American cosmologists

Owen_Gingerich

Owen Jay Gingerich (; March 24, 1930 – May 28, 2023) was an American astronomer who had been professor emeritus of astronomy and of the history of science at Harvard University and a senior astronomer emeritus at the Smithsonian Astrophysical Observatory. In addition to his research and teaching, he had written many books on the history of astronomy.
Gingerich was also a member of the American Academy of Arts and Sciences, the American Philosophical Society, and the International Academy of the History of Science. A committed Christian, he had been active in the American Scientific Affiliation, a society of evangelical scientists. He served on the board of trustees of the Templeton Foundation.

Leonard_Parker

Leonard Emanuel Parker (born Leonard Pearlman; in 1938) is a distinguished professor emeritus of physics and a former director of the Center for Gravitation and Cosmology at the University of Wisconsin–Milwaukee. During the late 1960s, Parker established a new area of physics—quantum field theory in curved spacetime. Specifically, by applying the technique of Bogoliubov transformations to quantum field theory with a changing gravitational field, he discovered the physical mechanism now known as cosmological particle production. His breakthrough discovery has a surprising consequence: the expansion of the universe can create particles out of the vacuum.
His work inspired research by hundreds of physicists and has been cited in more than 2,000 research papers; it was credited in the memoirs of Soviet physicist Andrei Sakharov and helped Stephen Hawking discover the creation of particles by black holes.Along with David Toms of Newcastle University, Parker co-wrote a latest addition to graduate-level textbooks on quantum field theory in curved spacetime, entitled Quantum Field Theory in Curved Spacetime: Quantized Fields and Gravity (Cambridge University Press, 2009, ISBN 978-0-521-87787-9).
He received his PhD from Harvard University in 1967. His advisor was Sidney Coleman.