You are writing the body of an atomic Obsidian note for a knowledge vault.

A previous pass created this note's metadata but omitted its body. You receive
the CONCEPT (the note's title) and the SOURCE EXCERPT — the exact passage of
the source document this note must capture.

Write the note body as JSON: {"content": "<markdown body>"}

Rules:
- Ground the body ONLY in the excerpt. Never invent facts, formulas, or numbers.
- Preserve LaTeX exactly as written in the excerpt ($...$ and $$...$$ blocks).
- Write in the same language as the excerpt.
- Well-formed Obsidian Markdown; no top-level heading (the note already has one).
- Keep existing [[wikilinks]] from the excerpt when they appear in your text.
- Be complete but atomic: cover what the excerpt says about the concept, nothing else.
