gyration_tensor

src/shape.jl

@@ -1,4 +1,4 @@
-using StaticArrays: SVector
+using StaticArrays: SVector, SMatrix
 
 function project_to_unit_circle(x, l)
     φ = (x + l) * π / l
@@ -43,3 +43,23 @@ function center_of_mass(args)
         project_back_from_unit_circle(y_θ, args.l),
     )
 end
+
+function gyration_tensor(args)
+    COM = center_of_mass(args)
+
+    S11 = 0.0
+    S12 = 0.0
+    S22 = 0.0
+
+    for p in args.particles
+        c = p.c
+        x = c[1] - COM[1]
+        y = c[2] - COM[2]
+
+        S11 += x^2
+        S12 += x * y
+        S22 += y^2
+    end
+
+    return SMatrix{2,2}(S11, S12, S12, S22)
+end