Modern Physics Letters A

In the LSND experiment at the Los Alamos National Laboratory, a larger than expected signal was observed and interpreted as evidence of the oscillation with Δm² in the range of 0.2–10 eV². Since such a Δm² range is incompatible with the widely accepted model of oscillations between three light neutrino species, and since there was no confirmation from other neutrino experiments, this finding became known as the "LSND anomaly". If true, it would require the existence of at least one "sterile" neutrino which calls the Standard Model of particle physics in a nontrivial way into question. This review discusses the current status of the "LSND anomaly", including the prospects of further experimental checks.

We introduce a set of two-parameter models for the dark energy equation of state (EOS) w(z) to investigate time-varying dark energy. The models are classified into two types according to their boundary behaviors at the redshift z = (0, ∞) and their local extremum properties. A joint analysis based on four observations (SNe + BAO + CMB + H₀) is carried out to constrain all the models. It is shown that all models get almost the same and the cosmological parameters (Ω_M, h, Ω_bh²) with the best-fit results (0.28, 0.70, 2.24), although the constraint results on two parameters (w₀, w₁) and the allowed regions for the EOS w(z) are sensitive to different models and a given extra model parameter. For three of Type I models which have similar functional behaviors with the so-called CPL model, the constrained two parameters w₀ and w₁ have negative correlation and are compatible with the ones in CPL model, and the allowed regions of w(z) get a narrow node at z~0.2. The best-fit results from the most stringent constraints in Model Ia give which may compare with the best-fit results in the CPL model. For four of Type II models which have logarithmic function forms and an extremum point, the allowed regions of w(z) are found to be sensitive to different models and a given extra parameter. It is interesting to obtain two models in which two parameters w₀ and w₁ are strongly correlative and appropriately reduced to one parameter by a linear relation w₁∝(1+w₀).

The systems with J = 0 and J = 1 are dynamically investigated within the framework of two constituent quark models: the chiral quark model and the quark delocalization color screening model. The model parameters are taken from our previous work, which gave a good description of the proton–antiproton S-wave elastic scattering cross-section experimental data. The elastic scattering processes with coupling to state are studied. The results show that, there is no s-wave bound state as indicated by an enhancement near the threshold of in J/ψ decay. However, a resonance state is given in the quark delocalization color screening model.

We study the thermodynamic geometry arising from the free energy for the two- and three-flavor finite temperature hot QCD near the critical temperature. We develop a geometric notion for QCD thermodynamics, relating it with the existing microscopic quantities, e.g. quark-number susceptibility, which appears naturally within an approximately self-consistent resummation of perturbative QCD. We further incorporate thermal fluctuations in the free energy, thus yielding the geometric properties of local and global chemical correlations. These investigations are perturbative in nature. Nevertheless, one could apply the same line of thought for the geometric realization of underlying quark susceptibilities, either in the fabric of lattice QCD or in that of nonperturbative QCD.

We obtain approximate analytical solutions of the two-body Spinless Salpeter equation under both Cornell (Funnel) and Kratzer potentials and thereby provide a basis to study semirelativistic two-body systems which frequently appear in physics. Apart from the physical significance, the work is mathematically appealing as we have actually reported approximate analytical solutions of the corresponding Heun equations which appear as one of the most challenging differential equations of mathematical physics.

By means of a class of nondegenerate models with a finite number of degrees of freedom, it is proved that given a Hamiltonian formulation of dynamics, there exists an equivalent second-order Lagrangian formulation whose configuration space coincides with the Hamiltonian phase-space. The above result is extended to scalar field theories in a Lorentz-covariant manner.

In a recent study, Cohen and Glashow argue that superluminal neutrinos of the type recently reported by OPERA should be affected by anomalous Cherenkov-like processes. This causes them to lose much of their energy before reaching the OPERA detectors. Related concerns were reported also by Gonzalez-Mestres, Bi et al., and Cowsik et al., who argued that pions cannot decay to superluminal neutrinos over part of the energy range studied by OPERA. We observe here that these arguments are set within a framework in which Lorentz symmetry is broken, by the presence of a preferred frame. We further show that these anomalous processes are forbidden if Lorentz symmetry is instead "deformed", preserving the relativity of inertial frames. These deformations add nonlinear terms to energy–momentum relations, conservation laws and Lorentz transformations in a way that is consistent with the relativity of inertial observers.