrational rotation algebras and other examples.

Approximation properties.  Tensor products,  exactness and nuclearity.

Other topics, as time permits. Cuntz algebras. Extensions. Completely positive mappings.

Text: There will be no text, but here is a list of recommended books and lecture notes.

Course and Grading Policies:  Attendance at all lectures is very strongly encouraged! In addition to class attendance and participation, a variety of homework problems and assignments will be provided that I hope will help deepen everyone’s understanding of the material discussed in class.   There will be no exams. Grades will be assessed on the basis of class participation (50%) and homework (50%).

Prerequisites: A good grasp of linear algebra; some familiarity with basic measure theory and basic functional analysis.  If in doubt, please contact me.

Academic Integrity: Academic integrity is the pursuit of scholarly activity in an open, honest and responsible manner. Academic integrity is a basic guiding principle for all academic activity at The Pennsylvania State University, and all members of the University community are expected to act in accordance with this principle. Consistent with this expectation, the University's Code of Conduct states that all students should act with personal integrity, respect other students' dignity, rights and property, and help create and maintain an environment in which all can succeed through the fruits of their efforts.

Students with Disabilities: Penn State welcomes students with disabilities into the University's educational programs. If you have a disability-related need for reasonable academic adjustments in this course, contact Student Disability Resources at 814-863-1807 (V/TTY). For further information, please visit Student Disability Resources web site: . In order to receive consideration for accommodations, you must contact SDR and provide documentation (see the  documentation guidelines at If the documentation supports your request for reasonable accommodations, SDR will provide you with an accommodation letter identifying appropriate academic adjustments. Please share this letter with me and discuss the accommodations with me as soon as possible.

Information on Available Counseling & Psychological Services: Students with an interest in obtaining counseling services may wish to contact the Penn State Counseling & Psychological Services Office.  More information about the Counseling & Psychological Services Office can be found here:


Nigel Higson - 2017