**Тип публикации: ** статья из журнала

**Год издания: ** 2019

**Идентификатор DOI: ** 10.21538/0134-4889-2019-25-4-107-117

**Ключевые слова: ** quasifield, semifield, near-field, maximal subfield, spectrum

**Аннотация: ** A semifield is a simple ring in which nonzero elements with respect to multiplication form a loop. Weakening distributivity from two-sided to one-sided yields the more general notion of quasifield (near-field under the condition of associativity). Problems of the structure of finite semifields and quasifields have been studied in vПоказать полностьюarious cases for a long time. In recent years, they have been mentioned in a number of papers. These problems were solved earlier for Knuth-Rua and Hentzel-Rua semifields, which are counterexamples of orders 32 and 64 to Wene's known hypothesis. The methods of computer algebra were used to describe some quasifields of small orders. It is known that the center of a finite semifield always contains the prime subfield. We show that the center of a finite near-field Q contains the prime subfield P except for Zassenhaus' four near-fields of orders 5(2), 7(2), 11(2), and 29(2). The kernel of a near-field Q always contains P. The maximal subfields of a finite near-field are enumerated under sufficiently general conditions. The automorphism groups of a near-field Q and of its multiplicative group Q* were found earlier. The group Q* is metacyclic, which makes it possible to explicitly find the spectrum of group orders of its elements.
A semifield is a simple ring in which nonzero elements with respect to multiplication form a loop. Weakening distributivity from two-sided to one-sided yields the more general notion of quasifield (near-field under the condition of associativity). Problems of the structure of finite semifields and quasifields have been studied in various cases for a long time. In recent years, they have been mentioned in a number of papers. These problems were solved earlier for Knuth-Rúa and Hentzel-Rúa semifields, which are counterexamples of orders 32 and 64 to Wene's known hypothesis. The methods of computer algebra were used to describe some quasifields of small orders. It is known that the center of a finite semifield always contains the prime subfield. We show that the center of a finite near-field Q contains the prime subfield P except for Zassenhaus' four near-fields of orders 52, 72, 112, and 292. The kernel of a near-field Q always contains P. The maximal subfields of a finite near-field are enumerated under sufficiently general conditions. The automorphism groups of a near-field Q and of its multiplicative group Q∗ were found earlier. The group Q∗ is metacyclic, which makes it possible to explicitly find the spectrum of group orders of its elements. © 2019 Krasovskii Institute of Mathematics and Mechanics. All rights reserved.

**Журнал: ** TRUDY INSTITUTA MATEMATIKI I MEKHANIKI URO RAN

**Выпуск журнала: ** Vol. 25, Is. 4

**Номера страниц: ** 107-117

**ISSN журнала: ** 01344889

**Место издания: ** YEKATERINBURG

**Издатель: ** KRASOVSKII INST MATHEMATICS & MECHANICS URAL BRANCH RUSSIAN ACAD SCIENCES

- Kravtsova O.V
*(Siberian Fed Univ, Phys Math, Krasnoyarsk 660041, Russia)* - Levchuk V.M.
*(Siberian Fed Univ, Krasnoyarsk 660041, RussiaArticle)*

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