Brownian scattering of a spinon in a Luttinger liquid

We consider strongly interacting one-dimensional electron liquids where elementary excitations carry either spin or charge. At small temperatures a spinon created at the bottom of its band scatters off low-energy spin- and charge-excitations and follows the diffusive motion of a Brownian particle in momentum space. We calculate the mobility characterizing these processes, and show that the resulting diffusion coefficient of the spinon is parametrically enhanced at low temperatures compared to that of a mobile impurity in a spinless Luttinger liquid. We briefly discuss that this hints at the relevance of spin in the process of equilibration of strongly interacting one-dimensional electrons, and comment on implications for transport in clean single channel quantum wires

Incoherent pair tunneling in the pseudogap phase of cuprates

Motivated by a recent experiment by Bergeal et al., we reconsider incoherent pair tunneling in a cuprate junction formed from an optimally doped superconducting lead and an underdoped normal metallic lead. We study the impact of the pseudogap on the pair tunneling by describing fermions in the underdoped lead with a model self-energy that has been developed to reproduce photoemission data. We find that the pseudogap causes an additional temperature dependent suppression of the pair contribution to the tunneling current. We discuss consistency with available experimental data and propose future experimental directions.Comment: 5 pages, 3 figure

Interaction-induced backscattering in short quantum wires

We study interaction-induced backscattering in clean quantum wires with adiabatic contacts exposed to a voltage bias. Particle backscattering relaxes such systems to a fully equilibrated steady state only on length scales exponentially large in the ratio of bandwidth of excitations and temperature. Here we focus on shorter wires in which full equilibration is not accomplished. Signatures of relaxation then are due to backscattering of hole excitations close to the band bottom which perform a diffusive motion in momentum space while scattering from excitations at the Fermi level. This is reminiscent to the first passage problem of a Brownian particle and, regardless of the interaction strength, can be described by an inhomogeneous Fokker-Planck equation. From general solutions of the latter we calculate the hole backscattering rate for different wire lengths and discuss the resulting length dependence of interaction-induced correction to the conductance of a clean single channel quantum wire.Comment: 10 pages, 4 figure

Interaction-induced corrections to conductance and thermopower in quantum wires

We study transport properties of weakly interacting spinless electrons in one-dimensional single channel quantum wires. The effects of interaction manifest as three-particle collisions due to the severe constraints imposed by the conservation laws on the two-body processes. We focus on short wires where the effects of equilibration on the distribution function can be neglected and collision integral can be treated in perturbation theory. We find that interaction-induced corrections to conductance and thermopower rely on the scattering processes that change number of right- and left-moving electrons. The latter requires transition at the bottom of the band which is exponentially suppressed at low temperatures. Our theory is based on the scattering approach that is beyond the Luttinger-liquid limit. We emphasize the crucial role of the exchange terms in the three-particle scattering amplitude that was not discussed in the previous studies.Comment: 4 pages, 2 figure

The Role of Financial Factors in the Trade Collapse: A Skeptic's View

This paper explores the role of financial factors in the 2008-9 collapse of U.S. imports and exports. Using highly disaggregated international trade data, we examine whether the cross-sectoral variation in how much imports or exports fell during this episode can be explained by financial variables. To do this, we employ a wide variety of possible indicators, such as standard measures of trade credit and external finance dependence, proxies for shipping lags at the sector level, and shares of intra-firm trade in each sector. Overall, there is very little evidence that financial factors played a role in the collapse of U.S. trade.2008-2009 Crisis, International Trade, Financial Factors

Nonlinear conductance of long quantum wires at a conductance plateau transition: Where does the voltage drop?

We calculate the linear and nonlinear conductance of spinless fermions in clean, long quantum wires where short-ranged interactions lead locally to equilibration. Close to the quantum phase transition where the conductance jumps from zero to one conductance quantum, the conductance obtains an universal form governed by the ratios of temperature, bias voltage and gate voltage. Asymptotic analytic results are compared to solutions of a Boltzmann equation which includes the effects of three-particle scattering. Surprisingly, we find that for long wires the voltage predominantly drops close to one end of the quantum wire due to a thermoelectric effect.Comment: 4+ pages, 3 figures plus supplementary material (2 pages, 1 figure); minor changes, references correcte

Openness of the insurance market for foreign entities: methodology and experience of Ukraine

The article is devoted to the development of methodical tools for determining the level of openness of the insurance market in Ukraine. The proposed level of openness of the insurance market of Ukraine should be considered as an opportunity (potential) for domestic insurers to interact effectively with foreign investors and financial intermediaries. It has been established that the mathematical tool for realizing the task should be a gravity modeling, which, taking into account the inflow and outflow of the characteristics of the openness of the insurance market of Ukraine, allows us to determine the degree of its remoteness from the insurance markets of Europe and the World. It is proved that the openness of the insurance market of Ukraine serves not only as an indicator of the level of readiness of the interaction of domestic financial intermediaries with foreign entities, but also fully characterizes the infrastructural level of the Ukrainian insurance market

Novel Quaternary Dilute Magnetic Semiconductor (Ga,Mn)(Bi,As): Magnetic and Magneto-Transport Investigations

Magnetic and magneto-transport properties of thin layers of the (Ga,Mn)(Bi,As) quaternary dilute magnetic semiconductor grown by the low-temperature molecular-beam epitaxy technique on GaAs substrates have been investigated. Ferromagnetic Curie temperature and magneto-crystalline anisotropy of the layers have been examined by using magneto-optical Kerr effect magnetometry and low-temperature magneto-transport measurements. Postgrowth annealing treatment has been shown to enhance the hole concentration and Curie temperature in the layers. Significant increase in the magnitude of magnetotransport effects caused by incorporation of a small amount of Bi into the (Ga,Mn)As layers revealed in the planar Hall effect (PHE) measurements, is interpreted as a result of enhanced spin-orbit coupling in the (Ga,Mn)(Bi,As) layers. Two-state behaviour of the planar Hall resistance at zero magnetic field provides its usefulness for applications in nonvolatile memory devices.Comment: 10 pages, 3 figures, to be published in the Proceedings of ICSM-2016 conferenc

The "Collapse in Quality" Hypothesis

This paper evaluates the hypothesis that during the 2008-2009 collapse in international trade, imports of higher quality goods experienced larger reductions compared to low-quality imports, using data on US imports disaggregated by HS-10 product category and source country. We find little, if any, robust econometric evidence in support of this hypothesis.