Bogoliubov transformations and exact isolated solutions for simple non-adiabatic Hamiltonians

We present a new method for finding isolated exact solutions of a class of non-adiabatic Hamiltonians of relevance to quantum optics and allied areas. Central to our approach is the use of Bogoliubov transformations of the bosonic fields in the models. We demonstrate the simplicity and efficiency of this method by applying it to the Rabi Hamiltonian.Comment: LaTeX, 16 pages, 1 figure. Minor additions and journal re

A Rich Example of Geometrically Induced Nonlinearity: From Rotobreathers and Kinks to Moving Localized Modes and Resonant Energy Transfer

We present an experimentally realizable, simple mechanical system with linear interactions whose geometric nature leads to nontrivial, nonlinear dynamical equations. The equations of motion are derived and their ground state structures are analyzed. Selective ``static'' features of the model are examined in the context of nonlinear waves including rotobreathers and kink-like solitary waves. We also explore ``dynamic'' features of the model concerning the resonant transfer of energy and the role of moving intrinsic localized modes in the process

Reduction of laser intensity scintillations in turbulent atmospheres using time averaging of a partially coherent beam

We demonstrate experimentally and numerically that the application of a partially coherent beam (PCB) in combination with time averaging leads to a significant reduction in the scintillation index. We use a simplified experimental approach in which the atmospheric turbulence is simulated by a phase diffuser. The role of the speckle size, the amplitude of the phase modulation, and the strength of the atmospheric turbulence are examined. We obtain good agreement between our numerical simulations and our experimental results. This study provides a useful foundation for future applications of PCB-based methods of scintillation reduction in physical atmospheres.Comment: 18 pages, 14 figure

Fibrillar templates and soft phases in systems with short-range dipolar and long-range interactions

We analyze the thermal fluctuations of particles that have a short-range dipolar attraction and a long-range repulsion. In an inhomogeneous particle density region, or "soft phase," filamentary patterns appear which are destroyed only at very high temperatures. The filaments act as a fluctuating template for correlated percolation in which low-energy excitations can move through the stable pattern by local rearrangements. At intermediate temperatures, dynamically averaged checkerboard states appear. We discuss possible implications for cuprate superconducting and related materials.Comment: 4 pages, 4 postscript figures. Discussion of implications for experiment and theory has been expande

Truth Discovery in Crowdsourced Detection of Spatial Events

Postprin

Traditional free-weight vs. variable resistance training applied to elite young soccer players during a short preseason: effects on strength, speed, and power performance

Maximizing the neuromuscular capacities of players is a critical challenge during short soccer preseasons. This study compared the effects of two strength-power training regimes, on the strength, speed, and power performance of elite young soccer players during a 4-week preseason. Twenty-five under-20 players from the same club were pair-matched in two training groups as follows: traditional training group (TTG) (n=13), athletes performed half-squat (HS) and jump-squat (JS) exercises as traditionally prescribed; and EB group (EBG) (n=12), athletes performed HS and JS with EB attached to the barbell. Vertical jump height, 20-m sprint velocity, change-of-direction (COD) speed, HS and JS power, and one-repetition maximum (1RM) in the HS were assessed pre, post 2-week, and post 4-week of training. An ANOVA two-way with repeated measures was used to assess the effects of both training protocols over the experimental period. Both strategies were effective for significantly improving HS and JS power (effect sizes [ES] 1.00 - 1.77), HS 1RM (ES = 1.68 and 1.51 for TTG and EBG, respectively), vertical jumping ability (ES 0.37 - 0.65), and COD speed (ES = 0.81 and 0.39 for TTG and EBG, respectively), when comparing pre- and post-measures. In contrast, both TTG and EBG failed to increase 20-m sprint velocity (ES ranging between -0.54 and 0.23). In conclusion, both training schemes were able to improve the strength and power performance, but not the sprint capacity of young soccer players. To accelerate strength gains over very-short time periods (i.e., 2-week), variable resistance training may be advantageous. Conversely, to optimize power adaptations in ballistic exercises across a similar time period, traditional FW training may be preferred

Phase Transitions in the Spin-Half J_1--J_2 Model

The coupled cluster method (CCM) is a well-known method of quantum many-body theory, and here we present an application of the CCM to the spin-half J_1--J_2 quantum spin model with nearest- and next-nearest-neighbour interactions on the linear chain and the square lattice. We present new results for ground-state expectation values of such quantities as the energy and the sublattice magnetisation. The presence of critical points in the solution of the CCM equations, which are associated with phase transitions in the real system, is investigated. Completely distinct from the investigation of the critical points, we also make a link between the expansion coefficients of the ground-state wave function in terms of an Ising basis and the CCM ket-state correlation coefficients. We are thus able to present evidence of the breakdown, at a given value of J_2/J_1, of the Marshall-Peierls sign rule which is known to be satisfied at the pure Heisenberg point (J_2 = 0) on any bipartite lattice. For the square lattice, our best estimates of the points at which the sign rule breaks down and at which the phase transition from the antiferromagnetic phase to the frustrated phase occurs are, respectively, given (to two decimal places) by J_2/J_1 = 0.26 and J_2/J_1 = 0.61.Comment: 28 pages, Latex, 2 postscript figure