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In the mathematical field of
differential geometry Differential geometry is a mathematical discipline that studies the geometry of smooth shapes and smooth spaces, otherwise known as smooth manifolds. It uses the techniques of differential calculus, integral calculus, linear algebra and multili ...
, a maximal surface is a certain kind of
submanifold In mathematics, a submanifold of a manifold ''M'' is a subset ''S'' which itself has the structure of a manifold, and for which the inclusion map satisfies certain properties. There are different types of submanifolds depending on exactly which p ...
of a
Lorentzian manifold In differential geometry, a pseudo-Riemannian manifold, also called a semi-Riemannian manifold, is a differentiable manifold with a metric tensor that is everywhere nondegenerate. This is a generalization of a Riemannian manifold in which the r ...
. Precisely, given a Lorentzian manifold , a maximal surface is a spacelike submanifold of whose
mean curvature In mathematics, the mean curvature H of a surface S is an ''extrinsic'' measure of curvature that comes from differential geometry and that locally describes the curvature of an embedded surface in some ambient space such as Euclidean space. The ...
is zero. As such, maximal surfaces in Lorentzian geometry are directly analogous to
minimal surface In mathematics, a minimal surface is a surface that locally minimizes its area. This is equivalent to having zero mean curvature (see definitions below). The term "minimal surface" is used because these surfaces originally arose as surfaces that ...
s in
Riemannian geometry Riemannian geometry is the branch of differential geometry that studies Riemannian manifolds, smooth manifolds with a ''Riemannian metric'', i.e. with an inner product on the tangent space at each point that varies smoothly from point to poin ...
. The difference in terminology between the two settings has to do with the fact that small regions in maximal surfaces are local maximizers of the area functional, while small regions in minimal surfaces are local minimizers of the area functional. In 1976,
Shiu-Yuen Cheng Shiu-Yuen Cheng (鄭紹遠) is a Hong Kong mathematician. He is currently the Chair Professor of Mathematics at the Hong Kong University of Science and Technology. Cheng received his Ph.D. in 1974, under the supervision of Shiing-Shen Chern, from ...
and
Shing-Tung Yau Shing-Tung Yau (; ; born April 4, 1949) is a Chinese-American mathematician and the William Caspar Graustein Professor of Mathematics at Harvard University. In April 2022, Yau announced retirement from Harvard to become Chair Professor of mathem ...
resolved the "Bernstein problem" for maximal hypersurfaces of
Minkowski space In mathematical physics, Minkowski space (or Minkowski spacetime) () is a combination of three-dimensional Euclidean space and time into a four-dimensional manifold where the spacetime interval between any two events is independent of the inerti ...
which are properly embedded, showing that any such hypersurface is a plane. This was part of the body of work for which Yau was awarded the
Fields medal The Fields Medal is a prize awarded to two, three, or four mathematicians under 40 years of age at the International Congress of the International Mathematical Union (IMU), a meeting that takes place every four years. The name of the award ho ...
in 1982. The Bernstein problem was originally posed by
Eugenio Calabi Eugenio Calabi (born 11 May 1923) is an Italian-born American mathematician and the Thomas A. Scott Professor of Mathematics, Emeritus, at the University of Pennsylvania, specializing in differential geometry, partial differential equations and ...
in 1970, who proved some special cases of the result. Simple examples show that there are a number of hypersurfaces of Minkowski space of zero mean curvature which fail to be spacelike. By an extension of Cheng and Yau's methods, Kazuo Akutagawa considered the case of spacelike hypersurfaces of constant mean curvature in Lorentzian manifolds of positive constant curvature, such as
de Sitter space In mathematical physics, ''n''-dimensional de Sitter space (often abbreviated to dS''n'') is a maximally symmetric Lorentzian manifold with constant positive scalar curvature. It is the Lorentzian analogue of an ''n''-sphere (with its canoni ...
. Luis Alías, Alfonso Romero, and Miguel Sánchez proved a version of Cheng and Yau's result, replacing Minkowski space by the warped product of a
closed Closed may refer to: Mathematics * Closure (mathematics), a set, along with operations, for which applying those operations on members always results in a member of the set * Closed set, a set which contains all its limit points * Closed interval, ...
