Utilitas Algorithmica (UA)

ISSN: xxxx-xxxx (print)

Utilitas Algorithmica (UA) is a premier, open-access international journal dedicated to advancing algorithmic research and its applications. Launched to drive innovation in computer science, UA publishes high-impact theoretical and experimental papers addressing real-world computational challenges. The journal underscores the vital role of efficient algorithm design in navigating the growing complexity of modern applications. Spanning domains such as parallel computing, computational geometry, artificial intelligence, and data structures, UA is a leading venue for groundbreaking algorithmic studies.

M. Cordero-Vourtsanis1
1 Department of Mathematics Texas Tech University Lubbock, Texas 79409
B. A. Anderson1
1Department of Mathematics Arizona State University Tempe, Arizona 85287
Abstract:

Golomb and Taylor (joined later by Etzion) have modified the notion of a complete Latin square to that of a Tuscan-\(k\) square. A Tuscan-\(k\) square is a row Latin square with the further property that for any two symbols \(a\) and \(b\) of the square, and for each \(m\) from \(1\) to \(k\), there is at most one row in which \(b\) is the \(m^{th}\) symbol to the right of \(a\). One question unresolved by a series of papers of the authors mentioned was whether or not \(n \times n\) Tuscan-\(2\) squares exist for infinitely many composite values of \(n+1\). It is shown here that if \(p\) is a prime and \(p \equiv 7 \pmod{12}\) or \(p \equiv 5 \pmod{24}\), then Tuscan-\(2\) squares of side \(2p\) exist. If \(p \equiv 7 \pmod{12}\), clearly \(2p + 1\) is always composite and if \(p \equiv 5 \pmod{24}\), \(2p+1\) is composite infinitely often. The squares constructed are in fact Latin squares that have the Tuscan-\(2\) property in both dimensions.

Aditya Shastri1
1 Tilak Chonk P.O. Banasthali Vidyapith – 304022 INDIA
Abstract:

It is shown that if \([n] = X_1 \cup X_2 \cup \cdots \cup X_l\) is a partition of \([n]\) and if \(S_t\) is a family of \(t\)-valued functions intersecting on at least one element of \(k\) (circularly) consecutive blocks, then \(|S_t| < t^{n-k}\). If given \(a_1 < a_2 < \cdots < a_y \leq l \), \(\acute{S}_t\) is a family of \(t\)-valued functions intersecting on at least one element of \(X_{a_{1}+m}, X_{a_{2}+m}, \ldots, X_{a_{k}+m}\) for some \(m\) with \(1-a_1 \leq m \leq n – a_k\), then \(|\acute{S}_t| \leq t^{n-k}\). Both these results were conjectured by Faudree, Schelp, and Sós [FSS]. The main idea of our proofs is that of anticlusters introduced by Griggs and Walker [GW] which we discuss in some detail. We also discuss several related intersection theorems about sets, \(2\)-valued functions, and \(t\)-valued functions.

A. Bialostocki1, P. Dierker1
1 Department of Mathematics and Statistics University of Idaho Moscow, Idaho 83843
Abstract:

Let the edges of the complete graph \(K_n\) be \(2\)-colored. A Simple Hamiltonian Cycle is a Hamiltonian cycle in \(K_n\) that is either monochromatic or is a union of two monochromatic paths. The main result of this paper is that if \(n\) is an even integer greater than \(4\), then for every \(2\)-coloring of the edges of \(K_n\), there is a Simple Hamiltonian Cycle in \(K_n\) which is either monochromatic, or is a union of two monochromatic paths, where each path is of even length.

Chong-Keang Lim1, Yee-Hock Peng2
1Department of Mathematics University of Malaya 59100 Kuala Lumpur, Malaysia
2Department of Mathematics University of Agriculture 43400 Serdang, Selangor, Malaysia
Abstract:

Uniquely pseudointersectable graphs are defined; this is closely related to the uniquely intersectable graphs introduced by Alter and Wang [1]. The S-property is necessary but not sufficient for a graph to be uniquely pseudointersectable. This condition is also sufficient for graphs with unique minimum cover. Finally, we show that for supercompact graphs, unique pseudointersectability and unique intersectability are equivalent. Thus we generalize some of the results in [1] to a wider class of graphs.

Songlin Tian1
1Department of Mathematics and Computer Science Central Missouri State University Warrensburg, MO U.S.A. 64093-5045
Abstract:

A connected graph \(G\) is unicentered if \(G\) has exactly one central vertex. It is proved that for integers \(r\) and \(d\) with \(1 \leq r < d \leq 2r\), there exists a unicentered graph \(G\) such that rad\((G) = r\) and diam\((G) = d\). Also, it is shown that for any two graphs \(F\) and \(G\) with rad\((F) = n \geq 4\) and a positive integer \(d\) (\(4 \leq d \leq n\)), there exists a connected graph \(H\) with diam\((H) = d\) such that the periphery and the center of \(H\) are isomorphic to \(F\) and \(G\), respectively.

D. V. Chopra1
1Wichita State University Wichita, Kansas 67208 (U.S.A.)
Abstract:

In this paper we obtain some inequalities on the existence of balanced arrays (\(B\)-arrays) of strength four in terms of its parameter by using Minkowski’s inequality.

Wandi Wei1, Benfu Yang2
1Department of Mathematics Sichuan University Chengdu, CHINA
2Department of Mathematics Chengdu Teacher’s College Chengdu, CHINA
Abstract:

Let \(q\) be a prime power, \({F}_{q^2}\) the finite field with \(q^2\) elements, \(U_n({F}_{q^2})\) the finite unitary group of degree \(n\) over \({F}_{q^2}\), and \(UV_n({F}_{q^2})\) the \(n\)-dimensional unitary geometry over \({F}_{q^2}\). It is proven that the subgroup consisting of the elements of \(U_n({F}_{q^2})\) which fix a given \((m, s)\)-type subspace of \(UV_n({F}_{q^2})\), acts transitively on some subsets of subspaces of \(UV_n({F}_{q^2})\). This observation gives rise to a number of Partially Balanced Incomplete Block Designs (PBIBD’s).

Cantian Lin1, W.D. Wallis1
1Department of Mathematics Southern Illinois University at Carbondale Carbondale, IL 62901-4408
Abstract:

There are two criteria for optimality of weighing designs. One, which has been widely studied, is that the determinant of \(XX^T\) should be maximal, where \({X}\) is the weighing matrix. The other is that the trace of \((XX^T)^{-1}\) should be minimal. We examine the second criterion. It is shown that Hadamard matrices, when they exist, are optimal with regard to the second criterion, just as they are for the first one.

R. Craigen1
1Dept. of Mathematics and Computer Science University of Lethbridge Lethbridge, Alberta Canada TIK 3M4
Abstract:

In 1988, Sarvate and Seberry introduced a new method of construction for the family of weighing matrices \(W(n^2(n-1), n^2)\), where \(n\) is a prime power. We generalize this result, replacing the condition on \(n\) with the weaker assumption that a generalized Hadamard matrix \(GH(n; G)\) exists with \(|G| = n\), and give conditions under which an analogous construction works for \(|G| < n\). We generalize a related construction for a \(W(13, 9)\), also given by Sarvate and Seberry, producing a whole new class. We build further on these ideas to construct several other classes of weighing matrices.

Special Issues

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