Celestial conformal field theory (CCFT) is a conjectured theory living on the celestial sphere of the asymptotic boundary of Minkowski. In analogy to the usual AdS/CFT dictionary, CCFTs would be dual to gravitational theories in the bulk, with bulk scattering amplitudes being dual to correlation functions on the celestial sphere. OPE coefficients are basic building blocks of CFTs which should also have an analogue in CCFTs. It has been shown that CCFT OPEs can be extracted from amplitudes with appropriate wavefunctions for external states, but there's still no direct computation using the CCFT itself since we lack a first principles definition. I will talk about recent work I have done computing these OPEs directly by using twistor strings, circumventing the issue of the target space theory. I will show how the worldsheet CFT of the twistor string gives a realization of the algebra of operators of the CCFT, reproducing the known leading OPE terms, as well as how it can be used to compute further regular terms in the OPE, beyond what is currently known. As a bonus, the worldsheet OPE also organizes the spectrum naturally in terms of the infinite dimensional symmetry algebras of CCFTs. [for zoom link please contact h(dot)jiang(at)qmul(dot)ac(dot)uk]

The Standard Model extended with non-renormalisable operators is increasingly becoming THE theory of the elementary particles and their interactions. A large part of current and future research is devoted to test this theory to the best possible accuracy. To this aim, though, substantial knowledge on its quantum structure is needed, both for theoretical reasons (constraints on the basis of relativity+quantum mechanics) and experimental ones (combine data gathered at very different energies). In this talk I will discuss the progress made over the years in this respect, with particular emphasis on major obstacles.

I will describe the space of effective field theories consistent with local, unitary, and analytic UV completions, which was termed the EFThedron. Recently the EFThedron was generalized to a non-projective geometry, which can be used to implement new constraints on spectral functions. These include the unitarity bound, which leads to analytic bounds on single Wilson coefficients (instead of bounds only on ratios), or the low spin dominance condition, which drastically reduces the landscape of allowed theories. [for zoom link please contact h(dot)jiang(at)qmul(dot)ac(dot)uk]