Internal resonances in a periodic magneto-electro-elastic structure

Propagation of electro-magneto-acoustic waves in a three phase magneto-electro-elastic periodic structure has been investigated with full coupling between mechanical, electric, and magnetic fields. Due to simultaneous piezoelectric and piezomagnetic effects, an orthogonally polarised electromagnetic wave couples with the similarly polarised lattice vibration, resulting in a both dielectric and magnetic phonon-polaritons. The closed form of dispersion relation has been used to demonstrate the phonon-polariton coupling not only in the long wave region at high acoustic microwave frequencies but also for shorter waves at optical infrared frequencies. The results also show that neither at acoustic nor at optical frequencies the magneto-electro-elastic effect affects the band structure due to the Bragg scattering

Propagation and control of shear waves in piezoelectric composite waveguides with metallized interfaces

This paper investigates coupled electro-elastic shear waves propagating along a piezoelectric finite width waveguide consisting of layers separated by metallized interfaces and arranged in a periodic way along the guide. The modified matrix method is applied to obtain the dispersion equation for a waveguide with straight walls. Bragg resonances and the presence of trapped modes and slow waves are revealed and analyzed for a periodic structure consisting of unit cells made up firstly from two different piezoelectric materials, and secondly from two identical piezoelectric materials. An analytical expression for the transmission coefficient for the waveguide with a defect layer is found that can be used to accurately detect and control the position of the passband within a stopband. This can be instrumental for constructing a tuneable waveguide made of layers of identical piezoelectric crystals separated by metallized interfaces

Magneto-electro-elastic polariton coupling in a periodic structure

Propagation of electro-magneto-acoustic waves in a magneto-electro-elastic (MEE) periodic structure has been investigated with a three phase coupling between mechanical, electric and magnetic fields in each constituent layer. Due to this coupling electromagnetic waves couple with lattice vibrations resulting in both dielectric and magnetic phonon–polaritons which couple via the magneto-electric effect. Propagation properties of acoustic longitudinal and transverse vibrations in this superlattice have been investigated. For longitudinal acoustic vibrations perpendicular to the poling direction, the coupling of piezoelectric and piezomagnetic polaritons results in a propagating mode. For transverse lattice vibrations with the coupled MEE wave propagating parallel to the poling direction, there is a coupled piezoelectric–piezomagnetic phonon polariton gap. The MEE superlattice produces either negative permittivity or negative permeability functions but not double negativity to result in negative refraction crystal

Determination of the strong coupling constant alpha(s) (m(Z)) in next-to-next-to-leading order QCD using H1 jet cross section measurements (vol 77, 791, 2017)

Abstract The determination of the strong coupling constant $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}})$$ α s ( m Z ) from H1 inclusive and dijet cross section data [1] exploits perturbative QCD predictions in next-to-next-to-leading order (NNLO) [2–4]. An implementation error in the NNLO predictions was found [4] which changes the numerical values of the predictions and the resulting values of the fits. Using the corrected NNLO predictions together with inclusive jet and dijet data, the strong coupling constant is determined to be $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}}) =0.1166\,(19)_{\mathrm{exp}}\,(24)_{\mathrm{th}}$$ α s ( m Z ) = 0.1166 ( 19 ) exp ( 24 ) th . Complementarily, $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}})$$ α s ( m Z ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}}) =0.1147\,(25)_{\mathrm{tot}}$$ α s ( m Z ) = 0.1147 ( 25 ) tot obtained is consistent with the determination from jet data alone. Corrected figures and numerical results are provided and the discussion is adapted accordingly