From adfa46ff8395142cdc233f9d69eff343267726ca Mon Sep 17 00:00:00 2001
From: Nuwan Yapa <yapanuwan@gmail.com>
Date: Tue, 25 Nov 2025 16:43:27 -0500
Subject: [PATCH] Understanding 1st quadrant behavior in p-space vs HO basis

---
 calculations/XZ/p_space_vs_HO.jl | 74 ++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 calculations/XZ/p_space_vs_HO.jl

diff --git a/calculations/XZ/p_space_vs_HO.jl b/calculations/XZ/p_space_vs_HO.jl
new file mode 100644
index 0000000..b3db2c5
--- /dev/null
+++ b/calculations/XZ/p_space_vs_HO.jl
@@ -0,0 +1,74 @@
+using Plots
+
+include("../EC.jl")
+include("../ho_basis.jl")
+include("../p_space.jl")
+
+function solve_E(H0, H1, c_vals, near_E)
+    out_E = ComplexF64[]
+    for c in c_vals
+        println("Solving for c = $c")
+
+        H = H0 + c .* H1
+
+        evals, _ = eigs(H, sigma=near_E, maxiter=5000, ritzvec=false, check=1)
+        new_E = nearest(evals, near_E)
+        push!(out_E, new_E)
+    end
+    return out_E
+end
+
+# paramters of the system
+
+angle = 0.0 * pi
+μ = 0.5
+l = 0
+V1 = -5
+R1 = sqrt(3)
+V2 = 2
+R2 = sqrt(10)
+
+n_EC = 8
+train_cs = (0.7 .+ 0.05 * randn(n_EC)) - 1im * (0.2 .+ 0.05 * randn(n_EC))
+near_E = 0.2 + 0.2im
+
+# HO basis
+
+HO_Es = zeros(ComplexF64, n_EC)
+begin
+    println("HO basis calculation")
+    μω_gen = 0.5 * exp(-1im * angle)
+    n_max = 40
+    ns = collect(0:n_max)
+    ls = fill(l, n_max + 1)
+
+    T = get_sp_T_matrix(ns, ls; μω_gen=μω_gen, μ=μ)
+    V = V1 .* V_Gaussian.(R1, l, ns, transpose(ns); μω_gen=μω_gen) + V2 .* V_Gaussian.(R2, l, ns, transpose(ns); μω_gen=μω_gen)
+
+    HO_Es .= solve_E(T, V, train_cs, near_E)    
+end
+
+# p-space
+
+p_space_Es = zeros(ComplexF64, n_EC)
+begin
+    println("p-space calculation")
+    vertices = [0, 4 * exp(-1im * angle)]
+    subdivisions = [256]
+    ks, ws = get_mesh(vertices, subdivisions)
+
+    V_of_r(r) = V1 * exp(-r^2 / R1^2) + V2 * exp(-r^2 / R2^2)
+    V_mat_elem(k, kp) = Vl_mat_elem(V_of_r, l, k, kp; atol=10^-5, maxevals=10^5, R_cutoff=16)
+    V = get_V_matrix(V_mat_elem, ks, ws)
+    T = get_T_matrix(ks, μ)
+
+    p_space_Es .= solve_E(T, V, train_cs, near_E)
+end
+
+# Plotting
+
+scatter(real.(HO_Es), imag.(HO_Es), label="HO basis", marker=:circle, color=:blue)
+scatter!(real.(p_space_Es), imag.(p_space_Es), label="p-space", marker=:circle, color=:red)
+xlabel!("Re(E)")
+ylabel!("Im(E)")
+savefig("temp/p_space_vs_HO.pdf")
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