Rainer Kurt "Ray" Sachs (born June 13, 1932) is a German-American mathematical physicist, with interests in general relativistic cosmology and astrophysics, as well as a computational radiation biologist. He is professor emeritus of Mathematics and Physics at the
University of California, Berkeley
The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...
, and adjunct professor at
Tufts Medical School
The Tufts University School of Medicine is the medical school of Tufts University, a private research university in Massachusetts. It was established in 1893 and is located on the university's health sciences campus in downtown Boston.
The '' ...
.
Life and career
Sachs was born in
Frankfurt am Main
Frankfurt, officially Frankfurt am Main (; Hessian: , "Frank ford on the Main"), is the most populous city in the German state of Hesse. Its 791,000 inhabitants as of 2022 make it the fifth-most populous city in Germany. Located on its na ...
in 1932, a son of the German Jewish metallurgist
George Sachs. In 1937 the family left Germany to flee from Nazi persecution, and settled in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
, so Rainer Sachs is generally considered an American scientist. He received his bachelor's degree in mathematics from
MIT
The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the m ...
in 1953 and his PhD in theoretical physics from
Syracuse University in 1959.
[Sachs Curriculum Vitae]
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In 1962 Joshua N. Goldberg and he proved the Goldberg–Sachs theorem
The Goldberg–Sachs theorem is a result in Einstein's theory of general relativity about vacuum solutions of the Einstein field equations relating the existence of a certain type of congruence with algebraic properties of the Weyl tensor.
More ...
. Later that year, he gave the first exposition of the asymptotically flat spacetime symmetry group, which he called the "generalized Bondi-Metzner group" and is now known as the Bondi–Metzner–Sachs group
In gravitational theory, the Bondi–Metzner–Sachs (BMS) group, or the Bondi–van der Burg–Metzner–Sachs group, is an asymptotic symmetry group of asymptotically flat, Lorentzian spacetimes at null (''i.e.'', light-like) infinity. It was o ...
.
In 1966 he and Ronald Kantowski were responsible for the Kantowski–Sachs dust solution
In general relativity, a dust solution is a fluid solution, a type of exact solution of the Einstein field equation, in which the gravitational field is produced entirely by the mass, momentum, and stress density of a perfect fluid that has ' ...
s to the Einstein field equation
In the general theory of relativity, the Einstein field equations (EFE; also known as Einstein's equations) relate the geometry of spacetime to the distribution of matter within it.
The equations were published by Einstein in 1915 in the form ...
. These are widely used family of anisotropic cosmological models.
In 1967, he and Arthur M. Wolfe were the authors of the Sachs–Wolfe effect, which concerns a property of the Cosmic microwave background radiation
In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space ...
. The Ehlers–Geren–Sachs theorem
The Ehlers–Geren–Sachs theorem, published in 1968 by Jürgen Ehlers, P. Geren and Rainer K. Sachs, shows that if, in a given universe, all freely falling observers measure the cosmic background radiation
Cosmic background radiation is e ...
, published in 1968 by Jürgen Ehlers
Jürgen Ehlers (; 29 December 1929 – 20 May 2008) was a German physicist who contributed to the understanding of Albert Einstein's theory of general relativity. From graduate and postgraduate work in Pascual Jordan's relativity research group ...
, P. Geren and R. Sachs, shows that if, in a given universe, there exists a reference frame at each event such that the cosmic background radiation
Cosmic background radiation is electromagnetic radiation from the Big Bang. The origin of this radiation depends on the region of the spectrum that is observed. One component is the cosmic microwave background. This component is redshifted p ...
is isotropic, then under certain conditions that universe is an isotropic and homogeneous FLRW spacetime.
From 1969 to 1993, he was Professor of Math and Physics at the University of California, Berkeley
The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...
(UCB), and from 1993 he has been Professor Emeritus at UCB. In 1994, he was appointed Research Professor of Mathematics UCB, and since 2005 he has been an adjunct professor at the Tufts medical school.
Until 1985, he worked on general relativistic cosmology and astrophysics. With Hung-Hsi Wu he co-wrote the books ''General Relativity and Cosmology'' in 1971 and ''General Relativity for Mathematicians'' in 1977.
From 1985, he has worked in mathematical and computational biology, especially radiation biology. His work in radiobiology has included research on radiation and cancer.Proceedings of the National Academy of Sciences
/ref>
References
{{DEFAULTSORT:Sachs, Rainer K
1932 births
Living people
Syracuse University alumni
Radiobiologists
American relativity theorists
University of California, Berkeley faculty
20th-century American astronomers
20th-century American biologists
Jewish emigrants from Nazi Germany to the United States