International Journal of Mathematics and Mathematical Sciences
Volume 27 (2001), Issue 3, Pages 189-195

Some examples of nontrivial homotopy groups of modules

C. Joanna Su

Department of Mathematical Sciences, State University of New York at Binghamton, Binghamton 13902-6000, NY, USA

Received 7 June 2000

Copyright © 2001 C. Joanna Su. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The concept of the homotopy theory of modules was discovered by Peter Hilton as a result of his trip in 1955 to Warsaw, Poland, to work with Karol Borsuk, and to Zurich, Switzerland, to work with Beno Eckmann. The idea was to produce an analog of homotopy theory in topology. Yet, unlike homotopy theory in topology, there are two homotopy theories of modules, the injective theory, π¯n(A,B), and the projective theory, π¯n(A,B). They are dual, but not isomorphic. In this paper, we deliver and carry out the precise calculation of the first known nontrivial examples of absolute homotopy groups of modules, namely, π¯n(/,/),π¯n(,/), and π¯n(,), where / and are regarded as Ck-modules with trivial action. One interesting phenomenon of the results is the periodicity of these homotopy groups, just as for the Ext groups.