Open Access

Erratum to "Fixed Points of Maps of a Nonaspherical Wedge"

  • Seungwon Kim1,
  • RobertF Brown2Email author,
  • Adam Ericksen3,
  • Nirattaya Khamsemanan4 and
  • Keith Merrill5
Fixed Point Theory and Applications20102010:820265

Received: 21 June 2010

Accepted: 17 July 2010

Published: 8 August 2010

The original article was published in Fixed Point Theory and Applications 2009 2009:531037


In the original paper, it was assumed that a selfmap of , the wedge of a real projective space and a circle , is homotopic to a map that takes to itself. An example is presented of a selfmap of that fails to have this property. However, all the results of the paper are correct for maps of the pair .

Let be the wedge of the real projective plane and the circle . As the example below demonstrates, the statement on page 3 of [1] "Given a map we may deform by a homotopy so that , its restriction to , maps to itself." is incorrect. If, instead of an arbitrary self-map of , we consider a map of pairs , the map can be put in the standard form defined on that page and then all the results of the paper are correct for such maps of pairs.

To describe the example, represent points of the unit -sphere by spherical coordinates where denotes the radius, the elevation and the azimuth. Let where is in or , if or , respectively. Let , where are the -spheres of radius one in with centers, in cartesian coordinates, at denotes the points for and the points for . Define in the following manner. For , let
in cartesian coordinates. For , set . Let be the poles and define by
Returning to cartesian coordinates, define by

We complete the definition of by setting for . Note that such that . We may embed in the universal covering space because is an infinite tree with a 2-sphere replacing each vertex in such a way that two edges are attached at each of two antipodal points. The embedding induces a monomorphism of homology. The map has been defined so that if are antipodal points of , then and therefore induces a map . If were homotopic to a map , then the homotopy would lift to cover by a map which sends to a single -sphere in . Therefore the image of would be either trivial or a single generator of . On the other hand, the image of in is nontrivial for three generators, so no such homotopy can exist. Therefore, if is a map whose restriction to is the map defined above, then it cannot be homotoped to a map that takes to itself.




The authors thank Francis Bonahon and Geoffrey Mess for their help with the example.

Authors’ Affiliations

Department of Mathematics, Kyungsung University
Department of Mathematics, University of California Los Angeles
Department of Mathematics, University of Southern California
Sirindhorn International Institute of Technology, Thammasat University
Department of Mathematics, Brandeis University


  1. Kim SW, Brown RF, Ericksen A, Khamsemanan N, Merrill K: Fixed points of maps of a nonaspherical wedge. Fixed Point Theory and Applications 2009, 2099:-18.Google Scholar


© Seungwon Kim et al. 2010

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.