Failure of Scattering Interference in the Pseudogap State of Cuprate Superconductors

We calculate scattering interference patterns for various electronic states proposed for the pseudogap regime of the cuprate superconductors. The scattering interference models all produce patterns whose wavelength changes as a function of energy, in contradiction to the energy-independent wavelength seen by scanning tunneling microscopy (STM) experiments in the pseudogap state. This suggests that the patterns seen in STM local density of states measurements are not due to scattering interference, but are rather the result of some form of ordering.Comment: To be submitted to Phys. Rev.

Many-Impurity Effects in Fourier Transform Scanning Tunneling Spectroscopy

Fourier transform scanning tunneling spectroscopy (FTSTS) is a useful technique for extracting details of the momentum-resolved electronic band structure from inhomogeneities in the local density of states due to disorder-related quasiparticle scattering. To a large extent, current understanding of FTSTS is based on models of Friedel oscillations near isolated impurities. Here, a framework for understanding many-impurity effects is developed based on a systematic treatment of the variance Delta rho^2(q,omega) of the Fourier transformed local density of states rho(q,\omega). One important consequence of this work is a demonstration that the poor signal-to-noise ratio inherent in rho(q,omega) due to randomness in impurity positions can be eliminated by configuration averaging Delta rho^2(q,omega). Furthermore, we develop a diagrammatic perturbation theory for Delta rho^2(q,omega) and show that an important bulk quantity, the mean-free-path, can be extracted from FTSTS experiments.Comment: 7 pages, 5 figures. A version of the paper with high resolution, colour figures is available at http://www.trentu.ca/physics/batkinson/FTSTS.ps.gz minor revisions in response to refree report + figure 5 is modifie

СССР и Красная армия глазами военного атташе Франции Э. Мандра. 1933–1934 гг.

The article, largely based on new documents from Russian and French archives, examines an important aspect of Franco-Soviet relations on the eve of the Second World War: the interaction between the militaries of the two countries. The question of cooperation between the two armies was raised immediately after the signing of the Franco-Soviet non-aggression pact in 1932. The following year, the first French military attaché, E. Mendras, arrived in Moscow. A proponent of the revival of the Franco-Russian alliance, he explored Soviet reality to determine the real potential of the USSR as a possible ally. Despite a number of shortcomings of the Soviet socio-political system, Mendras came to the conclusion that the political regime in the country was quite stable, and its armed forces had the necessary resources to conduct a European war. At the same time, he questioned Moscow's foreign policy goals and was critical of Soviet ideology as a factor in political decision-making. At first, the military attaché recommended that the French leadership enhance the alliance with the USSR. However, his attitude gradually changed against the background of a lack of complete mutual understanding with the Soviets and contradictions on the issue of rapprochement with Moscow, which cleaved the military-political leadership in Paris. In 1934, Mendras was skeptical about the prospects for cooperation with the USSR. This turn, in many ways, reflects a general change in the vector in Soviet-French relations in the mid-1930s, which led to their deterioration on the eve of the Second World War. © 2021 Saint-Petersburg State University. All rights reserved.The research was supported by the Russian Science Foundation (RSF), project no. 20-78-10014

Surface pinning of fluctuating charge order: an "extraordinary" surface phase transition

We study the mean-field theory of charge-density wave (CDW) order in a layered system, including the effect of the long-range Coulomb interaction and of screening by uncondensed electrons. We particularly focus on the conditions necessary for an ``extraordinary'' transition, in which the surface orders at a higher temperature, and is more likely to be commensurate, than the bulk. We interpret recent experiments on NaCCOC as indicating the presence of commensurate CDW at the surface that is not present in the bulk. More generally, we show that poor screening of the Coulomb interaction tends to stabilize incommensurate order, possibly explaining why the CDW order in LSCO and NbSe2 remains incommensurate to T -> 0, despite the small magnitude of the incommensurability.Comment: 9 pages, no figures, 31 references; 1 new figure and minor editing of the tex

Trends in vocational education and their impact on the staffing of the regional economy

На примере Свердловской области рассматриваются тенденции развития профессионального образования, исследуются факторы его влияния на кадровое обеспечение экономики региона и его территорийIn the article, on the example of Sverdlovsk region, tendencies of development of professional education, examines the factors of its influence on the staffing of the economy of the region and its territorie

Nilpotent Classical Mechanics

The formalism of nilpotent mechanics is introduced in the Lagrangian and Hamiltonian form. Systems are described using nilpotent, commuting coordinates $\eta$. Necessary geometrical notions and elements of generalized differential $\eta$-calculus are introduced. The so called $s-$geometry, in a special case when it is orthogonally related to a traceless symmetric form, shows some resemblances to the symplectic geometry. As an example of an $\eta$-system the nilpotent oscillator is introduced and its supersymmetrization considered. It is shown that the $R$-symmetry known for the Graded Superfield Oscillator (GSO) is present also here for the supersymmetric $\eta$-system. The generalized Poisson bracket for $(\eta,p)$-variables satisfies modified Leibniz rule and has nontrivial Jacobiator.Comment: 23 pages, no figures. Corrected version. 2 references adde