Riemannian manifold with an interval. As a problem of
partial differential equation In mathematics, a partial differential equation (PDE) is an equation which imposes relations between the various partial derivatives of a Multivariable calculus, multivariable function. The function is often thought of as an "unknown" to be sol ...
s,
Robert Bartnik Robert Bartnik (1956-2022) was an Australian mathematician based at Monash University. He is known for his contributions to the rigorous mathematical study of general relativity. He received his bachelor's and master's degrees from Melbourne Univ ...
and
Leon Simon Leon Melvyn Simon , born in 1945, is a Leroy P. Steele PrizeSee announcemen retrieved 15 September 2017. and Bôcher Memorial Prize, Bôcher Prize-winningSee . mathematician, known for deep contributions to the fields of geometric analysis, g ...
studied the boundary-value problem for maximal surfaces in Minkowski space. The general existence of maximal hypersurfaces in asymptotically flat Lorentzian manifolds, due to Bartnik, is significant in
Demetrios Christodoulou Demetrios Christodoulou ( el, Δημήτριος Χριστοδούλου; born 19 October 1951) is a Greek mathematician and physicist, who first became well known for his proof, together with Sergiu Klainerman, of the nonlinear stability of the ...
and
Sergiu Klainerman Sergiu Klainerman (born May 13, 1950) is a mathematician known for his contributions to the study of hyperbolic differential equations and general relativity. He is currently the Eugene Higgins Professor of Mathematics at Princeton University, w ...
's renowned proof of the nonlinear stability of Minkowski space under the
Einstein field equations 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 ...
. They use a ''maximal slicing'' of a general spacetime; the same approach is common in
numerical relativity 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 ...
.Gourgoulhon, chapter 10.2


References

Footnotes Books * John K. Beem, Paul E. Ehrlich, and Kevin L. Easley. ''Global Lorentzian geometry.'' Second edition. Monographs and Textbooks in Pure and Applied Mathematics, 202. Marcel Dekker, Inc., New York, 1996. xiv+635 pp. * Yvonne Choquet-Bruhat. ''General relativity and the Einstein equations.'' Oxford Mathematical Monographs. Oxford University Press, Oxford, 2009. xxvi+785 pp. * Demetrios Christodoulou and Sergiu Klainerman. ''The global nonlinear stability of the Minkowski space.'' Princeton Mathematical Series, 41. Princeton University Press, Princeton, NJ, 1993. x+514 pp. * Éric Gourgoulhon. ''3 + 1 formalism in general relativity. Bases of numerical relativity.'' Lecture Notes in Physics, 846. Springer, Heidelberg, 2012. xviii+294 pp. Articles * Kazuo Akutagawa. ''On spacelike hypersurfaces with constant mean curvature in the de Sitter space.'' Math. Z. 196 (1987), no. 1, 13–19. * Luis J. Alías, Alfonso Romero, and Miguel Sánchez. Uniqueness of complete spacelike hypersurfaces of constant mean curvature in generalized Robertson–Walker spacetimes. Gen. Relativity Gravitation 27 (1995), no. 1, 71–84. * Robert Bartnik and Leon Simon
''Spacelike hypersurfaces with prescribed boundary values and mean curvature.''
Comm. Math. Phys. 87 (1982), no. 1, 131–152. * Eugenio Calabi. ''Examples of Bernstein problems for some nonlinear equations.'' Proc. Sympos. Pure Math., Vol. XV (1970), pp. 223–230. Global Analysis. Amer. Math. Soc., Providence, R.I. * Shiu Yuen Cheng and Shing Tung Yau. ''Maximal space-like hypersurfaces in the Lorentz–Minkowski spaces.'' Ann. of Math. (2) 104 (1976), no. 3, 407–419. * Osamu Kobayashi. ''Maximal surfaces in the 3-dimensional Minkowski space .'' Tokyo J. Math. 6 (1983), no. 2, 297–309. {{refend Differential geometry