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We argue that Lee–Wick's complex ghost appearing in any higher derivative theory is stable and its asymptotic field exists. It may be more appropriate to call it "anti-unstable", in the sense that the more the ghost "decays" into lighter ordinary particles, the larger the probability that the ghost remains as itself becomes. This is explicitly shown by analyzing the two-point functions of the ghost Heisenberg field which is obtained as an exact result in the N → ∞ limit in a massive scalar ghost theory with light O (N)-vector scalar matter. The anti-instability is a consequence of the fact that the poles of the complex ghost propagator are located on the physical sheet in the complex plane of four-momentum squared. This should be contrasted with the case of the ordinary unstable particle, whose propagator has no pole on the physical sheet. [ABSTRACT FROM AUTHOR]

Theories with fourth-order derivatives, including the Lee–Wick finite QED model and quadratic gravity, have a better UV behavior, but the presence of negative metric ghost modes endangers unitarity. Noticing that the ghost acquires a complex mass by radiative corrections, Lee and Wick, in particular, claimed that such complex ghosts would never be created by collisions of physical particles because of energy conservation, so that the physical S -matrix unitarity must hold. We investigate the unitarity problem faithfully, working in the operator formalism of quantum field theory. When complex ghosts participate, a complex delta function (a generalization of the Dirac delta function) appears at each interaction vertex, which enforces a specific conservation law of complex energy. Its particular property implies that the naive Feynman rule is wrong if the four-momenta are assigned to the internal lines after taking account of the conservation law in advance. We show that complex ghosts are actually created and unitarity is violated in such fourth-order derivative theories. We also find a definite energy threshold below which ghosts cannot be created: The theories are unitary and renormalizable below the threshold. [ABSTRACT FROM AUTHOR]

Abstract I argue that the work of Zimmermann with Lowenstein on the massless ϕ 4 theory [1] can play an important role in going beyond the standard model of elementary particles. [ABSTRACT FROM AUTHOR]

We consider two realistic models for a scale invariant extension of the standard model, which couples with a hidden non-Abelian gauge sector. At energies around TeV, the hidden sector becomes strongly interacting, thereby generating a robust energy scale, which is transferred to the standard model sector, triggering the electroweak symmetry breaking. At a finite temperature, i.e. in the early Universe, the generation of the robust energy scale appears as a strong first-order phase transition. We calculate the gravitational wave background spectrum for both models, which is produced by the first-order phase transition. We compare the results with the experimental sensitivity of LISA and DECIGO and find the gravitational wave signal may be detected at DECIGO. [ABSTRACT FROM AUTHOR]

Abstract: We consider a recently proposed supersymmetric radiative seesaw model which is coupled with the minimal supergravity. The conventional R parity and invariance are imposed, which ensures the existence of a multi-component dark matter system. We assume that the pair of the lightest neutralino and the fermionic component of the inert Higgs supermultiplet is dark matter. If is lighter than , and the lightest neutral inert Higgs boson is kinematically forbidden to decay (third dark matter), the allowed region in the plane increases considerably, where and are the universal soft-supersymmetry-breaking scalar and gaugino mass, respectively, although the dominant component of the multi-component dark matter system is . There is a wide allowed region above the recent LHC limit. [Copyright &y& Elsevier]

The Cabibbo–Kobayashi–Maskawa (CKM) parameters are investigated in detail in recent predictive models which are based on low-energy non-Abelian discrete family symmetries. Some of the models can already be excluded at the present precision of the determination of the CKM parameters, while some of them seem to survive. We find that to make the uncertainties of the theoretical values comparable with the assumed uncertainties of ~1° and ~2° in ϕ2(α) and ϕ3(γ), respectively, at about 50 inverse atto barn achieved at a future B factory, it is necessary to reduce the uncertainties in the quark masses, especially that of the strange quark mass by more than 60%. [ABSTRACT FROM AUTHOR]

Abstract: The new contribution to the non-diagonal matrix element of the neutral meson system is investigated in a supersymmetric extension of the standard model based on the discrete family symmetry. We assume that CP is explicitly, but softly broken only by the b terms in the soft supersymmetry breaking sector. We find that the new contributions to are real, and that nevertheless there exists an observable difference in the CP phase compared with the standard model. We focus our attention on the flavor-specific CP asymmetry , and find that of the model is mostly negative and its size can be one order of magnitude larger the standard model value. This prediction is consistent with the current experimental value, and might be experimentally tested in future. [Copyright &y& Elsevier]

Abstract: The cosmic ray data of PAMELA/ATIC may be explained by dark matter decay with a decay rate , an energy scale which could not be understood within the framework of the standard model or its simple supersymmetric extension. We propose anomaly induced dark matter decay to exponentially suppress the decay rate, and apply to a supersymmetric extension of the Ma''s inert Higgs model of the radiative seesaw mechanism for neutrino masses. In this model the lightest right-handed neutrino and the lightest neutralino χ can fill the observed necessary dark matter relic, and we find that can decay into χ through anomaly with a right order of decay rate, emitting only leptons. All the emitted positrons are right-handed. [Copyright &y& Elsevier]

