9 research outputs found
Constructions for the optimal pebbling of grids
In [C. Xue, C. Yerger: Optimal Pebbling on Grids, Graphs and Combinatorics]
the authors conjecture that if every vertex of an infinite square grid is
reachable from a pebble distribution, then the covering ratio of this
distribution is at most . First we present such a distribution with
covering ratio , disproving the conjecture. The authors in the above paper
also claim to prove that the covering ratio of any pebble distribution is at
most . The proof contains some errors. We present a few interesting
pebble distributions that this proof does not seem to cover and highlight some
other difficulties of this topic
Optimal pebbling of grids
A pebbling move on a graph removes two pebbles at a vertex and adds
one pebble at an adjacent vertex. Rubbling is a version of pebbling
where an additional move is allowed. In this new move, one pebble
each is removed at vertices and adjacent to a vertex ,
and an extra pebble is added at vertex . A vertex is reachable
from a pebble distribution if it is possible to move a pebble to
that vertex using rubbling moves. The optimal pebbling (rubbling) number is
the smallest number needed to guarantee a pebble distribution of
pebbles from which any vertex is reachable using pebbling (rubbling) moves.
We determine the optimal rubbling number of ladders (), prisms
() and M\"oblus-ladders. We also give upper and lower
bounds for the optimal pebbling and rubbling numbers of large grids ()
More on the -restricted optimal pebbling number
Let be a simple graph. A function is called a configuration of pebbles on the vertices of and the
weight of is which is just the total number of
pebbles assigned to vertices. A pebbling step from a vertex to one of its
neighbors reduces by two and increases by one. A pebbling
configuration is said to be solvable if for every vertex , there
exists a sequence (possibly empty) of pebbling moves that results in a pebble
on . A pebbling configuration is a -restricted pebbling configuration
(abbreviated RPC) if for all . The -restricted
optimal pebbling number is the minimum weight of a solvable RPC
on . Chellali et.al. [Discrete Appl. Math. 221 (2017) 46-53] characterized
connected graphs having small -restricted optimal pebbling numbers and
characterization of graphs with stated as an open problem.
In this paper, we solve this problem. We improve the upper bound of the
-restricted optimal pebbling number of trees of order . Also, we study
-restricted optimal pebbling number of some grid graphs, corona and
neighborhood corona of two specific graphs.Comment: 12 pages, 11 figure
The optimal pebbling number of staircase graphs
Let G be a graph with a distribution of pebbles on its vertices. A pebbling move consists of removing two pebbles from one vertex and placing one pebble on an adjacent vertex. The optimal pebbling number of G is the smallest number of pebbles which can be placed on the vertices of G such that, for any vertex v of G, there is a sequence of pebbling moves resulting in at least one pebble on v. We determine the optimal pebbling number for several classes of induced subgraphs of the square grid, which we call staircase graphs. © 2018 Elsevier B.V
Optimal Pebbling Number of the Square Grid
A pebbling move on a graph removes two pebbles from a vertex and adds one
pebble to an adjacent vertex. A vertex is reachable from a pebble distribution
if it is possible to move a pebble to that vertex using pebbling moves. The
optimal pebbling number is the smallest number m needed to
guarantee a pebble distribution of m pebbles from which any vertex is
reachable. The optimal pebbling number of the square grid graph was investigated in several papers. In this paper, we present a new method
using some recent ideas to give a lower bound on . We apply this
technique to prove that . Our
method also gives a new proof for