From 3f31637dbc349493cd74a389d49413903f146bd1 Mon Sep 17 00:00:00 2001
From: Thomas Guillermo Albers Raviola <thomas@thomaslabs.org>
Date: Mon, 20 Jul 2026 14:18:41 +0200
Subject: Add wave operator

---
 tensors.mac | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'tensors.mac')

diff --git a/tensors.mac b/tensors.mac
index dea722a..6d7248a 100644
--- a/tensors.mac
+++ b/tensors.mac
@@ -19,3 +19,8 @@ contr(expr, var) ::= (
 
 /* Differentiate with respect to nth coordinate */
 cdiff(func, coord) := diff(func, ct_coords[coord])$
+
+/* Wave operator */
+box_op(func) := (
+  expand(contr(ug[μ,ν] * cdiff(cdiff(func, ν), μ), [μ,ν])
+    - contr(ug[μ,ν] * mcs[μ,ν,ρ] * cdiff(func, ρ), [μ,ν,ρ])))$
-- 
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