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Harold Ursell
Harold Douglas Ursell (1907–1969) was an English mathematician who is best known for Ursell function In statistical mechanics, an Ursell function or connected correlation function, is a cumulant of a random variable. It can often be obtained by summing over connected Feynman diagrams (the sum over all Feynman diagrams gives the correlation function .... References * 20th-century English mathematicians 1907 births 1969 deaths {{UK-mathematician-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
English People
The English people are an ethnic group and nation native to England, who speak the English language in England, English language, a West Germanic languages, West Germanic language, and share a common ancestry, history, and culture. The English identity began with the History of Anglo-Saxon England, Anglo-Saxons, when they were known as the , meaning "Angle kin" or "English people". Their ethnonym is derived from the Angles (tribe), Angles, one of the Germanic peoples who invaded Great Britain, Britain around the 5th century AD. The English largely descend from two main historical population groups: the West Germanic tribes, including the Angles, Saxons, and Jutes who settled in England and Wales, Southern Britain following the withdrawal of the Ancient Rome, Romans, and the Romano-British culture, partially Romanised Celtic Britons who already lived there.Martiniano, R., Caffell, A., Holst, M. et al. "Genomic signals of migration and continuity in Britain before the Anglo-Sa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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, mathematical structure, structure, space, Mathematical model, models, and mathematics#Calculus and analysis, change. History One of the earliest known mathematicians was Thales of Miletus (); he has been hailed as the first true mathematician and the first known individual to whom a mathematical discovery has been attributed. He is credited with the first use of deductive reasoning applied to geometry, by deriving four corollaries to Thales's theorem. The number of known mathematicians grew when Pythagoras of Samos () established the Pythagorean school, whose doctrine it was that mathematics ruled the universe and whose motto was "All is number". It was the Pythagoreans who coined the term "mathematics", and with whom the study of mathematics for its own sake begins. The first woman math ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ursell Function
In statistical mechanics, an Ursell function or connected correlation function, is a cumulant of a random variable. It can often be obtained by summing over connected Feynman diagrams (the sum over all Feynman diagrams gives the correlation functions). The Ursell function was named after Harold Ursell, who introduced it in 1927. Definition If ''X'' is a random variable, the moments ''s''''n'' and cumulants (same as the Ursell functions) ''u''''n'' are functions of ''X'' related by the exponential formula: : \operatorname(\exp(zX)) = \sum_n s_n \frac = \exp\left(\sum_n u_n \frac\right) (where \operatorname is the expectation). The Ursell functions for multivariate random variables are defined analogously to the above, and in the same way as multivariate cumulants. :u_n\left(X_1, \ldots, X_n\right) = \left.\frac \cdots \frac\log \operatorname\left(\exp\sum z_i X_i\right)\_ The Ursell functions of a single random variable ''X'' are obtained from these by setting . The first fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1907 Births
Events January * January 14 – 1907 Kingston earthquake: A 6.5 Mw earthquake in Kingston, Jamaica, kills between 800 and 1,000. February * February 9 – The " Mud March", the first large procession organised by The National Union of Women's Suffrage Societies ( NUWSS), takes place in London. * February 11 – The French warship ''Jean Bart'' sinks off the coast of Morocco. * February 12 – The steamship ''Larchmont'' collides with the ''Harry Hamilton'' in Long Island Sound; 183 lives are lost. * February 16 – SKF, a worldwide mechanical parts manufacturing brand (mainly, bearings and seals), is founded in Gothenburg, Sweden. * February 21 – The English mail steamship ''Berlin'' is wrecked off the Hook of Holland; 142 lives are lost. * February 24 – The Austrian Lloyd steamship ''Imperatrix'', from Trieste to Bombay, is wrecked on Cape of Crete and sinks; 137 lives are lost. March * March ** The steamship ''Congo'' collide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
