16,613 research outputs found

    Microlensing path parametrization for Earth-like Exoplanet detection around solar mass stars

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    We propose a new parametrization of the impact parameter u0 and impact angle {\alpha} for microlensing systems composed by an Earth-like Exoplanet around a Solar mass Star at 1 AU. We present the caustic topology of such system, as well as the related light curves generated by using such a new parametrization. Based on the same density of points and accuracy of regular methods, we obtain results 5 times faster for discovering Earth-like exoplanet. In this big data revolution of photometric astronomy, our method will impact future missions like WFIRST (NASA) and Euclid (ESA) and they data pipelines, providing a rapid and deep detection of exoplanets for this specific class of microlensing event that might otherwise be lost.Comment: 8 pages, 7 figures, accepted to be published in The Astronomical Journa

    Spin-glass behaviour on random lattices

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    The ground-state phase diagram of an Ising spin-glass model on a random graph with an arbitrary fraction ww of ferromagnetic interactions is analysed in the presence of an external field. Using the replica method, and performing an analysis of stability of the replica-symmetric solution, it is shown that w=1/2w=1/2, correponding to an unbiased spin glass, is a singular point in the phase diagram, separating a region with a spin-glass phase (w<1/2w<1/2) from a region with spin-glass, ferromagnetic, mixed, and paramagnetic phases (w>1/2w>1/2)

    Replica-symmetric solutions of a dilute Ising ferromagnet in a random field

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    We use the replica method in order to obtain an expression for the variational free energy of an Ising ferromagnet on a Viana-Bray lattice in the presence of random external fields. Introducing a global order parameter, in the replica-symmetric context, the problem is reduced to the analysis of the solutions of a nonlinear integral equation. At zero temperature, and under some restrictions on the form of the random fields, we are able to perform a detailed analysis of stability of the replica-symmetric solutions. In contrast to the behaviour of the Sherrington-Kirkpatrick model for a spin glass in a uniform field, the paramagnetic solution is fully stable in a sufficiently large random field
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