Search arXivSearch

arXiv · 1611.07007

Pullback Crossed Modules in the Category of Racks

Abstract

In this paper, we define the pullback crossed modules in the category of racks which mainly based on a pullback diagram of rack morphisms with extra crossed module data on some of its arrows. Furthermore we prove that the conjugation functor, which is defined between the category of crossed modules of groups and of racks, preserves the pullback crossed modules.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Kadir Emir, Hatice Gülsün Akay. 2016-11-21. Pullback Crossed Modules in the Category of Racks. https://doi.org/10.15672/hjms.2017.532

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

Borsuk-Ulam type theorem for Stiefel manifolds and orthogonal mass partitions

We prove a Borsuk--Ulam-type zero theorem for the Stiefel manifold $V_{n,k}$ equipped with a free action of the hyperoctahedral group $B_k=(\mathbb{Z}/2)^k\rtimes S_k$. The existence of a zero reduces to a nonvanishing condition for explicit polynomials in the truncated ring ${R}_{n,k}=\mathbb{F}_2[a_1,\ldots,a_k]/(a_1^n,a_2^{n-1},\ldots,a_k^{n-k+1})$, converting a topological problem into finite algebra over~$\mathbb{F}_2$. As an application we study equipartitions by mutually orthogonal hyperplanes. We prove that if $(P_{k,n})^m\ne0$ in the partition ring ${R}_{d,k}=\mathbb{F}_2[a_1,\ldots,a_k]/(a_1^{d+1},a_2^{d},\ldots,a_k^{d-k+2})$, then for any $m$ finite Borel measures in $\mathbb{R}^d$ there exist $k$ mutually orthogonal hyperplanes such that every $n$-element subfamily partitions each measure into $2^n$ equal parts. Let $Δ^*(m,k,n)$ denote the smallest such dimension~$d$. We prove lower bounds on $Δ^*(m,k,n)$ for all $m$, $k$, $n$ via a Sard-theoretic dimension argument, and the nonvanishing condition above provides algebraic upper bounds. We establish these bounds in several cases and derive exact values, including $Δ^*(2^j-1,k,2)=2^{j-1}(k+1)-1$ for all $j\ge1$, $k\ge2$. In particular, the MVZ upper bound on $Δ(m,k)$ \cite{MSZ} is achieved by mutually orthogonal hyperplanes: orthogonality comes for free.

math.AT

The discrete homotopy hypothesis for directed graphs

We develop a homotopy theory of directed graphs based on cubical homotopy groups, also known as $A$-groups or reduced GLMY homotopy groups. Localizing the category of directed graphs at morphisms that induce isomorphisms on these groups yields an $\infty$-category, denoted by ${\sf DGra}_\infty$. We prove that ${\sf DGra}_\infty$ is equivalent to the $\infty$-category of spaces, establishing a directed version of the discrete homotopy hypothesis of Carranza and Kapulkin.

math.AT

Homogeneous Milnor fibers and Kato--Matsumoto bounds via simplicial multiwedges

For every $n\geq 3$ and $s\geq 2$, we construct a homogeneous polynomial of degree $n(n+1)/2$ whose Milnor fiber is exactly $2s$-connected and whose rational cohomology contains a strictly defined nontrivial $n$-fold Massey product on classes of degree $2s+1$, implying that the Milnor fiber is non-formal, while attaining the Kato--Matsumoto connectivity bound. Our construction is based on the simplicial multiwedges of the nerve complexes of simple polytopes introduced by Limonchenko, combined with Suciu's realization of weighted homogeneous Milnor fibers. We thereby answer two problems posed by Suciu.

math.AT