Citation of the 2018 Nishina Asia Award
Contributions to uncovering hidden symmetries and structures in S-matrix ofgauge and gravity theories
Yu-tin Huang, Physics Department, National Taiwan University

As one of the leading experts in the world on the S-matrix for gauge and gravity
theories, Prof. Yu-tin Huang initiated, with amazing insight and endeavor, a seriesof surprising developments that have revolutionized our understanding about
scattering amplitudes in ﬁeld theories and gauge theories in various dimensions.
Scattering amplitudes are fundamental observables in ﬁeld theories, usuallyobtained by calculating and summing up thousands of diﬀerent Feynman diagramsfrom Lagrangians: even a calculation of a single diagram is very diﬃcult andinvolved. Each diagram does not respect the underlying symmetries such as thegauge or gravitational symmetries. But surprisingly, a summation of thousands ofdiagrams miraculously make the ﬁnal result of scattering amplitudes invariant
under these symmetries. It suggests that there must exist a clever method to obtainthe scattering amplitudes. The recent development of S-matrix theories bypasses
the complicated calculations of Feynman diagrams and the scattering amplitudes
are calculated in a much more clever, simple and systematic way. Yu-tin Huang
has produced very deep and inﬂuential papers on the subject and summarized therecent developments in the famous textbook (written with H. Elvang), ”Scattering
Amplitudes in Gauge Theories and Gravity”, published in 2015 from Cambridge
University Press. The book is now the standard reference on this topic and has
inﬂuenced many researchers.
Yu-tin Huang revealed hidden structures and relations between the scattering
amplitudes of gauge theories and gravity theories. It was conjectured that thegravity theory amplitudes are written as a double copy of the gauge theory
amplitudes. The ﬁrst paper [1] showed this double copy structure beyond the treelevel approximations by proving the duality relation of color and kinematicfactors. The realization led tremendous progress for loop level computations ofquantum gravity amplitudes at the ultra-violet energy scale.
1The second paper [2] established the presence of dual-superconformal
symmetry for three-dimensional N = 6 theories to all orders in perturbation
theory. Unlike the case of four-dimensional N = 4 super Yang-Mills theory, thissymmetry was not expected from the dual string picture, and hence theestablishment of its presence was an important ﬁeld theoretical accomplishment.
The result revealed hidden structures in the d= 3 gauge theories and led to highmultiplicity and higher loop computations of the Chern-Simons gauge theories.
Prof. Huang’s papers are of very high quality and have revealed various hidden structures of gauge theories and gravity theories. Yu-tin Huangdeserves the Nishina Asia Award.

References[1] Zvi Bern, Tristan Dennen, Yu-tin Huang, Michael Keirmaier, ”Gravity as the Square of Gauge Theory”, Physical Review, D82 (2010)
065003[2] Dongmin Gang, Yu-tin Huang, Eunkyung Koh, Sangmin Lee, Arthur
Lipstein, ”Tree-level Recursion Relation and Dual Superconformal Theory of ABJM”, JHEP 1103 (2011) 116

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