Sergei Kopeikin | |
---|---|
Born | |
Nationality | Russian/American |
Alma mater | Moscow State University Sternberg Astronomical Institute |
Known for | Research in Relativity and Gravitation and for Tests of General Relativity including the speed of gravity, pulsar timing, gravitomagnetism, cosmology, VLBI and relativistic geodesy |
Scientific career | |
Fields | Theoretical Physics General Relativity Gravitational Waves Cosmology Astrophysics Celestial Mechanics Astrometry Geodesy Metrology |
Institutions | University of Missouri-Columbia |
Thesis | General Relativistic Equations of Binary Motion for Extended Bodies with Conservative Corrections and Radiation Damping (1986) |
Doctoral advisors | Yakov Borisovich Zel'dovich Leonid Petrovich Grishchuk |
Notes | |
Sergei Kopeikin (born April 10, 1956) is a USSR-born theoretical physicist and astronomer presently living and working in the United States, where he holds the position of Professor of Physics at the University of Missouri in Columbia, Missouri. He specializes in the theoretical and experimental study of gravity and general relativity. He is also an expert in the field of the astronomical reference frames and time metrology. His general relativistic theory of the Post-Newtonian reference frames which he had worked out along with Victor A. Brumberg, was adopted in 2000 by the resolutions of the International Astronomical Union as a standard for reduction of ground-based astronomical observation. A computer program Tempo2 used to analyze radio observations of pulsars, [1] [2] includes several effects predicted by S. Kopeikin that are important for measuring parameters of the binary pulsars, [3] [4] [5] [6] for testing general relativity, [7] [8] and for detection of gravitational waves of ultra-low frequency. [9] Sergei Kopeikin has worked out a complete post-Newtonian theory of equations of motion of N extended bodies in scalar-tensor theory of gravity with all mass and spin multipole moments of arbitrary order [10] [11] and derived the Lagrangian of the relativistic N-body problem. [12]
In September 2002, S. Kopeikin led a team which conducted a high-precision VLBI experiment to measure the fundamental speed of gravity, [13] [14] thus, confirming the Einstein's prediction on the relativistic nature of gravitational field and its finite speed of propagation. [15]
He is also involved in studies concerning the capabilities of the Lunar Laser Ranging (LLR) technique to measure dynamical features of the General Theory of Relativity in the lunar motion. He has critically analyzed the claims of other scientists concerning the possibility of LLR to measure the gravitomagnetic interaction. [16] Prof. Kopeikin organized and chaired three international workshops on the advanced theory and model of the Lunar Laser Ranging experiment. The LLR workshops were held in the International Space Science Institute (Bern, Switzerland) in 2010-2012. [17]
Recently, S. Kopeikin has been actively involved in theoretical studies on relativistic geodesy and applications of atomic clocks for high-precision navigation and in geodetic datum. [18] He has provided an exact relativistic definition of geoid, [19] and worked out the post-Newtonian concepts of the Maclaurin spheroid [20] and normal gravity formula. [21] S. Kopeikin's workshop on spacetime metrology, clocks and relativistic geodesy is held in the International Space Science Institute (Bern, Switzerland). [22]
Kopeikin was born in Kashin, a small town near Moscow in what was then the USSR. He graduated with excellence from Department of Astrophysics of Moscow State University in 1983 where he studied general relativity under Leonid Grishchuk. In 1986, he obtained a Ph.D. in relativistic astrophysics from the Space Research Institute in Moscow. His Ph.D. thesis was advised by Yakov Borisovich Zel'dovich and presented a first general-relativistic derivation of the conservative and radiation reaction forces in the Post-Newtonian expansion of the gravitational field of a binary system of two extended, massive bodies. In 1991, he obtained a Doctor of Science degree in Physics and Mathematics from Moscow State University and moved to Tokyo (Japan) in 1993 to teach astronomy in Hitotsubashi University. He was adjunct staff member in National Astronomical Observatory of Japan in 1993-1996 and a visiting professor in the same observatory in 1996-1997. Kopeikin moved to Germany in 1997 and worked in the Institute for Theoretical Physics of Friedrich Schiller University of Jena and in Max Planck Institute for Radio Astronomy until 1999. He had joined Department of Physics and Astronomy of the University of Missouri in February 2000 where he got tenure in 2004.
