Manuscript I-B-G@2 · I-B-G-v2.tex · remark · 3b4d700f
Remark: Why a null-set argument would not suffice
The Sommerfeld–Carslaw–Dowker kernel › A precise class of kernel identities · lines 1311–1318
The extension across image boundaries in the proof is a joint-distribution construction. It is not justified merely by saying that the exceptional angular pairs have measure zero: a distribution can be supported on such a set. The heat and resolvent identities, together with Laplace uniqueness, fix the global distribution.