Magnetotransport and thermoelectricity in disordered graphene

We have studied the electric and thermal response of two-dimensional Dirac-fermions in a quantizing magnetic field in the presence of localized disorder. The electric and heat current operators in the presence of magnetic field are derived. The self-energy due to impurities is calculated self-consistently, and depends strongly on the frequency and field strength, resulting in asymmetric peaks in the density of states at the Landau level energies, and small islands connecting them. The Shubnikov-de Haas oscillations remain periodic in 1/B, in spite of the distinct quantization of quasiparticle orbits compared to normal metals. The Seebeck coefficient depends strongly on the field strength and orientation. For finite field and chemical potential, the Wiedemann-Franz law can be violated.Comment: 10 pages, 6 figure

Private-Sector Credit in Central & Eastern Europe: New (Over) Shooting Stars?

This paper analyzes the equilibrium level of private credit to GDP in 11 Central and Eastern European countries in order to see whether the high credit growth recently observed in some of these countries led to above equilibrium private credit to- GDP levels. We use estimation results obtained for a panel of small open OECD economies (out-of-sample sample) to derive the equilibrium credit level for a panel of transition economies (in-sample panel). We opt for this (out-of-sample) approach because the coefficient estimates for transition economies are fairly unstable. We show that there is a large amount of uncertainty to determine the equilibrium level of private credit. Yet our results indicate that a number of countries are very close or even above the estimated equilibrium levels, whereas others are still well below the equilibrium level.http://deepblue.lib.umich.edu/bitstream/2027.42/57232/1/wp852 .pd

Surface acoustic wave propagation in monolayer graphene

Surface acoustic wave (SAW) propagation is a powerful method to investigate 2D electron systems. We show how SAW observables are influenced by coupling to the 2D massless Dirac electrons of graphene and argue that Landau oscillations can be observed as function of gate voltage for constant field. Contrary to other transport measurements, the zero-field SAW propagation gives the wave vector dependence of graphene conductivity for small wave numbers. We predict a crossover from Schroedinger to Dirac like behaviour as a function of gate voltage, with no attenuation in the latter for clean samples.Comment: 5 pages, 4 figure

Local density of states in disordered graphene

We study two lattice models, the honeycomb lattice (HCL) and a special square lattice (SQL), both reducing to the Dirac equation in the continuum limit. In the presence of disorder (gaussian potential disorder and random vector potential), we investigate the behaviour of the density of states (DOS) numerically and analytically. While an upper bound can be derived for the DOS on the SQL at the Dirac point, which is also confirmed by numerical calculations, no such upper limit exists for the HCL in the presence of random vector potential. A careful investigation of the lowest eigenvalues indeed indicate, that the DOS can possibly be divergent at the Dirac point on the HCL. In spite of sharing a common continuum limit, these lattice models exhibit different behaviour.Comment: 12 pages, 10 figure

Reentrant Kondo effect in Landau quantized graphene

We have studied the interplay of an Anderson impurity in Landau quantized graphene, with special emphasis on the influence of the chemical potential. Within the slave-boson mean-field theory, we found reentrant Kondo behaviour by varying the chemical potential or gate voltage. Between Landau levels, the density of states is suppressed, and by changing the graphene's Fermi energy, we cross from metallic to semiconducting regions. Hence, the corresponding Kondo behaviour is also influenced. The f-level spectral function reveals both the presence of Landau levels in the conduction band and the Kondo resonance.Comment: 8 pages, 6 figure

Credit growth in Central and Eastern Europe: new (over)shooting stars?

This paper analyzes the equilibrium level of private credit to GDP in 11 Central and Eastern European countries in order to see whether the high credit growth recently observed in some of these countries led to above equilibrium private credit-to-GDP levels. We use estimation results obtained for a panel of small open OECD economies (out-of-sample panel) to derive the equilibrium credit level for a panel of transition economies (in-sample panel). We opt for this (out-of-sample) approach because the coefficient estimates for transition economies are fairly unstable. We show that there is a large amount of uncertainty to determine the equilibrium level of private credit. Yet our results indicate that a number of countries are very close or even above the estimated equilibrium levels, whereas others are still well below the equilibrium level. JEL Classification: C31, C33, E44, G21credit growth, credit to the private sector, equilibrium level of credit, initial undershooting, Transition Economies

Negotiating the End of Transition: A Network Approach to Political Discourse Dynamics, Hungary 1997

The initial question of this paper is how the large scale social process of postsocialist transition ends. We argue that transition is closed by discursive innovations in the political field, rather than just spontaneous crystallization. The political field is depicted as a dynamic symbolic structure that is an arena of local action. First the possible discourse positions are extracted from the two mode network of speech acts and statements. Then using these typical positions the dynamics of responses and responses to responses is explored. We give an account of an emergent univocal government position that represents a successful role claim (an exit from the loops of local action) on the government's side to coherently frame the end of transition

Rabi Oscillations in Landau-Quantized Graphene

We investigate the relation between the canonical model of quantum optics, the Jaynes-Cummings Hamiltonian and Dirac fermions in quantizing magnetic field. We demonstrate that Rabi oscillations are observable in the optical response of graphene, providing us with a transparent picture about the structure of optical transitions. While the longitudinal conductivity reveals chaotic Rabi oscillations, the Hall component measures coherent ones. This opens up the possibility of investigating a microscopic model of a few quantum objects in a macroscopic experiment with tunable parameters.Comment: 5 pages, 4 figure

Detecting Wage Under-reporting Using a Double Hurdle Model

We estimate a double hurdle (DH) model of the Hungarian wage distribution assuming censoring at the minimum wage and wage under-reporting (i.e. compensation consisting of the minimum wage, subject to taxation, and an unreported cash supplement). We estimate the probability of under-reporting for minimum wage earners, simulate their genuine earnings and classify them and their employers as 'cheaters' and 'non-cheaters'. In the possession of the classification we check how cheaters and non-cheaters reacted to the introduction of a minimum social security contribution base, equal to 200 per cent of the minimum wage, in 2007. The findings suggest that cheaters were more likely to raise the wages of their minimum wage earners to 200 per cent of the minimum wage thereby reducing the risk of tax audit. Cheating firms also experienced faster average wage growth and slower output growth. The results suggest that the DH model is able to identify the loci of wage under-reporting with some precision.tax evasion, double hurdle model, Hungary

Right man, right time, right place? - On the time course of the mediator orchestra in septic shock

Appropriate timing of treatment assumes particular importance in critical care. Lange and colleagues recently reported on the time course of the different nitric oxide synthase (NOS) isoforms, nitrosative stress, and poly(ADP-ribosylation) during Pseudomonas aeruginosa pneumonia-induced ovine septic shock. Initially, endothelial NOS expression was increased together with markers of peroxynitrite formation, DNA damage, and nuclear factor-kappa-B activation. Later on, measurable NOS activity and nitric oxide production resulted mainly from inducible NOS activation. These results emphasize the need for long-term, large-animal studies investigated over days so that future therapeutic interventions can be better tailored and matched to the exact time course of the activation of the mediator orchestra