Information: - Ukraine (tr. ) is a sovereign state in Eastern Europe, bordered by Russia to the east and northeast, Belarus to the northwest, Poland and Slovakia to the west, Hungary, Romania, and Moldova to the southwest, and the Black Sea and Sea of Azov to the south and southeast, respectively. Ukraine is currently in territorial dispute with Russia over the Crimean Peninsula which Russia annexed in 2014 but which Ukraine and most of the international community recognise as Ukrainian. Including Crimea, Ukraine has an area of , making it the largest country entirely within Europe and the 46th largest country in the world. It has a population of about 44.5 million, making it the 32nd most populous country in the world. - Physics (from , from "phusis" "nature") is the natural science that involves the study of matter and its motion and behavior through space and time, along with related concepts such as energy and force. One of the most fundamental scientific disciplines, the main goal of physics is to understand how the universe behaves. - A mathematician is someone who uses an extensive knowledge of mathematics in his/her work, typically to solve mathematical problems. - Tatyana Pavlovna Ehrenfest, later van Aardenne-Ehrenfest, (Vienna, October 28, 1905 Dordrecht, November 29, 1984) was a Dutch mathematician. She was the daughter of Paul Ehrenfest (18801933) and Tatyana Alexeyevna Afanasyeva (18761964). - Tatyana Alexeyevna Afanasyeva ( Russian : ) ( Kiev , 19 November 1876 -- Leiden , 14 April 1964 ) ( also known as Tatiana Ehrenfest - Afanaseva ) was a Russian / Dutch mathematician . On 21 December 1904 she was married to Paul Ehrenfest ( 1880 -- 1933 ) an Austrian physicist . They had two daughters and two sons ; one daughter , Tatyana Pavlovna Ehrenfest , also became a mathematician . Afanasyeva was born in Kiev , Ukraine , then part of the Russian Empire . After her father died she was brought up by an uncle in St Petersburg , Russia , where she attended a women 's pedagogical school and a Women 's College . In 1902 she transferred to Gottingen , where she met Ehrenfest . The couple got married in 1904 , and in 1907 they returned to St Petersburg . In 1912 they moved to Leiden , where Paul Ehrenfest was appointed to succeed H.A. Lorentz as professor at the University of Leiden . Tatyana collaborated closely with her husband , most famously on their classic review of the statistical mechanics of Boltzmann . She published many papers on various topics such as randomness and entropy , and teaching geometry to children . - Kiev or Kyiv is the capital and largest city of Ukraine, located in the north central part of the country on the Dnieper River. The population in July 2015 was (though higher estimated numbers have been cited in the press), making Kiev the 7th most populous city in Europe. - Paul Ehrenfest (January 18, 1880 September 25, 1933) was an Austrian and Dutch theoretical physicist, who made major contributions to the field of statistical mechanics and its relations with quantum mechanics, including the theory of phase transition and the Ehrenfest theorem. - A physicist is a scientist who has specialized knowledge in the field of physics, the exploration of the interactions of matter and energy across the physical universe. - The Dnieper River or (also known as: "Dnepr", "Dnyapro" or "Dnipro") is one of the major rivers of Europe (fourth by length), rising near Smolensk, Russia and flowing through Russia, Belarus and Ukraine to the Black Sea. It is the longest river of Ukraine and Belarus and the fourth longest river in Europe. The total length ranges between and with a drainage basin of . The river is noted for its dams and hydroelectric stations. The Dnieper is an important navigable waterway for the economy of Ukraine and is connected via the DnieperBug Canal to other waterways in Europe. - Dordrecht, colloquially Dordt , historically in English named Dort, is a city and municipality in the western Netherlands, located in the province of South Holland. It is the fourth largest city of the province, having a population of in . The municipality covers the entire Dordrecht Island, also often called "Het Eiland van Dordt" (the Island of Dordt), bordered by the rivers Oude Maas, Beneden Merwede, Nieuwe Merwede, Hollands Diep, and Dordtsche Kil. Dordrecht is the largest and most important city in the Drechtsteden and is also part of the Randstad, the main conurbation in the Netherlands. Dordrecht is the oldest city in the Holland area and has a rich history and culture. - Statistical mechanics is a branch of theoretical physics using probability theory to study the average behaviour of a mechanical system, where the state of the system is uncertain. - The term phase transition is most commonly used to describe transitions between solid, liquid and gaseous states of matter, and, in rare cases, plasma. A phase of a thermodynamic system and the states of matter have uniform physical properties. During a phase transition of a given medium certain properties of the medium change, often discontinuously, as a result of the change of some external condition, such as temperature, pressure, or others. For example, a liquid may become gas upon heating to the boiling point, resulting in an abrupt change in volume. The measurement of the external conditions at which the transformation occurs is termed the phase transition. Phase transitions are common in nature and used today in many technologies. - Leiden (in English and archaic Dutch also Leyden) is a city and municipality in the Dutch province of South Holland. The municipality of Leiden has a population of 122,915, but the city forms one densely connected agglomeration with its suburbs Oegstgeest, Leiderdorp, Voorschoten and Zoeterwoude with 206,647 inhabitants. The Netherlands Central Bureau of Statistics (CBS) further includes Katwijk in the agglomeration which makes the total population of the Leiden urban agglomeration 270,879, and in the larger Leiden urban area also Teylingen, Noordwijk, and Noordwijkerhout are included with in total 348,868 inhabitants. Leiden is located on the Oude Rijn, at a distance of some from The Hague to its south and some from Amsterdam to its north. The recreational area of the Kaag Lakes (Kagerplassen) lies just to the northeast of Leiden. - The Ehrenfest theorem, named after Paul Ehrenfest, an Austrian theoretical physicist at Leiden University, relates the time derivative of the expectation values of the position and momentum operators "x" and "p" to the expectation value of the force Given the information above, choose from the list below the object entity that exhibits the relation 'field of work' with the subject 'tatyana afanasyeva'. Choices: - economy - english - exploration - gas - history - mathematician - mechanics - nature - physicist - physics - probability theory - river - russia - statistics
A:
probability theory