Martin Hertweck's homepage 
German version
(currently not available) Last update: March 19, 2009 
I am Privatdozent (unsalaried lecturer) within the
Department of Mathematics at the
University of Stuttgart, located on
Campus Vaihingen. Postal address:
Email: hertweck@mathematik.unistuttgart.de 
PUBLICATIONS  

Please follow IMU's recommendation and make available electronically as much of your own work as feasible. Perhaps a good place to post preprints is the arXiv. I try my best!
The excercises, together with solutions (in german!): DVI or PS.
In a
preprint
from 2003,
Inger Christin Borge and
Olav Arnfinn Laudal
claimed to have answered the modular isomorphism problem in the affirmative.
But see their
own remark (seen on Benson's
Preprint
Archive).
Marco and I have written a note,
Central pgroup extensions: Laudal obstruction spaces revisited
(version DVI
and version PDF),
where we at least give an accessible and unified presention of
Borge's and Laudal's approach, and also briefly explain at what point
the proof breaks down.
A joke, only for the few who can understand it: I omitted the word "WIDE".
Units in integral group rings? The group of units in ZS_{3}, the integral group ring of the symmetric group on three letters, has some well known descriptions. I like in particular the geometric approach given by Marciniak and Sehgal [Units in group rings and geometry, Methods in ring theory (Levico Terme, 1997)] which yields nice generators and relations for the group of units. I have written it up for my own, Units in ZS_{3} (after Marciniak and Sehgal) (version DVI and PDF), since I wanted to see some pictures included. The original (often the better one) is available from Sehgal's homepage.
Problem/Challenge (Zassenhaus Conjecture for some "small groups"): Suppose that G is a finite group having a normal abelian 2group A with quotient G/A isomorphic to the symmetric group S_{3}. Is it true that units of 2power order in ZG are rationally conjugate to elements of ±G?
Integral group ring community. Research groups in different places of the world join efforts in the area of (integral) group rings, discussing topics such as algebraic structure, representation theory, and units, of group rings. Here is an incomplete list of those people. (You are missing? Something wrong? Then please mail to me.)

More 
If I were a SpringerVerlag Graduate Text in Mathematics, I would be Saunders Mac Lane's Categories for the Working Mathematician. I provide an array of general ideas useful in a wide variety of fields. Starting from foundations, I illuminate the concepts of category, functor, natural transformation, and duality. I then turn to adjoint functors, which provide a description of universal constructions, an analysis of the representation of functors by sets of morphisms, and a means of manipulating direct and inverse limits.  
Which Springer GTM would you be? The Springer GTM Test 

Finally, want to see some math pictures? Then click here.