Ising Field Theory is a (Euclidean) quantum field theory emerging in the scaling limit of 2D Ising model with a magnetic field, near its critical point $T=T_c, H=0$. It describes baisic universality class of criticality in 2D, including Curie point in ferromagnets and liquid-vapor critical point in 2D gasses, as well as quntum criticality in 1D spin chain. Away from the critical point IFT is massive, and defines a relativistic particle theory.
In the presence of nonzero magnetic field IFT is not integrable (except for certain special "integrable points"), and it displays rich spectrum of stable particles and resonances. In this lectures I will discuss some properties of IFT, including analytic properties of the scaling functions, with the role of nucleation singularity, Yang-Lee singularity, and complex spinodal. I will also discuss some features of the associated particle theory, such as the confinement in the low-T regime (the so called McCoy-Wu scenario), and properties of certain resonance states.
I will assume basic familiarity with the zero-field Ising model and its exact treatment in terms of free fermions. I will occasionally use terms and concepts of 2D CFT and notions of integrable QFT with minimal explanations.