1,466 research outputs found

    Cosmic ray experiments /elementary particle physics/ in a manned orbiting laboratory

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    High energy cosmic ray experiments in manned orbiting laborator

    Beauty in the Classroom: Professors' Pulchritude and Putative Pedagogical Productivity

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    Adjusted for many other determinants, beauty affects earnings; but does it lead directly to the differences in productivity that we believe generate earnings differences? We take a large sample of student instructional ratings for a group of university professors, acquire six independent measures of their beauty and a number of other descriptors of them and their classes. Instructors who are viewed as better looking receive higher instructional ratings, with the impact of a move from the 10th to the 90th percentile of beauty being substantial. This impact exists within university departments and even within particular courses, and is larger for male than for female instructors. Disentangling whether this outcome represents productivity or discrimination is, as with the issue generally, probably impossible.

    Classification of Dimension 5 Lorentz Violating Interactions in the Standard Model

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    We give a complete classification of mass dimension five Lorentz-non-invariant interactions composed from the Standard Model fields, using the effective field theory approach. We identify different classes of Lorentz violating operators, some of which are protected against transmutation to lower dimensions even at the loop level. Within each class of operators we determine a typical experimental sensitivity to the size of Lorentz violation.Comment: 26 page

    Tools or Toys? The Impact of High Technology on Scholarly Productivity

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    Toys. The impact of computers on productivity has been examined directly on macro data and indirectly (on wages) using microeconomic data. This study examines the direct impact on the productivity of scholarship by considering how high technology might alter patterns of coauthoring of articles in economics and their influence. Using all coauthored articles in three major economics journals from 1970-79 and 1992-96, we find: 1) Sharp growth in the percentage of distant coauthorships (those between authors who were not in the same metropolitan areas in the four years prior to publication), as the theory predicts. Contrary to the theory: 2) Lower productivity (in terms of subsequent citations) of distant than close-coauthored papers; and 3) No decline in their relative disadvantage between the 1970s and 1990s. These findings are reconciled by the argument that high-technology functions as a consumption rather than an investment good. As such, it can be welfare-increasing without increasing productivity.

    Food Stamps as Money and Income

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    Food Stamps represent nearly $11 billion of personal income in the United States. The coupons that are issued to represent the purchasing power available to recipients are also reserves for the commercial banking system.This study asks how closely these coupons are substitutable for what is usually considered as money, and how well Food Stamps function as a fiscal stabilizer (whether they increase consumption more than does ordinary income). The results, based on estimates for 1959-1981, suggest that Food Stamp coupons are perfectly substitutable for Ml, and a revised money-supply series including "Food Stamp Money" is included in an Appendix. Estimates of consumption functions indicate that the MPC out of income in the form of Food Stamps is higher than that out of ordinary income. Taken together, the results suggest that the Food Stamp program is an automatic fiscal and monetary stabilizer -- under its provisions, both the money stock and disposable income are increased during a recession.

    Spin-Current-Induced Charge Accumulation and Electric Current in Semiconductor Nanostructures with Rashba Spin-Orbit Coupling

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    We demonstrate that the flow of a longitudinal spin current with different spin polarization will induce different patterns of charge accumulation in a two-terminal strip, or electric current distribution in a four-terminal Hall-bar structure, of two-dimensional electron gas with Rashba spin-orbit coupling (RSOC). For an in-plane polarized spin current, charges will accumulate either by the two lateral edges or around the center of the strip structure while, for an out-of-plain polarized spin current, charge densities will show opposite signs by the two lateral edges leading to a Hall voltage. Our calculation offers a new route to experimentally detect or differentiate pure spin currents with various spin polarization.Comment: 4 pages, 3 figure

    A sufficient condition for the absence of the sign problem in the fermionic quantum Monte-Carlo algorithm

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    Quantum Monte-Carlo (QMC) simulations involving fermions have the notorious sign problem. Some well-known exceptions of the auxiliary field QMC algorithm rely on the factorizibility of the fermion determinant. Recently, a fermionic QMC algorithm [1] has been found in which the fermion determinant may not necessarily factorizable, but can instead be expressed as a product of complex conjugate pairs of eigenvalues, thus eliminating the sign problem for a much wider class of models. In this paper, we present general conditions for the applicability of this algorithm and point out that it is deeply related to the time reversal symmetry of the fermion matrix. We apply this method to various models of strongly correlated systems at all doping levels and lattice geometries, and show that many novel phases can be simulated without the sign problem.Comment: 14 pages, 7 figures, to appear in Phys. Rev.

    Symmetries and collective excitations in large superconducting circuits

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    The intriguing appeal of circuits lies in their modularity and ease of fabrication. Based on a toolbox of simple building blocks, circuits present a powerful framework for achieving new functionality by combining circuit elements into larger networks. It is an open question to what degree modularity also holds for quantum circuits -- circuits made of superconducting material, in which electric voltages and currents are governed by the laws of quantum physics. If realizable, quantum coherence in larger circuit networks has great potential for advances in quantum information processing including topological protection from decoherence. Here, we present theory suitable for quantitative modeling of such large circuits and discuss its application to the fluxonium device. Our approach makes use of approximate symmetries exhibited by the circuit, and enables us to obtain new predictions for the energy spectrum of the fluxonium device which can be tested with current experimental technology

    Exotic spin, charge and pairing correlations of the two-dimensional doped Hubbard model: a symmetry entangled mean-field approach

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    Intertwining of spin, charge and pairing correlations in the repulsive two-dimensional Hubbard model is shown through unrestricted variational calculations, with projected wavefunctions free of symmetry breaking. A crossover from incommensurate antiferromagnetism to stripe order naturally emerges in the hole-doped region when increasing the on-site coupling. Although effective pairing interactions are identified, they are strongly fragmented in several modes including d-wave pairing and more exotic channels related to an underlying stripe. We demonstrate that the entanglement of a mean-field wavefunction by symmetry restoration can largely account for interaction effects.Comment: Minor corrections, one reference adde
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