{"title":"Sharpness of saturated fusion systems on a Sylow $p$-subgroup of $mathrm{G}_2 (p)$","authors":"Valentina Grazian, Ettore Marmo","doi":"10.4310/hha.2023.v25.n2.a14","DOIUrl":"https://doi.org/10.4310/hha.2023.v25.n2.a14","url":null,"abstract":"We prove that the Díaz–Park sharpness conjecture holds for saturated fusion systems defined on a Sylow $p$-subgroup of the group $mathrm{G}_2 (p)$, for $p geqslant 5$.","PeriodicalId":55050,"journal":{"name":"Homology Homotopy and Applications","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138520629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Classifying space via homotopy coherent nerve","authors":"Kensuke Arakawa","doi":"10.4310/hha.2023.v25.n2.a16","DOIUrl":"https://doi.org/10.4310/hha.2023.v25.n2.a16","url":null,"abstract":"We prove that the classifying space of a simplicial group is modeled by its homotopy coherent nerve. We will also show that the claim remains valid for simplicial groupoids.","PeriodicalId":55050,"journal":{"name":"Homology Homotopy and Applications","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138520611","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"$K$-theory of real Grassmann manifolds","authors":"Sudeep Podder, Parameswaran Sankaran","doi":"10.4310/hha.2023.v25.n2.a17","DOIUrl":"https://doi.org/10.4310/hha.2023.v25.n2.a17","url":null,"abstract":"Let $G_{n,k}$ denote the real Grassmann manifold of $k$-dimensional vector subspaces of $mathbb{R}^n$. We compute the complex $K$-ring of $G_{n,k}:$, up to a small indeterminacy, for all values of $n,k$ where $2 leqslant k leqslant n - 2$. When $n equiv 0 (operatorname{mod} 4), k equiv 1 (operatorname{mod} 2)$, we use the Hodgkin spectral sequence to determine the $K$-ring completely.","PeriodicalId":55050,"journal":{"name":"Homology Homotopy and Applications","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138520624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On bialgebras, comodules, descent data and Thom spectra in $infty$-categories","authors":"Jonathan Beardsley","doi":"10.4310/hha.2023.v25.n2.a10","DOIUrl":"https://doi.org/10.4310/hha.2023.v25.n2.a10","url":null,"abstract":"This paper establishes several results for coalgebraic structure in $infty$-categories, specifically with connections to the spectral noncommutative geometry of cobordism theories. We prove that the categories of comodules and modules over a bialgebra always admit suitably structured monoidal structures in which the tensor product is taken in the ambient category (as opposed to a relative (co)tensor product over the underlying algebra or coalgebra of the bialgebra). We give two examples of higher coalgebraic structure: first, following Hess we show that for a map of $mathbb{E}_n$-ring spectra $varphi : A to B$, the associated $infty$-category of descent data is equivalent to the $infty$-category of comodules over $B otimes_A B$, the so-called descent coring; secondly, we show that Thom spectra are canonically equipped with a highly structured comodule structure which is equivalent to the $infty$-categorical Thom diagonal of Ando, Blumberg, Gepner, Hopkins and Rezk (which we describe explicitly) and that this highly structured diagonal decomposes the Thom isomorphism for an oriented Thom spectrum in the expected way indicating that Thom spectra are good examples of spectral noncommutative torsors.","PeriodicalId":55050,"journal":{"name":"Homology Homotopy and Applications","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138520610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Zig-zag modules: cosheaves and $k$-theory","authors":"Ryan Grady, Anna Schenfisch","doi":"10.4310/hha.2023.v25.n2.a11","DOIUrl":"https://doi.org/10.4310/hha.2023.v25.n2.a11","url":null,"abstract":"Persistence modules have a natural home in the setting of stratified spaces and constructible cosheaves. In this article, we first give explicit constructible cosheaves for common data-motivated persistence modules, namely, for modules that arise from zig‑zag filtrations (including monotone filtrations), and for augmented persistence modules (which encode the data of instantaneous events). We then identify an equivalence of categories between a particular notion of zig‑zag modules and the combinatorial entrance path category on stratified $mathbb{R}$. Finally, we compute the algebraic $K$-theory of generalized zig‑zag modules and describe connections to both Euler curves and $K_0$ of the monoid of persistence diagrams as described by Bubenik and Elchesen.","PeriodicalId":55050,"journal":{"name":"Homology