
Preface
Very early in my study of physics, Weyl be-
came one of my gods. I use the wor d “god”
rather than, say, “outstanding teacher” for the
ways of gods are mysterious, inscrutable, and
beyond the comprehension of ordinary mor-
tals.
Julian Schwinger
This book gives an introduction to combinatorial aspects of normal ordering in the Weyl
algebra and some of its close relatives. For our considerations, the Weyl algebra is the
complex algebra generated by two letters U and V (with unit I) satisfying the commutation
relation
UV − VU = I.
A concrete representation is given by the operators D =
d
dx
and X,where(Xf)(x)=xf(x)
for any function f. In this represent ...