Contragenic Functions of Three Variables
  It is shown that harmonic functions from a simply connected domain in R^3 to R^3 cannot always be expressed as a sum of a monogenic (hyperholomorphic) function and an antimonogenic function, in contrast to the situation for complex numbers or quaternions. Harmonic functions orthogonal in L_2 to all such sums are termed "contragenic" and their properties are studied. A "Bergman kernel" and is derived, whose corresponding operator vanishes precisely on the contragenic functions. A graded orthonormal basis for the contragenic function in the ball B^3 is given. 
Cynthia Alvarez-Pe\~na and R. Michael Porter
math.CV