Daliang Li

Daliang Li's picture
Senior AI Research Engineer
Google
Research Areas: 
Particle Physics
Research Type: 
Theorist
Education: 
Ph.D., Yale University, 2015
Advisor: 
Witold Skiba
Dissertation Title: 
Covariant Methods for Superconformal Field Theories
Dissertation Abstract: 

In this thesis, we develop manifestly covariant methods for 4 dimensional, N = 1 superconformal field theories. First, we generalize the embedding formalism in conformal field theories (CFTs) to N = 1 superconformal field theories (SCFTs). As applications we construct manifestly superconformally covariant expressions for 2- and 3-point correlation functions involving the supercurrent multiplet or the global symmetry current superfield. Next, we combine this superembedding formalism with the shadow formalism in CFTs into a new method for computing superconformal blocks appearing in 4-point functions of SCFTs. This new method, called the supershadow formalism, expresses a superconformal block as manifestly covariant integrations over a product of 3-point functions. The supershadow formalism is much more efficient computationally than the brute force methods used previously in the literature. We obtain the superconformal blocks appearing in the 4-point functions of general scalar operator and then specialize to the 4-point functions involving chiral and global symmetry current multiplets. The results in the chiral case can be further generalized to N = 2 SCFTs. Finally, we present a systematic algorithm to extract the correlation functions of conformal primary component operators from the superfield correlation functions. We implemented this algorithm in Mathematica and applied it to the superfield 2-point function between general operators, from which we obtain all the component 2-point functions and all possible shortening conditions for an N = 1 superconformal multiplet. We also discuss a few potential directions for future researches.