Vol XXVIII 2018 – 2019

Vol XXVIII 2018 – 2019

Geombinatorics

A quarterly journal on open problems of combinatorial and discrete geometry and related areas.

July 2018 – April 2019

Issue 1   Issue 2   Issue 3    Issue 4 


Issue 1 (July 2018)


CONTENTS XXVIII (1)

Editor’s Page………………….…………………………………..4

New Essays

  • Progress in My Favorite Open Problem of Mathematics, Chromatic
    Number of the Plane: An Étude in Five Movements ………..……5
    by Alexander Soifer

 

 

  • Computing Small Unit-Distance Graphs with Chromatic
    Number 5…………………………………………………………..32
    by Marijn J.H. Heule

 

  • The Hadwiger-Nelson problem with two
    forbidden distances……………………………………………….51
    by Geoffrey Exoo and Dan Ismailescu

Recent Books……………………………..………….………69

 


Issue 2 (October 2018)


CONTENTS XXVIII (2)

Editor’s Page………………….…………………………………………..76

New Essays

  • The Chromatic Number of  The Taxicab Plane ……………………………..……77
    by John Donnelly

 

 

  • Extensions of Möbius-Kantor Configurations…………………………………..93
    by J. Lanyon and R. Padmanabhan

 

  • Why Asset-Based Approach to Teaching Is More Effective
    than 
    the Usual Deficit-Based Approach, and Why the New
    Approach 
    Is Not Easy to Implement: A Simple Geometric
    Explanation
    …………………………………………………………………………..…….…….99
    by Olga Kosheleval and Vladik Kreinovich

 

  • Truth, Like Water, Finds Its Way Out……………………………………………..106
    by Alexander Soifer

 

  • Revisiting Bodies having Constant HA-Measurements………………….112
    by Joseph Zaks

 


Issue 3 (January 2019)


CONTENTS XXVIII (3)

Editor’s Page………………….……………………………………….120

New Essays

 

 

  • Inseparability
    by Sara Zaks…………..…………………………………………………..124

 

  • Branko
    by Moshe Rosenfeld………..…………………………………………..127

 

  • Branko Grünbaum in Many Dimensions
    by Matthew Kahle…………………………………………………….…132

 

  • Branko, My Teacher, Collaborator, and Friend
    by Alexander Soifer………..……………………………………….…..139

 

 


Issue 4 (April 2019)


CONTENTS XXVIII (4)

Editor’s Page………………….……………………………………………..….176

New Essays

 

  • On the Independence Numbers of the Van der Waerden and cyclic Van der Waerden Hypergraphs W(k; t) and Wc(k; t) when and Are Powers of the Same Prime
    by Peter Johnson and Zechun Yang ………..…………………….191

 

  • Tiling the plane with equilateral triangles
    by János Pach and Gábor Tardos………..……………………..…197

 

  • Chromatic Problems and Prizes
    by Alexander Soifer………..……………………………………..…..206

 

  • Revisiting the 2Neighborly d-simplices in Ed
    by Joseph Zaks…………………………………………………….…..211

 

Subscription Form…………….……….……………….…………….215