116892885
Nonrelativistic Cousin of QCD
Based on the uniqueness and universality of gravity, it is clear that theories with different dynamical exponents are related in the holographic approach. Concretely, we construct an M-theory background from pure QCD dual and show that a deformed $Sch_{6}^{4}$ geometry is obtained by compactification from the same background. The deformed $Sch_{6}^{4}$ geometry is considered as the geometrical realization of a four-dimensional nonrelativistic field theory. Several aspects of this nonrelativistic field theory are studied in the holographic picture.
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.
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.
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.
36290076
Embedding flipped SU(5) into SO(10)
We embed the flipped SU(5) models into the SO(10) models. After the SO(10) gauge symmetry is broken down to the flipped SU(5) x U(1)(X) gauge symmetry, we can split the five/one-plets and ten-plets in the spinor 16 and 16 Higgs fields via the stable sliding singlet mechanism. As in the flipped SU(5) models, these ten-plet Higgs fields can break the flipped SU(5) gauge symmetry down to the Standard Model gauge symmetry. The doublet-triplet splitting problem can be solved naturally by the missing partner mechanism, and the Higgsino-exchange mediated proton decay can be suppressed elegantly. Moreover, we show that there exists one pair of the light Higgs doublets for the electroweak gauge symmetry breaking. Because there exist two pairs of additional vector-like particles with similar intermediate-scale masses, the SU(5) and U(1)(X) gauge couplings can be unified at the GUT scale which is reasonably (about one or two orders) higher than the SU(2)(L) x SU(3)(C) unification scale. Furthermore, we briefly discuss the simplest SO(10) model with flipped SU(5) embedding, and point out that it can not work without fine-tuning.
119288545
Constraints on the Brans-Dicke gravity theory with the Planck data
Based on the new cosmic CMB temperature data from the Planck satellite, the 9 year polarization data from the WMAP, the BAO distance ratio data from the SDSS and 6dF surveys, we place a new constraint on the Brans-Dicke theory. We adopt a parametrization $\zeta=\ln(1+1/\omega})$, where the general relativity (GR) limit corresponds to $\zeta = 0$. We find no evidence of deviation from general relativity. At 95% probability, $-0.00246 0$ (i.e. $\omega >0$) case, then the 95% probability interval is $\zeta 181.65$. We can also translate this result to a constraint on the variation of gravitational constant, and find the variation rate today as $\dot{G}=-1.42^{+2.48}_{-2.27} \times 10^{-13} $yr$^{-1} $ ($1\sigma$ error bar), the integrated change since the epoch of recombination is $\delta G/G = 0.0104^{+0.0186}_{-0.0067} $ ($1\sigma$ error bar). These limits on the variation of gravitational constant are comparable with the precision of solar system experiments.
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.