4,747 research outputs found

    Evolution of the Pancaking Effect in a LCDM Cosmology

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    We explore the evolution of the large-scale anisotropy in the velocity field caused by the gravitational pancaking effect assuming a LCDM universe. The Millennium Run halo catalogs at four different redshifts, z=0, 0.5, 1 and z=2 are analyzed to find that the pancaking effect starts to intervene the hierarchical structure formation at redshift z=2 when a characteristic pancake scale is around 3 Mpc/h. It is also clearly shown how the degree and scale of the pancaking effect changes with time. An analytic model based on the Zel'dovich approximation is presented to explain quantitatively the evolution of the velocity-pancake alignment. A cosmological implication of our finding and a possibility of detecting a signal in real universe are discussed.Comment: accepted by ApJ, 21 pages, 6 figures, discussion and error analysis improve

    Direct sampling of the Susskind-Glogower phase distributions

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    Coarse-grained phase distributions are introduced that approximate to the Susskind--Glogower cosine and sine phase distributions. The integral relations between the phase distributions and the phase-parametrized field-strength distributions observable in balanced homodyning are derived and the integral kernels are analyzed. It is shown that the phase distributions can be directly sampled from the field-strength distributions which offers the possibility of measuring the Susskind--Glogower cosine and sine phase distributions with sufficiently well accuracy. Numerical simulations are performed to demonstrate the applicability of the method.Comment: 10 figures using a4.st

    Detecting the degree of macroscopic quantumness using an overlap measurement

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    We investigate how to experimentally detect a recently proposed measure to quantify macroscopic quantum superpositions [Phys. Rev. Lett. 106, 220401 (2011)], namely, "macroscopic quantumness" I\mathcal{I}. Schemes based on overlap measurements for harmonic oscillator states and for qubit states are extensively investigated. Effects of detection inefficiency and coarse-graining are analyzed in order to assess feasibility of the schemes.Comment: 12 pages, 8 figures, to be published in J. Opt. Soc. Am.

    Position-dependent diffusion of light in disordered waveguides

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    Diffusion has been widely used to describe a random walk of particles or waves, and it requires only one parameter -- the diffusion constant. For waves, however, diffusion is an approximation that disregards the possibility of interference. Anderson localization, which manifests itself through a vanishing diffusion coefficient in an infinite system, originates from constructive interference of waves traveling in loop trajectories -- pairs of time-reversed paths returning to the same point. In an open system of finite size, the return probability through such paths is reduced, particularly near the boundary where waves may escape. Based on this argument, the self-consistent theory of localization and the supersymmetric field theory predict that the diffusion coefficient varies spatially inside the system. A direct experimental observation of this effect is a challenge because it requires monitoring wave transport inside the system. Here, we fabricate two-dimensional photonic random media and probe position-dependent diffusion inside the sample from the third dimension. By varying the geometry of the system or the dissipation which also limits the size of loop trajectories, we are able to control the renormalization of the diffusion coefficient. This work shows the possibility of manipulating diffusion via the interplay of localization and dissipation.Comment: 24 pages, 6 figure
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