Question: When was the English theoretical physicist died who's theory is Dirac hole?
Context: Nikolay Nikolayevich Bogolyubov (Russian: Никола́й Никола́евич Боголю́бов ; 21 August 1909 – 13 February 1992), also transliterated as Bogoliubov and Bogolubov, was a Soviet mathematician and theoretical physicist known for a significant contribution to quantum field theory, classical and quantum statistical mechanics, and the theory of dynamical systems; He was the recipient of the 1992 Dirac Prize. Dirac hole theory is a theory in quantum mechanics, named after English theoretical physicist Paul Dirac.  The theory poses that the continuum of negative energy states, that are solutions to the Dirac equation, are filled with electrons, and the vacancies in this continuum (holes) are manifested as positrons with energy and momentum that are the negative of those of the state.  The discovery of the positron in 1929 gave a considerable support to the Dirac hole theory. Curtis Gove Callan, Jr. (born October 11, 1942) is a theoretical physicist and a professor at Princeton University.  He has conducted research in gauge theory, string theory, instantons, black holes, strong interactions, and many other topics.  He was awarded the Sakurai Prize in 2000 ("For his classic formulation of the renormalization group, his contributions to instanton physics and to the theory of monopoles and strings") and the Dirac Medal in 2004. The Dirac sea is a theoretical model of the vacuum as an infinite sea of particles with negative energy.  It was first postulated by the British physicist Paul Dirac in 1930 to explain the anomalous negative-energy quantum states predicted by the Dirac equation for relativistic electrons.  The positron, the antimatter counterpart of the electron, was originally conceived of as a hole in the Dirac sea, well before its experimental discovery in 1932. Sir John Brian Pendry, FRS FInstP (born 4 July 1943) is an English theoretical physicist known for his research into refractive indices and creation of the first practical "Invisibility Cloak".  He is a professor of theoretical solid state physics at Imperial College London where he was head of the department of physics (1998–2001) and principal of the faculty of physical sciences (2001–2002).  He is an honorary fellow of Downing College, Cambridge, (where he was an undergraduate) and an IEEE fellow.  He received the Kavli Prize in Nanoscience “for transformative contributions to the field of nano-optics that have broken long-held beliefs about the limitations of the resolution limits of optical microscopy and imaging.” , together with Stefan Hell, and Thomas Ebbesen, in 2014 Andrei Dmitriyevich Linde (Russian: Андре́й Дми́триевич Ли́нде ; born March 2, 1948) is a Russian-American theoretical physicist and the Harald Trap Friis Professor of Physics at Stanford University.  Linde is one of the main authors of the inflationary universe theory, as well as the theory of eternal inflation and inflationary multiverse.  He received his Bachelor of Science degree from Moscow State University.  In 1975, Linde was awarded a Ph.D. from the Lebedev Physical Institute in Moscow.  He worked at CERN (European Organization for Nuclear Research) since 1989 and moved to the USA in 1990 where he became Professor of Physics at Stanford University.  Among the various awards he's received for his work on inflation, in 2002 he was awarded the Dirac Medal, along with Alan Guth of MIT and Paul Steinhardt of Princeton University.  In 2004 he received, along with Alan Guth, the Gruber Prize in Cosmology for the development of inflationary cosmology.  In 2012 he, along with Alan Guth, was an inaugural awardee of the Fundamental Physics Prize.  In 2014 he received the Kavli Prize in Astrophysics “for pioneering the theory of cosmic inflation", together with Alan Guth and Alexei Starobinsky. Stephen William Hawking, {'1': ", '2': ", '3': ", '4': "} ( born 8 January 1942) is an English theoretical physicist, cosmologist, author and Director of Research at the Centre for Theoretical Cosmology within the University of Cambridge.  His scientific works include a collaboration with Roger Penrose on gravitational singularity theorems in the framework of general relativity and the theoretical prediction that black holes emit radiation, often called Hawking radiation.  Hawking was the first to set out a theory of cosmology explained by a union of the general theory of relativity and quantum mechanics.  He is a vigorous supporter of the many-worlds interpretation of quantum mechanics. In science and mathematics, the Dirac delta function, or δ function, is a generalized function, or distribution that was historically introduced by the physicist Paul Dirac for modelling the density of an idealized point mass or point charge, as a function that is equal to zero everywhere except for zero and whose integral over the entire real line is equal to one.  As there is no function that has these properties, the computations that were done by the theoretical physicists appeared to mathematicians as nonsense, until the introduction of distributions by Laurent Schwartz, for formalizing and validating mathematically these computations.  This amounts, in particular, to define Dirac delta function as a linear functional, which maps every function to its value at zero.  The Kronecker delta function, which is usually defined on a discrete domain and takes values 0 and 1, is a discrete analog of Dirac delta function. Peter R. Holland is an English theoretical physicist, known for his work on foundational problems in quantum physics and in particular his book on the pilot wave theory and the de Broglie-Bohm causal interpretation of quantum mechanics. Paul Adrien Maurice Dirac {'1': ", '2': ", '3': ", '4': "} ( ; 8 August 1902 – 20 October 1984) was an English theoretical physicist who made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics.  He was the Lucasian Professor of Mathematics at the University of Cambridge, a member of the Center for Theoretical Studies, University of Miami, and spent the last decade of his life at Florida State University.
Answer: 20 October 1984