1 files changed, 9 insertions, 0 deletions
diff --git a/param.ccl b/param.ccl
index 415358c..21cd349 100644
--- a/param.ccl
+++ b/param.ccl
@@ -105,6 +105,15 @@ boolean print_timing_stats \
 {
 } "false"
 
+# By default, we find apparent horizons by solving the equation
+#  Theta(h) = 0
+# This parameter allows the RHS to be set to any specified constant,
+# to find a surface of constant expansion.
+real surface_expansion[11] "search for a surface with this (constant) expansion"
+{
+*:* :: "any real number"
+} 0.0
+
 ################################################################################
 
 #