Nuclear orientation study of160Tb impurity in gadolinium single crystal

The low temperature nuclear orientation of¹⁶⁰Tb in gadolinium single crystal has been studied in the temperature range 5–60 mK and in the external magnetic field B_ext ≤9 T, applied both in the a- and c-axis directions. The obtained results indicate the noncollinearity between the Tb magnetic moments and the magnetization of the gadolinium matrix.     

Radiative kinks and fermionic zero modes in a (λφ6)1+1 model

We consider bidimensional scalar models including kink solutions _k (x). Using the hidden supersymmetric properties of the Dirac equation, we describe a general method to find normalizable fermionic zero modes. In particular, we apply the technique to a ( ⁶)₁₊₁ model. Going to the one-loop order of the effective potential, the emergence of a radiative kink provides an interesting scalar background in order to discuss the Dirac equation.     

Conductance noise spectrum of mesoscopic systems

We investigate the shape as well as the size- and temperature-dependence of the conductance noise spectrum of a small system containing electrons and both fixed and mobile scatterers. If the number of mobile scatterers within a phase-coherent region is sufficiently large, the temporal variation of the conductance can be viewed as a random walk process limited by the universal conductance fluctuations, resulting in a practically Lorentzian power spectrum. We discuss the conditions under which the noise spectrum of a system consisting of many phase-coherent regions is either Lorentzian or 1/f-like. The temperature-dependence of the power spectrum is determined by the hopping mechanism and the variation of the phase breaking length. As a function of temperature the spectrum satisfies power law scaling relations with exponents depending on the dimension and the temperature range; the spectral intensity can both increase and decrease with decreasing temperature.     

Mechanisms determining the salience of coloration in echoed sound: influence of interaural time and level differences

This study investigates whether the salience of the pitch associated with a single reflection of a broadband sound, such as noise, is determined by the monaural information mediated by the stimuli at the two ears, or by the relative locations of the primary sound and the reflection. Pitch strength was measured as a function of the reflection delay and the lateral displacement between the primary sound and the reflection. Thereby, lateral displacement was produced by means of interaural time differences (ITDs) in experiment 1 and interaural level differences (ILDs) in experiment 3. The results from both experiments are in accordance with the assumption that the strength of the pitch associated with a reflection is based on a central average of the internal representations of the stimuli at the two ears. This notion was corroborated by experiment 2, which showed that the results from experiment 1 could be mimicked by simply adding the stimuli from the two ears and presenting the merged stimulus identically to both ears.     

Control of spontaneous emission by complex nanostructures

Spontaneous emission in the presence of complex nanostructures is discussed by use of a calculational scheme that permits us to deal with interfaces of arbitrary shape. Control over the field associated with the emission is shown to be attainable. In particular, decay rates are offered for geometries that lead to focusing and collimation of near- and far-field distributions. Emission from axially symmetric gratings is shown to lead to narrow angular distributions of emission, and focusing at the foci of dielectric ellipsoids is achieved for dimensions comparable with the wavelength. In the latter case the total emission rate for two atoms in an ellipsoidal cavity is shown to be enhanced in a way that deviates from the predictions of the Dicke effect by means of intermediate- and far-field contributions.     

Higgs bosons in the standard model,the MSSM and beyond

I summarize the basic theory and selected phenomenology for the Higgs boson(s) of the standard model, the minimal supersymmetric model and some extensions thereof, including the next-to-minimal supersymmetric model.