Congkao Wen

Loop corrections to soft theorems in gauge theories and gravity

A bstractIn this paper, we study loop corrections to the recently proposed new soft theorems of Cachazo and Strominger [1], for both gravity and gauge theory amplitudes. We first review the proof of its tree-level validity based on BCFW recursion relations, which also establishes an infinite series of universals soft functions for MHV amplitudes, and a generalization to supersymmetric cases. For loop corrections, we focus on infrared finite, rational amplitudes at one loop, and apply recursion relations with boundary or double-pole contributions. For all-plus amplitudes, we prove that the subleading soft theorems are exact to all multiplicities for gauge theory and up to 12-points for gravity amplitudes. For single-minus amplitudes, while the subleading soft theorems are again exact for the minus-helicity soft leg, for plus-helicity loop corrections are required. Using recursion relations, we identify the source of such mismatch as stemming from the special contribution containing double poles, and obtain the all multiplicity one-loop corrections to the subleading soft behavior in Yang-Mills theory. We also comment on the derivation of soft theorems using BCFW recursion in arbitrary dimensions.

More on Soft Theorems: Trees, Loops and Strings

The work of S. H. is supported by Zurich Financial Services Membership and the Ambrose Monell Foundation. The work of Y.-t. H. is supported by the National Science Foundation Grant No. PHY-1314311 and MOST Grant No. 103-2112-M002-025-MY3. The work of C. W. is supported by the Science and Technology Facilities Council Consolidated Grant No. ST/J000469/1, “String theory, gauge theory and duality.” The work of M. B. is partially supported by the ERC Advanced Grant No. 226455, “Superfields,

Three-Loop Leading Singularities and BDS Ansatz for Five Particles

We use the leading singularity technique to determine the planar three-loop five-particle amplitude in N=4 super Yang-Mills in terms of a simple basis of integrals. We analytically compute the integral coefficients for both the parity-even and the parity-odd parts of the amplitude. The parity-even part involves only dual conformally invariant integrals. Using the method of obstructions we numerically evaluate two previously unfixed coefficients that appear in the three-loop Bern Dixon Smirnov ansatz.

Double soft theorems in gauge and string theories

A bstractWe investigate the tree-level S-matrix in gauge theories and open superstring theory with several soft particles. We show that scattering amplitudes with two or three soft gluons of non-identical helicities behave universally in the limit, with multi-soft factors which are not the product of individual soft gluon factors. The results are obtained from the BCFW recursion relations in four dimensions, and further extended to arbitrary dimensions using the CHY formula. We also find new soft theorems for double soft limits of scalars and fermions in N=4

The Positive orthogonal Grassmannian and loop amplitudes of ABJM

\mathcal{N}=4

New Fermionic Soft Theorems for Supergravity Amplitudes

and pure N=2

Generalized Wilson-Fisher Critical Points from the Conformal Operator Product Expansion

\mathcal{N}=2