Alexander Šostak

Prof. Alexander Šostak

1. Department of Mathematics, University of Latvia, LV-1004 Riga, Latvia
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Research Focus & Metrics

Academic Career Length

20Years (2007-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 May 2013 in Computational and Applied Mathematics
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SHSang-Eon Han
Sang-Eon Han
Alexander ŠostakAlexander Šostak
Alexander Šostak

23 August 2018 in Axioms
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Alexander ŠostakAlexander Šostak
Alexander Šostak
In this note, we present an alternative approach to the concept of a fuzzy metric, calling it a revised fuzzy metric. In contrast to the traditional approach to the theory of fuzzy metric spaces which is based on the use of a t-norm, we proceed from a t-conorm in the definition of a revised fuzzy metric. Here, we restrict our study to the case of fuzzy metrics as they are defined by George-Veeramani, however, similar revision can be done also for some other approaches to the concept of a fuzzy metric.

25 September 2017 in Soft Computing
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SHSang-Eon Han
Sang-Eon Han
Alexander ŠostakAlexander Šostak
Alexander Šostak

8 July 2020 in Axioms
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OGOlga Grigorenko
Olga Grigorenko
JMJuan-José Miñana
Juan-José Miñana
Alexander ŠostakAlexander Šostak
Alexander Šostak
Oscar ValeroOscar Valero
Oscar Valero
We present an alternative approach to the concept of a fuzzy (pseudo)metric using t-conorms instead of t-norms and call them t-conorm based fuzzy (pseudo)metrics or just CB-fuzzy (pseudo)metrics. We develop the basics of the theory of CB-fuzzy (pseudo)metrics and compare them with “classic” fuzzy (pseudo)metrics. A method for construction CB-fuzzy (pseudo)metrics from ordinary metrics is elaborated and topology induced by CB-fuzzy (pseudo)metrics is studied. We establish interrelations between CB-fuzzy metrics and modulars, and in the process of this study, a particular role of Hamacher t-(co)norm in the theory of (CB)-fuzzy metrics is revealed. Finally, an intuitionistic version of a CB-fuzzy metric is introduced and applied in order to emphasize the roles of t-norms and a t-conorm in this context.

1 January 2018 in Filomat
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Alexander ŠostakAlexander Šostak
Alexander Šostak
An important class of spaces was introduced by I.A. Bakhtin (under the name ?metric-type?) and independently rediscovered by S. Czerwik (under the name ?b-metric?). Metric-type spaces generalize ?classic? metric spaces by replacing the triangularity axiom with a more general axiom d(x,z)? k? (d(x,y)+ d(y,z)) for all x,y,z ? X where k ? 1 is a fixed constant. Recently R. Saadadi has introduced the fuzzy version of ?metric-type? spaces. In this paper we consider topological and sequential properties of such spaces, illustrate them by several examples and prove a certain version of the Baire Category Theorem.

27 March 2020 in Journal of Applied Mathematics and Computing
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MDM. K. Dubey
M. K. Dubey
STS. P. Tiwari
S. P. Tiwari
Alexander ŠostakAlexander Šostak
Alexander Šostak