{"title":"Amenability problem for Thompson's group $F$: state of the art","authors":"Guba, Victor","doi":"10.46298/jgcc.2023.15.1.11315","DOIUrl":"https://doi.org/10.46298/jgcc.2023.15.1.11315","url":null,"abstract":"This is a survey of our recent results on the amenability problem for Thompson's group $F$. They mostly concern esimating the density of finite subgraphs in Cayley graphs of $F$ for various systems of generators, and also equations in the group ring of $F$. We also discuss possible approaches to solve the problem in both directions.","PeriodicalId":41862,"journal":{"name":"Groups Complexity Cryptology","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135666569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Bounding conjugacy depth functions for wreath products of finitely generated abelian groups","authors":"Michal Ferov, Mark Pengitore","doi":"10.46298/jgcc.2023.15.1.11728","DOIUrl":"https://doi.org/10.46298/jgcc.2023.15.1.11728","url":null,"abstract":"In this article, we study the asymptotic behaviour of conjugacy separability for wreath products of abelian groups. We fully characterise the asymptotic class in the case of lamplighter groups and give exponential upper and lower bounds for generalised lamplighter groups. In the case where the base group is infinite, we give superexponential lower and upper bounds. We apply our results to obtain lower bounds for conjugacy depth functions of various wreath products of groups where the acting group is not abelian.","PeriodicalId":41862,"journal":{"name":"Groups Complexity Cryptology","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135387425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"An axiomatization for the universal theory of the Heisenberg group","authors":"A. Gaglione, D. Spellman","doi":"10.46298/jgcc.2023..12200","DOIUrl":"https://doi.org/10.46298/jgcc.2023..12200","url":null,"abstract":"The Heisenberg group, here denoted $H$, is the group of all $3times 3$ upper\u0000unitriangular matrices with entries in the ring $mathbb{Z}$ of integers. A.G.\u0000Myasnikov posed the question of whether or not the universal theory of $H$, in\u0000the language of $H$, is axiomatized, when the models are restricted to\u0000$H$-groups, by the quasi-identities true in $H$ together with the assertion\u0000that the centralizers of noncentral elements be abelian. Based on earlier\u0000published partial results we here give a complete proof of a slightly stronger\u0000result.","PeriodicalId":41862,"journal":{"name":"Groups Complexity Cryptology","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89856287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lindsay Marjanski, Vincent Solon, Frank Zheng, Kathleen Zopff
{"title":"Geodesic Growth of Numbered Graph Products","authors":"Lindsay Marjanski, Vincent Solon, Frank Zheng, Kathleen Zopff","doi":"10.46298/jgcc.2023.14.2.10019","DOIUrl":"https://doi.org/10.46298/jgcc.2023.14.2.10019","url":null,"abstract":"In this paper, we study geodesic growth of numbered graph products; these are\u0000a generalization of right-angled Coxeter groups, defined as graph products of\u0000finite cyclic groups. We first define a graph-theoretic condition called\u0000link-regularity, as well as a natural equivalence amongst link-regular numbered\u0000graphs, and show that numbered graph products associated to link-regular\u0000numbered graphs must have the same geodesic growth series. Next, we derive a\u0000formula for the geodesic growth of right-angled Coxeter groups associated to\u0000link-regular graphs. Finally, we find a system of equations that can be used to\u0000solve for the geodesic growth of numbered graph products corresponding to\u0000link-regular numbered graphs that contain no triangles and have constant vertex\u0000numbering.","PeriodicalId":41862,"journal":{"name":"Groups Complexity Cryptology","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83545543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Fine, A. Gaglione, M. Kreuzer, G. Rosenberger, D. Spellman
{"title":"The Axiomatics of Free Group Rings","authors":"B. Fine, A. Gaglione, M. Kreuzer, G. Rosenberger, D. Spellman","doi":"10.46298/jgcc.2021.13.2.8796","DOIUrl":"https://doi.org/10.46298/jgcc.2021.13.2.8796","url":null,"abstract":"In [FGRS1,FGRS2] the relationship between the universal and elementary theory\u0000of a group ring $R[G]$ and the corresponding universal and elementary theory of\u0000the associated group $G$ and ring $R$ was examined. Here we assume that $R$ is\u0000a commutative ring with identity $1 ne 0$. Of course, these are relative to an\u0000appropriate logical language $L_0,L_1,L_2$ for groups, rings and group rings\u0000respectively. Axiom systems for these were provided in [FGRS1]. In [FGRS1] it\u0000was proved that if $R[G]$ is elementarily equivalent to $S[H]$ with respect to\u0000$L_{2}$, then simultaneously the group $G$ is elementarily equivalent to the\u0000group $H$ with respect to $L_{0}$, and the ring $R$ is elementarily equivalent\u0000to the ring $S$ with respect to $L_{1}$. We then let $F$ be a rank $2$ free\u0000group and $mathbb{Z}$ be the ring of integers. Examining the universal theory\u0000of the free group ring ${mathbb Z}[F]$ the hazy conjecture was made that the\u0000universal sentences true in ${mathbb Z}[F]$ are precisely the universal\u0000sentences true in $F$ modified appropriately for group ring theory and the\u0000converse that the universal sentences true in $F$ are the universal sentences\u0000true in ${mathbb Z}[F]$ modified appropriately for group theory. In this paper\u0000we show this conjecture to be true in terms of axiom systems for ${mathbb\u0000Z}[F]$.","PeriodicalId":41862,"journal":{"name":"Groups Complexity Cryptology","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83076767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Finitely generated subgroups of free groups as formal languages and\u0000 their cogrowth","authors":"A. Darbinyan, R. Grigorchuk, Asif Shaikh","doi":"10.46298/jgcc.2021.13.2.7617","DOIUrl":"https://doi.org/10.46298/jgcc.2021.13.2.7617","url":null,"abstract":"For finitely generated subgroups $H$ of a free group $F_m$ of finite rank\u0000$m$, we study the language $L_H$ of reduced words that represent $H$ which is a\u0000regular language. Using the (extended) core of Schreier graph of $H$, we\u0000construct the minimal deterministic finite automaton that recognizes $L_H$.\u0000Then we characterize the f.g. subgroups $H$ for which $L_H$ is irreducible and\u0000for such groups explicitly construct ergodic automaton that recognizes $L_H$.\u0000This construction gives us an efficient way to compute the cogrowth series\u0000$L_H(z)$ of $H$ and entropy of $L_H$. Several examples illustrate the method\u0000and a comparison is made with the method of calculation of $L_H(z)$ based on\u0000the use of Nielsen system of generators of $H$.","PeriodicalId":41862,"journal":{"name":"Groups Complexity Cryptology","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74748874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}