Center for Theoretical Physics

We study the contributions of supersymmetric models with a \(U(1)\) horizontal symmetry and only spontaneous CP breaking to various lepton flavor observables, such as \(\mu \to e\gamma\) and the electron electric dipole moment. We show that both a horizontal symmetry and a lack of explicit CP violation can alleviate the existing bounds from such observables. The undetermined \(\mathcal{O}(1)\) coefficients in such mass matrix models muddle the interpretation of the bounds from various flavor observables. To overcome this, we define a new fine-tuning measure for different observables in such setups. This allows us to study how naturally the observed IR flavor observables can emerge from a given mass matrix model. We use our flavor-naturalness measure in study of our supersymmetric models and quantify the degree of fine tuning required by the bounds from various lepton flavor observables at each mass scale of sleptons, neutralinos, and charginos. We also comment on implications of the observed discrepancy in the anomalous magnetic moment of the muon for our supersymmetric models.

We discuss why AI is hard and why physics is simple. We discuss how physical intuition and the approach of theoretical physics can be brought to bear on the field of artificial intelligence and specifically machine learning. We suggest that the underlying project of machine learning and the underlying project of physics are strongly coupled through the principle of sparsity, and we call upon theoretical physicists to work on AI as physicists. As a first step in that direction, we discuss an upcoming book on the principles of deep learning theory that attempts to realize this approach.

We study the effect of a first-order phase transition in a confining \(SU(N)\) dark sector with heavy dark quarks. The baryons of this sector are the dark matter candidate. During the confinement phase transition the heavy quarks are trapped inside isolated, contracting pockets of the deconfined phase, giving rise to a second stage of annihilation that dramatically suppresses the dark quark abundance. The surviving abundance is determined by the local accidental asymmetry in each pocket. The correct dark matter abundance is obtained for \(\mathcal{O}(1-100)\) PeV dark quarks, above the usual unitarity bound.

Parton distribution functions (PDFs) and light-cone distribution amplitudes (LCDAs) are central non-perturbative objects of interest in high-energy inelastic and elastic scattering, respectively. As a result, an ab-initio determination of these objects is highly desirable. In this paper we present theoretical details required for the calculation of the moments of the PDF and LCDA using a heavy-quark operator product expansion method. This article also provides results of the relevant Wilson coefficients for the unpolarized PDF, helicity PDF and meson LCDA which are an essential ingredient in this approach. In addition, we discuss the use of our method to determine the dependence on the parton momentum fraction \(\xi\) in the PDFs and LCDAs through a matching condition between these quantities and the relevant hadronic amplitudes.