Waveform Selectivity at the Same Frequency

Electromagnetic properties depend on the composition of materials, i.e. either angstrom scales of molecules or, for metamaterials, subwavelength periodic structures. Each material behaves differently in accordance with the frequency of an incoming electromagnetic wave due to the frequency dispersion or the resonance of the periodic structures. This indicates that if the frequency is fixed, the material always responds in the same manner unless it has nonlinearity. However, such nonlinearity is controlled by the magnitude of the incoming wave or other bias. Therefore, it is difficult to distinguish different incoming waves at the same frequency. Here we present a new concept of circuit-based metasurfaces to selectively absorb or transmit specific types of waveforms even at the same frequency. The metasurfaces, integrated with schottky diodes as well as either capacitors or inductors, selectively absorb short or long pulses, respectively. The two types of the circuit elements are then combined to absorb or transmit specific waveforms in between. This waveform selectivity gives us another freedom to control electromagnetic waves in various fields including wireless communications, as our simulation reveals that the metasurfaces are capable of varying bit error rates in response to waveforms

Exact N3LO results for qq ′ → H + X

We compute the contribution to the total cross section for the inclusive production of a Standard Model Higgs boson induced by two quarks with different flavour in the initial state. Our calculation is exact in the Higgs boson mass and the partonic center-of-mass energy. We describe the reduction to master integrals, the construction of a canonical basis, and the solution of the corresponding differential equations. Our analytic result contains both Harmonic Polylogarithms and iterated integrals with additional letters in the alphabet. © 2015, The Author(s)

A Component Based Heuristic Search Method with Evolutionary Eliminations

Nurse rostering is a complex scheduling problem that affects hospital personnel on a daily basis all over the world. This paper presents a new component-based approach with evolutionary eliminations, for a nurse scheduling problem arising at a major UK hospital. The main idea behind this technique is to decompose a schedule into its components (i.e. the allocated shift pattern of each nurse), and then to implement two evolutionary elimination strategies mimicking natural selection and natural mutation process on these components respectively to iteratively deliver better schedules. The worthiness of all components in the schedule has to be continuously demonstrated in order for them to remain there. This demonstration employs an evaluation function which evaluates how well each component contributes towards the final objective. Two elimination steps are then applied: the first elimination eliminates a number of components that are deemed not worthy to stay in the current schedule; the second elimination may also throw out, with a low level of probability, some worthy components. The eliminated components are replenished with new ones using a set of constructive heuristics using local optimality criteria. Computational results using 52 data instances demonstrate the applicability of the proposed approach in solving real-world problems.Comment: 27 pages, 4 figure

Quantum Hall Transitions in (TMTSF)2_2PF6_6

We have studied the temperature dependence of the integer quantum Hall transitions in the molecular crystal (TMTSF)$_2$PF$_6$. We find that the transition width between the quantum Hall plateaus does not exhibit the universal power-law scaling behavior of the integer quantum Hall effect observed in semiconducting devices. Instead, the slope of the $\rho_{xy}$ risers, $d\rho_{xy}/dB$, and the (inverse) width of the $\rho_{xx}$ peaks, $(\Delta B)^{-1}$, show a BCS-like energy gap temperature dependence. We discuss these results in terms of the field-induced spin-density wave gap and order parameter of the system.Comment: 10 pages, RevTeX, 4 PostScript figure

SDW and FISDW transition of (TMTSF)2_2ClO4_4 at high magnetic fields

The magnetic field dependence of the SDW transition in (TMTSF)$_2$ClO$_4$ for various anion cooling rates has been measured, with the field up to 27T parallel to the lowest conductivity direction $c^{\ast}$. For quenched (TMTSF)$_2$ClO$_4$, the SDW transition temperature $T_{\rm {SDW}}$ increases from 4.5K in zero field up to 8.4K at 27T. A quadratic behavior is observed below 18T, followed by a saturation behavior. These results are consistent with the prediction of the mean-field theory. From these behaviors, $T_{\rm {SDW}}$ is estimated as $T_{\rm {SDW_0}}$=13.5K for the perfect nesting case. This indicates that the SDW phase in quenched (TMTSF)$_2$ClO$_4$, where $T_{\rm {SDW}}$ is less than 6K, is strongly suppressed by the two-dimensionality of the system. In the intermediate cooled state in which the SDW phase does not appear in zero field, the transition temperature for the field-induced SDW shows a quadratic behavior above 12T and there is no saturation behavior even at 27T, in contrast to the FISDW phase in the relaxed state. This behavior can probably be attributed to the difference of the dimerized gap due to anion ordering.Comment: 4pages,5figures(EPS), accepted for publication in PR

Spin-density-wave transition of (TMTSF)2_2PF6_6 at high magnetic fields

The transverse magnetoresistance of the Bechgaard salt (TMTSF)$_2$PF$_6$ has been measured for various pressures, with the field up to 24 T parallel to the lowest conductivity direction c$^{\ast}$. A quadratic behavior is observed in the magnetic field dependence of the spin-density-wave (SDW) transition temperature $T_{\rm {SDW}}$. With increasing pressure, $T_{\rm {SDW}}$ decreases and the coefficient of the quadratic term increases. These results are consistent with the prediction of the mean-field theory based on the nesting of the quasi one-dimensional Fermi surface. Using a mean field theory, $T_{\rm {SDW}}$ for the perfect nesting case is estimated as about 16 K. This means that even at ambient pressure where $T_{\rm {SDW}}$ is 12 K, the SDW phase of (TMTSF)$_2$PF$_6$ is substantially suppressed by the two-dimensionality of the system.Comment: 11pages,6figures(EPS), accepted for publication in PR

Electronic structure of NiS1−x_{1-x}Sex_x across the phase transition

We report very highly resolved photoemission spectra of NiS(1-x)Se(x) across the so-called metal-insulator transition as a function of temperature as well as composition. The present results convincingly demonstrate that the low temperature, antiferromagnetic phase is metallic, with a reduced density of states at E$_F$. This decrease is possibly due to the opening of gaps along specific directions in the Brillouin zone caused by the antiferromagnetic ordering.Comment: Revtex, 4 pages, 3 postscript figure

Quantum oscillations in quasi-one-dimensional metals with spin-density-wave ground states

We consider the magnetoresistance oscillation phenomena in the Bechgaard salts (TMTSF)(2)X, where X = ClO4, PF6, and AsF6 in pulsed magnetic fields to 51 T. Of particular importance is the observation of a new magnetoresistance oscillation for X = ClO4 in its quenched state. In the absence of any Fermi-surface reconstruction due to anion order at low temperatures, all three materials exhibit nonmonotonic temperature dependence of the oscillation amplitude in the spin-density-wave (SDW) state. We discuss a model where, below a characteristic temperature T* within the SDW state, a magnetic breakdown gap opens. [S0163-1829(99)00904-2]