Solvability of Sturm-Liouville problems on time scales at resonance

Under the appropriate growth conditions on the inhomogeneous term, we present the existence of the nontrivial solution for Sturm-Liouville boundary value problems on time scales at resonance by making use of coincidence degree theory of Mawhin. The interesting point is the nonlinearity f which is involved with first-order Δ-derivative explicitly.     

Certain properties of Cesàro derivatives of higher orders

It is shown that a function with a Cesàro C ₂-derivative greater than ?∞ everywhere on a segment is not necessarily VBG. We also construct a function having a finite approximate derivative almost everywhere on a segment, but its C ₂-derivative is equal to +∞ almost everywhere.     

Derivatives of the Efficient Point Multifunction in Parametric Vector Optimization Problems

In this paper, we deal with the sensitivity analysis in vector optimization. More specifically, formulae for inner and outer evaluating the S-derivative of the efficient point multifunction in parametric vector optimization problems are established. These estimating formulae are presented via the set of efficient/weakly efficient points of the S-derivative of the original multifunction, a composite multifunction of the objective function and the constraint mapping. The elaboration of the formulae in vector optimization problems, having multifunction constraints and semiinfinite constraints, is also undertaken. Furthermore, examples are provided for analyzing and illustrating the obtained results.     

On Linear Dynamics in Quantum Calculus

In this paper, we are concerned with establishing some new elements of q-harmonic analysis. Namely, we prove a generalized q-Paley-Wiener theorem. As a consequence, we obtain some results of linear dynamics related to the symmetric q-derivative.     

q-Derivative Operators and Basic Hypergeometric Series

By means of q-derivative operators, we investigate formal power series expansions. Two main expansion formulae in terms of q-derivative operators are established which can be considered as extensions of the corresponding results due to Carlitz (1973) and Liu (2002). Their applications to basic hypergeometric evaluations and transformations are discussed through series compositions and their q-derivative operations. Direct verification of the two main theorems are also presented.     

Open irredundance and maximum degree in graphs

A necessary and sufficient condition for an open irredundant set of vertices of a graph to be maximal is obtained. This result is used to show that the smallest cardinality amongst the maximal open irredundant sets in an n-vertex isolate-free graph with maximum degree Δ is at least n(3Δ−1)/(2Δ³−5Δ²+8Δ−1) for Δ≥5, n/8 for Δ=4 and 2n/11 for Δ=3. The bounds are the best possible.     

Irredundance, secure domination and maximum degree in trees

It is shown that the lower irredundance number and secure domination number of an n vertex tree T with maximum degree Δ?3, are bounded below by 2(n+1)/(2Δ+3)(T≠K_1,Δ) and (Δn+Δ-1)/(3Δ-1), respectively. The bounds are sharp and extremal trees are exhibited.     

Injective colorings of planar graphs with few colors

An injective coloring of a graph is a vertex coloring where two vertices have distinct colors if a path of length two exists between them. In this paper some results on injective colorings of planar graphs with few colors are presented. We show that all planar graphs of girth ≥ 19 and maximum degree Δ are injectively Δ-colorable. We also show that all planar graphs of girth ≥ 10 are injectively (Δ+1)-colorable, that Δ+4 colors are sufficient for planar graphs of girth ≥ 5 if Δ is large enough, and that subcubic planar graphs of girth ≥ 7 are injectively 5-colorable.     

Betti numbers of Stanley–Reisner rings determine hierarchical Markov degrees

There are two seemingly unrelated ideals associated with a simplicial complex Δ: one is the Stanley–Reisner ideal I _Δ , the monomial ideal generated by minimal non-faces of Δ, well-known in combinatorial commutative algebra; the other is the toric ideal I _M(Δ) of the facet subring of Δ, whose generators give a Markov basis for the hierarchical model defined by Δ, playing a prominent role in algebraic statistics. In this note we show that the complexity of the generators of I _M(Δ) is determined by the Betti numbers of I _Δ . The unexpected connection between the syzygies of the Stanley–Reisner ideal and degrees of minimal generators of the toric ideal provide a framework for further exploration of the connection between the model and its many relatives in algebra and combinatorics.     

On the f- and h-triangle of the barycentric subdivision of a simplicial complex

For a simplicial complex Δ we study the behavior of its f- and h-triangle under the action of barycentric subdivision. In particular we describe the f- and h-triangle of its barycentric subdivision sd(Δ). The same has been done for f- and h-vector of sd(Δ) by F. Brenti, V. Welker (2008). As a consequence we show that if the entries of the h-triangle of Δ are nonnegative, then the entries of the h-triangle of sd(Δ) are also nonnegative. We conclude with a few properties of the h-triangle of sd(Δ).     

Solution to the presentation problem for powers of the augmentation ideal of torsion free and torsion abelian groups

This paper solves for torsion free and torsion abelian groups G the problem of presenting nth powers Δⁿ(G) of the augmentation ideal Δ(G) of an integral group ring , in terms of the standard additive generators of Δⁿ(G). A concrete basis for Δⁿ(G) is obtained when G itself has a basis and is torsion. The results are applied to describe the homology of the sequence Δn(N)G?Δn(G)?Δn(G/N).     

