Dirichlet principal eigenvalue comparison theorems in geometry with torsion

We describe min-max formulas for the principal eigenvalue of a V-drift Laplacian defined by a vector field V on a geodesic ball of a Riemannian manifold N. Then we derive comparison results for the principal eigenvalue with the one of a spherically symmetric model space endowed with a radial vector field, under pointwise comparison of the corresponding radial sectional and Ricci curvatures, and of the radial component of the vector fields. These results generalize the known case V=0.