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We prove that various spaces of constrained positive scalar curvature metrics on compact 3-manifolds with boundary, when not empty, are contractible. The constraints we mostly focus on are given in terms of local conditions on the mean…

Differential Geometry · Mathematics 2023-02-22 Alessandro Carlotto , Chao Li

Uniform measures are defined as the functionals on the space of bounded uniformly continuous functions that are continuous on bounded uniformly equicontinuous sets. If every cardinal has measure zero then every countably additive measure is…

Functional Analysis · Mathematics 2007-05-23 Jan Pachl

We define the notion of computability of F{\o}lner sets for finitely generated amenable groups. We prove, by an explicit description, that the Kharlampovich group, a finitely presented solvable group with unsolvable word problem, has…

Group Theory · Mathematics 2018-07-04 Matteo Cavaleri

We propose a new PAC-Bayesian bound and a way of constructing a hypothesis space, so that the bound is convex in the posterior distribution and also convex in a trade-off parameter between empirical performance of the posterior distribution…

Machine Learning · Computer Science 2017-08-25 Niklas Thiemann , Christian Igel , Olivier Wintenberger , Yevgeny Seldin

In this note, we construct torsion-free countable, amenable, weakly mixing groups, which answer a question of V. Bergelson. Some results related to verbal subgroups and crystallographic groups are also presented.

Dynamical Systems · Mathematics 2016-07-04 Rostislav Grigorchuk , Rostyslav Kravchenko , Alexander Olshanskii

We prove definable versions of the Universal Coefficient Theorems of Eilenberg--Mac Lane expressing the (Steenrod) homology groups of a compact metrizable space in terms of its integral cohomology groups, and the (\v{C}ech) cohomology…

Algebraic Topology · Mathematics 2020-10-13 Martino Lupini

We obtain several results concerning the concept of isotypic structures. Namely we prove that any field of finite transcendence degree over a prime subfield is defined by types; then we construct isotypic but not isomorphic structures with…

Logic · Mathematics 2025-06-18 Pavel Gvozdevsky

The basic methods of constructing the sets of mutually unbiased bases in the Hilbert space of an arbitrary finite dimension are discussed and an emerging link between them is outlined. It is shown that these methods employ a wide range of…

Quantum Physics · Physics 2009-11-10 Michel R. P. Planat , Haret Rosu , Serge Perrine , Metod Saniga

We introduce the notion of hyperfiniteness for permutation actions of countable groups on countable sets and give a geometric and analytic characterization, similar to the known characterizations for amenable actions. We also answer a…

Group Theory · Mathematics 2011-07-12 Miklos Abert , Gabor Elek

A full characterization of the boundedness of Laplace--Carleson embeddings on $L^\infty$ is provided, in terms of the Carleson intensity of the respective measure and of a suitable weighted Berezin transform of the measure. Moreover,…

Functional Analysis · Mathematics 2026-04-14 Birgit Jacob , Jonathan R. Partington , Sandra Pott , Eskil Rydhe , Felix L. Schwenninger

In this paper we introduce for a group $G$ the notion of ultralimit of measure class preserving actions of it, and show that its Furstenberg-Poisson boundaries can be obtained as an ultralimit of actions on itself, when equipped with…

Group Theory · Mathematics 2023-12-27 Elad Sayag , Yehuda Shalom

In this work the problem about an existence of non-measurable automorphisms of Lie groups finite and as well infinite dimensional over the field of real numbers and also over the non-archimedean local fields is investigated.…

Functional Analysis · Mathematics 2018-12-18 S. V. Ludkovsky

Quasi-invariant and pseudo-differentiable measures on a Banach space $X$ over a non-Archimedean locally compact infinite field with a non-trivial valuation are defined and constructed. Measures are considered with values in non-Archimedean…

General Mathematics · Mathematics 2007-05-23 Sergey V. Ludkovsky

We study positive operator-valued measures generated by orbits of projective unitary representations of locally compact Abelian groups. It is shown that integration over such a measure defines a family of contractions being multiples of…

Quantum Physics · Physics 2023-05-24 Grigori Amosov

An explicit family of Folner sets is constructed for some directed groups acting on a rooted tree of sublogarithmic valency by alternate permutations. In the case of bounded valency, these groups were known to be amenable by probabilistic…

Group Theory · Mathematics 2013-09-09 Jeremie Brieussel

We introduce definitions of computable PAC learning for binary classification over computable metric spaces. We provide sufficient conditions for learners that are empirical risk minimizers (ERM) to be computable, and bound the strong…

Machine Learning · Computer Science 2021-11-30 Nathanael Ackerman , Julian Asilis , Jieqi Di , Cameron Freer , Jean-Baptiste Tristan

In this article, we shall explore the constructions of Bernstein sets, and prove that every Bernstein set is nonmeasurable and doesn't have the property of Baire. We shall also prove that Bernstein sets don't have the perfect set property.

Classical Analysis and ODEs · Mathematics 2011-12-06 Cheng Hao

The notion of a complete type can be generalized in a natural manner to allow assigning a value in an arbitrary Boolean algebra B to each formula. We show some basic results regarding the effect of the properties of B on the behavior of…

Logic · Mathematics 2022-01-19 Itay Kaplan , Ori Segel , Saharon Shelah

We present necessary and sufficient conditions for the existence of a countably additive measure on a complete Boolean algebra.

Functional Analysis · Mathematics 2007-05-23 Thomas Jech

We prove a pointwise ergodic theorem and a maximal inequality for actions of amenable groups on noncommutative measure spaces. To do so, we establish a square function estimate quantifying the difference between ergodic averages and some…

Operator Algebras · Mathematics 2025-08-29 Léonard Cadilhac , Simeng Wang
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