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Magnitude homology is a bigraded homology theory for finite graphs defined by Hepworth and Willerton, categorifying the power series invariant known as magnitude which was introduced by Leinster. We analyze the structure and implications of…

Combinatorics · Mathematics 2020-01-01 Radmila Sazdanovic , Victor Summers

Magnitude, obtained as a special case of Euler characteristic of enriched category, represents a sense of the size of metric spaces and is related to classical notions such as cardinality, dimension, and volume. While the studies have…

Machine Learning · Statistics 2025-09-16 Byungchang So

Magnitude is a real-valued invariant of metric spaces which, in the finite setting, can be understood as recording the 'effective number of points' in a space as the scale of the metric varies. Motivated by applications in topological data…

Metric Geometry · Mathematics 2025-01-28 Hirokazu Katsumasa , Emily Roff , Masahiko Yoshinaga

We investigate \emph{magnitude} as a new unary and strictly Pareto-compliant quality indicator for finite approximation sets to the Pareto front in multiobjective optimization. Magnitude originates in enriched category theory and metric…

Optimization and Control · Mathematics 2026-04-21 Michael T. M. Emmerich

The notion of the magnitude of a metric space was introduced by Leinster in [8] and developed in [10], [9], [11] and [16], but the magnitudes of familiar sets in Euclidean space are only understood in relatively few cases. In this paper we…

Metric Geometry · Mathematics 2016-07-14 Juan Antonio Barcelo , Anthony Carbery

Magnitude of a finite metric space and the related notion of magnitude functions on metric spaces is an active area of research in algebraic topology. Magnitude originally arose in the context of biology, where it represents the number of…

Algebraic Topology · Mathematics 2019-08-08 Glenn Fung , Eric Bunch , Dan Dickinson

Magnitude is a measure of size defined for certain classes of metric spaces; it arose from ideas in category theory. In particular, magnitude is defined for compact subsets of Euclidean space and, in arXiv:1507.02502, Barcel\'o and Carbery…

Metric Geometry · Mathematics 2018-04-09 Simon Willerton

Metric magnitude is a measure of the "size" of point clouds with many desirable geometric properties. It has been adapted to various mathematical contexts and recent work suggests that it can enhance machine learning and optimization…

Machine Learning · Computer Science 2024-09-09 Rayna Andreeva , James Ward , Primoz Skraba , Jie Gao , Rik Sarkar

There is a general notion of the magnitude of an enriched category, defined subject to hypotheses. In topological and geometric contexts, magnitude is already known to be closely related to classical invariants such as Euler characteristic…

Rings and Algebras · Mathematics 2016-01-11 Joseph Chuang , Alastair King , Tom Leinster

The main result of this article is a geometric interpretation of magnitude, a real-valued invariant of metric spaces. We introduce a Euclidean embedding of a (suitable) finite metric space $X$ such that the magnitude of $X$ can be expressed…

Metric Geometry · Mathematics 2025-10-22 Karel Devriendt

Magnitude homology of enriched categories, and in particular of metric spaces, was recently introduced by T. Leinster and M. Shulman. In this article, we prove that metric spaces satisfying a reasonably mild condition have vanishing…

Metric Geometry · Mathematics 2018-03-15 Benoit Jubin

Magnitude homology was introduced by Hepworth and Willerton in the case of graphs, and was later extended by Leinster and Shulman to metric spaces and enriched categories. Here we introduce the dual theory, magnitude cohomology, which we…

Algebraic Topology · Mathematics 2022-04-25 Richard Hepworth

The notion of the magnitude of a compact metric space was considered in arXiv:0908.1582 with Tom Leinster, where the magnitude was calculated for line segments, circles and Cantor sets. In this paper more evidence is presented for a…

Metric Geometry · Mathematics 2009-10-30 Simon Willerton

We propose a definition of magnitude for a length space with a Borel measure, which involves integrals over the set of geodesics. This quantity agrees with the magnitude of finite metric spaces, up to re-scaling the metric to ensure the…

Differential Geometry · Mathematics 2026-05-25 Yoshinori Hashimoto

In this article, we give a framework for studying the Euler characteristic and its categorification of objects across several areas of geometry, topology and combinatorics. That is, the magnitude theory of filtered sets enriched categories.…

Algebraic Topology · Mathematics 2023-07-26 Yasuhiko Asao

We describe a modification of the usual definition of astronomical magnitudes, replacing the usual logarithm with an inverse hyperbolic sine function; we call these modified magnitudes `asinh magnitudes'. For objects detected at…

Astrophysics · Physics 2008-11-26 Robert Lupton , Jim Gunn , Alex Szalay

We study the geometric significance of Leinster's notion of magnitude for a smooth manifold with boundary of arbitrary dimension, motivated by open questions for the unit disk in $\mathbb{R}^2$. For a large class of distance functions,…

Differential Geometry · Mathematics 2025-11-18 Heiko Gimperlein , Magnus Goffeng , Nikoletta Louca

For an algebraic number $\alpha$, the metric Mahler measure $m_1(\alpha)$ was first studied by Dubickas and Smyth in 2001 and was later generalized to the $t$-metric Mahler measure $m_t(\alpha)$ by the author in 2010. The definition of…

Number Theory · Mathematics 2019-12-23 Charles L. Samuels

We study Leinster's notion of magnitude for a compact metric space. For a smooth, compact domain $X\subset \mathbb{R}^{2m-1}$, we find geometric significance in the function $\mathcal{M}_X(R) = \mathrm{mag}(R\cdot X)$. The function…

Metric Geometry · Mathematics 2023-01-31 Heiko Gimperlein , Magnus Goffeng

Quantifying the distance between datasets is a fundamental question in mathematics and machine learning. We propose \textit{magnitude distance}, a novel distance metric defined on finite datasets using the notion of the \emph{magnitude} of…

Machine Learning · Computer Science 2026-02-10 Sahel Torkamani , Henry Gouk , Rik Sarkar