Initial commit

Base modular structure (phase space, Fermi function)
Initial .gitignore

beta_spectrum/components/phase_space.py

@@ -0,0 +1,19 @@
+# components/phase_space.py
+import numpy as np
+from ..base import SpectrumComponent
+
+
+class PhaseSpace(SpectrumComponent):
+    def __init__(self, W0: float, m_nu: float = 0.0):
+        self.W0 = W0
+        self.m_nu = m_nu
+
+    def __call__(self, W: np.ndarray) -> np.ndarray:
+        p = np.sqrt(W**2 - 1.0)
+        Wv = self.W0 - W
+
+        # neutrino mass generalization
+        if self.m_nu == 0:
+            return p * W * Wv**2
+        else:
+            return p * W * Wv * np.sqrt(Wv**2 - self.m_nu**2)