Hyper-Hermitian metrics with symmetry

We show that any four-dimensional hyper-Hermitian manifold admitting a non-trivial triholomorphic Killing vector field is locally determined by the solution of a monopole-like equation on a three-dimensional Einstein-Weyl space of a special type. Conversely, any four-dimensional hyper-Hermitian manifold admitting a non-trivial tri-holomorphic Killing vector field arises in this way.     

Density-metric unimodular gravity: Vacuum maximal symmetry

We have investigated the vacuum maximally symmetric solutions of recently proposed density-metric unimodular gravity theory. The results are widely different from inflationary scenario. The exponential dependence on time in deSitter space is substituted by a power law. Open space–times with non-zero cosmological constant are excluded.     

Mott insulators without symmetry breaking

We present theoretical models, in one and two space dimensions, that exhibit Mott insulating ground states at fractional occupations without any symmetry breaking. The Hamiltonians of these models are nonlocal in configuration space, but local in phase space.     

Vacuum instabilities in models with spontaneous symmetry breaking

Adopting as a reference a simple model with spontaneously broken symmetry we show that the extra massless field present in the three approximation in addition to the true Goldstone bosons may induce, through the radiative corrections to its vacuum expectation value, infrared effects which are not compensable without spoiling the symmetry itself. We further extend the analysis to generic lagrangian field models with spontaneous symmetry breaking and prove that the only constraint to their renormalizability arises from the radiative corrections to the vacuum expectation value of the massless fields, except for the true Goldstone bosons which never induce such pathologies.     

Warped electroweak breaking without custodial symmetry

We propose an alternative to the introduction of an extra gauge (custodial) symmetry to suppress the contribution of KK modes to the T   parameter in warped theories of electroweak breaking. The mechanism is based on a general class of warped 5D metrics and a Higgs propagating in the bulk. The metrics are nearly AdS in the UV region but depart from AdS in the IR region, towards where KK fluctuations are mainly localized, and have a singularity outside the slice between the UV and IR branes. This gravitational background is generated by a bulk stabilizing scalar field which triggers a natural solution to the hierarchy problem. Depending on the model parameters, gauge-boson KK modes can be consistent with present bounds on EWPT for mKK?1 TeV$m_{\mathit{KK}}?1\text{TeV}$ at 95% CL. The model contains a light Higgs mode which unitarizes the four-dimensional theory. The reduction in the precision observables can be traced back to a large wave function renormalization for this mode.     

Spin-isospin mixing without spontaneous symmetry breakdown

The phenomenon advertised in the title is demonstrated in an exactly symmetricSU(2) classical gauge theory with a scalar isodoublet of matter fields. Possible implications for chromodynamics are discussed briefly.     

Singularities in separable metrics with spherical,plane, and hyperbolic symmetry

We obtain all possible solutions to the Einstein equations for a perfect fluid with a metric of the form

The static metrics with cylindrical symmetry describing a model of cosmic strings

We discuss a set of static metrics with cylindrical symmetry describing the interior and exterior space-time of a model of cosmic strings considered recently in cosmology. The interior metric depends on one arbitrary function and the exterior on one constant. We find the relation between this constant and the linear mass density of the cosmic string. A cosmic string can be also treated as a line source in the framework of the distribution-valued curvature formalism which allows us to obtain again the same relation.     

Higgs phenomenon without symmetry breaking order parameter

We discuss symmetry-breaking order parameters, e.g. 〈?〉, in gauge theories with Higgs scalars, ?, in suitable gauges. We show that, typically, 〈?〉 = 0. A complete set of gauge-invariant, observable composite fields for such theories, local ones and ones localized near strings (paths) is constructed. We then examine the validity of standard perturbation theory, based on assuming that 〈?〉 ≠ 0, and reformulate it in terms of our gauge-invariant fields and without assuming that 〈?〉 ≠ 0. Finally, we classify classical field configurations with non-trivial topology (“defects”) in such theories and propose a defect-gas approach to predict their effects.     

Solutions of five-dimensional general relativity without spatial symmetry

Conformastationary solutions of the five-dimensional vacuum Einstein equations, depending on one or two harmonic potentials, are constructed. The solutions depending on one potential fall in three distinct classes. Solutions of two of these classes may be combined to yield a class of solutions depending on two potentials, which correspond to the Israel-Wilson-Perjès solutions of the Einstein-Maxwell theory. The asymptotically flat solutions of this class describe systems of rotating electric or magnetic monopoles.     

Radiative transfer in plane media without azimuthal symmetry

A rigorous integral theory is presented in this paper for the solution of radiative heat transfer problems in stratified media, when dependence on the azimuth of the propagating radiation must be taken into account. Anisotropy of scattering and specular and diffuse reflection from the bounding walls are incorporated in the final system of linear integral equations of Fredholm's type. A simple case of physical interest is considered in more detail, and solved explicitly by a constructive technique. Numerical results are reported and briefly discussed.     

Vacuum structure,chiral symmetry breaking and electric dipole moment of neutron

Considering a CP-violating QCD interaction, the electric dipole moment of neutron (EDMN) is estimated in a quark model of light mesons with a dynamical breaking of chiral symmetry through a non-trivial vacuum structure. Pion and kaon, being treated consistently within the model, yield to the constituent quark wave functions as well as the dynamical quark masses and thus determine the constituent quark field operators with respect to light quark flavors. Using the translationally invariant hadronic states and these constituent quark field operators, the EDMN estimated here remains well within the recent experimental bound ofD _n<11 × 10⁻²⁶ e-cm with the CP-violation parameter |ϑ|=10⁻⁸, which in fact accounts for a strong CP-violation.     

Vacuum Cerenkov radiation in Lorentz-violating theories without CPT violation

In theories with broken Lorentz symmetry, Cerenkov radiation may be possible even in vacuum. We analyze the Cerenkov emissions that are associated with the least constrained Lorentz-violating modifications of the photon sector, calculating the threshold energy, the frequency spectrum, and the shape of the Mach cone. In order to obtain sensible results for the total power emitted, we must make use of information contained within the theory which indicates at what scale new physics must enter.