Exact λ-numbers of generalized Petersen graphs of certain higher-orders and on Möbius strips

  • Authors:
  • Sarah Spence Adams;Paul Booth;Harold Jaffe;Denise Sakai Troxell;S. Luke Zinnen

  • Affiliations:
  • Franklin W. Olin College of Engineering, Olin Hall, Olin Way, Needham, MA 02492, USA;Franklin W. Olin College of Engineering, Olin Hall, Olin Way, Needham, MA 02492, USA;Franklin W. Olin College of Engineering, Olin Hall, Olin Way, Needham, MA 02492, USA;Mathematics and Science Division, Babson College, Babson Park, MA 02457, USA;Franklin W. Olin College of Engineering, Olin Hall, Olin Way, Needham, MA 02492, USA

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2012

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Abstract

An L(2,1)-labeling of a graph G is an assignment f of nonnegative integers to the vertices of G such that if vertices x and y are adjacent, |f(x)-f(y)|=2, and if x and y are at distance two, |f(x)-f(y)|=1. The @l-number of G is the minimum span over all L(2,1)-labelings of G. A generalized Petersen graph (GPG) of order n consists of two disjoint copies of cycles on n vertices together with a perfect matching between the two vertex sets. By presenting and applying a novel algorithm for identifying GPG-specific isomorphisms, this paper provides exact values for the @l-numbers of all GPGs of orders 9, 10, 11, and 12. For all but three GPGs of these orders, the @l-numbers are 5 or 6, improving the recently obtained upper bound of 7 for GPGs of orders 9, 10, 11, and 12. We also provide the @l-numbers of several infinite subclasses of GPGs that have useful representations on Mobius strips.