Serdica Mathematical Journal

Volume 46, Number 2, 2020




C O N T E N T S

· Darji, K. N., R. G. Vyas. A note on double Fourier coefficients (pp. 101−108)
· Lezama, O., H. Venegas. The center of the total ring of fractions (pp. 109−120)
· Szabó, S. Modulo q greatest common divisor algorithms (pp. 121−134)
· Kostov, V. P. Hyperbolic polynomials and canonical sign patterns (pp. 135−150)
· Aleksieva, Ya., V. Milousheva. Quasi-minimal Lorentz surfaces in pseudo-Euclidean 4-space with neutral metric (pp. 151−164)
· Boyvalenkov, P., N. Safaei. On 3-distance spherical 5-designs (pp. 165−174)
· Kurdachenko, L. A., I. Ya. Subbotin, V. S. Yashchuk. Leibniz algebras whose subalgebras are left ideals (pp. 175−194)
· Oliynyk, B., B. Ponomarchuk. Metric dimension of ultrametric spaces (pp. 195−206)

A B S T R A C T S


A NOTE ON DOUBLE FOURIER COEFFICIENTS
Kiran N. Darji darjikiranmsu@gmail.com,
Rajendra G. Vyas drrgvyas@yahoo.com

2020 Mathematics Subject Classification: 42B05, 26B30, 26D15.
Key words: double Fourier series, order of magnitude, functions of (ϕ, ψ)-(Λ, Γ)-bounded variation.


THE CENTER OF THE TOTAL RING OF FRACTIONS
Oswaldo Lezama jolezamas@unal.edu.co,
Helbert Venegas hjvenegasr@unal.edu.co

2020 Mathematics Subject Classification: Primary: 16S85, 16U70. Secondary: 16P90, 16S36.
Key words: Ore domains, total ring of fractions, center of a ring, Gelfand−Kirillov dimension, skew PBW extensions.


MODULO q GREATEST COMMON DIVISOR ALGORITHMS
Sándor Szabó sszabo7@hotmail.com

2020 Mathematics Subject Classification: Primary 11A05; Secondary 11Y16.
Key words: binary gcd algorithm, extended gcd algorithm.


HYPERBOLIC POLYNOMIALS AND CANONICAL SIGN PATTERNS
Vladimir Petrov Kostov vladimir.kostov@unice.fr

2020 Mathematics Subject Classification: 26C10, 30C15.
Key words: real polynomial in one variable, hyperbolic polynomial, sign pattern, Descartes' rule of signs.


QUASI-MINIMAL LORENTZ SURFACES IN PSEUDO-EUCLIDEAN 4-SPACE WITH NEUTRAL METRIC
Yana Aleksieva yana_a_n@fmi.uni-sofia.bg,
Velichka Milousheva vmil@math.bas.bg

2020 Mathematics Subject Classification: Primary 53B30, Secondary 53A35, 53B25.
Key words: Quasi-minimal surface, marginally trapped surface, pseudo-Euclidean 4-space, Fundamental theorem.


ON 3-DISTANCE SPHERICAL 5-DESIGNS
Peter Boyvalenkov peter@math.bas.bg,
Navid Safaei navid_safaei@gsme.sharif.edu

2020 Mathematics Subject Classification: 05B30, 52C17.
Key words: spherical designs, maximal codes, few distance codes.


LEIBNIZ ALGEBRAS WHOSE SUBALGEBRAS ARE LEFT IDEALS
L. A. Kurdachenko lkurdachenko@i.ua,
I. Ya. Subbotin isubboti@nu.edu,
V. S. Yashchuk viktoriia.s.yashchuk@gmail.com

2020 Mathematics Subject Classification: 17A32, 17A60, 17A99.
Key words: Leibniz algebra, Lie algebra, ideal, left ideal, nilpotent Leibniz algebra, extraspecial algebra.


METRIC DIMENSION OF ULTRAMETRIC SPACES
Bogdana Oliynyk oliynyk@ukma.edu.ua,
Bogdan Ponomarchuk ponomarchuk.bogdan@gmail.com

2020 Mathematics Subject Classification: 05B25, 05C12, 68R12.
Key words: metric dimension, ultrametric space, rooted tree, polynomial-time algorithm.


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