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Register a new userRadiative corrections to the mass of the Kink: a small modification due to the different renormalization procedure
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We compute of the lowest order quantum radiative correction to the mass of the kink in $phi^4$ theory in 1+1 dimensions using an alternative renormalization procedure which has been introduced earlier. We use the standard mode number cutoff in conjunction with the above program. Our results show a small correction to the previously reported values.[The paper has been withdraw by the authors because a new version is been written to better emphasize on renormalization in problems with nontrivial background. The new version has been submitted by our new co-author (arXiv:1205.2775).]
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Concerning the gravitational corrections to the running of gauge couplings two different results were reported. Some authors claim that gravitational correction at the one-loop level indicates an interesting effect of universal gravitational decreasing of gauge couplings, that is, gravitational correction works universally in the direction of asymptotic freedom no matter how the gauge coupling behaves without gravity, while others reject the presence of gravitational correction at the one-loop level at all. Being these calculations done in the framework of an effective field theory approach to general relativity, we wanted to draw attention to a recently discovered profound quantum-gravitational effect of space-time dimension running that inevitably affects the running of gauge couplings. The running of space-time dimension indicating gradual reduction of dimension as one gets into smaller scales acts on the coupling constants in the direction of asymptotic freedom and therefore in any case manifests the plausibility of this quantum-gravitational effect. Curiously enough, the results are also in perfect quantitative agreement with those of Robinson and Wilczek.
We consider a model with arbitrary numbers of Majorana fermion fields and real scalar fields $varphi_a$, general Yukawa couplings and a $mathbb{Z}_4$ symmetry that forbids linear and trilinear terms in the scalar potential. Moreover, fermions become massive only after spontaneous symmetry breaking of the $mathbb{Z}_4$ symmetry by vacuum expectation values (VEVs) of the $varphi_a$. Introducing the shifted fields $h_a$ whose VEVs vanish, $overline{mbox{MS}}$ renormalization of the parameters of the unbroken theory suffices to make the theory finite. However, in this way, beyond tree level it is necessary to perform finite shifts of the tree-level VEVs, induced by the finite parts of the tadpole diagrams, in order to ensure vanishing one-point functions of the $h_a$. Moreover, adapting the renormalization scheme to a situation with many scalars and VEVs, we consider the physical fermion and scalar masses as derived quantities, $textit{i.e.}$ as functions of the coupling constants and VEVs. Consequently, the masses have to be computed order by order in a perturbative expansion. In this scheme we compute the selfenergies of fermions and bosons and show how to obtain the respective one-loop contributions to the tree-level masses. Furthermore, we discuss the modification of our results in the case of Dirac fermions and investigate, by way of an example, the effects of a flavour symmetry group.
QED radiative corrections to the cross-section of muon-antimuon annihilation into Higgs boson and photon are calculated within the 1-loop approximation. We write down the expression for cross-section in the form of Drell-Yan process, taking into account higher order leading logs. The non-singlet structure functions of fermions are shown to obey here evolution equations of twist-3 operators. Numerical estimation shows an importance of the correction in the region close to the threshold of Higgs production.
Radiative muon decay in the kinematics similar to the neutrinoless decay $muto egamma$ is considered. Radiative corrections due to 1-loop virtual photons and emission of additional soft or hard photons are taken into account. Analytical expressions and numerical estimations are presented.
We analyze the quark mass dependence of the Roper mass to one-loop order in relativistic baryon chiral perturbation theory. The loop integrals are evaluated using infrared regularization which preserves chiral symmetry and establishes a chiral counting scheme. The derived chiral expansion of the Roper mass may prove useful for chiral extrapolations of lattice data. For couplings of natural size the quark mass dependence of the Roper mass is similar to the one of the nucleon.
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