fixed typo

physicalloss-code.ipynb

@@ -90,7 +90,7 @@
     "\n",
     "Next, we set up a simple NN with 8 fully connected layers and `tanh` activations with 20 units each. \n",
     "\n",
-    "We'll also define the `boundary_tx` function which gives an array of constraints for the solution (all for $=0.5$ in this example), and the `open_boundary` function which stores constraints for $x= \\pm1$ being 0."
+    "We'll also define the `boundary_tx` function which gives an array of constraints for the solution (all for $t=0.5$ in this example), and the `open_boundary` function which stores constraints for $x= \\pm1$ being 0."
    ]
   },
   {