refactor: Move Lorentz Group

HepLean/Lorentz/Group/Restricted.lean

@@ -0,0 +1,33 @@
+/-
+Copyright (c) 2024 Joseph Tooby-Smith. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Joseph Tooby-Smith
+-/
+import HepLean.Lorentz.Group.Basic
+import HepLean.Lorentz.Group.Proper
+import HepLean.Lorentz.Group.Orthochronous
+import HepLean.Meta.Informal
+/-!
+# The Restricted Lorentz Group
+
+This file is currently a stub.
+
+-/
+/-! TODO: Add definition of the restricted Lorentz group. -/
+/-! TODO: Prove member of the restricted Lorentz group is combo of boost and rotation. -/
+/-! TODO: Prove restricted Lorentz group equivalent to connected component of identity. -/
+
+noncomputable section
+
+open Matrix
+open Complex
+open ComplexConjugate
+
+namespace LorentzGroup
+
+informal_definition Restricted where
+  math :≈ "The subgroup of the Lorentz group consisting of elements which
+    are proper and orthochronous."
+  deps :≈ [``LorentzGroup, ``IsProper, ``IsOrthochronous]
+
+end LorentzGroup