The ChPT: top-down and bottom-up

In this work, higher-derivative corrections of the non-linear sigma model of both even and odd intrinsic-parity sectors are systematically studied, focusing on ordered amplitudes of flavor scalars in massless limit. It should correspond to a theory known as chiral perturbation theory (ChPT) without external sources and with only single-trace operators. We briefly overview its formal development and apply new S-matrix methods to its amplitude constructions. The bottom-up analysis of the tree-level amplitudes of different orders and multiplicities focuses on the formal structure of general ChPT. Possible theoretical simplifications based on the Kleiss-Kuijf and Bern-Carrasco-Johansson relations are presented. Finally, in the same context, the comparison with the so-called Z-function, which is connected with string theory, is also discussed.

Contribution of QCD condensates to the OPE of Green functions of chiral currents

A framework of operator product expansion (OPE) allows us to study high-energy behaviour of Green functions. A calculation of such Green functions within chiral perturbation theory (χPT) or resonance chiral theory (RχT) and subsequent matching of the result to the OPE enables us to determine constraints for unknown parameters of the effective theories. We present such procedure for Green functions in the odd-intrinsic parity sector of QCD.

Two-component solitons in a chain of dimers with Parity-Time symmetric nonlinearity

We introduced a coupled waveguide arrays with intrinsic Parity-Time (PT)-symmetric nonlinearity. The system is described by a set of coupled Schrödinger equations with linear couplings and a complex nonlinearity. Two-component soliton modes are found to exist in this system. The stability of the solitons are investigated and the stable map is plotted numerically in the parameter plane of linear coupling and the strength of PT nonlinearity. The effects of the PT nonlinearity on the amplitude and the effective area of the soliton modes are studied. It is found that the PT nonlinearity can manipulate the amplitude and the propagation constant of the soliton modes. The mobility of these soliton modes are studied numerically. The soliton modes can be kicked to move and increase the PT nonlinearity will enhance the mobility. Collision of two soliton modes are investigated and the results indicates that we can control the types and properties of the collision by adjusting the linear coupling and the PT nonlinearity.