We demonstrate that waves excited on a fluid surface produce local surface rotation owing to hydrodynamic nonlinearity. We examine theoretically the effect and obtain an explicit formula for the vertical vorticity in terms of the surface elevation. Our theoretical predictions are confirmed by measurements of surface motion in a cell with water where surface waves are excited by vertical and harmonic shaking the cell. The experimental data are in good agreement with the theoretical predictions. We discuss physical consequences of the effect.
Using proton-proton collision data corresponding to an integrated luminosity of 3.0fb−1, recorded by the LHCb detector at centre-of-mass energies of 7 and 8TeV, the Bc+ → D0K+ decay is observed with a statistical significance of 5.1 standard deviations. By normalising to B+ → D0π+ decays, a measurement of the branching fraction multiplied by the production rates for Bc+ relative to B+ mesons in the LHCb acceptance is obtained,
R 0 =fc ×B(B+→D0K+)=(9.3+2.8±0.6)×10−7, DKfu c −2.5
where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first Bc+ decay of this nature to be observed.
A highly significant structure is observed in the Λ+cK−π+π+ mass spectrum, where the Λ+c baryon is reconstructed in the decay mode pK−π+. The structure is consistent with originating from a weakly decaying particle, identified as the doubly charmed baryon Ξ++cc. The difference between the masses of the Ξ++cc and Λ+c states is measured to be 1334.94±0.72(stat)±0.27(syst MeV/c2, and the Ξ++cc mass is then determined to be 3621.40±0.72(stat)±0.27(syst±0.14(Λ+c) MeV/c2, where the last uncertainty is due to the limited knowledge of the Λ+c mass. The state is observed in a sample of proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.7 fb−1, and confirmed in an additional sample of data collected at 8 TeV.
We observe a series of sharp resonant features in the differential conductance of graphene-hexagonal boron nitride-graphene tunnel transistors over a wide range of bias voltages between 10 and 200 mV. We attribute them to electron tunneling assisted by the emission of phonons of well-defined energy. The bias voltages at which they occur are insensitive to the applied gate voltage and hence independent of the carrier densities in the graphene electrodes, so plasmonic effects can be ruled out. The phonon energies corresponding to the resonances are compared with the lattice dispersion curves of graphene–boron nitride heterostructures and are close to peaks in the single phonon density of states.
Separating between the ordinary Hall effect and anomalous Hall effect in the paramagnetic phase of Mn1−xFexSi reveals an ordinary Hall effect sign inversion associated with the hidden quantum critical (QC) point x ∼ 0.11. The effective hole doping at intermediate Fe content leads to verifiable predictions in the field of fermiology, magnetic interactions, and QC phenomena in Mn1−xFexSi. The change of electron and hole concentrations is considered as a “driving force” for tuning the QC regime in Mn1−xFexSi via modifying the Ruderman-Kittel-Kasuya-Yosida exchange interaction within the Heisenberg model of magnetism.