cft_brtrg_implemented (#18)

* cft_brtrg_implemented * hello * aaa * aaa * remove ipynb checkpoint and add it to gitignore --------- Co-authored-by: victor <[email protected]>
VictorVanthilt · Feb 12, 2025 · 591cccf · 591cccf
1 parent a9b25ac
commit 591cccf
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Showing 2 changed files with 31 additions and 2 deletions.
diff --git a/.gitignore b/.gitignore
@@ -1,2 +1,3 @@
 Manifest.toml
+.ipynb_checkpoints
 .vscode
diff --git a/src/utility/cft.jl b/src/utility/cft.jl
@@ -24,8 +24,36 @@ function cft_data(scheme::TNRScheme; v=1, unitcell=1)
     return unitcell * (1 / (2π * v)) * log.(data[1] ./ data)
 end
 
-function cft_data(scheme::BTRG; v=1, unitcell=1)
-    throw(NotImplementedError("BTRG requires extra care with the environment tensors, this method will be implemented later"))
+function cft_data(scheme::BTRG; v=1, unitcell=1, is_real=true)
+    # make the indices
+    indices = [[i, -i, i + 1, -(i + unitcell)] for i in 1:unitcell]
+    indices[end][3] = 1
+
+    @tensor T_unit[-1 -2; -3 -4] := scheme.T[1 2; -3 -4] * scheme.S1[-2; 2] *
+                                    scheme.S2[-1; 1]
+    T = ncon(fill(T_unit, unitcell), indices)
+
+    outinds = Tuple(collect(1:unitcell))
+    ininds = Tuple(collect((unitcell + 1):(2unitcell)))
+
+    T = permute(T, outinds, ininds)
+    D, _ = eig(T)
+
+    data = zeros(ComplexF64, dim(space(D, 1)))
+
+    i = 1
+    for (_, b) in blocks(D)
+        for I in LinearAlgebra.diagind(b)
+            data[i] = b[I]
+            i += 1
+        end
+    end
+    data = filter(x -> real(x) > 0, data)
+    data = sort(data; by=x -> real(x), rev=true)
+    if is_real
+        data = real(data)
+    end
+    return unitcell * (1 / (2π * v)) * log.(data[1] ./ data)
 end
 
 function central_charge(scheme::TNRScheme, trunc::TensorKit.TruncationScheme,