arXiv Computer Vision By Faian Conrad

Existence of Minimizers for the Gaussian Mumford-Shah Model via Covariance Floors on the Value Distribution

Read the original on arXiv Computer Vision →

The paper investigates the Gaussian Mumford–Shah model, which segments images by minimizing a Gaussian negative log‑likelihood plus a perimeter penalty. It shows that the energy can become unbounded below if a region’s covariance degenerates, but imposing a quantitative covariance floor (or equivalently a uniform Hölder continuity condition on the histogram’s one‑dimensional marginals) guarantees a lower bound and ensures the existence of a minimizer. The authors argue that such covariance floors are generic for noisy images, cannot be scale‑independent, and use the theory to prove convergence of practical regularized models and numerical methods.

Machine-generated by The Flow from the publisher's headline and feed description — not written or checked by a human. The full article lives at arXiv Computer Vision.

arXiv Machine Learning
Sep 15

Riemannian ascent--descent for nonconvex nonconcave minimax landscapes: convergence to basin saddle points and applications to distributionally robust optimization

The paper introduces a new convergence framework for solving distributionally robust optimization problems formulated as nonconvex, nonconcave minimax problems over a Euclidean space and a Riemannian manifold. It defines a "basin saddle point"—a locally defined Nash equilibrium—and proves that a Riemannian gradient ascent–descent algorithm converges to such points under a local Łojasiewicz growth condition. The authors apply this theory to a statistical risk DRO problem over Gaussian measures, deriving explicit convergence rates and constants in terms of data dimension, loss moments, and reference covariance.

By Rishabh Dixit, Pranav Upadrashta, Alex Cloninger
arXiv Machine Learning
Sep 23

Relative Wasserstein Angle and the Problem of the $W_2$-Nearest Gaussian Distribution

The paper introduces a geometric framework for measuring how far empirical datasets deviate from the Gaussian family using optimal transport theory. It defines two new quantities—the relative Wasserstein angle and the orthogonal projection distance—based on the cone structure of the relative translation invariant quadratic Wasserstein space, and shows that the usual moment‑matching Gaussian is not generally the $W_2$‑nearest Gaussian. Closed‑form expressions are derived for one‑dimensional and several location–scale families, while a numerical approximation is proposed for higher dimensions, with experiments demonstrating convergence, stability, and the angle’s robustness as a non‑Gaussianity indicator.

By Binshuai Wang, Peng Wei