353,762 research outputs found

    Tailorable infrared sensing device with strain layer superlattice structure

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    An infrared photodetector is formed of a heavily doped p-type Ge sub x Si sub 1-x/Si superlattice in which x is pre-established during manufacture in the range 0 to 100 percent. A custom-tailored photodetector that can differentiate among close wavelengths in the range of 2.7 to 50 microns is fabricated by appropriate selection of the alloy constituency value, x, to establish a specific wavelength at which photodetection cutoff will occur

    Diffusion semigroup on manifolds with time-dependent metrics

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    Let Lt:=Δt+ZtL_t:=\Delta_t +Z_t , t[0,Tc)t\in [0,T_c) on a differential manifold equipped with time-depending complete Riemannian metric (gt)t[0,Tc)(g_t)_{t\in [0,T_c)}, where Δt\Delta_t is the Laplacian induced by gtg_t and (Zt)t[0,Tc)(Z_t)_{t\in [0,T_c)} is a family of C1,1C^{1,1}-vector fields. We first present some explicit criteria for the non-explosion of the diffusion processes generated by LtL_t; then establish the derivative formula for the associated semigroup; and finally, present a number of equivalent semigroup inequalities for the curvature lower bound condition, which include the gradient inequalities, transportation-cost inequalities, Harnack inequalities and functional inequalities for the diffusion semigroup

    On Bayesian Oracle Properties

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    When model uncertainty is handled by Bayesian model averaging (BMA) or Bayesian model selection (BMS), the posterior distribution possesses a desirable "oracle property" for parametric inference, if for large enough data it is nearly as good as the oracle posterior, obtained by assuming unrealistically that the true model is known and only the true model is used. We study the oracle properties in a very general context of quasi-posterior, which can accommodate non-regular models with cubic root asymptotics and partial identification. Our approach for proving the oracle properties is based on a unified treatment that bounds the posterior probability of model mis-selection. This theoretical framework can be of interest to Bayesian statisticians who would like to theoretically justify their new model selection or model averaging methods in addition to empirical results. Furthermore, for non-regular models, we obtain nontrivial conclusions on the choice of prior penalty on model complexity, the temperature parameter of the quasi-posterior, and the advantage of BMA over BMS.Comment: 31 page

    Validity of two Higgs doublet models with a scalar color octet up to a high energy scale

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    We have recently studied theoretical constraints on the parameters of a 2HDM augmented with a color-octet scalar. In this paper we consider the consequences of requiring the model to remain valid up to very high energy scales, such as the GUT scale. The acceptable region of parameter space is reduced when one insists on vacuum stability, perturbative unitarity and the absence of Landau poles below a given scale. As the scale to which we require the model to be valid is increased, the acceptable region of parameter space for the 2HDM sector is reduced in such a way that it approaches the alignment limit, cos(βα)0\cos(\beta-\alpha)\to 0, and the masses of H0H^0, AA and H±H^\pm are pushed closer to each other. The parameters of the color octet sector are also restricted to an increasingly smaller region.Comment: 16 pages, 5 figures; referenced added; typos fixe
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