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Assuming the Generalized Continuum Hypothesis, this paper answers the question: when is the tensor product of two ultrafilters equal to their Cartesian product? It is necessary and sufficient that their Cartesian product is an ultrafilter;…

Logic · Mathematics 2025-06-11 Gabriel Goldberg

In this work we study microlocal regularity of hyperfunctions defining in this context a class of generalized FBI transforms first introduced for distributions by Berhanu and Hounie. Using a microlocal decomposition of a hyperfunction and…

Analysis of PDEs · Mathematics 2022-06-22 Gustavo Hoepfner , Luis F. Ragognette

Hyperuniformity is a property of certain heteroneous media in which density fluctuations in the long wavelength range decay to zero. In reciprocal space this behavior translates into a decay of Fourier intensities in the range near small…

Applied Physics · Physics 2023-09-08 Mario Lázaro , Luis M. García-Raffi

We prove many new results about interacting Fock spaces. We pose many open problems; for most of them we prove that their solutions have no choice but being nontrivial. We ask the kind reader to consult the extended abstract in the paper.

Operator Algebras · Mathematics 2023-05-10 Malte Gerhold , Michael Skeide

In this paper, we present the proof of superlensing an arbitrary object using complementary media and we study reflecting complementary media for electromagnetic waves. The analysis is based on the reflecting technique and new results on…

Mathematical Physics · Physics 2016-03-29 Hoai-Minh Nguyen

We prove that a polar foliation of codimension at least three in an irreducible compact symmetric space is hyperpolar, unless the symmetric space has rank one. For reducible symmetric spaces of compact type, we derive decomposition results…

Differential Geometry · Mathematics 2014-01-10 Alexander Lytchak

This paper constructs a foundation to analyze semi-group actions, group actions, filtrations, and decompositions in a unified manner. In fact, though the studies of decomposition can be applied to foliated spaces and group actions, they can…

Dynamical Systems · Mathematics 2023-08-16 Tomoo Yokoyama

Motivated by problems arising in geometric flows, we prove several regularity results for systems of local and nonlocal equations, adapting to the parabolic case a neat argument due to Caffarelli. The geometric motivation of this work comes…

Analysis of PDEs · Mathematics 2020-05-11 Agnid Banerjee , Gonzalo Dávila , Yannick Sire

We show a global existence result of weak solutions for a class of generalized Surface Quasi-Geostrophic equation in the inviscid case. We also prove the global regularity of such solutions for the equation with slightly supercritical…

Analysis of PDEs · Mathematics 2018-02-22 Omar Lazar , Liutang Xue

The aim of this article is to show that systems of linear partial differential equations on filtered manifolds, which are of weighted finite type, can be canonically rewritten as first order systems of a certain type. This leads immediately…

Differential Geometry · Mathematics 2013-01-24 Katharina Neusser

We introduce topological conditions on a broad class of functionals that ensure that the persistent homology modules of their associated sublevel set filtration admit persistence diagrams, which, in particular, implies that they satisfy…

Algebraic Topology · Mathematics 2024-01-08 Ulrich Bauer , Anibal M. Medina-Mardones , Maximilian Schmahl

In this paper we consider existence and multiplicity results concerning affine connections on $C^{k}$-manifolds $M$ whose coefficients are as regular as one needs, following the regularity theory introduced in arXiv:1908.04442. We show that…

Differential Geometry · Mathematics 2021-02-09 Yuri Ximenes Martins , Rodney Josué Biezuner

The contour of a family of filters along a filter is a set-theoretic lower limit. Topologicity and regularity of convergences can be characterized with the aid of the contour operation. Contour inversion is studied, in particular, for…

General Topology · Mathematics 2019-01-31 Szymon Dolecki , Andrzej Starosolski

We survey some connections between topological dynamics, semigroups of ultrafilters, and combinatorics. As an application, we give a proof, based on ideas of Bergelson and Hindman, of the Hales-Jewett partition theorem.

Logic · Mathematics 2009-09-25 Andreas Blass

We present a decomposition of finitely supported filters ( aka instrument function PSF) as a composition of invertible and non-invertible filters. The invertible component can be inverted directly and the non-invertible component is shown…

Numerical Analysis · Mathematics 2022-05-17 Yury Tyurin , Anastasia Tyurina

We study seminormalization of affine complex varieties. We show that polynomials on the seminormalization correspond to the rational functions which are continuous for the Euclidean topology. We further study this type of functions which…

Algebraic Geometry · Mathematics 2022-04-08 François Bernard

We propose a number of variational regularisation methods for the estimation and decomposition of motion fields on the $2$-sphere. While motion estimation is based on the optical flow equation, the presented decomposition models are…

Optimization and Control · Mathematics 2014-03-05 Clemens Kirisits , Lukas F. Lang , Otmar Scherzer

If $\mathcal P$ is a family of filters over some set $I$, a topological space $X$ is \emph{sequencewise $\mathcal P$-\brfrt compact} if, for every $I$-indexed sequence of elements of $X$, there is $F \in \mathcal P$ such that the sequence…

General Topology · Mathematics 2016-08-30 Paolo Lipparini

In this paper we introduce generalized Spencer cohomology for finite depth Z-graded Lie (super)algebras. We develop a method of finding filtered deformations of such Z-graded Lie (super)algebras based on this cohomology. As an application…

Representation Theory · Mathematics 2008-11-26 Shun-Jen Cheng , Victor G. Kac

We study spaces of ultradifferentiable functions which contain Gevrey classes. Although the corresponding defining sequences do not satisfy Komatsu's condition (M.2)', we prove appropriate continuity properties under the action of…

Functional Analysis · Mathematics 2016-05-24 Nenad Teofanov , Filip Tomic