Optimal Sobolev inequalities in the hyperbolic space

This paper characterizes the optimal rearrangement-invariant function norm on the left-hand side of the mmth order Sobolev inequality in nn-dimensional hyperbolic space for $1 \leq m < n,providingconcreteexamplesthatyieldnew,improvedinequalitiesindelicatelimitingcases,particularlywhen, providing concrete examples that yield new, improved inequalities in delicate limiting cases, particularly when m \geq 3$.

Zdeněk Mihula2026-03-05🔢 math

Adaptive Multilevel Newton: A Quadratically Convergent Optimization Method

This paper introduces an adaptive multilevel Newton-type method that automatically switches to full Newton steps once quadratic convergence is achievable, thereby overcoming the initial slow convergence of standard Newton methods while consistently outperforming both first-order and classical multilevel approaches on strongly convex and self-concordant functions.

Nick Tsipinakis, Panagiotis Tigkas, Panos Parpas2026-03-05🔢 math

Non-minimality and instability of brake orbits for natural Lagrangians on Riemannian manifolds

This paper establishes that non-constant periodic brake orbits in natural Lagrangian systems on Riemannian manifolds are never action minimizers and are generally linearly or spectrally unstable under specific dimensional and non-degeneracy conditions, a result derived by analyzing local index contributions via Seifert collar coordinates and illustrated through explicit computations for classical mechanical systems.

Luca Asselle, Xijun Hu, Alessandro Portaluri + 1 more2026-03-05🔢 math