We establish a duality between the quantum wave vector spectrum and the eigenmodes of the classical Liouvillian dynamics for integrable billiards. Signatures of the classical eigenmodes appear as peaks in the correlation function of the quantum wave vector spectrum. A semiclassical derivation and numerical calculations are presented in support of the results. These classical eigenmodes can be o...

The possibility of charge density oscillations in a finite-thickness two-dimensional system is investigated for strong magnetic fields and integer filling factors. Using an effective action formalism, it is shown that an oscillatory charge density (OCD) is generated in a self-consistent way and is favored energetically over homogeneous distributions. It is smooth on the scale of the sample thic...

We investigate pattern formation in two-dimensional anisotropic systems under an external spatially periodic modulation force. Electrohydrodynamic convection or RayleighB6nard convection of nematic liquid crystals are typical examples of anisotropic pattern forming systems. We are especially interested in the situation where the wave vector of the convection rolls and the wave vector of the ext...

The nature of the magnetic ordering in TbNi2B2C has been investigated using neutron diffraction techniques on powdered polycrystalline samples. The results show that the Tb moments order below 15.5 K into an incommensurate magnetic structure. The magnetic order consists of a longitudinal modulation of the Tb moments with a wave vector of (0.556 0 0) at 1.5 K along the a*-direction. On increasin...

The dispersion of quantum-well resonances in ultrathin epitaxial Al films on Si(111) reveals energy- and wave vector-dependent reflection properties at the Al/Si interface. The substrate electronic structure strongly influences the phase shift of the electron waves upon reflection at the interface. Thus the details of the substrate electronic structure need to be taken into account for a comple...

Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constants, and for the [110] Dresselhauss model, a new type of SU(2) spin rotation symmetry is discovered. This symmetry is robust against spin-independent disorder and interactions and is generated by operators whose wave vector depends on the coupling strengt...

The wave-vector dependence of electron-hole exchange interaction is investigated. For the yellow 1S exciton in Cu2O the exchange is derived up to the order k 2. The theoretical predictions are verified experimentally by high-resolution absorption experiments. In agreement with theory the fine structure shows a characteristic dependence on the direction of the wave vector. The exchange splitting...

We report combined x-ray photon correlation spectroscopy (XPCS) and neutron spin echo (NSE) measurements of the layer-displacement fluctuations in smectic liquid-crystal membranes in the range from 10 ns to 10 micros. NSE reveals a new regime, determined by bulk elasticity, in which relaxation times decrease with the wave vector of the fluctuations. XPCS probes slower surface-tension-dominated ...

A review of light-cone, covariant and gauge-invariant wave-functions of mesons is presented. They are basic non-perturbative objects needed for hard exclusive processes and for the method of light-cone QCD sum rules. The emphasis is on the vector mesons and a new (model-independent) way of computing the mass corrections of vector-meson wave functions is given. Key-Words: Non-pertrubative QCD, C...

We characterize the director structures in electroconvection patterns of nematic liquid crystals by means of polarising microscopy. This study was stimulated by a theory put forward by Rossberg et al. [1] who propose a mechanism for chevron texture formation. We characterize the relation between the wave vector modulation and in-plane twist modulations of the director field. In addition to the ...