Modern Physics Letters A

In this review, we present and discuss all the experimental information about the charged exotic charmonium states, which have been observed over the last five years. We try to understand their properties such as masses and decay widths with QCD sum rules. We describe this method, show the results and compare them with the experimental data and with other theoretical approaches.

In this paper, we study the Dirac quasinormal modes of an uncharged 2+1 black hole proposed by Mandal et al. and referred to as MSW black hole. The quasinormal mode is studied using WKB approximation method. The study shows that the imaginary part of quasinormal frequencies increases indicating that the oscillations are damping and hence the black hole is stable against Dirac perturbations.

Based on the fermion operators' s-ordered rule, we introduce a new kind of s-ordered quasiprobability distributions , which is defined by the supertrace different from the other definition introduced by Cahill and Glauber [Phys. Rev. A59, 1538 (1999)]. We further obtain the s-parametrized operator expansion formula of fermion density operator for multi-mode case. At last, we apply it to deriving new multi-mode fermion-counting formula, which would be convenient to calculate the probability of counting n fermions.

The principle of stationary variance is advocated as a viable variational approach to quantum field theory (QFT). The method is based on the principle that the variance of energy should be at its minimum when the state of a quantum system reaches its best approximation for an eigenstate. While not too much popular in quantum mechanics (QM), the method is shown to be valuable in QFT and three special examples are given in very different areas ranging from Heisenberg model of antiferromagnetism (AF) to quantum electrodynamics (QED) and gauge theories.

The ⁸Be nucleus decays into two ⁴He nuclei. This decay constant is theoretically estimated using Fermi golden rule and the ground state wave functions of the ⁴He and ⁸Be nuclei. The estimated result agrees pretty well with the reported experimental value.

In this paper, the gauge structure of non-Abelian Chern–Simons model is investigated. Non-Abelian Chern–Simons model, unlike first class constraints systems is not a gauge theory, primarily due to the appearance of two second class constraints in its algebra. These two second class constraints were converted into first ones using gauge unfixing formalism. The model Lagrangian and Hamiltonian were obtained, aiming to satisfy first class algebra and hence making it into a fully gauge theory. Partition function of the model was finally evaluated and presented here.