Powered by OpenAIRE graph
Found an issue? Give us feedback
image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ Mathematical Proceed...arrow_drop_down
image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
Mathematical Proceedings of the Cambridge Philosophical Society
Article . 2008 . Peer-reviewed
License: Cambridge Core User Agreement
Data sources: Crossref
https://dx.doi.org/10.48550/ar...
Article . 2007
License: arXiv Non-Exclusive Distribution
Data sources: Datacite
versions View all 5 versions
addClaim

This Research product is the result of merged Research products in OpenAIRE.

You have already added 0 works in your ORCID record related to the merged Research product.

On the intersection of free subgroups in free products of groups

Authors: Dicks, Warren; Ivanov, S.V.;

On the intersection of free subgroups in free products of groups

Abstract

AbstractLet (Gi|i∈I) be a family of groups, letFbe a free group, and let$G = F \ast \mathop{\text{\Large $*$}}_{i\in I} G_i,$the free product ofFand all theGi.Let$\mathcal{F}$denote the set of all finitely generated subgroupsHofGwhich have the property that, for eachg∈Gand eachi∈I,$H \cap G_i^{g} = \{1\}.$By the Kurosh Subgroup Theorem, every element of$\mathcal{F}$is a free group. For each free groupH, thereduced rankofH, denotedr(H), is defined as$\max \{\rank(H) -1, 0\} \in \naturals \cup \{\infty\} \subseteq [0,\infty].$To avoid the vacuous case, we make the additional assumption that$\mathcal{F}$contains a non-cyclic group, and we defineWe are interested in precise bounds for$\upp$. In the special case whereIis empty, Hanna Neumann proved that$\upp$∈ [1,2], and conjectured that$\upp$= 1; fifty years later, this interval has not been reduced.With the understanding that ∞/(∞ − 2) is 1, we defineGeneralizing Hanna Neumann's theorem we prove that$\upp \in [\fun, 2\fun]$, and, moreover,$\upp = 2\fun$wheneverGhas 2-torsion. Since$\upp$is finite,$\mathcal{F}$is closed under finite intersections. Generalizing Hanna Neumann's conjecture, we conjecture that$\upp = \fun$wheneverGdoes not have 2-torsion.

Keywords

20E06, Grups, Teoria dels, FOS: Mathematics, 512 - Àlgebra, Group Theory (math.GR), Mathematics - Group Theory

  • BIP!
    Impact byBIP!
    citations
    This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
    15
    popularity
    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
    Average
    influence
    This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
    Top 10%
    impulse
    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
    Top 10%
Powered by OpenAIRE graph
Found an issue? Give us feedback
citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
15
Average
Top 10%
Top 10%
Green
bronze