Artistic forms and complexity

We discuss the inter-relationship between various concepts of complexity by introducing a complexity 'triangle' featuring objective complexity, subjective complexity and social complexity. Their connections are explored using visual and musical compositions of art. As examples, we quantify the complexity embedded within the paintings of the Jackson Pollock and the musical works of Johann Sebastian Bach. We discuss the challenges inherent in comparisons of the spatial patterns created by Pollock and the sonic patterns created by Bach, including the differing roles that time plays in these investigations. Our results draw attention to some common intriguing characteristics suggesting 'universality' and conjecturing that the fractal nature of art might have an intrinsic value of more general significance.     

(Li/Ag)CoO2: a new intergrowth cobalt oxide composed of rock salt and delafossite layers

A new ordered (Li/Ag)CoO(2) layered compound with an unusual oxygen packing combining rock salt and delafossite layers is obtained during the (Li(+), Na(+))/Ag(+) ionic exchange from the OP4-(Li/Na)CoO(2) precursor. This compound is actually an intermediate step to the final D4-AgCoO(2) delafossite and can be isolated thanks to the kinetics difference between the Li(+)/Ag(+) and Na(+)/Ag(+) exchange processes. It crystallizes in the P6(3)/mmc space group with cell parameters a(hex.) = 2.848(3) ? and c(hex.) = 21.607(7) ?. The details of the structure as well as its thermal stability and transport properties are presented and discussed.     

Crumpled-to-tubule transition in anisotropic polymerized membranes: beyond the ϵ expansion

Anisotropic D-dimensional polymerized phantom membranes are investigated within a nonperturbative renormalization group framework. One focuses on the transition between a high-temperature, crumpled phase and a low-temperature, tubular phase where the membrane is flat along one direction and crumpled along the other ones. While the upper critical dimension--D(uc)=5/2--is close to D=2, the weak-coupling perturbative approach is qualitatively and quantitatively wrong. We show that our approach is free of the problems encountered within the perturbative framework and provides physically meaningful critical quantities.     

Ultrafast nonadiabatic fragmentation dynamics of doubly charged uracil in a gas phase

A combination of time-dependent density functional theory and Born-Oppenheimer molecular dynamics methods is used to investigate fragmentation of doubly charged gas-phase uracil in collisions with 100 keV protons. The results are in good agreement with ion-ion coincidence measurements. Orbitals of similar energy and/or localized in similar bonds lead to very different fragmentation patterns, thus showing the importance of intramolecular chemical environment. In general, the observed fragments do not correspond to the energetically most favorable dissociation path, which is due to dynamical effects occurring in the first few femtoseconds after electron removal.     

Pressure-induced valence crossover in superconducting CeCu2Si2

Measurement of the Ce valence in the heavy fermion CeCu(2)Si(2) is reported for the first time under pressure and at low temperature (T=14 K) in proximity of the superconducting region. CeCu(2)Si(2) is considered as a strong candidate for a new type of pairing mechanism related to critical valence fluctuations which could set in at high pressure in the vicinity of the second superconducting dome. A quantitative estimate of the valence in this pressure region was achieved from the measurements of the Ce L(3) edge in the high-resolution partial-fluorescence yield mode and subsequent analysis of the spectra within the Anderson impurity model. While a clear increase of the Ce valence is found, the weak electron transfer and the continuous valence change under pressure suggests a crossover regime with the hypothetical valence line terminating at a critical end point T(cr) close to zero.     

How to detect the Chandler and the annual wobble of the Earth with a large ring laser gyroscope

We demonstrate a 16 m(2) helium-neon ring laser gyroscope with sufficient sensitivity and stability to directly detect the Chandler wobble of the rotating Earth. The successful detection of both the Chandler and the annual wobble is verified by comparing the time series of the ring laser measurements against the "C04 series" of Earth rotation data from the International Earth Rotation and Reference System Service.     

What is the surface specific area of porous cement-based material? A nuclear magnetic relaxation dispersion approach

We propose a new NMR method to measure and follow the evolution of the surface specific area, Sp, of a porous cement-based material. This method, that does not require any preliminary drying process, uses nuclear magnetic relaxation dispersion (NMRD), the measurement of spin-lattice relaxation rate as a function of magnetic field strength or nuclear Larmor frequency. The method is applied for three different mortars samples prepared by mixing cement, sand, silica fume, water and superplasticizer with a water to cement ratio w/c=0.25, 0.38 and 0.65, respectively. The evolution of Sp grows linearly with the degree of advancement of chemical reactions measured by thermal heating and we evidence two relaxation processes independent of the w/c ratio.     

Magnetic reversal of the ferroelectric polarization in a multiferroic spinel oxide

Ferroelectric transition has been detected in a ferrimagnetic spinel oxide of CoCr2O4 upon the transition to the conical spin order below 25 K. The direction [110] of the spontaneous polarization is normal to both the magnetization easy axis [001] and to the propagation axis [110] of the transverse spiral component, in accord with the prediction based on the spin-current model. The reversal of the spontaneous magnetization by a small magnetic field (approximately 0.1 T) induces the reversal of the spontaneous polarization, indicating the clamping of the ferromagnetic and ferroelectric domain walls.     

Scaling tests of the cross section for deeply virtual Compton scattering

We present the first measurements of the e[over -->]p-->epgamma cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region. The Q(2) dependence (from 1.5 to 2.3 GeV(2)) of the helicity-dependent cross section indicates the twist-2 dominance of DVCS, proving that generalized parton distributions (GPDs) are accessible to experiment at moderate Q(2). The helicity-independent cross section is also measured at Q(2)=2.3 GeV(2). We present the first model-independent measurement of linear combinations of GPDs and GPD integrals up to the twist-3 approximation.     

Semiconductor waveguide source of counterpropagating twin photons

We experimentally demonstrate an integrated semiconductor source of counterpropagating twin photons in the telecom range. A pump beam impinging on top of an AlGaAs waveguide generates parametrically two counterpropagating, orthogonally polarized signal/idler guided modes. A 2 mm long waveguide emits at room temperature one average photon pair per pump pulse, with a spectral linewidth of 0.15 nm. The twin character of the emitted photons is ascertained through a time-correlation measurement. This work opens a route towards new guided-wave semiconductor quantum devices.