The chromatic sum Σ(G) of a graph G is the smallest sum of colors among all proper colorings with natural numbers. The strength s(G) of G is the minimum number of colors needed to achieve the chromatic sum. We construct for each positive integer k a tree Tk with strength k that has maximum degree only 2k − 2. The result is best possible.

For an arbitrary matrix A of n×n symbols, consider its submatrices of size k×k, obtained by deleting n−k rows and n−k columns. Optionally, the deleted rows and columns can be selected symmetrically or independently. We consider the problem of whether these multisets determine matrix A. Following the ideas of Krasikov and Roditty in the reconstruction of sequences from subsequences, we replace t...

We present a new way to encode weighted sums into unweighted pairwise constraints, obtaining the following results. – Define the k-SUM problem to be: given n integers in [−n, n] are there k which sum to zero? (It is well known that the same problem over arbitrary integers is equivalent to the above definition, by linear-time randomized reductions.) We prove that this definition of k-SUM remains...

A Direct Sum Theorem holds in a model of computation, when for every problem solving some k input instances together is k times as expensive as solving one. We show that Direct Sum Theorems hold in the models of deterministic and randomized decision trees for all relations. We also note that a near optimal Direct Sum Theorem holds for quantum decision trees for boolean functions.

Let $kgeq 1$ be an integer, and let $G$ be a graph. A {it$k$-rainbow dominating function} (or a {it $k$-RDF}) of $G$ is afunction $f$ from the vertex set $V(G)$ to the family of all subsetsof ${1,2,ldots ,k}$ such that for every $vin V(G)$ with$f(v)=emptyset $, the condition $bigcup_{uinN_{G}(v)}f(u)={1,2,ldots,k}$ is fulfilled, where $N_{G}(v)$ isthe open neighborhood of $v$. The {it weight} o...

In this paper we construct trigonometric functions of the sum Tp(h, k), which is called Dedekind type DC-(Dahee and Changhee) sums. We establish analytic properties of this sum. We find trigonometric representations of this sum. We prove reciprocity theorem of this sums. Furthermore, we obtain relations between the Clausen functions, Polylogarithm function, Hurwitz zeta function, generalized La...

Let G be a bipartite graph, with k j e(G). The zero-sum bipartite Ramsey number B(G; Z k) is the smallest integer t such that in every Z k-coloring of the edges of K t;t , there is a zero-sum mod k copy of G in K t;t. In this paper we give the rst proof which determines B(G; Z 2) for all possible bipartite graphs G. In fact, we prove a much more general result from which B(G; Z 2) can be deduce...