DUALITY OF NORMALLY PRESENTED VARIETIES
Abstract
Let 
be a variety of the form 
where 
is a finite subdirectly irreducible algebra. We show that if 
is naturally dualizable (in the sense of D. M. Clark and B. A. Davey, i.e. with respect to the discrete topology) then the variety 
determined by all normal identities of 
(the so called nilpotent shift of 
) is also naturally dualizable. We give a finite algebra 
and a relational system 
, constructed explicitly from the system 
for 
, such that 
and 
dualizes 
.
The financial support provided by NATO Collaborative Research Grant LG 930302 and by the Council of Czech Government J14/98:153100011 is gratefully acknowledged. The paper was prepared during the 3rd and 4th authors' visit to Palacký University Olomouc in May 1995, June 1996 and during the 1st and 2nd authors' visit to Université de Montréal in October 1995.
