Meson and diquark condensates in the NJL model and the Fermi momentum

Quark–anti quark and diquark condensation have been investigated in the framework of the NJL model. The Pauli–Villars regularization scheme have been used for the investigation of meson condensation in three dimension whereas the four dimensional case has been studied using the Schwinger–Dyson equation considering the Hartree approximation. Diquark condensation in three and four dimension have also been studied considering the Pauli–Villars regularization scheme. Using the Fermi momentum [Formula: see text] of the particle as cut-off parameter, the gap energy/coherence length for meson condensation [Formula: see text] have been investigated whereas for diquark [Formula: see text] the critical gap energy/critical coherence length (the distance over which there would be no diquark condensation) have been extracted. The variation of the coherence length/gap energy with [Formula: see text] have also been investigated. The results are compared with exciting data. Some interesting observations are made.

Quantum breathers in XXZ ferromagnetic chains with on-site easy-plane anisotropy

The existence and properties of quantum breathers in a one-dimensional XXZ ferromagnetic Heisenberg spin chain with single-ion easy-plane anisotropy are investigated analytically in the Hartree approximation. We show that the system can support the appearance of quantum breathers, and discuss their existence conditions and properties. In addition, our results show that, for quantum breathers in this system, both the corresponding energy and magnetic moment are quantized.