He has been married to Zoia Kopeikina (daughter of Solomon Borisovich Pikelner) since 1980, they have four daughters, four granddaughters and three grandsons. As of December 2019 the family lives in Columbia, Missouri and Texas.
Prof. Kopeikin has published 198 scientific papers and 2 books. He was an editor of two other books on advances in relativistic celestial mechanics. According to Google Scholar Citations program, the h-index of S.M. Kopeikin is 41, his i10-index is 97, while the total number of citations is 5636. As of August 2024, NASA ADS returns for him an h-index of 33, while his tori [23] and riq [23] indices are 53.7 and 174, respectively.
General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of second-order partial differential equations.
In theories of quantum gravity, the graviton is the hypothetical quantum of gravity, an elementary particle that mediates the force of gravitational interaction. There is no complete quantum field theory of gravitons due to an outstanding mathematical problem with renormalization in general relativity. In string theory, believed by some to be a consistent theory of quantum gravity, the graviton is a massless state of a fundamental string.
The following is a timeline of gravitational physics and general relativity.
In physics, an effective field theory is a type of approximation, or effective theory, for an underlying physical theory, such as a quantum field theory or a statistical mechanics model. An effective field theory includes the appropriate degrees of freedom to describe physical phenomena occurring at a chosen length scale or energy scale, while ignoring substructure and degrees of freedom at shorter distances. Intuitively, one averages over the behavior of the underlying theory at shorter length scales to derive what is hoped to be a simplified model at longer length scales. Effective field theories typically work best when there is a large separation between length scale of interest and the length scale of the underlying dynamics. Effective field theories have found use in particle physics, statistical mechanics, condensed matter physics, general relativity, and hydrodynamics. They simplify calculations, and allow treatment of dissipation and radiation effects.
The Pioneer anomaly, or Pioneer effect, was the observed deviation from predicted accelerations of the Pioneer 10 and Pioneer 11 spacecraft after they passed about 20 astronomical units (3×109 km; 2×109 mi) on their trajectories out of the Solar System. The apparent anomaly was a matter of much interest for many years but has been subsequently explained by anisotropic radiation pressure caused by the spacecraft's heat loss.
PSR J0737−3039 is the first known double pulsar. It consists of two neutron stars emitting electromagnetic waves in the radio wavelength in a relativistic binary system. The two pulsars are known as PSR J0737−3039A and PSR J0737−3039B. It was discovered in 2003 at Australia's Parkes Observatory by an international team led by the Italian radio astronomer Marta Burgay during a high-latitude pulsar survey.
Tests of general relativity serve to establish observational evidence for the theory of general relativity. The first three tests, proposed by Albert Einstein in 1915, concerned the "anomalous" precession of the perihelion of Mercury, the bending of light in gravitational fields, and the gravitational redshift. The precession of Mercury was already known; experiments showing light bending in accordance with the predictions of general relativity were performed in 1919, with increasingly precise measurements made in subsequent tests; and scientists claimed to have measured the gravitational redshift in 1925, although measurements sensitive enough to actually confirm the theory were not made until 1954. A more accurate program starting in 1959 tested general relativity in the weak gravitational field limit, severely limiting possible deviations from the theory.
Numerical relativity is one of the branches of general relativity that uses numerical methods and algorithms to solve and analyze problems. To this end, supercomputers are often employed to study black holes, gravitational waves, neutron stars and many other phenomena described by Albert Einstein's theory of general relativity. A currently active field of research in numerical relativity is the simulation of relativistic binaries and their associated gravitational waves.
