Reinhard Diestel

  1. Locally finite graphs with ends: a topological approach.

    Authors: Reinhard Diestel
    Subjects: Combinatorics
    Abstract

    This paper is intended as an introductory survey of a newly emerging field: a
    topological approach to the study of locally finite graphs that crucially
    incorporates their ends. Topological arcs and circles, which may pass through
    ends, assume the role played in finite graphs by paths and cycles.

  2. On the homology of locally compact spaces with ends.

    Authors: Reinhard Diestel, Philipp Sprüssel
    Subjects: Algebraic Topology
    Abstract

    We propose a homology theory for locally compact spaces with ends in which
    the ends play a special role. The approach is motivated by results for graphs
    with ends, where it has been highly successful. But it was unclear how the
    original graph-theoretical definition could be captured in the usual language
    for homology theories, so as to make it applicable to more general spaces.

  3. The fundamental group of a locally finite graph with ends.

    Authors: Reinhard Diestel, Philipp Sprüssel
    Subjects: Combinatorics
    Abstract

    We characterize the fundamental group of a locally finite graph G with ends
    combinatorially, as a group of infinite words. Our characterization gives rise
    to a canonical embedding of this group in the inverse limit of the (free)
    fundamental groups of the finite subgraphs of G.

  4. On the homology of locally finite graphs.

    Authors: Reinhard Diestel, Philipp Sprüssel
    Subjects: Combinatorics
    Abstract

    We show that the topological cycle space of a locally finite graph is a
    canonical quotient of the first singular homology group of its Freudenthal
    compactification, and we characterize the graphs for which the two coincide. We
    construct a new singular-type homology for non-compact spaces with ends, which
    in dimension~1 captures precisely the topological cycle space of graphs but
    works in any dimension.

  5. Every rayless graph has an unfriendly partition.

    Authors: Henning Bruhn, Reinhard Diestel, Agelos Georgakopoulos, Philipp Sprüssel
    Subjects: Combinatorics
    Abstract

    We prove that every rayless graph has an unfriendly partition.

  6. Every rayless graph has an unfriendly partition.

    Authors: Henning Bruhn, Reinhard Diestel, Agelos Georgakopoulos, Philipp Sprüssel
    Subjects: Combinatorics
    Abstract

    We prove that every rayless graph has an unfriendly partition.

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