Manuscript X-C-ST@1 · X-C-ST.tex · proposition · b679954e
Proposition: Three-term variation
Three-term variation and the completed identity › Proof of record · lines 1541–1623 · proof included or linked
X-C-ST@1#prop:variation, X-C-ST@1#eq:variation, X-C-ST@1#eq:var1, X-C-ST@1#eq:var2
For arbitrary smooth classical backgrounds and arbitrary compact interior generators,
The first term is coefficientwise in . The other two are the dressed coordinate and switch defects.
Writing
the coefficient formulae are
Proof. Let . By Lemma lem:advanced,
The defect definitions give
Subtracting,
The right-hand side is a compact formal source: has support in , and the coefficients of have compact generator support.
The difference is advanced-type. Indeed, are advanced-type, and each coefficient of has compact generator support. No assumption that an unexpanded diffeomorphism preserves the completion causal relation is needed.
Advanced uniqueness therefore yields
Subtract and apply . Using proves (eq:variation).
Every coefficient of is a smooth compact function, so its -image lies in . Finally expand
The degree-one and degree-two coefficients are exactly (eq:var1) and (eq:var2).
Displayed formulas in this passage
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X-C-ST@1#eq:var2 · line 1564
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