Professor of Mathematics
Director of Undergraduate Studies in the Department of Mathematics
Professor Bray uses differential geometry to understand general relativity, and general relativity to motivate interesting problems in differential geometry. In 2001, he published his proof of the Riemannian Penrose Conjecture about the mass of black holes using geometric ideas related to minimal surfaces, scalar curvature, conformal geometry, geometric flows, and harmonic functions. He is also interested in the large-scale unexplained curvature of the universe, otherwise known as dark matter, which makes up most of the mass of galaxies. Professor Bray has proposed geometric explanations for dark matter which he calls "wave dark matter," which motivate very interesting questions about geometric partial differential equations.
Professor Bray has supervised 8 math Ph.D. graduates at Duke from 2006 to 2017. He is currently supervising one math Ph.D. student and one physics Ph.D. student. His most recent Ph.D. graduate, Henri Roesch, proved a Null Penrose Conjecture, open since 1973, as his thesis. While the physical motivation about the mass of black holes is the same as for the Riemannian Penrose Conjecture, the geometry involved is almost unrecognizably different, and may be viewed as a fundamental result about null geometry.
Bray, H. L., and K. Iga. “Superharmonic Functions in R^n and the Penrose Inequality in General Relativity.” Communications in Analysis and Geometry, vol. 10, no. 5, 2002, pp. 999–1016.
Bray, H. L. “Black Holes, Geometric Flows, and the Penrose Inequality in General Relativity.” Notices of the American Mathematical Society, vol. 49, no. 11, 2002, pp. 1372–81.
Bray, H. L. “Proof of the riemannian penrose inequality using the positive mass theorem.” Journal of Differential Geometry, vol. 59, no. 2, Jan. 2001, pp. 177–267. Scopus, doi:10.4310/jdg/1090349428. Full Text
Bray, H., et al. “Wavelet variations on the Shannon sampling theorem..” Bio Systems, vol. 34, no. 1–3, Jan. 1995, pp. 249–57. Epmc, doi:10.1016/0303-2647(94)01457-i. Full Text
From Pythagoras to Einstein: How Geometry Describes the Large-Scale Structure of the Universe (Part 1) (Broad Audience Talk). Duke University Graduate Student Recruiting Weekend. Duke University. March 26, 2011
From Pythagoras to Einstein: How Geometry Describes the Large-Scale Structure of the Universe (Part 2) (Broad Audience Talk). Duke University Graduate Student Recruiting Weekend. Duke University. March 26, 2011
From Black Holes and the Big Bang to Dark Energy and (maybe even) Dark Matter: Successes of Einstein's Theory of General Relativity (Broad Audience Talk) : 45 minutes. University of Tennessee. December 13, 2010