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We remark a variant of the existence part of the fundamental theorem of calculus, which, together with the Lebesgue differentiation theorem, constitute a new proof that every Riemann-integrable function on a compact interval having limit…

General Mathematics · Mathematics 2020-06-09 Yu-Lin Chou

A skew-morphism $\varphi$ of a finite group $A$ is a permutation on $A$ such that $\varphi(1)=1$ and $\varphi(xy)=\varphi(x)\varphi^{\pi(x)}(y)$ for all $x,y\in A$ where $\pi:A\to\mathbb{Z}_{|\varphi|}$ is an integer function. A…

Group Theory · Mathematics 2018-06-20 Naer Wang , Kan Hu , Kai Yuan , Junyang Zhang

Computational image reconstruction algorithms generally produce a single image without any measure of uncertainty or confidence. Regularized Maximum Likelihood (RML) and feed-forward deep learning approaches for inverse problems typically…

Machine Learning · Computer Science 2020-12-18 He Sun , Katherine L. Bouman

$\lambda\varphi^4$ theory at finite temperature suffers from infrared divergences near the temperature at which the symmetry is restored. These divergences are handled using renormalization group methods. Flow equations which use a fiducial…

High Energy Physics - Theory · Physics 2007-05-23 F. Freire , Denjoe O'Connor , C. R. Stephens , M. A. van Eijck

Theoretical guarantees for the robust solution of inverse problems have important implications for applications. To achieve both guarantees and high reconstruction quality, we propose learning a pixel-based ridge regularizer with a…

Optimization and Control · Mathematics 2025-01-07 Sebastian Neumayer , Fabian Altekrüger

For two-parameter families of dissipative twist maps, we investigate the dynamics of invariant graphs as well as the thresholds for their existence and breakdown. Our main results are as follows: (1) For arbitrarily small $C^r$…

Dynamical Systems · Mathematics 2025-07-15 Qi Li , Lin Wang

In the finite dimensional case, mean-type mappings, their invariant means, relations between the uniqueness of invariant means and convergence of orbits of the mapping, are considered. In particular it is shown, that the uniqueness of an…

Classical Analysis and ODEs · Mathematics 2022-06-10 Janusz Matkowski , Paweł Pasteczka

We introduce a combinatorial method to construct indefinite Ricci-flat metrics on nice nilpotent Lie groups. We prove that every nilpotent Lie group of dimension $\leq6$, every nice nilpotent Lie group of dimension $\leq7$ and every…

Differential Geometry · Mathematics 2020-07-10 Diego Conti , Viviana del Barco , Federico A. Rossi

Generative (diffusion) priors demonstrate remarkable performance in addressing inverse problems in imaging. Yet, for scientific and medical imaging, it is crucial that reconstruction techniques remain stable and reliable under imperfect…

Image and Video Processing · Electrical Eng. & Systems 2026-05-12 Alexander Denker , Johannes Hertrich , Sebastian Neumayer

In this paper we discuss convexity, its average principle, an extrinsic average variational method in the Calculus of Variations, an average method in Partial Differential Equations, a link of convexity to $p$-subharmonicity, subsolutions…

Analysis of PDEs · Mathematics 2023-09-11 Shihshu Walter Wei

We study invariant measures for random countable (finite or infinite) conformal iterated function systems (IFS) with arbitrary overlaps. We do not assume any type of separation condition. We prove, under a mild assumption of finite entropy,…

Dynamical Systems · Mathematics 2015-03-24 Eugen Mihailescu , Mariusz Urbanski

For a compact $(2n+1)$-dimensional smooth manifold, let $\mu_M : B Diff_\partial (D^{2n+1}) \to B Diff (M)$ be the map that is defined by extending diffeomorphisms on an embedded disc by the identity. By a classical result of Farrell and…

Algebraic Topology · Mathematics 2023-08-02 Johannes Ebert

We prove that homological filling functions over a ring $R$ equipped with the discrete norm are quasi-isometry invariants for all groups of type $\mathrm{FP}_n$. This confirms a conjecture of Bader-Kropholler-Vankov in the case of discrete…

Group Theory · Mathematics 2026-03-10 Jannis Weis

This paper addresses two questions: (a) can we identify a sensible class of 2-parameter persistence modules on which the rank invariant is complete? (b) can we determine efficiently whether a given 2-parameter persistence module belongs to…

Algebraic Topology · Mathematics 2022-02-07 Magnus Bakke Botnan , Vadim Lebovici , Steve Oudot

We introduce a new regularizer in the total variation family that promotes reconstructions with a given Lipschitz constant (which can also vary spatially). We prove regularizing properties of this functional and investigate its connections…

Numerical Analysis · Mathematics 2019-03-13 Martin Burger , Yury Korolev , Carola-Bibiane Schönlieb , Christiane Stollenwerk

Machine learning models often generalize poorly to out-of-distribution (OOD) data as a result of relying on features that are spuriously correlated with the label during training. Recently, the technique of Invariant Risk Minimization (IRM)…

Machine Learning · Computer Science 2023-01-18 Dongsung Huh , Avinash Baidya

This paper proposes bimorphic recursion, which is restricted polymorphic recursion such that every recursive call in the body of a function definition has the same type. Bimorphic recursion allows us to assign two different types to a…

Logic in Computer Science · Computer Science 2011-06-08 Makoto Tatsuta , Ferruccio Damiani

We study the Ricci flow for initial metrics which are C^0 small perturbations of the Euclidean metric on R^n. In the case that this metric is asymptotically Euclidean, we show that a Ricci harmonic map heat flow exists for all times, and…

Differential Geometry · Mathematics 2007-06-05 Oliver C. Schnürer , Felix Schulze , Miles Simon

We show that any left invariant metric with harmonic curvature on a solvable Lie group is Ricci-parallel. We show the same result for any Lie group of dimension $\leq$ 6.

Differential Geometry · Mathematics 2022-04-20 Ilyes Aberaouze , Mohamed Boucetta

For a word $\pi$ and integer $i$, we define $L^i(\pi)$ to be the length of the longest subsequence of the form $i(i+1)\cdots j$, and we let $L(\pi):=\max_i L^i(\pi)$. In this paper we estimate the expected values of $L^1(\pi)$ and $L(\pi)$…

Combinatorics · Mathematics 2021-10-22 Alexander Clifton , Bishal Deb , Yifeng Huang , Sam Spiro , Semin Yoo