Zvi Bern
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Zvi Bern (born 17 September 1960) is an American theoretical particle physicist. He is a professor at
University of California, Los Angeles The University of California, Los Angeles (UCLA) is a public university, public Land-grant university, land-grant research university in Los Angeles, California, United States. Its academic roots were established in 1881 as a normal school the ...
(UCLA). Bern studied physics and mathematics at the
Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...
and earned his doctorate in 1986 in theoretical physics from the
University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...
under the supervision of Martin Halpern. Bern's dissertation manuscript can currently be found in Lawrence Berkeley Laboratory's archives, examining "possible nonperturbative continuum regularization schemes for quantum field theory which are based upon the Langevin equation of Parisi and Wu." Bern developed new methods for the computation of
Feynman diagram In theoretical physics, a Feynman diagram is a pictorial representation of the mathematical expressions describing the behavior and interaction of subatomic particles. The scheme is named after American physicist Richard Feynman, who introduced ...
s that were originally introduced in
quantum electrodynamics In particle physics, quantum electrodynamics (QED) is the Theory of relativity, relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quant ...
for the perturbative computation of scattering amplitudes. In more complicated
quantum field theories In theoretical physics, quantum field theory (QFT) is a theoretical framework that combines field theory and the principle of relativity with ideas behind quantum mechanics. QFT is used in particle physics to construct physical models of subatom ...
such as
Yang–Mills theory Yang–Mills theory is a quantum field theory for nuclear binding devised by Chen Ning Yang and Robert Mills in 1953, as well as a generic term for the class of similar theories. The Yang–Mills theory is a gauge theory based on a special un ...
or quantum field theories with gravity, the computer calculation of the perturbative evolution using Feynman diagrams quickly reached its limits due to the exponential growth in diagrams. The new theoretical developments of the 1990s and 2000s came in time for a renewed interest in extensive calculations in the context of the experiments at the
Large Hadron Collider The Large Hadron Collider (LHC) is the world's largest and highest-energy particle accelerator. It was built by the CERN, European Organization for Nuclear Research (CERN) between 1998 and 2008, in collaboration with over 10,000 scientists, ...
. Bern and colleagues developed twistor-space methods applied to gauge-theory amplitudes. Bern and colleagues developed the method of "generalized unitarity as a means for obtaining loop amplitudes from on-shell tree amplitudes". The method of generalized unitarity provided new insights into the perturbative treatment of N = 8
supergravity In theoretical physics, supergravity (supergravity theory; SUGRA for short) is a modern field theory that combines the principles of supersymmetry and general relativity; this is in contrast to non-gravitational supersymmetric theories such as ...
and showed that there is a smaller degree of divergence than expected; higher-loop evidence suggested that "N = 8 supergravity has the same degree of divergence as N = 4 super-Yang–Mills theory and is ultraviolet finite in four dimensions". Prior to this, it had been generally assumed that quantum gravitation from three loops resulted in uncontrollable divergences. In 2010, with his students Carrasco and Johansson, Bern found that diagrams for supersymmetric gravitational theories are equivalent to those of two copies of supersymmetric Yang–Mills theories (theories with
gluon A gluon ( ) is a type of Massless particle, massless elementary particle that mediates the strong interaction between quarks, acting as the exchange particle for the interaction. Gluons are massless vector bosons, thereby having a Spin (physi ...
s), which is known as double copy theory. They used a previously found duality between kinematics and color degrees of freedom. Instead of previously around 10^ terms, only 10 terms had to be evaluated in 3 loops, and correspondingly in 4 loops around 100 terms versus 10^ terms, and in 5 loops around 1000 terms versus 10^ terms; furthermore, there were no uncontrollable divergences in three and four loops — such uncontrollable divergences were predicted by the majority of experts in the 1980s and constituted one of the reasons for favoring
string theory In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. String theory describes how these strings propagate through space and intera ...
. Bern was elected in 2004 a fellow of the
American Physical Society The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of ...
. In 2014, he received the Sakurai Prize with David A. Kosower and
Lance J. Dixon Lance Jenkins Dixon (born 22 June 1961, in Pasadena, California) is an American theoretical particle physicist. He is a professor in the SLAC Theory Group at the Stanford Linear Accelerator Center (SLAC) at Stanford University. Dixon received in ...
for "pathbreaking contributions to the calculation of perturbative scattering amplitudes, which led to a deeper understanding of quantum field theory and to powerful new tools for computing
QCD In theoretical physics Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain, and predict List of natural phenomena, natural phenomena. This is in ...
processes." In 2023, Bern and his collaborators David A Kosower and Lance J Dixon were awarded Galileo Galilei Medal from Italy’s Instituto Nazionale di Fisica. Bern's
Erdős number The Erdős number () describes the "collaborative distance" between mathematician Paul Erdős and another person, as measured by authorship of mathematical papers. The same principle has been applied in other fields where a particular individual ...
is three. Currently, Bern is the director of the
Mani Lal Bhaumik Mani Lal Bhaumik (born 30 March 1931) is an Indian American physicist and an internationally bestselling author, celebrated lecturer, entrepreneur and philanthropist. Early life Mani Lal Bhaumik was born in a Bengali Mahishya family on 30 Ma ...
Institute for Theoretical Physics at UCLA, which aims to "provide an exceptional environment for excellence in theoretical physics research". He was elected a Member of the
National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...
in 2024.https://www.nasonline.org/news-and-multimedia/news/2024-nas-election.html


Selected publications

* Bern, Dixon, Kosower "Quantum "Graviton" Particles May Resemble Ordinary Particles of Force", ''Scientific American'', May 2012 * Bern, John Joseph Carrasco, Henrik Johansso
"Progress on UV Finiteness of Supergravity"
Erice Lectures 2008 * Bern, Carrasco, Johansso
New Relations for Gauge Theory Amplitudes
Physical Review D, 78, 2008, 085011 * Bern, Carrasco, Johansso
"Perturbative quantum gravity as a double copy of gauge theory"
2010 * Bern, Carrasco, Johansso
"The Structure of Multiloop Amplitudes in Gauge and Gravity Theories"
in ''Loops and Legs in Quantum Field Theory'', Woerlitz 2010, Nucl. Phys. Proc. Suppl. 205–206, 2010, pp. 54–60] * * * * Ber
"Perturbative Quantum Gravity and its relation to Gauge Theory"
''Living Reviews of Relativity'', 2002


References


External links

* * * * {{DEFAULTSORT:Bern, Zvi 1960 births Living people Massachusetts Institute of Technology School of Science alumni UC Berkeley College of Letters and Science alumni University of California, Los Angeles faculty Fellows of the American Physical Society American particle physicists 21st-century American physicists J. J. Sakurai Prize for Theoretical Particle Physics recipients Members of the United States National Academy of Sciences