International Journal of Modern Physics A

We present the embedding of the SM gauge group in SO10, a simple, compact unifying gauge group, with each of the three basic spin 1/2 families forming a unitary, irreducible 16-dimensional representation of spin10, which is complex, i.e. chiral. Subtle differences to the mixed representations of SU5, contained in the SO10 scheme, are pointed out. These have consequences for neutrino flavors, which become paired in a light ${\mathrm{\text{SU2}}}_L$-active doublet mode and a heavy SM singlet mode, one $\nu$, ${𝒩}$-pair per family.

A massive neutrino has nonzero magnetic moment and is involved in the electromagnetic interactions with external fields and photons. The electromagnetic neutrino moving in matter can emit the spin light $(SL\nu )$ in the process of transition between two quantum states in matter. In quite resembling way an electron can emit spin light in moving background composed of neutrinos, that is “the spin light of an electron in neutrino flux” $(SL{e}_{\nu })$. In this paper we obtain the exact solution for the wave function and energy spectrum for an electron moving in a neutrino flux and consider the $SL{e}_{\nu }$ as the transition process between two electron quantum states in the background. The $SL{e}_{\nu }$ radiation rate, power and emitted photon energy are calculated. Notably, the energy spectrum of the emitted $SL{e}_{\nu }$ photons can span up to gamma-rays. We argue that the considered $SL{e}_{\nu }$ can be of interest for astrophysical applications, for supernovae processes in particular.

Neutrinoless double beta decay, lepton number violating collider processes and the Baryon Asymmetry of the Universe (BAU) are intimately related. In particular, lepton number violating processes at low energies in combination with sphaleron transitions will typically erase any preexisting BAU. In this contribution, we briefly review the tight connection between neutrinoless double beta decay, lepton number violating processes at the LHC and constraints from successful baryogenesis. We argue that far-reaching conclusions can be drawn unless the baryon asymmetry is stabilized via some newly introduced mechanism.

In this paper canonical quantum gravity on noncommutative space–time is considered. The corresponding generalized classical theory is formulated by using the Moyal star product, which enables the representation of the field quantities depending on noncommuting coordinates by generalized quantities depending on usual coordinates. But not only the classical theory has to be generalized in analogy to other field theories. Besides, the necessity arises to replace the commutator between the gravitational field operator and its canonical conjugated quantity by a corresponding generalized expression on noncommutative space–time. Accordingly the transition to the quantum theory has also to be performed in a generalized way and leads to extended representations of the quantum theoretical operators. If the generalized representations of the operators are inserted to the generalized constraints, one obtains the corresponding generalized quantum constraints including the Hamiltonian constraint as dynamical constraint. After considering quantum geometrodynamics under incorporation of a coupling to matter fields, the theory is transferred to the Ashtekar formalism. The holonomy representation of the gravitational field as it is used in loop quantum gravity opens the possibility to calculate the corresponding generalized area operator.

The standard model ascribes distinct properties to different chiralities of fermions. We show how to incorporate this aspect in an extended space–time-property framework involving two different attributes using a generalized metric which includes gauge fields as well as gravitation. Because the gauge fields are accompanied by coupling constants, all such schemes, including ours, necessitate coupling unification at high energy to ensure universality of gravitational interactions with matter.

We study a new kind of Courant algebroid on Poisson manifolds, which is a variant of the generalized tangent bundle in the sense that the roles of tangent and the cotangent bundle are exchanged. Its symmetry is a semidirect product of $\beta$-diffeomorphisms and $\beta$-transformations. It is a starting point of an alternative version of the generalized geometry based on the cotangent bundle, such as Dirac structures and generalized Riemannian structures. In particular, $R$-fluxes are formulated as a twisting of this Courant algebroid by a local $\beta$-transformations, in the same way as $H$-fluxes are the twist of the generalized tangent bundle. It is a three-vector classified by Poisson three-cohomology and it appears in a twisted bracket and in an exact sequence.

We consider conformally coupled scalar with ${ɸ}^4$ coupling in ${\text{AdS}}_4$ and study its various boundary conditions on AdS boundary. We have obtained perturbative solutions of equation of motion of the conformally coupled scalar with power expansion order by order in ${ɸ}^4$ coupling $\lambda$ up to ${\lambda }^2$ order. In its dual CFT, we get 2, 4 and 6 point functions by using this solution with Dirichlet and Neumann boundary conditions via AdS/CFT dictionary. We also consider marginal deformation on AdS boundary and get its on-shell and boundary effective actions.

In this work, we analyze the propagation of photons in an environment where a strong magnetic field (perpendicular to the photon momenta) coexists with an oscillating cold axion background with the characteristics expected from dark matter in the galactic halo. Qualitatively, the main effect of the combined background is to produce a three-way mixing among the two photon polarizations and the axion. It is interesting to note that in spite of the extremely weak interaction of photons with the cold axion background, its effects compete with those coming from the magnetic field in some regions of the parameter space. We determine (with one plausible simplification) the proper frequencies and eigenvectors as well as the corresponding photon ellipticity and induced rotation of the polarization plane that depend both on the magnetic field and the local density of axions. We also comment on the possibility that some of the predicted effects could be measured in optical table-top experiments.

We study the static gluon and quark propagator of the Hamiltonian approach to quantum chromodynamics in Coulomb gauge in one-loop Rayleigh–Schrödinger perturbation theory. We show that the results agree with the equal-time limit of the four-dimensional propagators evaluated in the functional integral (Lagrangian) approach.

A calculation of the one loop gravitational self-energy graph in non-anticommutative quantum gravity reveals that graviton loops are damped by internal momentum dependent factors in the modified propagator and the vertex functions. The non-anticommutative quantum gravity perturbation theory is finite for matter-free gravity and for matter interactions.

The 3-3-1 model proposed in 2011 based on discrete symmetry $S_4$ responsible for the neutrino and quark masses is updated, in which the nonzero ${\theta }_{13}$ is focused. Neutrino masses and mixings are consistent with the most recent data on neutrino oscillations without perturbation. The new feature is adding a new $SU{(3)}_L$ anti-sextet lying in doublet under $S_4$ which can result the nonzero ${\theta }_{13}$ without perturbation, and consequently, the number of Higgs multiplets required is less than those of other models based on non-Abelian discrete symmetries and the 3-3-1 models. The exact tribimaximal form obtained with the breaking $S_4\to Z_3$ in charged lepton sector and $S_4\to {𝒦}$ in neutrino sector. If both breakings $S_4\to {𝒦}$ and ${𝒦}\to Z_2$ are taken place in neutrino sector, the realistic neutrino spectrum is obtained without perturbation. The upper bound on neutrino mass and the effective mass governing neutrinoless double beta decay at the tree level are presented. The model predicts the Dirac CP violation phase $\delta =292.45°$ in the normal spectrum (with ${\theta }_{23}\ne \frac{\pi }{4}$) and $\delta =303.14°$ in the inverted spectrum.

We present a model-independent analysis of CP violation, inspired by recent experimental observations, in charmed meson decays. The topological diagram approach is used to study direct CP asymmetries for singly Cabibbo-suppressed two-body hadronic decays of charmed mesons. We extract the magnitudes and relative phases of the corresponding topological amplitudes from available experimental information. In order to get more precise and reliable estimates of direct CP asymmetries, we take into account contributions from all possible strong penguin amplitudes, including the internal $b$-quark penguin contributions. We also study flavor SU(3) symmetry breaking effects in these decay modes and consequently predict direct CP asymmetries of unmeasured modes.