Modern Physics Letters A

Supersymmetry is one of the best motivated new physics scenarios. To build a realistic supersymmetric standard model, however, a companion symmetry is necessary to address various issues. While R-parity is a popular candidate that can address the proton and dark matter issues simultaneously, it is not the only option for such a property. We review how a TeV scale U(1)′ gauge symmetry can replace the R-parity. Discrete symmetries of the U(1)′ can make the model still viable and attractive with distinguishable phenomenology. For instance, with a residual discrete symmetry of the U(1)′, Z₆ = B₃ × U₂, the proton can be protected by the baryon triality (B₃) and a hidden sector dark matter candidate can be protected by the U-parity (U₂).

The chiral parametrization of gluons in SU(3) QCD is proposed extending an approach developed earlier for SU(2) case. A color chiral field is introduced, gluons are chirally rotated, and vector component of rotated gluons is defined on condition that no new color variables appeared with the chiral field. This condition associates such a vector component with SU(3)/U(2) coset plus a U(2) field. The topological action in SU(3) QCD is derived. It is expressed in terms of axial vector component of rotated gluons. The vector field in CP² sector is studied in new variables of chiral parametrization.

We show that, by using resummation techniques based on the extension of the methods of Yennie, Frautschi and Suura to Feynman's formulation of Einstein's theory, we get quantum field theoretic predictions for the UV fixed-point values of the dimensionless gravitational and cosmological constants. Connections to the phenomenological asymptotic safety analysis of Planck scale cosmology by Bonanno and Reuter are discussed.

We discuss conformal symmetry on the two-dimensional noncommutative plane equipped with Moyal product in the twist deformed context. We show that the consistent use of the twist procedure leads to results which are free from ambiguities. This lends support to the importance of the use of twist symmetries in noncommutative geometry.

We show that we are able to extract the pion electromagnetic form factor by using the recent charged pion electroproduction data from JLab and a simple t-channel diagram. For this purpose we have performed the Q²-independent and dependent analyses. The result of the first analysis is in good agreement with those of previous works and fit the Maris and Tandy model as well as the monopole parametrization which describes a pion radius of 0.672 fm. The result of the second analysis corroborates the findings in the first analysis. Our findings therefore provide a direct proof that at the given kinematics the t-channel diagram really dominates the process. This could also set a new constraint to the phenomenological models that try to describe the process.

We study the radiative lepton flavor violating l_i→l_jγγ decays in the case that the lepton flavor violation is induced by the scalar unparticle mediation. We restrict the scaling dimension d_u and the scalar unparticle–photon–photon coupling by using the experimental upper limit of the branching ratio of the decay μ→eγγ. Furthermore, we predict the BRs of the other radiative decays by using the restrictions we get. We observe that the measurements of upper limits of BRs of these decays ensure considerable information for testing the possible signals coming from unparticle physics.

Models of particle physics with Noncommutative Geometry (NCG) generally suffer from a manifestly non-Wilsonian coupling of infrared and ultraviolet degrees of freedom known as the "IR/UV Problem" which would tend to compromise their phenomenological relevance. In this letter we explicitly show how one may remedy this by coupling NCG to gravity. In the simplest scenario, the Lagrangian gets multiplied by a nonconstant background metric; in ϕ-4 theory the theorem that ∫ d⁴x ϕ⋆ϕ=∫ d⁴x ϕ² is no longer true and the field propagator gets modified by a factor which depends on both NCG and the variation of the metric. A suitable limit of this factor as the propagating momentum gets asymptotically large then eradicates the IR/UV problem. With gravity and NCG coupled to each other, one might expect antisymmetric components to arise in the metric. Cosmological implications of such are subsequently discussed.