119306365
TeV scale Lee-Wick fields out of large extra dimensional gravity
We study the gravitational corrections to the Maxwell, Dirac, and Klein-Gordon theories in the large extra dimension model in which the gravitons propagate in the (4 + n)-dimensional bulk, while the gauge and matter fields are confined to the four-dimensional world. The corrections to the two-point Green's functions of the gauge and matter fields from the exchanges of virtual Kaluza-Klein gravitons are calculated in the gauge independent background field method. In the framework of effective field theory, we show that the modified one-loop renormalizable Lagrangian due to quantum gravitational effects contains a TeV scale Lee-Wick partner of every gauge and matter field as extra degrees of freedom in the theory. Thus the large extra dimension model of gravity provides a natural mechanism for the emergence of these exotic particles which were recently used to construct an extension of the standard model.
8450139
Electrodynamics modified by some dimension-five Lorentz-violating interactions: radiative corrections
We study radiative corrections to massless quantum electrodynamics modified by two dimension-five LV interactions $$\bar{\Psi } \gamma ^{\mu } b'^{\nu } F_{\mu \nu }\Psi $$Ψ¯γμb′νFμνΨ and $$\bar{\Psi }\gamma ^{\mu }b^{\nu } \tilde{F}_{\mu \nu } \Psi $$Ψ¯γμbνF~μνΨ in the framework of effective field theories. All divergent one-particle-irreducible Feynman diagrams are calculated at one-loop order and several related issues are discussed. It is found that massless quantum electrodynamics modified by the interaction $$\bar{\Psi } \gamma ^{\mu } b'^{\nu } F_{\mu \nu }\Psi $$Ψ¯γμb′νFμνΨ alone is one-loop renormalizable and the result can be understood on the grounds of symmetry. In this context the one-loop Lorentz-violating beta function is derived and the corresponding running coefficients are obtained.
117791238
What can we learn from a measurement of sin(2 beta + gamma)?
The constraints on the value of the Cabibbo-Kobayashi-Maskawa phase $\ensuremath{\gamma}$ that may be achieved by prospective measurements of $\mathrm{sin}2\ensuremath{\beta}$ and $\mathrm{sin}(2\ensuremath{\beta}+\ensuremath{\gamma})$ are discussed. Significant constraints require quite small errors, and may depend on assumptions about strong phases. The measurement of $\mathrm{sin}(2\ensuremath{\beta}+\ensuremath{\gamma})$ combined with other experiments could provide valuable limits on new physics in ${B}_{d}\ensuremath{-}$ mixing.
119283253
Aspects of electrodynamics modified by some dimension-five Lorentz-violating interactions
Assuming Lorentz symmetry is broken by some fixed vector background, we study the spinor electrodynamics modified by two dimension-five Lorentz-violating interactions between fermions and photons. The effective polarization and magnetization are identified from the modified Maxwell equations, and the theoretical consequences are investigated. We also compute the corrections to the relativistic energy levels of hydrogen atom induced by these Lorentz-violating operators in the absence and presence of uniform external fields in first-order perturbation theory. We find that the hydrogen spectrum is insensitive to the breakdown of Lorentz boost symmetry.
8866225
AdS/QCD phenomenological models from a back-reacted geometry
We construct a fully back-reacted holographic dual of a four-dimensional field theory which exhibits chiral symmetry breaking. Two possible models are considered by studying the effects of a five-dimensional field, dual to the qq operator. One model has smooth geometry at all radii and the other dynamically generates a cutoff at finite radius. Both of these models satisfy Einstein's field equations. The second model has only three free parameters, as in QCD, and we show that this gives phenomenologically consistent results. We also discuss the possibility that in order to obtain linear confinement from a back-reacted model it may be necessary to consider the condensate of a dimension two operator.
119233126
Higher derivative operators in the noncommutative Schwinger model
Abstract A study of the noncommutative Schwinger model is presented. It is shown that the Schwinger mass is not modified by the noncommutativity of spacetime till the first nontrivial order in the noncommutative parameter. Instead, a higher derivative kinetic term is dynamically generated by the lowest-order vacuum polarization diagrams. We argue that in the framework of the Seiberg–Witten map the feature of non-unitarity for a field theory with spacetime noncommutativity is characterized by the presence of higher derivative kinetic terms. The θ-expanded version of a unitary theory will not generate the lowest-order higher derivative quadratic terms.
119187103
Reducing the Tension Between the BICEP2 and the Planck Measurements: A Complete Exploration of the Parameter Space
A large inflationary tensor-to-scalar ratio r0.002 = 0.20 +0.07 0.05 is reported by the BICEP2 team based on their B-mode polarization detection, which is outside of the 95% confidence level of the Planck best fit model. We explore several possible ways to red uce the tension between the two by considering a model in whichαs, nt, ns and the neutrino parameters Neff andmν are set as free parameters. Using the Markov Chain Monte Carlo (MCMC) technique to survey the complete parameter space with and without the BICEP2 data, we find that the resulting constraints on r0.002 are consistent with each other and the apparent tension seems to be relaxed. Further detailed investigations on those fittin gs suggest that Neff probably plays the most important role in reducing the tension. We also find that the results obtained from fittin g without adopting the consistency relation do not deviate much from the consistency relation. With available Planck, WMAP, BICEP2 and BAO datasets all together, we obtain r0.002 = 0.14 +0.05 0.11 , nt = 0.35 +0.28 0.47 , ns = 0.98 +0.02 0.02 , andαs = 0.0086 +0.0148 0.0189 ; if the consistency relation is adopted, we get r0.002 = 0.22 +0.05 0.06 .
118566169
Role of t-channel meson exchange in S-wave pi N and K N scattering
The low-energy S-wave pi N and K N scatterings are studied by the K-matrix approach within the meson exchange framework. The t-channel meson exchanges, especially rho and sigma exchanges, are found to play a very important role in these two processes. The t-channel rho exchange determines the isospin structure of the scattering amplitudes, it gives attractive force in the low isospin state but repulsive force in the high isospin state. The t-channel sigma exchange gives a very large contribution in these two processes, while it is negligible in meson-meson S-wave scatterings.