Exact Integration of the High Energy Scale in Doped Mott Insulators

We expand on our earlier work (cond-mat/0612130, Phys. Rev. Lett. {\bf 99}, 46404 (2007)) in which we constructed the exact low-energy theory of a doped Mott insulator by explicitly integrating (rather than projecting) out the degrees of freedom far away from the chemical potential. The exact low-energy theory contains degrees of freedom that cannot be obtained from projective schemes. In particular a new charge $\pm 2e$ bosonic field emerges at low energies that is not made out of elemental excitations. Such a field accounts for dynamical spectral weight transfer across the Mott gap. At half-filling, we show that two such excitations emerge which play a crucial role in preserving the Luttinger surface along which the single-particle Green function vanishes. In addition, the interactions with the bosonic fields defeat the artificial local SU(2) symmetry that is present in the Heisenberg model. We also apply this method to the Anderson-U impurity and show that in addition to the Kondo interaction, bosonic degrees of freedom appear as well. Finally, we show that as a result of the bosonic degree of freedom, the electron at low energies is in a linear superposition of two excitations--one arising from the standard projection into the low-energy sector and the other from the binding of a hole and the boson.Comment: Published veriso

Electronic properties of the diamond films with nitrogen impurities: An x-ray absorption and photoemission spectroscopy study

[[abstract]]X-ray absorption near-edge structure (XANES) measurements have been performed for nitrogen (N) containing diamond films with three different N concentrations at the C K-edge using the sample drain current mode. The C K-edge XANES spectra of these diamond films resemble that of the pure diamond regardless of the N concentration, which suggests that the overall bonding configuration of the C atom is unaltered. N impurities are found to reduce the intensities of both the sp2- and sp3-bond derived resonance features in the XANES spectra. The valence-band photoelectron spectra indicate that N atoms cause the broadening of the valence band σ- and π-bond features and the enhancement and reduction of the σ- and π-bond features, respectively.[[booktype]]紙本[[booktype]]電子

A tunable common mode inductor with an auxiliary winding network

Paper 1593Track no. 5 - Devices and ComponentsIn conventional switching converter, the parasitic capacitance between switching circuit and ground introduces common mode (CM) noise problem. A CM inductor is inserted in the power feeding paths to produce a high impedance to attenuate the CM noise. However, this parasitic capacitance and the CM inductor create low-frequency resonance near the switching frequency and its harmonics. Thus, the filtering performance is diminished. Increasing the CM inductance to shift the resonant frequency to low-frequency range is one of the methods to tackle this problem. However, this approach leads to increase the power losses (both core and winding losses) of the CM inductor reducing the efficiency of the converter. In this paper, a tunable CM inductor with a small-space auxiliary winding is proposed. The auxiliary winding can be connected to a passive network to alter the frequency response of the CM inductor without affecting the original inductance. As a result, the influence of the low-frequency resonance can be mitigated. A proof-of-concept protytpe is constructed and its performance is experimentally measured. Results show that the proposed tunable CM inductor operates as theoretically anticipated. © IEEE.published_or_final_versio

Much Ado about Zeros: The Luttinger Surface and Mottness

We prove that the Mott insulating state is characterized by a divergence of the electron self energy at well-defined values of momenta in the first Brillouin zone. When particle-hole symmetry is present, the divergence obtains at the momenta of the Fermi surface for the corresponding non-interacting system. Such a divergence gives rise to a surface of zeros (the Luttinger surface) of the single-particle Green function and offers a single unifying principle of Mottness from which pseudogap phenomena, spectral weight transfer, and broad spectral features emerge in doped Mott insulators. We also show that only when particle-hole symmetry is present does the volume of the zero surface equal the particle density. We identify that the general breakdown of Luttinger's theorem in a Mott insulator arises from the breakdown of a perturbative expansion for the self energy in the single-particle Green function around the non-interacting limit. A modified version of Luttinger's theorem is derived for special cases.Comment: New version proves explicitly that only when particle-hole symmetry is present does the volume of the surface of zeros equal the particle density thereby generalising recent perturbative argument

One-arcsecond line-of-sight pointing control on exoplanetsat, a three-unit CubeSat

ExoplanetSat is a proposed 10×10×34-cm space telescope designed to detect down to Earth-sized exoplanets in an orbit out to the habitable zone of bright, Sun-like stars via the transit method. Achieving this science objective requires one-arcsecond line-of-sight pointing control for the science CCD detector, an unprecedented requirement for CubeSats. A two-stage control architecture that coordinates coarse rigid-body attitude control with fine line-of-sight pointing control will be employed to meet this challenging pointing requirement. Detailed testing of the reaction wheels and CMOS detectors has been performed to extract key performance parameters used in simulations. The results of these simulations indicate that a 1.4 arcsecond pointing precision (3σ) is achievable. To meet the 1.0-arcsecond pointing requirement, several options are analyzed. In particular, a new technique to estimate reaction wheel vibrations for feed forward cancellation of reaction wheel vibrations is presented. This estimator adaptively estimates disturbances from noisy sensor measurements and effectively stores disturbance amplitude and phase in memory as a function of wheel speed. In addition to these simulation results, testing results from a hardware-in-the-loop (HWIL) testbed demonstrate the capability of the fine pointing control loop. Future plans for complete HWIL testing of the coarse and fine control loops are presented

Selective advantage of implementing optimal contributions selection and timescales for the convergence of long-term genetic contributions

Additional file 1: Figure S1. Accumulation of long-term genetic contributions over time with a line of best fit

Strategies to overcome physician shortages in northern Ontario: A study of policy implementation over 35 years

<p>Abstract</p> <p>Background</p> <p>Shortages and maldistibution of physicians in northern Ontario, Canada, have been a long-standing issue. This study seeks to document, in a chronological manner, the introduction of programmes intended to help solve the problem by the provincial government over a 35-year period and to examine several aspects of policy implementation, using these programmes as a case study.</p> <p>Methods</p> <p>A programme analysis approach was adopted to examine each of a broad range of programmes to determine its year of introduction, strategic category, complexity, time frame, and expected outcome. A chronology of programme initiation was constructed, on the basis of which an analysis was done to examine changes in strategies used by the provincial government from 1969 to 2004.</p> <p>Results</p> <p>Many programmes were introduced during the study period, which could be grouped into nine strategic categories. The range of policy instruments used became broader in later years. But conspicuous by their absence were programmes of a directive nature. Programmes introduced in more recent years tended to be more complex and were more likely to have a longer time perspective and pay more attention to physician retention. The study also discusses the choice of policy instruments and use of multiple strategies.</p> <p>Conclusion</p> <p>The findings suggest that an examination of a policy is incomplete if implementation has not been taken into consideration. The study has revealed a process of trial-and-error experimentation and an accumulation of past experience. The study sheds light on the intricate relationships between policy, policy implementation and use of policy instruments and programmes.</p