Homotopy and Applications","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138520609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Homology transfer products on free loop spaces: orientation reversal on spheres","authors":"Philippe Kupper","doi":"10.4310/hha.2023.v25.n2.a7","DOIUrl":"https://doi.org/10.4310/hha.2023.v25.n2.a7","url":null,"abstract":"We consider the space $Lambda M := H^1 (S^1, M)$ of loops of Sobolev class $H^1$ of a compact smooth manifold $M$, the so-called free loop space of $M$. We take quotients $Lambda M / G$ where $G$ is a finite subgroup of $O(2)$ acting by linear reparametrization of $S^1$. We use the existence of transfer maps $operatorname{tr} : H_ast (Lambda M / G) to H_ast (Lambda M)$ to define a homology product on $Lambda M / G$ via the Chas–Sullivan loop product. We call this product $P_G$ the transfer product. The involution $vartheta : Lambda M to Lambda M$ which reverses orientation, $vartheta ( gamma (t) := gamma (1-t)$, is of particular interest to us. We compute $H_ast (Lambda S^n / vartheta ; mathbb{Q}), n gt 2$, and the product[P_vartheta : H_i (Lambda S^n / vartheta ; mathbb{Q}) times H_j (Lambda S^n / vartheta ; mathbb{Q)} to H_{i+j-n} (Lambda Sn/vartheta ; mathbb{Q})]associated to orientation reversal. Rationally Pvartheta can be realized “geometrically” using the concatenation of equivalence classes of loops. There is a qualitative difference between the homology of $Lambda S^n / vartheta$ and the homology of $Lambda S^n / G$ when $G subset S^1 subset O(2)$ does not “contain” the orientation reversal. This might be interesting with respect to possible differences in the number of closed geodesics between non-reversible and reversible Finsler metrics on $S^n$, the latter might always be infinite.","PeriodicalId":55050,"journal":{"name":"Homology Homotopy and Applications","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138520608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Haefliger’s approach for spherical knots modulo immersions","authors":"Neeti Gauniyal","doi":"10.4310/hha.2023.v25.n2.a4","DOIUrl":"https://doi.org/10.4310/hha.2023.v25.n2.a4","url":null,"abstract":"$defEmb{overline{Emb}}$We show that for the spaces of spherical embeddings modulo immersions $Emb (S^n, S^{n+q})$ and long embeddings modulo immersions $Emb_partial (D^n, D^{n+q})$, the set of connected components is isomorphic to $pi_{n+1} (SG, SG_q)$ for $q geqslant 3$. As a consequence, we show that all the terms of the long exact sequence of the triad $(SG; SO, SG_q)$ have a geometric meaning relating to spherical embeddings and immersions.","PeriodicalId":55050,"journal":{"name":"Homology Homotopy and Applications","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138520630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Homotopy types of truncated projective resolutions","authors":"W. Mannan","doi":"10.4310/HHA.2007.v9.n2.a16","DOIUrl":"https://doi.org/10.4310/HHA.2007.v9.n2.a16","url":null,"abstract":"We work over an arbitrary ring R. Given two truncated projective\u0000resolutions of equal length for the same module, we consider\u0000their underlying chain complexes. We show they may be\u0000stabilized by projective modules to obtain a pair of complexes\u0000of the same homotopy type","PeriodicalId":55050,"journal":{"name":"Homology Homotopy and Applications","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42199405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Duality in the homology of 5-manifolds","authors":"W. Mannan","doi":"10.4310/HHA.2017.v19.n1.a9","DOIUrl":"https://doi.org/10.4310/HHA.2017.v19.n1.a9","url":null,"abstract":"We show that the homological properties of a 5-manifold M with fundamental group G are encapsulated in a G-invariant stable form on the dual of the third syzygy of Z. In this notation one may express an even stronger version of Poincare duality for M. However we find an obstruction to this duality.","PeriodicalId":55050,"journal":{"name":"Homology Homotopy and Applications","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41756829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The homotopy types of $Sp(n)$-gauge groups over $mathbb{C}P^2$","authors":"Sajjad Mohammadi","doi":"10.4310/hha.2023.v25.n1.a11","DOIUrl":"https://doi.org/10.4310/hha.2023.v25.n1.a11","url":null,"abstract":"","PeriodicalId":55050,"journal":{"name":"Homology Homotopy and Applications","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70435079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}