Resonant Spacetime Hypothesis 2.0

Compute the spiral-phase coherence:  

```python  

from healpy import alm2map, map2alm  

def phase_gradient(map_Q, map_U, L):  

    # Compute B-mode alm  

    alm_B = map2alm(map_Q + 1j * map_U, lmax=L)[2]  # B-mode alms  

    # Calculate [arg(B)]  

    grad_phase = np.zeros(L)  

    for l in range(2, L):  

        m_values = np.arange(-l, l + 1)  

        phases = np.angle(alm_B[ssht.elm2ind(l, m_values)])