Modern Physics Letters A

We review different contributions to the neutrino masses in the context of R-parity violating supersymmetry in a basis independent manner. We comment on the generic spectrum expected in such a scenario comparing different contributions.

We discuss the Schwarzschild solution in the Dvali–Gabadadze–Porrati (DGP) model. We obtain a perturbative expansion and find the explicit form of the lowest-order contribution. By keeping off-diagonal terms in the metric, we arrive at a perturbative expansion which is valid both far from and near the Schwarzschild radius. We calculate the lowest-order contribution explicitly and obtain the form of the metric both on the brane and in the bulk. As we approach the Schwarzschild radius, the perturbative expansion yields the standard four-dimensional Schwarzschild solution on the brane which is non-singular in the decoupling limit. This non-singular behavior is similar to the Vainshtein solution in massive gravity demonstrating the absence of the van Dam–Veltman–Zakharov (vDVZ) discontinuity in the DGP model.

Data indicate that ΔI=3/2 transitions account for 4.5–4.7% of both CP conserving and CP violating K→2π decays, as well as CP conserving radiative K→ππγ processes. Observed K→ππγ/ππ branching ratios are shown to scale near α/π or α/2π. The K_L–K_S mixing angle ϕ and the semileptonic weak-rate asymmetry δ are reviewed, and theory is shown to be consistent with data. Also, K→2π ΔI=1/2 dominance is studied in the context of the chiral constituent quark model, displaying again excellent agreement with data. Finally, indirect and direct kaon CP violation (CPV) are successfully described in the framework of photon-mediated quark-loop graphs. This suggests that kaon CPV can be understood via second-order weak transitions, radiatively corrected.

A generalized second-order differential realization of intertwining operator is given and isospectral partners of complex PT invariant Scarf II potential are obtained.

The pentaquark state of has been observed to decay with two decay modes: Θ⁺→nK⁺ and Θ⁺→pK⁰. The decay probability ratio of the two decay modes is studied with general symmetry consideration of isospin, spin and parity. We arrive at a result of the ratio , which is valid for the Θ⁺ state to be a pure isoscalar or isovector state, or an isoscalar and isovector mixing state, or an isotensor state with mixture of isoscalar and isovector components with coefficients α and β. The dependence on spin and parity of the pentaquark Θ⁺ state is found to be small due to small difference between the center-of-mass decay momenta k₁ and k₂ of the two decay modes. We also provide an analysis on the constraint of the isospin of Θ⁺ from the absence of a peak in the pK⁺ invariant mass distribution in the γp→pK⁺K^- process. Future experimental results about the decay probability ratio may provide information about the properties of the pentaquark Θ⁺ state.

We present a formulation of the stationary bosonic string sector of the whole toroidally compactified effective field theory of the heterotic string as a double Ernst system which, in the framework of general relativity describes, in particular, a pair of interacting spinning black holes; however, in the framework of low-energy string theory the double Ernst system can in particular be interpreted as the rotating field configuration of two interacting sources of black hole type coupled to dilaton and Kalb–Ramond fields. We clarify the rotating character of the B_tφ-component of the antisymmetric tensor field of Kalb–Ramond and discuss on its possible torsion nature. We also recall the fact that the double Ernst system possesses a discrete symmetry which is used to relate physically different string vacua. Therefore we apply the normalized Harrison transformation (a charging symmetry which acts on the target space of the low-energy heterotic string theory preserving the asymptotics of the transformed fields and endowing them with multiple electromagnetic charges) on a generic solution of the double Ernst system and compute the generated field configurations for the 4-D effective field theory of the heterotic string. This transformation generates the U(1)ⁿ vector field content of the whole low-energy heterotic string spectrum and gives rise to a pair of interacting rotating black holes endowed with dilaton, Kalb–Ramond and multiple electromagnetic fields where the charge vectors are orthogonal to each other.