Operator-norm bounds and a quadratic lower-growth example for the special Euclidean algebra se(3)

Abstract

We prove operator-norm and gradient Lipschitz bounds for exponential-map parameterizations on the special Euclidean algebra se(3), providing an explicit example of intermediate polynomial growth behavior. Using the contraction property of the SO(3) left Jacobian, we show that ||exp(theta)||_op <= 1 + ||theta||_F for all theta in se(3). We then derive a self-contained O(R^2) upper bound for the gradient Lipschitz constant, with explicit constant 4.02, and construct an objective J* satisfying L_J*(R; se(3)) >= 0.0505 R^2 for R >= 2. These results place se(3) between compact Lie algebras, where the Lipschitz constant remains bounded, and Lie algebras with hyperbolic elements, where it grows exponentially. The upper and lower bounds are obtained for different objective classes; no minimax optimality claim is made.