Improve knowledge base

1 files changed, 1 insertions, 1 deletions

diff --git a/source/know/concept/kubo-formula/index.md b/source/know/concept/kubo-formula/index.md
index 41fda3c..774ddf7 100644
--- a/source/know/concept/kubo-formula/index.md
+++ b/source/know/concept/kubo-formula/index.md
@@ -105,7 +105,7 @@ Where we have defined the **retarded correlation function** $$C^R_{A H_1}(t, t')
 $$\begin{aligned}
     \boxed{
         C^R_{A H_1}(t, t')
-        \equiv - \frac{i}{\hbar} \Theta(t \!-\! t') \Expval{\Comm{\hat{A}_I(t)}{\hat{H}_{1,I}(t')}}_0
+        \equiv - \frac{i}{\hbar} \Theta(t - t') \Expval{\Comm{\hat{A}_I(t)}{\hat{H}_{1,I}(t')}}_0
     }
 \end{aligned}$$