I'll discuss recent results on line and surface defects in the N=4 Super-Yang-Mills (SYM) beyond perturbation theory. In addition to providing new observables in the SYM that capture the gauge theory dynamics in the presence of impurities, these non-perturbative results detect the nontrivial SL(2,Z) structure and provide an exact order parameter for the deconfinement phase transition. Furthermore, via AdS/CFT, they lead to novel predictions for the world-volume action of branes in type IIB string theory at finite string coupling and present a new perspective on the Hawking-Page transition for black holes in AdS.

Non-Gaussianity, which denotes the non-Gaussian feature of the CMB temperature fluctuation, is potentially the most promising probe of inflation. In this talk, we discuss some recent research topics in this field, namely non-Gaussianity for DBI inflation, quasi-single field inflation and multi-stream inflation. Special attention is paid on the relation between non-Gaussianity and string theory.