Quasi-Particles, Conformal Field Theory, and qq-Series

We review recent results concerning the representation of conformal field theory characters in terms of fermionic quasi-particle excitations, and describe in detail their construction in the case of the integrable three-state Potts chain. These fermionic representations are q-series which are generalizations of the sums occurring in the Rogers-Ramanujan identities

Existence and Vanishing of the Breathing Mode in Strongly Correlated Finite Systems

One of the fundamental eigenmodes of finite interacting systems is the mode of {\em uniform radial expansion and contraction} -- the ``breathing'' mode (BM). Here we show in a general way that this mode exists only under special conditions: i) for harmonically trapped systems with interaction potentials of the form $1/r^\gamma$ $(\gamma\in\mathbb{R}_{\neq0})$ or $\log(r)$, or ii) for some systems with special symmetry such as single shell systems forming platonic bodies. Deviations from the BM are demonstrated for two examples: clusters interacting with a Lennard-Jones potential and parabolically trapped systems with Yukawa repulsion. We also show that vanishing of the BM leads to the occurence of multiple monopole oscillations which is of importance for experiments

Terahertz wave transmission in flexible polystyrene-lined hollow metallic waveguides for the 2.5-5 THz band.

A low-loss and low-dispersive optical-fiber-like hybrid HE11 mode is developed within a wide band in metallic hollow waveguides if their inner walls are coated with a thin dielectric layer. We investigate terahertz (THz) transmission losses from 0.5 to 5.5 THz and bending losses at 2.85 THz in a polystyrene-lined silver waveguides with core diameters small enough (1 mm) to minimize the number of undesired modes and to make the waveguide flexible, while keeping the transmission loss of the HE11 mode low. The experimentally measured loss is below 10 dB/m for 2 < ? < 2.85 THz (∼4-4.5 dB/m at 2.85 THz) and it is estimated to be below 3 dB/m for 3 < ? < 5 THz according to the numerical calculations. At ∼1.25 THz, the waveguide shows an absorption peak of ∼75 dB/m related to the transition between the TM11-like mode and the HE11 mode. Numerical modeling reproduces the measured absorption spectrum but underestimates the losses at the absorption peak, suggesting imperfections in the waveguide walls and that the losses can be reduced further. © 2013 Optical Society of America

Self consistent theory of unipolar charge-carrier injection in metal/insulator/metal systems

A consistent device model to describe current-voltage characteristics of metal/insulator/metal systems is developed. In this model the insulator and the metal electrodes are described within the same theoretical framework by using density of states distributions. This approach leads to differential equations for the electric field which have to be solved in a self consistent manner by considering the continuity of the electric displacement and the electrochemical potential in the complete system. The model is capable of describing the current-voltage characteristics of the metal/insulator/metal system in forward and reverse bias for arbitrary values of the metal/ insulator injection barriers. In the case of high injection barriers, approximations are provided offering a tool for comparison with experiments. Numerical calculations are performed exemplary using a simplified model of an organic semiconductor.Comment: 21 pages, 8 figure

Interaction between dust grains near a conducting wall

The effect of the conducting electrode on the interaction of dust grains in a an ion flow is discussed. It is shown that two grains levitating above the electrode at the same height may attract one another. This results in the instability of a dust layer in a plasma sheath.Comment: 9 pages. 3 figures. Submitted to Plasma Physics Report

Magnetization reversal and local switching fields of ferromagnetic Co/Pd microtubes with radial magnetization

Three-dimensional nanomagnetism is a rapidly growing field of research covering both noncollinear spin textures and curved magnetic geometries including microtubular structures. We spatially resolve the field-induced magnetization reversal of free-standing ferromagnetic microtubes utilizing multifrequency magnetic force microscopy (MFM). The microtubes are composed of Co/Pd multilayer films with perpendicular magnetic anisotropy that translates to an anisotropy with radial easy axis upon rolling-up. Simultaneously mapping the topography and the perpendicular magnetostatic force derivative, the relation between surface angle and local magnetization configuration is evaluated for a large number of locations with slopes exceeding 45 degrees. The angle-dependence of the switching field is concurrent with the Kondorsky model, i.e., the rolled-up nanomembrane behaves like a planar magnetic film with perpendicular anisotropy and a pinning dominated magnetization reversal. Additionally, we discuss methodological challenges when detecting magnetostatic force derivatives near steep surfaces

Self-consistent model of unipolar transport in organic semiconductor diodes: accounting for a realistic density-of-states distribution

A self-consistent, mean-field model of charge-carrier injection and unipolar transport in an organic semiconductor diode is developed utilizing the effective transport energy concept and taking into account a realistic density-of-states distribution as well as the presence of trap states in an organic material. The consequences resulting from the model are discussed exemplarily on the basis of an indium tin oxide/organic semiconductor/metallic conductor structure. A comparison of the theory to experimental data of a unipolar indium tin oxide/poly-3-hexyl-thiophene/Al device is presented.Comment: 6 pages, 2 figures; to be published in Journal of Applied Physic

Multiculturalism and American Democracy

Multiculturalism: is it the face of twenty-first century America or merely a passing intellectual fad? With its celebration of ethnic diversity and strong advocacy of tolerance, this contemporary movement provides philosophical justification for many who seek to correct social inequities. But while its proponents see it as a means of promoting self-esteem among marginalized groups, its critics see it as a dangerous form of relativism that culminates, paradoxically, in a new form of intolerance. The fourteen essays in this volume address the pros and cons of multiculturalism and explore its relationship with liberal democracy. A team of stellar contributors—C. Vann Woodward, Linda Chavez, Stanley Fish, and others—offers viewpoints on multiculturalism from the perspectives of political theory, history, philosophy, and fiction. The editors first help explain multiculturalism by contrasting it with the Sixties counterculture. How is it, they ask, that yesterday\u27s radicals, so concerned with economic justice, have given way to the multiculturalist preoccupation with identity politics? The contributors then explore different facets of the multiculturalism issue: they present disparate views of the stakes involved as older notions of pluralism and assimilation give way to multiculturalism; examine it in its relation to the principles of liberal democracy; and assess its place in public education. In a final section, the role of the arts in the multiculturalism debate is addressed by celebrated novelists J. M. Coetzee and Mario Vargas Llosa. Because multiculturalism is a movement without a leader or guiding document, its tenets remain difficult to define. This book not only tells what the controversy is about but also clarifies the concerns it should raise for thoughtful citizens. The points of view expressed here will prove helpful to those who are trying to frame their own opinions about multiculturalism—and they are guaranteed to spark new debate among those who have already chosen sides. Description Arthur Melzer is professor of political science at Michigan State University. He is the author, editor, or coeditor of eleven books, including The Supreme Court and the Idea of Constitutionalism. Jerry Weinberger is University Distinguished Professor Emeritus of political science at Michigan State University. He has written, edited, and coedited several books on political thought, including Benjamin Franklin Unmasked: On the Unity of His Moral, Religious, and Political Thought. M. Richard Zinman is University Distinguished Professor Emeritus of political theory in James Madison College at Michigan State University. With Melzer and Weinberger, he has co-edited several books on democracy and modern politics. This Kansas Open Books title is funded by a grant from the National Endowment for the Humanities and the Andrew W. Mellon Foundation Humanities Open Book Program.https://digitalcommons.pittstate.edu/kansas_open_books/1045/thumbnail.jp