Pointwise Comparison of PCM and Σ Δ Quantization

A quantitative comparison of Pulse Code Modulation (PCM) and Sigma–Delta (Σ Δ) quantization methods is made in the setting of finite frames. Frames allow for redundant, overcomplete signal decompositions. PCM and Σ Δ are two industry-standard quantization methods, and the setting of finite frames is appropriate for a host of modern applications. Previous results for this comparison are known for upper error bounds, where Σ Δ performs better in the setting of frames, as opposed to orthonormal bases, where PCM is optimal. We answer the following question: For which signals x is the PCM error, that is, the norm of the difference between x and its PCM approximant, less than the Σ Δ error? We prove that, typically, in the setting of frames, Σ Δ outperforms PCM, but not always.     

A note on the strong chromatic index of bipartite graphs

The strong chromatic index s^′(G) is the minimum integer t such that there is an edge-coloring of G with t colors in which every color class is an induced matching. Brualdi and Quinn conjecture that for every bipartite graph G, s^′(G) is bounded by Δ₁Δ₂, where Δ₁ and Δ₂ are the maximum degrees among vertices in the two partite sets. We give the affirmative answer for Δ₁=2.     

Linear colorings of simplicial complexes and collapsing

A vertex coloring of a simplicial complex Δ is called a linear coloring if it satisfies the property that for every pair of facets (F₁,F₂) of Δ, there exists no pair of vertices (v₁,v₂) with the same color such that v₁∈F₁?F₂ and v₂∈F₂?F₁. The linear chromatic numberlchr(Δ) of Δ is defined as the minimum integer k such that Δ has a linear coloring with k colors. We show that if Δ is a simplicial complex with lchr(Δ)=k, then it has a subcomplex Δ^′ with k vertices such that Δ is simple homotopy equivalent to Δ^′. As a corollary, we obtain that lchr(Δ)?Homdim(Δ)+2. We also show in the case of linearly colored simplicial complexes, the usual assignment of a simplicial complex to a multicomplex has an inverse. Finally, we show that the chromatic number of a simple graph is bounded from above by the linear chromatic number of its neighborhood complex.     

Minimizing mean squared deviation of completion times with maximum tardiness constraint

We consider a nonpreemptive single-machine scheduling problem to minimize mean squared deviation of job completion times about a common due date with maximum tardiness constraint (MSD/T_max problem), where the common due date is large enough so that it does not constrain the minimization of MSD.The MSD/T_max problem is classified into three cases according to the value of maximum allowable tardiness Δ: Δ-unconstrained, Δ-constrained and tightly Δ-constrained cases. It is shown that the Δ-unconstrained MSD/T_max problem is equivalent to the unconstrained MSD problem and that the tightly Δ-constrained MSD/T_max problem with common due date d is equivalent to the tightly constrained MSD problem with common due date Δ. We also provide bounds to decide when the MSD/T_max problem is Δ-unconstrained or Δ-constrained. Then a solution procedure to the MSD/T_max problem is presented with several examples.     

A note on the density of a subset of all integrable holomorphic quadratic differentials

Let T0(Δ) be the subset of the universal Teichm¨uller space, which consists all of the elements with boundary dilatation 1. Let SQ(Δ) be the unit ball of the space Q(Δ) of all integrable holomorphic quadratic differentials on the unit disk Δ and Q0(Δ) be defined as Q0(Δ) = {? ∈ SQ(Δ) : there exists a k ∈(0, 1) such that [kˉ? |?|] ∈ T0(Δ)}. In this paper, we show that Q0(Δ) is dense in SQ(Δ).     

Independence,irredundance, degrees and chromatic number in graphs

Let β(G) and IR(G) denote the independence number and the upper irredundance number of a graph G. We prove that in any graph of order n, minimum degree δ and maximum degree Δ≠0, IR(G)⩽n/(1+δ/Δ) and IR(G)−β(G)⩽((Δ−2)/2Δ)n. The two bounds are attained by arbitrarily large graphs. The second one proves a conjecture by Rautenbach related to the case Δ=3. When the chromatic number χ of G is less than Δ, it can be improved to IR(G)−β(G)⩽((χ−2)/2χ)n in any non-empty graph of order n⩾2.     

Dendrites with a countable closure of the set of end points

We investigate the problem of existence of universal elements in some families of dendrites with a countable closure of the set of end points. In particular, we prove that for each integer κ?3 and for each ordinal α?1 there exists a universal element in the family of all dendrites X such that ord(X)?κ and the α-derivative of the set clXE(X) contains at most one point.     

Planar graphs with maximum degree 8 and without adjacent triangles are 9-totally-colorable

The Total Coloring Conjecture, in short, TCC, says that every simple graph is (Δ+2)-totally-colorable where Δ is the maximum degree of the graph. Even for planar graphs this conjecture has not been completely settled yet. However, every planar graph with Δ≥9 has been proved to be (Δ+1)-totally-colorable. In this paper, we prove that planar graphs with maximum degree 8 and without adjacent triangles are 9-totally-colorable.