Results 61 to 70 of about 235 (167)

Algebraic singular functions are not always dense in the ideal of C∗$C^*$‐singular functions

Bulletin of the London Mathematical Society, Volume 58, Issue 5, May 2026.
Abstract We give the first examples of étale (non‐Hausdorff) groupoids G$\mathcal {G}$ whose C∗$C^*$‐algebras contain singular elements that cannot be approximated by singular elements in Cc(G)$\mathcal {C}_c(\mathcal {G})$. We provide two examples: one is a bundle of groups and the other a minimal and effective groupoid constructed from a self‐similar
Diego Martínez, Nóra Szakács
wiley   +1 more source

Manifestly unitary higher Hilbert spaces

Journal of the London Mathematical Society, Volume 113, Issue 5, May 2026.
Abstract Higher idempotent completion gives a formal inductive construction of the n$n$‐category of finite‐dimensional n$n$‐vector spaces starting with the complex numbers. We propose a manifestly unitary construction of low‐dimensional higher Hilbert spaces, formally constructing the C∗$\mathrm{C}^*$‐3‐category of 3‐Hilbert spaces from Baez's 2 ...
Quan Chen, Giovanni Ferrer, Brett Hungar, David Penneys, Sean Sanford   +4 more
wiley   +1 more source

Counting 5‐isogenies of elliptic curves over Q$\mathbb {Q}$

Journal of the London Mathematical Society, Volume 113, Issue 5, May 2026.
Abstract We show that the number of 5‐isogenies of elliptic curves defined over Q$\mathbb {Q}$ with naive height bounded by H>0$H > 0$ is asymptotic to C5·H1/6(logH)2$C_5\cdot H^{1/6} (\log H)^2$ for some explicitly computable constant C5>0$C_5 > 0$. This settles the asymptotic count of rational points on the genus zero modular curves X0(m)$\mathcal {X}
Santiago Arango‐Piñeros, Changho Han, Oana Padurariu, Sun Woo Park   +3 more
wiley   +1 more source

On finitary power monoids of linearly orderable monoids

A commutative monoid $M$ is called a linearly orderable monoid if there exists a total order on $M$ that is compatible with the monoid operation. The finitary power monoid of a commutative monoid $M$ is the monoid consisting of all nonempty finite subsets of $M$ under the so-called sumset.
Dani, Jiya, Gotti, Felix, Hong, Leo, Li, Bangzheng, Schlessinger, Shimon   +4 more
openaire   +2 more sources

Hopf Monoids of Ordered Simplicial Complexes

International Mathematics Research Notices
Abstract We study Hopf classes: families of pure ordered simplicial complexes that give rise to Hopf monoids under join and deletion/contraction. The prototypical Hopf class is the family of ordered matroids. The idea of a Hopf class leads to a systematic study of simplicial complexes related to matroids, including shifted complexes and ...
Castillo, Federico, Martin, Jeremy L., Samper, Jose A.   +2 more
openaire   +6 more sources

On the ET0L subgroup membership problem in bounded automata groups

Journal of the London Mathematical Society, Volume 113, Issue 4, April 2026.
Abstract We are interested in the subgroup membership problem in groups acting on rooted d$d$‐regular trees and a natural class of subgroups, the stabilisers of infinite rays emanating from the root. These rays, which can also be viewed as infinite words in the alphabet with d$d$ letters, form the boundary of the tree.
Alex Bishop, Daniele D'Angeli, Francesco Matucci, Tatiana Nagnibeda, Davide Perego, Emanuele Rodaro   +5 more
wiley   +1 more source

Assembly of constructible factorization algebras

Journal of Topology, Volume 19, Issue 1, March 2026.
Abstract We provide a toolbox of extension, gluing, and assembly techniques for factorization algebras. Using these tools, we fill various gaps in the literature on factorization algebras on stratified manifolds, the main one being that constructible factorization algebras form a sheaf of symmetric monoidal ∞$\infty$‐categories.
Eilind Karlsson, Claudia I. Scheimbauer, Tashi Walde   +2 more
wiley   +1 more source

The ∞$\infty$‐categorical reflection theorem and applications

Journal of Topology, Volume 19, Issue 1, March 2026.
Abstract We prove an ∞$\infty$‐categorical version of the reflection theorem of AdÁmek and Rosický [Arch. Math. 25 (1989), no. 1, 89–94]. Namely, that a full subcategory of a presentable ∞$\infty$‐category that is closed under limits and κ$\kappa$‐filtered colimits is a presentable ∞$\infty$‐category.
Shaul Ragimov, Tomer M. Schlank
wiley   +1 more source

Scissors congruence K$K$‐theory for equivariant manifolds

Bulletin of the London Mathematical Society, Volume 58, Issue 1, January 2026.
Abstract We introduce a scissors congruence K$K$‐theory spectrum that lifts the equivariant scissors congruence groups for compact G$G$‐manifolds with boundary, and we show that on π0$\pi _0$, this is the source of a spectrum‐level lift of the Burnside ring‐valued equivariant Euler characteristic of a compact G$G$‐manifold.
Mona Merling, Ming Ng, Julia Semikina, Alba Sendón Blanco, Lucas Williams   +4 more
wiley   +1 more source

Profinite direct sums with applications to profinite groups of type ΦR$\Phi _R$

Bulletin of the London Mathematical Society, Volume 58, Issue 1, January 2026.
Abstract We show that the ‘profinite direct sum’ is a good notion of infinite direct sums for profinite modules, having properties similar to those of direct sums of abstract modules. For example, the profinite direct sum of projective modules is projective, and there is a Mackey's formula for profinite modules described using these sums.
Jiacheng Tang
wiley   +1 more source