Definition. Ordered Berezin coefficients [fdip-008F]
AGENTDRAFTED
Let \(V\) be an \(N\)-dimensional vector space over
\(\mathbb k=\mathbb R\) or \(\mathbb C\), with an ordered basis
\(\xi _1,\ldots ,\xi _N\) of \(V^*\). The
Grassmann algebra on these generators is the
exterior algebra \(\Lambda (V^*)\). Multiplication is
written by juxtaposition, so
\[\xi _i\xi _j=-\xi _j\xi _i,\qquad \xi _i^2=0.\]
Its basis consists of \(1\) and the increasing words
\(\xi _{i_1}\cdots \xi _{i_r}\) with \(i_1<\cdots <i_r\); its
dimension is \(2^N\). A word of length \(r\) has degree \(r\).
Elements of even degree commute with every homogeneous element;
two homogeneous elements of degrees \(r,s\) commute with sign
\((-1)^{rs}\).
The Berezin integral with reversed top order is
the linear functional
\[I_\xi (f)=\text {coefficient of }\xi _N\cdots \xi _1
\text { in }f.\]
Thus \(I_\xi (\xi _N\cdots \xi _1)=1\) and it vanishes on all
lower degrees. Relative to the increasing top coefficient it
has the sign \((-1)^{N(N-1)/2}\). For \(N=0\) it is the identity
on \(\mathbb k\). This is the purely odd coefficient definition
of [etingof2024mathematical, v2, Definition 9.6, p. 128],
with the top order stated explicitly.
For \(n\) complex pairs, take \(2n\) independent generators
\(\psi _1,\bar \psi _1,\ldots ,\psi _n,\bar \psi _n\) and use
the paired functional
\[J_n(f)=\text {coefficient of }
\psi _1\bar \psi _1\cdots \psi _n\bar \psi _n
\text { in }f.\]
The bars label independent generators, not complex conjugates.
The symbols \(I_\xi \) and \(J_n\) keep these two top-order
conventions distinct. They are coefficient functionals, not
positive measures on ordinary field configurations.
For a positive-degree nilpotent element \(q\), define
\(e^q=\sum _{r\ge 0}q^r/r!\); only finitely many terms survive.
For a quadratic \(q\) in \(N\) generators, terms with \(2r>N\)
vanish. No analytic convergence is involved. The ordered
monomial basis is supplied formally by
Module.Basis.ExteriorAlgebra; this supports the
algebraic coordinates, not the Berezin or Gaussian identities.