Amperean pairing and the pseudogap phase of cuprate superconductors

The enigmatic pseudogap phase in underdoped cuprate high T_c superconductors has long been recognized as a central puzzle of the T_c problem. Recent data show that the pseudogap is likely a distinct phase, characterized by a medium range and quasi-static charge ordering. However, the origin of the ordering wavevector and the mechanism of the charge order is unknown. At the same time, earlier data show that precursive superconducting fluctuations are also associated with this phase. We propose that the pseudogap phase is a novel pairing state where electrons on the same side of the Fermi surface are paired, in strong contrast with conventional BCS theory which pair electrons on opposite sides of the Fermi surface. In this state the Cooper pair carries a net momentum and belong to a general class called pair density wave (PDW). The microscopic pairing mechanism comes from a gauge theory formulation of the resonating valence bond (RVB) picture, where electrons traveling in the same direction feel an attractive force in analogy with Ampere's effects in electromagnetism. We call this Amperean pairing. Charge order automatically appears as a subsidiary order parameter. Our theory gives a prediction of the ordering wavevector which is in good agreement with experiment. Furthermore, the quasiparticle spectrum from our model explains many of the unusual features reported in photoemission experiments. The Fermi arc and the unusual way the tip of the arc terminates also come out naturally. We also discuss how the onset of the Kerr effect in this state can be accommodated. Finally, we propose an experiment which can directly test the notion of Amperean pairing.Comment: (v4) added phase diagram, Appendix A on the incompatibility of CDW model, and more discussion of low-temperature properties; (v3) expanded supplementary section, added figures and discussion on Fermi arc; (v2) added references, improved figures, corrected typo in Eq.(4

Hermetically sealed explosive release mechanism Patent

Hermetically sealed explosive release mechanism for actuator devic

Operations of 1 Canadian Infantry Divisional Artillery, 24 August-22 September 1944

In January 1944 1st Canadian Infantry Division reverted to command of I Canadian Corps after seven months of campaigning in Sicily and Italy under a British Corps. The story of the division’s resentment toward the level of paperwork foisted on them by H.D.G. Crerar’s untried corps headquarters is legendary. Modern military historians assume this rancour is indicative of a 1914–18 mindset among Second World War Canadian senior officers which prevented them from adapting to the fast–paced nature of modern mechanized warfare in the 1940s.1 Ironically, much of that “paper–pushing” appears to have contributed to the Canadian Army’s victories over German forces in the great battles of 1944–45. Among the most labourious administrative chores were the operational narratives and lessons learned reports requiring battle participants to analyze recent actions and draw conclusions for improving combat efficiency. These reports do indeed date back to the Great War. Most First World War historians agree that such documents were a key ingredient to the remarkable success of the Canadian Corps in 1915–1918.2 The following report was prepared by the 1st Canadian Divisional Artillery staff in late September 1944, during the brief pause between the breakthrough of the Gothic and Rimini Lines and the subsequent pursuit into the Po Valley. In the weeks prior to that pause, I Canadian Corps suffered their heaviest losses to date against the most determined German resistance encountered during the Italian Campaign. They also demonstrated remarkable military skill and professionalism, and won their greatest victories of the entire war. Readers may note that the report is tightly focussed on exacting every possible ounce of combat power out of an already effective organization. Continual refinements to the Anglo–Canadian system were essential given that Alliedforces in Italy usually possessed the barest minimum of resources necessary to accomplish their strategic mission of preventing German formations from withdrawing to more decisive fronts. Similar reports are found in the war diaries of all units and formations in the Canadian Army in the Second World War. What is most significant about this process is the rapidity with which recommended improvements were put into practice during subsequent operations

Insights from Project FeederWatch: Changes in the abundance and occurrence of birds in New Hampshire over the past 24 years

Changes in the climate and land use over time can lead to changes in the composition of wildlife communities. Using data from Project FeederWatch, we examine trends in the abundance and occurrence of birds documented in the winters from 1988 to 2012 in New Hampshire. Changes in abundance and occurrence are summarized for individual bird species as well as across species based on life history traits. In addition, we examined trends for the state as a whole as well as in subregions. We discuss these changes with regards to the variations of climate and land use that are occurring throughout New Hampshire

Computer program MCAP-TOSS calculates steady-state fluid dynamics of coolant in parallel channels and temperature distribution in surrounding heat-generating solid

Computer program calculates the steady state fluid distribution, temperature rise, and pressure drop of a coolant, the material temperature distribution of a heat generating solid, and the heat flux distributions at the fluid-solid interfaces. It performs the necessary iterations automatically within the computer, in one machine run