Effects of boundary roughness on a Q-factor of whispering-gallery-mode lasing microdisk cavities

We perform numerical studies of the effect of sidewall imperfections on the resonant state broadening of the optical microdisk cavities for lasing applications. We demonstrate that even small edge roughness causes a drastic degradation of high-Q whispering gallery (WG) mode resonances reducing their Q-values by many orders of magnitude. At the same time, low-Q WG resonances are rather insensitive to the surface roughness. The results of numerical simulation obtained using the scattering matrix technique, are analyzed and explained in terms of wave reflection at a curved dielectric interface combined with the examination of Poincare surface of sections in the classical ray picture.Comment: 4 pages, 3 figure

Orthogonality catastrophe and Kondo effect in graphene

Anderson's orthogonality catastrophe in graphene, at energies close to the Dirac point, is analyzed. It is shown that, in clean systems, the orthogonality catastrophe is suppressed, due to the vanishing density of states at the Dirac point. In the presence of preexisting localized states at the Dirac energy, the orthogonality catastrophe shows similar features to those found in normal metals with a finite density of states at the Fermi level. The implications for the Kondo effect induced by magnetic impurities, and for the Fermi edge singularities in tunneling processes are also discussed.Comment: 7 pages, 7 figure

Force Distributions in Frictional Granular Media

We report a joint experimental and theoretical investigation of the probability distribution functions (pdf's) of the normal and tangential (frictional) forces in amorphous frictional media. We consider both the joint pdf of normal and tangential forces together, and the marginal pdf's of normal forces separately and tangential forces separately. A maximum entropy formalism is utilized for all these cases after identifying the appropriate constraints. Excellent agreements with both experimental and simulational data are reported. The proposed joint pdf (which appears new to the literature) predicts giant slip events at low pressures, again in agreement with observations.Comment: 13 pages, 15 figure

Analysis of network by generalized mutual entropies

Generalized mutual entropy is defined for networks and applied for analysis of complex network structures. The method is tested for the case of computer simulated scale free networks, random networks, and their mixtures. The possible applications for real network analysis are discussed

The Multiple Dimensions of Gender Stereotypes: A Current Look at Men’s and Women’s Characterizations of Others and Themselves

We used a multi-dimensional framework to assess current stereotypes of men and women. Specifically, we sought to determine (1) how men and women are characterized by male and female raters, (2) how men and women characterize themselves, and (3) the degree of convergence between self-characterizations and charcterizations of one’s gender group. In an experimental study, 628 U.S. male and female raters described men, women, or themselves on scales representing multiple dimensions of the two defining features of gender stereotypes, agency and communality: assertiveness, independence, instrumental competence, leadership competence (agency dimensions), and concern for others, sociability and emotional sensitivity (communality dimensions). Results indicated that stereotypes about communality persist and were equally prevalent for male and female raters, but agency characterizations were more complex. Male raters generally descibed women as being less agentic than men and as less agentic than female raters described them. However, female raters differentiated among agency dimensions and described women as less assertive than men but as equally independent and leadership competent. Both male and female raters rated men and women equally high on instrumental competence. Gender stereotypes were also evident in self-characterizations, with female raters rating themselves as less agentic than male raters and male raters rating themselves as less communal than female raters, although there were exceptions (no differences in instrumental competence, independence, and sociability self-ratings for men and women). Comparisons of self-ratings and ratings of men and women in general indicated that women tended to characterize themselves in more stereotypic terms – as less assertive and less competent in leadership – than they characterized others in their gender group. Men, in contrast, characterized themselves in less stereotypic terms – as more communal. Overall, our results show that a focus on facets of agency and communality can provide deeper insights about stereotype content than a focus on overall agency and communality

Absorption of Ultrashort Laser Pulses in Strongly Overdense Targets

We report on the first absorption experiments of sub-10 fs high-contrast Ti:Sa laser pulses incident on solid targets. The very good contrast of the laser pulse assures the formation of a very small pre-plasma and the pulse interacts with the matter close to solid density. Experimental results indicate that p-polarized laser pulses are absorbed up to 80 percent at 80 degrees incidence angle. The simulation results of PSC PIC code clearly confirm the observations and show that the collisionless absorption works efficiently in steep density profiles

Direct Identification of the Glass Transition: Growing Length Scale and the Onset of Plasticity

Understanding the mechanical properties of glasses remains elusive since the glass transition itself is not fully understood, even in well studied examples of glass formers in two dimensions. In this context we demonstrate here: (i) a direct evidence for a diverging length scale at the glass transition (ii) an identification of the glass transition with the disappearance of fluid-like regions and (iii) the appearance in the glass state of fluid-like regions when mechanical strain is applied. These fluid-like regions are associated with the onset of plasticity in the amorphous solid. The relaxation times which diverge upon the approach to the glass transition are related quantitatively.Comment: 5 pages, 5 figs.; 2 figs. omitted, new fig., quasi-crystal discussion omitted, new material on relaxation time

Reduzierung von Missing Wedge Artefakten mit DIRECTT

Wir stellen eine Prozedur vor, mit der typische Missing Wedge MW Artefakte in CT Rekonstruktionen effektiv unterdrückt werden können. Dazu wird der iterative DIRECTT Algorithmus Direkte Iterative Rekonstruktion Computertomographischer Trajektorien mit einigen Zyklen diskreter Rekonstruk tion eingesetzt. Die Kernfunktionen des Algorithmus , die wiederholte Auswahl und Gewichtung von Elementen einer Zwischenrekonstruktion, werden beibehalten. Abgesehen von Sonderfällen der Röntgen und Neutronentomographie tritt die MW Restriktion neben einer Vielzahl anderer in Standardkonfigurationen der Elektronentomographie auf. Um den MW Effekt isoliert zu untersuchen und beurteilen zu können, werden hier vollständige experimentelle Datensätze einer bekannten Porenstruktur um einen Sektor beschnitten sowie MW Rekonstruktionen von Porenmodellen erzeugt. Die Ergebnisse werden mit zurzeit verbreiteten Algorithmen Gefilterte Rückprojektion FBP und ART Varianten verglichen. Die Bewertung im Fourierraum zeigt, dass DIRECTT die fehlende Information im MW erfolgreich ergänzt. Zur quantitativen Bewertung der lokalen Rekonstruktions qualität werden Methoden der räumlichen Statistik eingesetz

The direct evaluation of attosecond chirp from a streaking measurement

We derive an analytical expression, from classical electron trajectories in a laser field, that relates the breadth of a streaked photoelectron spectrum to the group-delay dispersion of an isolated attosecond pulse. Based on this analytical expression, we introduce a simple, efficient and robust procedure to instantly extract the attosecond pulse's chirp from the streaking measurement.Comment: 4 figure