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In this work we investigate the Weihrauch degree of the problem $\mathsf{DS}$ of finding an infinite descending sequence through a given ill-founded linear order, which is shared by the problem $\mathsf{BS}$ of finding a bad sequence…

Logic · Mathematics 2024-01-31 Jun Le Goh , Arno Pauly , Manlio Valenti

The principle $ADS$ asserts that every linear order on $\omega$ has an infinite ascending or descending sequence. This has been studied extensively in the reverse mathematics literature, beginning with the work of Hirschfeldt and Shore. We…

Logic · Mathematics 2016-05-23 Eric P. Astor , Damir D. Dzhafarov , Reed Solomon , Jacob Suggs

We explore the low levels of the structure of the continuous Weihrauch degrees of first-order problems. In particular, we show that there exists a minimal discontinuous first-order degree, namely that of $\accn$, without any determinacy…

Logic · Mathematics 2024-01-24 Arno Pauly , Giovanni Soldà

We study the computational content of various theorems with reverse mathematical strength around Arithmetical Transfinite Recursion ($\mathsf{ATR}_0$) from the point of view of computability-theoretic reducibilities, in particular Weihrauch…

Logic · Mathematics 2019-05-17 Jun Le Goh

We introduce the notion of the \emph{first-order part} of a problem in the Weihrauch degrees. Informally, the first-order part of a problem $\mathsf{P}$ is the strongest problem with codomaixn $\omega$ that is Weihrauch reducible to…

Logic · Mathematics 2023-01-31 Damir D. Dzhafarov , Reed Solomon , Keita Yokoyama

An algorithm is proposed for solving optimization problems arising in neural network training for supervised learning. The unique feature of the algorithm is the use of an auxiliary loss, in addition to the original loss employed for model…

Optimization and Control · Mathematics 2026-05-11 Yunlang Zhu , Lingjun Guo , Zahra Khatti , Xiaoyi Qu , Chia-Yuan Wu , Lara Zebiane , Frank E. Curtis

We study long chains of iterated weak* derived sets, that is sets of all weak* limits of bounded nets, of subspaces with the additional property that the penultimate weak* derived set is a proper norm dense subspace of the dual. We extend…

Functional Analysis · Mathematics 2024-08-05 Zdeněk Silber

In this paper we study the notion of first-order part of a computational problem, first introduced by Dzhafarov, Solomon, and Yokoyama, which captures the "strongest computational problem with codomain $\mathbb{N}$ that is Weihrauch…

Logic · Mathematics 2023-05-01 Giovanni Solda , Manlio Valenti

In this paper we study Weihrauch reducibility for multi-valued functions on represented spaces. We call the corresponding equivalence classes Weihrauch degrees and we show that the corresponding partial order induces a lower semi-lattice…

Logic · Mathematics 2011-01-07 Vasco Brattka , Guido Gherardi

The Weihrauch degrees and strong Weihrauch degrees are partially ordered structures representing degrees of unsolvability of various mathematical problems. Their study has been widely applied in computable analysis, complexity theory, and…

Logic · Mathematics 2017-04-06 Damir Dzhafarov

The Weihrauch degrees are a tool to gauge the computational difficulty of mathematical problems. Often, what makes these problems hard is their discontinuity. We look at discontinuity in its purest form, that is, at otherwise constant…

Logic · Mathematics 2024-07-19 Rupert Hölzl , Keng Meng Ng

Matthias Schr\"oder has asked the question whether there is a weakest discontinuous problem in the continuous version of the Weihrauch lattice. Such a problem can be considered as the weakest unsolvable problem. We introduce the…

Logic · Mathematics 2025-10-14 Vasco Brattka

We demonstrate that techniques of Weihrauch complexity can be used to get easy and elegant proofs of known and new results on initial value problems. Our main result is that solving continuous initial value problems is Weihrauch equivalent…

Logic in Computer Science · Computer Science 2025-10-14 Vasco Brattka , Hendrik Smischliaew

This paper is the second in a series of works on weak convergence of one-step schemes for solving stochastic differential equations (SDEs) with one-sided Lipschitz conditions. It is known that the super-linear coefficients may lead to a…

Numerical Analysis · Mathematics 2024-10-29 Yuying Zhao , Xiaojie Wang , Zhongqiang Zhang

In this paper, we establish the well-posedness of Cauchy problems for weak solutions to second-order degenerate parabolic equations with a non-smooth, time-dependent degenerate elliptic part that includes both bounded and unbounded…

Analysis of PDEs · Mathematics 2025-12-04 Khalid Baadi

We prove the global-in-time existence of nonnegative weak solutions to a class of fourth order partial differential equations on a convex bounded domain in arbitrary spatial dimensions. Our proof relies on the formal gradient flow structure…

Analysis of PDEs · Mathematics 2015-07-21 Daniel Loibl , Daniel Matthes , Jonathan Zinsl

We propose a First-Order System Least Squares (FOSLS) method based on deep-learning for numerically solving second-order elliptic PDEs. The method we propose is capable of dealing with either variational and non-variational problems, and…

Numerical Analysis · Mathematics 2022-12-15 Francisco M. Bersetche , Juan Pablo Borthagaray

Many theorems of mathematics have the form that for a certain problem, e.g. a differential equation or polynomial (in)equality, there exists a solution. The sequential version then states that for a sequence of problems, there is a sequence…

Logic · Mathematics 2024-03-21 Dag Normann , Sam Sanders

We propose a deep learning approach to the obstacle problem inspired by the first-order system least-squares (FOSLS) framework. This method reformulates the problem as a convex minimization task; by simultaneously approximating the…

Numerical Analysis · Mathematics 2025-08-28 Gabriel Acosta , Eugenia Belén , Francisco M. Bersetche , Juan Pablo Borthagaray

Given a computable sequence of natural numbers, it is a natural task to find a G\"odel number of a program that generates this sequence. It is easy to see that this problem is neither continuous nor computable. In algorithmic learning…

Logic · Mathematics 2023-02-09 Vasco Brattka
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