Strong lensing interferometry for compact binaries

We propose a possibility to improve the current precision measurements on compact binaries. When the orbital axis is almost perpendicular to our line of sight, a pulsar behind its companion can form two strong-lensing images. These images cannot be resolved, but we can use multi-wavelength interferometry to accurately determine the passage through superior conjunction. This method does not depend strongly on the stability of the pulse profile, and applies equally well to both slow and fast pulsars. We discuss the possible improvement this can bring to the bound on stochastic gravitational wave background and to determine black hole spin. We also discuss the possibility of discovering a suitable binary system by the Square Kilometer Array that our method can apply to.Comment: 5 pages, 5 figure

Variation in habitat choice and delayed reproduction: Adaptive queuing strategies or individual quality differences?

In most species, some individuals delay reproduction or occupy inferior breeding positions. The queue hypothesis tries to explain both patterns by proposing that individuals strategically delay breeding (queue) to acquire better breeding or social positions. In 1995, Ens, Weissing, and Drent addressed evolutionarily stable queuing strategies in situations with habitat heterogeneity. However, their model did not consider the non - mutually exclusive individual quality hypothesis, which suggests that some individuals delay breeding or occupy inferior breeding positions because they are poor competitors. Here we extend their model with individual differences in competitive abilities, which are probably plentiful in nature. We show that including even the smallest competitive asymmetries will result in individuals using queuing strategies completely different from those in models that assume equal competitors. Subsequently, we investigate how well our models can explain settleme! nt patterns in the wild, using a long-term study on oystercatchers. This long-lived shorebird exhibits strong variation in age of first reproduction and territory quality. We show that only models that include competitive asymmetries can explain why oystercatchers' settlement patterns depend on natal origin. We conclude that predictions from queuing models are very sensitive to assumptions about competitive asymmetries, while detecting such differences in the wild is often problematic.

Spin and orbital excitation spectrum in the Kugel-Khomskii model

We discuss spin and orbital ordering in the twofold orbital degenerate superexchange model in three dimensions relevant to perovskite transition metal oxides. We focus on the particular point on the classical phase diagram where orbital degeneracy is lifted by quantum effects exclusively. Dispersion and damping of the spin and orbital excitations are calculated at this point taking into account their mutual interaction. Interaction corrections to the mean-field order parameters are found to be small. We conclude that quasi-one-dimensional Neel spin order accompanied by the uniform d_{3z^2-r^2}-type orbital ordering is stable against quantum fluctuations.Comment: 4 pages with 3 PS figures, 1 table, RevTeX, accepted to Phys. Rev. B. Rapid Communicatio

Trimer Formation and Metal-Insulator Transition in Orbital Degenerate Systems on a Triangular Lattice

As a prototypical self-organization in the system with orbital degeneracy, we theoretically investigate trimer formation on a triangular lattice, as observed in LiVO2. From the analysis of an effective spin-orbital coupled model in the strong correlation limit, we show that the previously-proposed orbital-ordered trimer state is not the lowest-energy state for a finite Hund's-rule coupling. Instead, exploring the ground state in a wide range of parameters for a multiorbital Hubbard model, we find an instability toward a different orbital-ordered trimer state in the intermediately correlated regime in the presence of trigonal crystal field. The trimer phase appears in the competing region among a paramagnetic metal, band insulator, and Mott insulator. The underlying mechanism is nesting instability of the Fermi surface by a synergetic effect of Coulomb interactions and trigonal-field splitting. The results are compared with experiments in triangularlattice compounds, LiVX2 (X=O, S, Se) and NaVO2.Comment: 4 pages, 4 figures, accepted for publication in J. Phys. Soc. Jp

Optimization of the Process of Synthesis of Lignin – Phenol -Formaldehyde Organic Aerogels

Методом экспериментально-статистического анализа изучено влияние массового соотношения фенола и лигнина (Х1) и массового соотношения их смеси с формальдегидом (Х2) на значения параметров пористой структуры получаемых органических лигнин- фенол-формальдегидный аэрогелей. На основании оценки полученной математической модели установлено, что при соблюдении условий Х1 = 0,65-0,78, а Х2 = 1,7 прогнозируемые максимальные значения удельной поверхности и объема мезопор получаемого органического аэрогеля составляют 485 м2/г и 1,85 г/см3 соответственно. При оптимальных значениях Х1 = 0,25, а Х2 = 1,25 рассчитанные значения объема макропор достигают 4,05 см3/г, а общего объема пор – 4,67 см3/гThe method of experimental statistical analysis was applied to study the effect of mass ratio of phenol and lignin (factor X1) and the weight ratio of thereof mixture with formaldehyde (factor X2) on the values of specific parameters of the porous structure obtained organic lignin – phenolformaldehyde aerogels. Based on the evaluation of the mathematical model was established that under the observance terms of X1 = 0,65-0,78 and X2 = 1,7 the maximum predicted values of the specific surface area and mesopore volume of obtained organic aerogels are 485 m2 /g and 1,83 cm3/g, accordingly. Under optimal values of X1 = 0.25, and X2 = 1.25 calculated values reach a macropore volume of 4.05 cm3 /g and total pore volume – 4.67 cm 3 /