Abstract: We propose a model for neutrino mass generation based on both the tree-level seesaw mechanism with a single right-handed neutrino and one-loop radiative effects in a non-supersymmetric framework. The generated mass matrix is composed of two parts which have the same texture and produce neutrino mass eigenvalues and mixing suitable for the explanation of neutrino oscillations. The model has a good CDM candidate which contributes to the radiative neutrino mass generation. The stability of the CDM candidate is ensured by which is the residual symmetry of a spontaneously broken . We discuss the values of and also estimate the masses of the relevant fields to realize an appropriate abundance of the CDM. [Copyright &y& Elsevier]

Abstract: Two of the most important and pressing questions in cosmology and particle physics are: (1) what is the nature of cold dark matter? and (2) will near-future experiments on neutrinoless double beta decay be able to ascertain that the neutrino is a Majorana particle, i.e. its own antiparticle? We show that these two seemingly unrelated issues are intimately connected if neutrinos acquire mass only because of their interactions with dark matter. [Copyright &y& Elsevier]

Abstract: Extra dimension deconstructed on a closed chain has naturally the symmetry of a regular polygon, the dihedral symmetry . We assume that the fields are irreducible representations of the binary dihedral group , which is the covering group of . It is found that although the orbifold boundary conditions break the dihedral invariance explicitly, the symmetry appears as an intact, internal global flavor symmetry at low energies. A concrete predictive model based on with an odd N is given. [Copyright &y& Elsevier]

The leptonic sector in a recently proposed minimal extension of the standard model, in which the permutation symmetry S3 is assumed to be an exact flavor symmetry at the weak scale, is revisited. We find that S3 with an additional ZN symmetry allows one CP violating phase φν in the neutrino mixing. The leptonic sector contains six real parameters besides the phase φν to describe charged lepton and neutrino masses and the neutrino mixing. The model predicts: an inverted spectrum of neutrino mass, the absence of CP violating Dirac phase, tanθ23=1+O(me2/mμ2) and sinθ13=0.0034+O(memμ/mτ2). Neutrino mass as well as the effective Majorana mass 〈mee〉 in the neutrinoless double-β decay can be expressed in a closed form as a function of φν,Δm221,Δm223 and tanθ12. The model also predicts 〈mee〉⩾(0.036–0.066) eV. [Copyright &y& Elsevier]

The exact discrete flavor symmetry, S3 in the hadronic sector and S3×Z2 in the leptonic sector, which has been recently found, is introduced in a supersymmetric extension of the standard model. We investigate the supersymmetric flavor problem, and explicitly find that thanks to the flavor symmetry the dangerous FCNC processes and CP-violating phases are sufficiently suppressed. [Copyright &y& Elsevier]

Abstract: We derive anomaly constraints for Abelian and non-Abelian discrete symmetries using the path integral approach. We survey anomalies of discrete symmetries in heterotic orbifolds and find a new relation between such anomalies and the so-called ‘anomalous’ U(1). [Copyright &y& Elsevier]

Abstract: Family symmetry could explain large mixing of the atmospheric neutrinos. The same symmetry could explain why the flavor changing current processes in supersymmetric standard models can be so suppressed. It also may be able to explain why the proton is so stable. We investigate these questions in a supersymmetric, renormalizable extension of the standard model, which possess a family symmetry based on a binary dihedral group . We find that the amplitude for enjoys a suppression factor proportional to , and that , where is the neutrino mixing matrix. [Copyright &y& Elsevier]

The muon anomalous magnetic moment measurement has, for more than a decade, been a long-standing anomaly hinting the physics beyond the Standard Model (BSM). The recently announced results from muon g − 2 collaboration, corresponding to 3.3 σ deviation from Standard Model value (4.2 σ in combination with previous measurement) are strengthening the need for new physics coupled to muons. In this letter, we propose a novel scenario in which Standard Model (SM) is augmented by an axion-like particle (ALP) and vector-like fermions. We find that such a model admits an excellent interpretation of recent muon g − 2 measurement through quantum process featuring ALP interacting with muons and newly introduced fermions. Previously proposed explanations with ALPs utilize interactions with photons and/or SM fermions. Therefore, in this letter we complement and extend such scenarios. We also discuss collider prospects for the model as well as the possibility that ALP is long lived or stable dark matter (DM) candidate. [ABSTRACT FROM AUTHOR]

We propose a new mechanism to generate the electroweak scale within the framework of QCD, which is extended to include conformally invariant scalar degrees of freedom belonging to a larger irreducible representation of SU(3)c. The electroweak symmetry breaking is triggered dynamically via the Higgs portal by the condensation of the colored scalar field around 1 TeV. The mass of the colored boson is restricted to be 350  GeV≲mS≲3  TeV, with the upper bound obtained from perturbative renormalization group evolution. This implies that the colored boson can be produced at the LHC. If the colored boson is electrically charged, the branching fraction of the Higgs boson decaying into two photons can slightly increase, and moreover, it can be produced at future linear colliders. Our idea of nonperturbative electroweak scale generation can serve as a new starting point for more realistic model building in solving the hierarchy problem.