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For a separable finite diffuse measure space $\mathcal{M}$ and an orthonormal basis $\{\varphi_n\}$ of $L^2(\mathcal{M})$ consisting of bounded functions $\varphi_n\in L^\infty(\mathcal{M})$, we find a measurable subset…

Functional Analysis · Mathematics 2018-10-16 Zhirayr Avetisyan , Martin Grigoryan , Michael Ruzhansky

For any pair of bounded observables $A$ and $B$ with pure point spectra, we construct an associated "joint observable" which gives rise to a notion of a joint (projective) measurement of $A$ and $B$, and which conforms to the intuition that…

Quantum Physics · Physics 2015-06-22 Richard DeJonghe , Kimberly Frey , Tom Imbo

For function spaces equipped with Muckenhoupt weights, the validity of continuous Sobolev embeddings in case $p_0\leq p_1$ is characterized. Extensions to Jawerth-Franke embeddings, vector-valued spaces and examples involving some prominent…

Functional Analysis · Mathematics 2014-09-09 Martin Meyries , Mark Veraar

Let $L^{m,p}(\mathbb{R}^n)$ be the homogeneous Sobolev space for $p \in (n,\infty)$, $\mu$ be a Borel regular measure on $\mathbb{R}^n$, and $L^{m,p}(\mathbb{R}^n) + L^p(d\mu)$ be the space of Borel measurable functions with finite seminorm…

Functional Analysis · Mathematics 2022-12-21 Marjorie K. Drake

For given set of $m$ positive numbers satisfying the conditions: $$ a_1 \geq a_2 \geq , ... \geq a_m \geq 0, $$ the inequality $$ \sum_{s=1}^{m} (-1)^{s-1}a^r_s \geq \left[ \sum_{s=1}^{m} (-1)^{s-1}a_s\right]^r, \quad r > 1, $$ was proved…

Classical Analysis and ODEs · Mathematics 2024-07-22 Hailu Bikila Yadeta

By seeing whether a Liouville type theorem holds for positive, bounded, and/or finite energy $p$-harmonic and $p$-quasiharmonic functions, we classify proper metric spaces equipped with a locally doubling measure supporting a local…

Metric Geometry · Mathematics 2023-02-15 Anders Bjorn , Jana Bjorn , Nageswari Shanmugalingam

It has been known that sharp Sobolev embeddings into weak Lebesgue spaces are non-compact but the question of whether the measure of non-compactness of such an embedding equals to its operator norm constituted a well-known open problem. The…

Functional Analysis · Mathematics 2023-03-20 Jan Lang , Vít Musil , Miroslav Olšák , Luboš Pick

Each $x\in (0,1]$ can be uniquely expanded as a power-2-decaying Gauss-like expansion, in the form of \begin{equation*} x=\sum_{i=1}^{\infty}2^{-(d_1(x)+d_2(x)+\cdots+d_i(x))},\qquad d_i(x)\in \mathbb{N}. \end{equation*} Let…

Number Theory · Mathematics 2024-05-30 Zhihui Li , Xin Liao , Dingding Yu

In this paper, we study the behaviour at infinity of $p$-Sobolev functions in the setting of Ahlfors $Q$-regular metric measure spaces supporting a $p$-Poincar\'e inequality. By introducing the notions of sets which are $p$-thin at…

Functional Analysis · Mathematics 2025-05-27 Josh Kline , Pekka Koskela , Khanh Nguyen

We characterize the restrictions of first order Sobolev functions to regular subsets of a homogeneous metric space and prove the existence of the corresponding linear extension operator.

Functional Analysis · Mathematics 2007-05-23 Pavel Shvartsman

In this note we prove that, for $p>0$, $L_{p}[0,1]\smallsetminus\bigcup_{q\in(p,\infty)}L_{q}[0,1]$ is $(\alpha,\mathfrak{c})$-spaceable if, and only if, $\alpha<\aleph_{0}$. Such a problem first appears in [V. F\'avaro, D. Pellegrino, D.…

Functional Analysis · Mathematics 2023-04-20 Gustavo Araújo , Anderson Barbosa , Anselmo Raposo , Geivison Ribeiro

For continuous maps on a compact manifold M, particularly for those that do not preserve the Lebesgue measure m, we define the observable invariant probability measures as a generalization of the physical measures. We prove that any…

Dynamical Systems · Mathematics 2012-03-01 E. Catsigeras , H. Enrich

A Sobolev type embedding for radially symmetric functions on the unit ball $B$ in $\mathbb R^n$, $n\geq 3$, into the variable exponent Lebesgue space $L_{2^\star + |x|^\alpha} (B)$, $2^\star = 2n/(n-2)$, $\alpha>0$, is known due to J.M. do…

Analysis of PDEs · Mathematics 2020-04-23 Quôc Anh Ngô , Van Hoang Nguyen

We establish a new global endpoint Sobolev inequality for measures that extends the classical theorem of Meyers-Ziemer by placing a maximal function on the right-hand side. This result has several significant consequences. It extends…

Classical Analysis and ODEs · Mathematics 2026-03-06 Simon Bortz , Kabe Moen , Andrea Olivo , Carlos Pérez , Ezequiel Rela

We prove that if the Hausdorff dimension of a compact subset of ${\mathbb R}^d$ is greater than $\frac{d+1}{2}$, then the set of angles determined by triples of points from this set has positive Lebesgue measure. Sobolev bounds for…

Classical Analysis and ODEs · Mathematics 2011-11-01 Alex Iosevich , Mihalis Mourgoglou , Eyvindur Palsson

We prove that a local, weak Sobolev inequality implies a global Sobolev estimate using existence and regularity results for a family of $p$-Laplacian equations. Given $\Omega\subset\mathbb{R}^n$, let $\rho$ be a quasi-metric on $\Omega$,…

Analysis of PDEs · Mathematics 2018-01-30 David Cruz-Uribe , Scott Rodney , Emily Rosta

Let $X$ be a Borel and Borel-regular metric measure space whose closed balls are of positive and finite measure. In this paper, we shall give equivalent conditions for averaging operators on non-reflexive Lebesgue spaces $L^1(X)$ and…

Functional Analysis · Mathematics 2026-02-26 Katsuhisa Koshino

Rademacher theorem states that every Lipschitz function on the Euclidean space is differentiable almost everywhere, where "almost everywhere" refers to the Lebesgue measure. In this paper we prove a differentiability result of similar type,…

Classical Analysis and ODEs · Mathematics 2015-03-27 Giovanni Alberti , Andrea Marchese

On a general open set of the euclidean space, we study the relation between the embedding of the homogeneous Sobolev space $\mathcal{D}^{1,p}_0$ into $L^q$ and the summability properties of the distance function. We prove that in the…

Analysis of PDEs · Mathematics 2023-01-31 Lorenzo Brasco , Francesca Prinari , Anna Chiara Zagati

Inspired by the work of Borwein and Erdelyi \cite{BE1997JAMS} on generalizations of M\"{u}ntz's theorem, we investigate the properties of the system $\{x^{\lambda_n}\}_{n=1}^{\infty}$ in weighted $L^p (A)$ spaces, for $p\ge 1$, denoted by…

Functional Analysis · Mathematics 2025-09-04 Elias Zikkos