Gap In Presence Research Articles

Study of superconducting gap in presence of antiferromagnetism in iron pnictide superconductors

A Hamiltonian model of the pnictide composite superconductors is presented to study the Superconducting(SC) gap. The total Hamiltonian has been solved by writing equations of motion for single particle Greens function of Zubarev type. Equations for appropriate single particle correlation functions are derived and the order parameters corresponding to superconductivity and antiferromagnetism are determined. The equations for superconducting gap and antiferromagnetic gap are solved self-consistently and numerically. The multi-gap superconductivity is studied for different values of interlayer coupling constant parameters and Debye frequencies.

Persistence of gaps in the interacting anisotropic Hofstadter model

The energy spectrum of the Hofstadter model has a fractal structure with infinitely many gaps. We prove the persistence of each gap in presence of Hubbard interaction in the case of small transversal hopping, even when the coupling is much larger than the non interacting gaps. The proof relies on a subtle interplay of Renormalization Group arguments combined with number-theoretic properties of the incommensurate frequencies.

Planning While Flying: A Measurement-Aided Dynamic Planning of Drone Small Cells

The deployment of drone small cells has emerged as a promising solution to agile provisioning of Internet backbone access for Internet of Things devices, and many other types of users/devices. In this paper, we consider the problem of deploying a set of drone cells operating on multiple channels in a target area to provide access to the backbone/core network, which is formulated as a combinatorial network utility maximization problem. Since an offline and centralized solution to such a problem is not feasible, a low-complexity and distributed online algorithm is highly desired. Therefore, we propose a measurement-aided dynamic planning (MAD-P) algorithm, where the dispatched drones perform position and channel configurations autonomously on the fly based on the real-time measurement of network throughput to solve the problem in a distributed fashion during flight with minimal centralized control. We prove that the proposed MAD-P algorithm is asymptotically optimal, and investigate how long it takes for the convergence to stationarity under the MAD-P algorithm by giving a mixing time analysis. We also derive an upper bound of the performance gap in presence of measurement errors. Simulation results are provided to validate our analytic results and demonstrate the effectiveness of our algorithm.

Effect of International Labour Mobility on Wage Gap in Presence of Non Traded Agricultural Sector: A Theoretical Analysis

Effect of International Labour Mobility on Wage Gap in Presence of Non Traded Agricultural Sector: A Theoretical Analysis

Output Gap in Presence of Financial Frictions and Monetary Policy Trade-offs

The recent global financial crisis illustrates that financial frictions are a significant source of volatility in the economy. This paper investigates monetary policy stabilization in an environment where financial frictions are a relevant source of macroeconomic fluctuation. We derive a measure of output gap that accounts for frictions in financial market. Furthermore we illustrate that, in the presence of financial frictions, a benevolent central bank faces a substantial trade-off between nominal and real stabilization; optimal monetary policy significantly reduces fluctuations in price and wage inflations but fails to alleviate the output gap volatility. This suggests a role for macroprudential policies.

Output Gap in Presence of Financial Frictions and Monetary Policy Trade-Offs

The recent global financial crisis illustrates that financial frictions are a significant source of volatility in the economy. This paper investigates monetary policy stabilization in an environment where financial frictions are a relevant source of macroeconomic fluctuation. We derive a measure of output gap that accounts for frictions in financial market. Furthermore we illustrate that, in the presence of financial frictions, a benevolent central bank faces a substantial trade-off between nominal and real stabilization; optimal monetary policy significantly reduces fluctuations in price and wage inflations but fails to alleviate the output gap volatility. This suggests a role for macroprudential policies.

Feedback mechanism for the stability of the band gap of CuInSe2

We report on experimental results on band gap and lattice distortion in CuInSe${}_{2}$ for various degrees of Cu deficiency. The band gap is measured by optical methods, and the Cu vacancy density and anion displacement parameter are determined by neutron scattering. Our data show that the band gap decreases for Cu-poor compositions, and the anion displacement is weakly dependent on the concentration of Cu vacancies. This is in apparent contradiction with ab initio calculations that always predict a larger band gap in presence of Cu vacancies. To shed light on this issue, we studied the overall dependence of the band gap on the anion displacement and on the concentration of Cu vacancies using a self-consistent $GW$ approach and hybrid functionals, including a feedback mechanism that was recently proposed. Our calculations illustrate consistently the remarkable stability of the band gap of chalcopyrite semiconductors and explain the experimental observations by a coupled effect of Cu vacancies and lattice distortions within the feedback model.

Study of superconducting gap in presence of lattice strain

A theoretical model for the band Jahn-Teller (BJT) distortion versus s -wave superconductivity competition is proposed for the hole and electron doped cuprates like R 2− x M x CuO 4 (R=Nd, La,… and M=Sr,Ce) in presence of rare-earth impurity f level electron and hybridization using Zubarev’s technique. The temperature dependent superconducting gap equation, the mixed pairing parameter and the Kondo excitations are analyzed microscopically. The lattice strain shows spontaneous suppression at temperatures below the superconducting transition temperature. The superconducting pair breaking effect is explained from the self-consistent model calculations.