Tensor–vector–scalar gravity (TeVeS), developed by Jacob Bekenstein in 2004, is a relativistic generalization of Mordehai Milgrom's Modified Newtonian dynamics (MOND) paradigm.
A binary pulsar is a pulsar with a binary companion, often a white dwarf or neutron star. Binary pulsars are one of the few objects which allow physicists to test general relativity because of the strong gravitational fields in their vicinities. Although the binary companion to the pulsar is usually difficult or impossible to observe directly, its presence can be deduced from the timing of the pulses from the pulsar itself, which can be measured with extraordinary accuracy by radio telescopes.
Gravitational waves are transient displacements in a gravitational field – generated by the motion or acceleration of gravitating masses – that radiate outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1893 and then later by Henri Poincaré in 1905 as the gravitational equivalent of electromagnetic waves. In 1916, Albert Einstein demonstrated that gravitational waves result from his general theory of relativity as ripples in spacetime.
Gravitational-wave astronomy is a subfield of astronomy concerned with the detection and study of gravitational waves emitted by astrophysical sources.
In classical theories of gravitation, the changes in a gravitational field propagate. A change in the distribution of energy and momentum of matter results in subsequent alteration, at a distance, of the gravitational field which it produces. In the relativistic sense, the "speed of gravity" refers to the speed of a gravitational wave, which, as predicted by general relativity and confirmed by observation of the GW170817 neutron star merger, is equal to the speed of light (c).
Modified Newtonian dynamics (MOND) is a theory that proposes a modification of Newton's second law to account for observed properties of galaxies. Its primary motivation is to explain galaxy rotation curves without invoking dark matter, and is one of the most well-known theories of this class. However, it has not gained widespread acceptance, with the majority of astrophysicists supporting the Lambda-CDM model as providing the better fit to observations.
Frame-dragging is an effect on spacetime, predicted by Albert Einstein's general theory of relativity, that is due to non-static stationary distributions of mass–energy. A stationary field is one that is in a steady state, but the masses causing that field may be non-static — rotating, for instance. More generally, the subject that deals with the effects caused by mass–energy currents is known as gravitoelectromagnetism, which is analogous to the magnetism of classical electromagnetism.
Modern searches for Lorentz violation are scientific studies that look for deviations from Lorentz invariance or symmetry, a set of fundamental frameworks that underpin modern science and fundamental physics in particular. These studies try to determine whether violations or exceptions might exist for well-known physical laws such as special relativity and CPT symmetry, as predicted by some variations of quantum gravity, string theory, and some alternatives to general relativity.
A binary black hole (BBH), or black hole binary, is a system consisting of two black holes in close orbit around each other. Like black holes themselves, binary black holes are often divided into binary stellar black holes, formed either as remnants of high-mass binary star systems or by dynamic processes and mutual capture; and binary supermassive black holes, believed to be a result of galactic mergers.
In astrophysics, the chirp mass of a compact binary system determines the leading-order orbital evolution of the system as a result of energy loss from emitting gravitational waves. Because the gravitational wave frequency is determined by orbital frequency, the chirp mass also determines the frequency evolution of the gravitational wave signal emitted during a binary's inspiral phase. In gravitational wave data analysis, it is easier to measure the chirp mass than the two component masses alone.
Bimetric gravity or bigravity refers to two different classes of theories. The first class of theories relies on modified mathematical theories of gravity in which two metric tensors are used instead of one. The second metric may be introduced at high energies, with the implication that the speed of light could be energy-dependent, enabling models with a variable speed of light.
Within general relativity (GR), Einstein's relativistic gravity, the gravitational field is described by the 10-component metric tensor. However, in Newtonian gravity, which is a limit of GR, the gravitational field is described by a single component Newtonian gravitational potential. This raises the question to identify the Newtonian potential within the metric, and to identify the physical interpretation of the remaining 9 fields.