Regina Iosifovna Tyshkevich ( be, Рэгіна Іосіфаўна Тышкевіч; 20 October 1929 – 17 November 2019) was a

Belarus Belarus,, , ; alternatively and formerly known as Byelorussia (from Russian ). officially the Republic of Belarus,; rus, Республика Беларусь, Respublika Belarus. is a landlocked country in Eastern Europe. It is bordered by R ...

ian

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

, an expert in

graph theory In mathematics, graph theory is the study of ''graphs'', which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of '' vertices'' (also called ''nodes'' or ''points'') which are conne ...

, Doctor of Physical and Mathematical Sciences,

professor Professor (commonly abbreviated as Prof.) is an Academy, academic rank at university, universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a "person who pr ...

of the

Belarusian State University Belarusian State University (BSU) ( be, links=no, Белару́скі дзяржа́ўны ўніверсітэ́т, ; russian: links=no, Белору́сский госуда́рственный университе́т) is a university in Mins ...

..(retrieved February 8, 2007);
archive; text-only
(retrieved May 11, 2016)) Her main scientific interests included

Intersection graph In graph theory, an intersection graph is a graph that represents the pattern of intersections of a family of sets. Any graph can be represented as an intersection graph, but some important special classes of graphs can be defined by the types o ...

degree sequence In graph theory, the degree (or valency) of a vertex of a graph is the number of edges that are incident to the vertex; in a multigraph, a loop contributes 2 to a vertex's degree, for the two ends of the edge. The degree of a vertex v is denoted ...

s, and the

reconstruction conjecture Informally, the reconstruction conjecture in graph theory says that graphs are determined uniquely by their subgraphs. It is due to KellyKelly, P. J.A congruence theorem for trees ''Pacific J. Math.'' 7 (1957), 961–968. and Ulam.Ulam, S. M. ...

. She was also known for an independent introduction and investigation of the class of

split graph In graph theory, a branch of mathematics, a split graph is a graph in which the vertices can be partitioned into a clique and an independent set. Split graphs were first studied by , and independently introduced by . A split graph may have m ...

s and for her contributions to line graphs of hypergraphs. In 1998, she was awarded the Belarus State Prize for her book ''Lectures in Graph Theory''. Of note is her textbook ''An Introduction into Mathematics'', written together with her two colleagues. In October 2009 an international conference "Discrete Mathematics, Algebra, and their Applications", sponsored by the

Central European Initiative The Central European Initiative (CEI) is a forum of regional cooperation in Central and Eastern Europe, counting 18 member states. It was formed in Budapest in 1989. The body was developed on the basis of earlier experiences with The Alps-Adriatic ...

, was held in

Minsk Minsk ( be, Мінск ; russian: Минск) is the capital and the largest city of Belarus, located on the Svislach and the now subterranean Niamiha rivers. As the capital, Minsk has a special administrative status in Belarus and is the admi ...

, Belarus in honor of her 80th anniversary.Conference announcement
Regina Tyshkevich was a direct descendant of the

Tyszkiewicz Tyszkiewicz is the name of the Tyszkiewicz family, a Polish–Lithuanian magnate noble family of Ruthenian origin. The Lithuanian equivalent is Tiškevičius; it is frequently transliterated from Russian and Belarusian as Tyshkevich. Other peopl ...

magnate The magnate term, from the late Latin ''magnas'', a great man, itself from Latin ''magnus'', "great", means a man from the higher nobility, a man who belongs to the high office-holders, or a man in a high social position, by birth, wealth or ot ...

family, therefore her colleagues sometimes called her "the countess of graph theory", which is a

pun A pun, also known as paronomasia, is a form of word play that exploits multiple meanings of a term, or of similar-sounding words, for an intended humorous or rhetorical effect. These ambiguities can arise from the intentional use of homophoni ...

in the

Russian language Russian (russian: русский язык, russkij jazyk, link=no, ) is an East Slavic languages, East Slavic language mainly spoken in Russia. It is the First language, native language of the Russians, and belongs to the Indo-European langua ...

: the Russian word "граф" (graf) is a

homonym In linguistics, homonyms are words which are homographs (words that share the same spelling, regardless of pronunciation), or homophones (equivocal words, that share the same pronunciation, regardless of spelling), or both. Using this definition, ...

for two words meaning "

count Count (feminine: countess) is a historical title of nobility in certain European countries, varying in relative status, generally of middling rank in the hierarchy of nobility. Pine, L. G. ''Titles: How the King Became His Majesty''. New York: ...

" and "

graph Graph may refer to: Mathematics *Graph (discrete mathematics), a structure made of vertices and edges **Graph theory, the study of such graphs and their properties *Graph (topology), a topological space resembling a graph in the sense of discre ...

Books and selected publications

* (With ) "Commutative Matrices", 1968,

Academic Press Academic Press (AP) is an academic book publisher founded in 1941. It was acquired by Harcourt, Brace & World in 1969. Reed Elsevier bought Harcourt in 2000, and Academic Press is now an imprint of Elsevier. Academic Press publishes reference ...

**Russian original: "Perestanovochnye matritsy" 1966, 2nd edition: 2003, * (With Emilichev, V. A., Melnikov, O. I., Sarvanov, V. I.) "Lectures on Graph Theory", B. I. Wissenschaftsverlag, 1994 **Russian original: "Lektsii po teorii grafov", 1990 *(With O. Melnikov and V. Sarvanov, etc.) "Exercises in Graph Theory",

Kluwer Academic Publishers Springer Science+Business Media, commonly known as Springer, is a German multinational publishing company of books, e-books and peer-reviewed journals in science, humanities, technical and medical (STM) publishing. Originally founded in 1842 in ...

, 1998, * "Linear Algebra and Analytical Geometry (Линейная алгебра и аналитическая геометрия) * Кононов С.Г., Тышкевич Р.И., Янчевский В.И. "Введение в математику" ("An Introduction into Mathematics") 3 volumes, Minsk, Belarusian State University, 2003 * R.I. Tyshkevich. Decomposition of graphical sequences and unigraphs // Discrete Math., 2000, Vol. 220, p. 201 - 238. * Yury Metelsky, Regina Tyshkevich: Line Graphs of Helly Hypergraphs.

SIAM Journal on Discrete Mathematics '' SIAM Journal on Discrete Mathematics'' is a peer-reviewed mathematics journal published quarterly by the Society for Industrial and Applied Mathematics (SIAM). The journal includes articles on pure and applied discrete mathematics. It was estab ...

16(3): 438-448 (2003)

State awards

*1979 (Почетная грамота Министерства высшего и среднего образования БССР «За многолетнюю плодотворную научно-методическую деятельность»);"Тышкевич Регина Иосифовна"
a Belarus State University webpage (retrieved May 9, 2016) *1985: Veteran of Labor Medal (Медаль «Ветеран труда»); *1992: (почетное звание «Заслуженный работник народного образования Республики Беларусь») *1998: Belarus State Prize (государственная премия Республики Беларусь); *2009:

References

{{DEFAULTSORT:Tyshkevich, Regina Belarusian women mathematicians 20th-century Belarusian mathematicians 21st-century Belarusian mathematicians Graph theorists 2019 deaths 1929 births Scientists from Minsk Belarusian State University alumni 20th-century women mathematicians 21st-century women mathematicians