Nonlinear current response of one- and two-band superconductors

We have calculated the nonlinear current of a number of single band s-wave electron-phonon superconductors. Among issues considered were those of dimensionality, strong electron-phonon coupling, impurities, and comparison with BCS. For the case of two bands, particular attention is paid to the role of anisotropy, the integration effects of the off-diagonal electron-phonon interaction, as well as inter- and intraband impurities. For the specific case of MgB2, we present results based on the known microscopic parameters of band theory.Comment: 10 pages, 6 figure

Theory of the critical current in two-band superconductors with application to MgB2

Using a Green's function formulation of the superfluid current j_s, where a momentum q_s is applied to the Cooper pair, we have calculated j_s as a function of q_s, temperature, and impurity scattering for a two-band superconductor. We consider both renormalized BCS and full strong-coupling Eliashberg theory. There are two peaks in the current as a function of q_s due to the two energy scales for the gaps and this can give rise to non-standard behavior for the critical current. The critical current j_c, which is given as the maximum in j_s, can exhibit a kink as a function of temperature as the maximum is transferred from one peak to other. Other temperature variations are also possible and the universal BCS behavior is violated. The details depend on the material parameters of the system, such as the amount of coupling between the bands, the gap anisotropy, the Fermi velocities, and the density of states of each band. The Ginzburg-Landau relation between j_c, the penetration depth lambda_L and thermodynamic critical field H_c, is modified. Using Eliashberg theory with the electron-phonon spectral densities given from bandstructure calculations, we have applied our calculations for j_s and j_c to the case of MgB2 and find agreement with experiment.Comment: 13 pages, 7 figures, submitted to PR

Prediction of an undimerized, insulating, antiferromagnetic ground-state in halogen-bridged linear-chain Ni compounds

A parameter-free, mean-field, multi-orbital Hubbard model with nonspherical Coulomb and exchange interactions, implemented around all-electron local-density approximation (LDA) calculations, correctly predicts the band-gap energy, the absence of dimerization, and the antiferromagnetic ground state of halogen-bridged linear-chain Ni compounds. This approach also reproduces the insulating ground state and dimerization in PtX linear-chain compounds in agreement with experiment and previous calculations. Three "ps" figures are included at the end of the RevTex file and compressed using uufiles.Comment: 11 RevTex pages and three ps figures. Paper accepted by PRB Rapid Com

Parameter Compilation

In resolving instances of a computational problem, if multiple instances of interest share a feature in common, it may be fruitful to compile this feature into a format that allows for more efficient resolution, even if the compilation is relatively expensive. In this article, we introduce a formal framework for classifying problems according to their compilability. The basic object in our framework is that of a parameterized problem, which here is a language along with a parameterization---a map which provides, for each instance, a so-called parameter on which compilation may be performed. Our framework is positioned within the paradigm of parameterized complexity, and our notions are relatable to established concepts in the theory of parameterized complexity. Indeed, we view our framework as playing a unifying role, integrating together parameterized complexity and compilability theory

Parameter trails

Successful communication is vital for the success of any design project. However, communication often fails, adversely affecting design process efficiency and product quality.understand the connections between different aspects of design and don–t know where to find out more information or who to talk to. This paper presents a new model, developed from current project planning techniques, which supports communication using parameter-specific data. It enables designers to question information, inform their colleagues pro-actively and assess the impact of changing parameter values on subsequent design tasks. Such interaction is critical in allowing designers to see how their own tasks fit into the overall product design

Perubahan Parameter Parameter Marshal Akibat Perbedaan Jumlah Tumbukan Pada Aspal Concrete – Wearing Course (ACWC) Gradasi Halus

This study was conducted to see the changes in the value of the parameter values marshall afterthe number of collisions in the standards vary the amount of the collision then analyzed thenumber of collision and then analyzed the number of collisions are most effective assessed on thevalue of the characteristic marshall. In the Marshall planning standard for the number ofcollisions of heavy traffic conditions compaction test specimen as 2x75 collision with a mixturecavity boundary between 3.5-5%.This study uses gradation Asphalt Concrete - Wearing Course (AC-WC) smooth gradations formiddle and upper limits. From the data obtained aggregate gradation and asphalt aggregatedemand needs are used to find the optimum bitumen content that is used in the manufacture of testspecimens for variations in the number of collisions is 2x55, 2x65, 2x75, 2x85, and 2x95. Marshallthen test to see the number of collisions are most effective against the characteristics of asphaltmixture.Based on the analysis of the data processing is obtained that the value content of asphalt is used tolimit the middle that is 5.7% and the upper limit of 6.5%. Total Collision 2x75 and 2x85 that meetsall the parameters marshall. For the number of collisions 2x55 and 2x65 obtained small stability,voids In The Mix (VIM) is great and does not make the specification, to the number of collisions2x95, obtained great stability and voids In The Mix (VIM) is small and does not get in thespecification

Magnetic S-parameter

We propose a direct test of the existence of gauge duals for nonsupersymmetric asymptotically free gauge theories developing an infrared fixed point by computing the S-parameter in the electric and dual magnetic description. In particular we show that at the lower bound of the conformal window the magnetic S-parameter, i.e. the one determined via the dual magnetic gauge theory, assumes a simple expression in terms of the elementary magnetic degrees of freedom. The results further support our recent conjecture of the existence of a universal lower bound on the S parameter and indicates that it is an ideal operator for counting the active physical degrees of freedom within the conformal window. Our results can be directly used to unveil possible four dimensional gauge duals and constitute the first explicit computation of a nonperturbative quantity, in the electric variables, via nonsupersymmetric gauge duality.Comment: RevTeX 4, 4 pages, two columns. Version to match the published version in Phys. Rev. Let