Competition between Hund's coupling and Kondo effect in a one-dimensional extended periodic Anderson model

We study the ground-state properties of an extended periodic Anderson model to understand the role of Hund's coupling between localized and itinerant electrons using the density-matrix renormalization group algorithm. By calculating the von Neumann entropies we show that two phase transitions occur and two new phases appear as the hybridization is increased in the symmetric half-filled case due to the competition between Kondo-effect and Hund's coupling. In the intermediate phase, which is bounded by two critical points, we found a dimerized ground state, while in the other spatially homogeneous phases the ground state is Haldane-like and Kondo-singlet-like, respectively. We also determine the entanglement spectrum and the entanglement diagram of the system by calculating the mutual information thereby clarifying the structure of each phase.Comment: 9 pages, 9 figures, revised version, accepted for publication in PR

Quantum criticality and first-order transitions in the extended periodic Anderson model

We investigate the behavior of the periodic Anderson model in the presence of $d$-$f$ Coulomb interaction ($U_{df}$) using mean-field theory, variational calculation, and exact diagonalization of finite chains. The variational approach based on the Gutzwiller trial wave function gives a critical value of $U_{df}$ and two quantum critical points (QCPs), where the valence susceptibility diverges. We derive the critical exponent for the valence susceptibility and investigate how the position of the QCP depends on the other parameters of the Hamiltonian. For larger values of $U_{df}$, the Kondo regime is bounded by two first-order transitions. These first-order transitions merge into a triple point at a certain value of $U_{df}$. For even larger $U_{df}$ valence skipping occurs. Although the other methods do not give a critical point, they support this scenario.Comment: 8 pages, 7 figure

Control of Systems with Limited Capacity

Virtually all real life systems are such that they present some kind of limitation on one or many of its variables, physical quantities. These systems are designated in this thesis as systems with limited capacity. This work is treating control related problems of a subclass of such systems, where the limitation is a critical factor. The thesis is composed of four parts. The first part is treating the control of tire slip in a braking car. The Anti-lock Braking System (ABS) is an important component of a complex steering system for the modern car. In the latest generation of brake-by-wire systems, the controllers have to maintain a specified tire slip for each wheel during braking. This thesis proposes a design model and based on that a hybrid controller that regulates the tire-slip. Simulation and results from drive tests are presented. In the second part, a design method for robust PID controllers is presented for a class of systems with limited capacity. Robustness is ensured with respect to a cone bounded static nonlinearity acting on the plant. Additional constraints on maximum sensitivity are also considered. The design procedure has been successfully applied in the synthesis of the proposed ABS controller. The third part studies the trajectory convergence for a general class of nonlinear systems. The servo problem for piecewise linear systems is presented. Convex optimization is used to describe the behavior of system trajectories of a piecewise linear system with respect to some input signals. The obtained results are then applied for the study of anti-windup compensators. The last part of the thesis is treating the problem of voltage stability in power systems. Voltage at the load end of a power system has to be controlled within prescribed tolerances. In case of emergencies such as sudden line failures, this task ca n be very challenging. The main contribution of this chapter is a method for improving the stability properties of the power system by dynamic compensation of the reference load voltage. Moreover, a complete compensation scheme is proposed where load shedding is the secondary control variable. This control scheme is shown to stabilize different power system models

A Synthesis Method for Static Anti-Windup Compensators

Synthesis of static anti-windup compensators is considered. LMIconditions are established for stability and performance analysis of the closedloop system. The performance criterion describes the servo problem forthe resulting closed-loop piecewise linear system. The synthesisof the anti-windup compensators will be given by some bilinear matrix inequalities

Tearing at the Seams of (In)visibility: Anti-counterfeiting, Harper’s Bazaar, and the Project of Neocolonization

This essay examines the role of the (counterfeit) fashion industry in shaping democracy, citizenship, and human rights ideals in the United States. Using the Harper\u27s Bazaar “Fakes are Never in Fashion” anti-counterfeiting advertisement campaign as a case study, I explore how race, class, gender, law, and human rights discourse, coalesce to systematically maintain exploited garment workers voiceless/rights-less while simultaneously preserving the material interest(s) of a White, capitalist, patriarchal, hegemonic global order. This study presents important implications for larger discussions of rights and justice. Ultimately, this campaign demonstrates how, through the creation of a self-regulatory system that seeks to control the extent to which consumers and people of color participate in the (counterfeit) industry, and by appealing to domestic law to police global practices, elite fashion leaders are shifting the larger concerns for human and labor rights violations within the industry to one that allows elite fashion leaders to maintain a global monopoly on the luxury fashion goods production

Metal-Insulator Transition of the Quasi-One Dimensional Luttinger Liquid Due to the Long-Range Character of the Coulomb Interaction

An instability of the quasi-1D Luttinger liquid associated with the metal - insulator transition is considered. The homogeneous metal ground state of this liquid is demonstrated to be unstable and the charge-density wave arises in the system. The wavevector of this wave has nonzero component both along the direction of the chains and in the perpendicular direction. The ground state of the system has a dielectric gap at the Fermi surface, the value of this gap being calculated.Comment: RevTex, 10 page