Non-equilibrium h-2 formation in the early universe: energy exchanges, rate coefficients, and spectral distortions

Energy exchange processes play a crucial role in the early universe, affecting the thermal balance and the dynamical evolution of the primordial gas. In the present work we focus on the consequences of a non-thermal distribution of the level populations of H2: first, we determine the excitation temperatures of vibrational transitions and the non-equilibrium heat transfer; second, we compare the modifications to chemical reaction rate coefficients with respect to the values obtained assuming local thermodynamic equilibrium; and third, we compute the spectral distortions to the cosmic background radiation generated by the formation of H2 in vibrationally excited levels. We conclude that non-equilibrium processes cannot be ignored in cosmological simulations of the evolution of baryons, although their observational signatures remain below current limits of detection. New fits to the equilibrium and non-equilibrium heat transfer functions are provided

Adaptively Transforming Graph Matching

Recently, many graph matching methods that incorporate pairwise constraint and that can be formulated as a quadratic assignment problem (QAP) have been proposed. Although these methods demonstrate promising results for the graph matching problem, they have high complexity in space or time. In this paper, we introduce an adaptively transforming graph matching (ATGM) method from the perspective of functional representation. More precisely, under a transformation formulation, we aim to match two graphs by minimizing the discrepancy between the original graph and the transformed graph. With a linear representation map of the transformation, the pairwise edge attributes of graphs are explicitly represented by unary node attributes, which enables us to reduce the space and time complexity significantly. Due to an efficient Frank-Wolfe method-based optimization strategy, we can handle graphs with hundreds and thousands of nodes within an acceptable amount of time. Meanwhile, because transformation map can preserve graph structures, a domain adaptation-based strategy is proposed to remove the outliers. The experimental results demonstrate that our proposed method outperforms the state-of-the-art graph matching algorithms

Efficient Algorithms for Image and High Dimensional Data Processing Using Eikonal Equation on Graphs

International audienceIn this paper we propose an adaptation of the static eikonal equation over weighted graphs of arbitrary structure using a framework of discrete operators. Based on this formulation, we provide explicit solu- tions for the L1,L2 and L∞ norms. Efficient algorithms to compute the explicit solution of the eikonal equation on graphs are also described. We then present several applications of our methodology for image processing such as superpixels decomposition, region based segmentation or patch- based segmentation using non-local configurations. By working on graphs, our formulation provides an unified approach for the processing of any data that can be represented by a graph such as high-dimensional data

Effects of primordial chemistry on the cosmic microwave background

Previous works have demonstrated that the generation of secondary CMB anisotropies due to the molecular optical depth is likely too small to be observed. In this paper, we examine additional ways in which primordial chemistry and the dark ages might influence the CMB. We present a detailed and updated chemical network and give an overview of the interactions of molecules with the CMB. We consider the optical depth due to line absorption, photoionization, photodissociation and free-free processes, and estimate the resulting changes in the CMB temperature and its power spectrum. The most promising results are obtained for the negative hydrogen ion \HM and the \HeHII molecule. The free-free process of \HM yields a relative change in the CMB temperature of up to $2\times10^{-11}$, and leads to a frequency-dependent change in the power spectrum of the order $10^{-7}$ at 30 GHz. With a change of the order $10^{-10}$ in the power spectrum, our result for the bound-free process of \HM is significantly below a previous suggestion. \HeHII efficiently scatters CMB photons and smears out primordial fluctuations, leading to a change in the power spectrum of the order $10^{-8}$. Improvements in the accuracy of future CMB experiments may thus help to constrain and finally detect these interesting signals from the dark ages of the universe.Comment: 16 pages, 15 figures, accepted for publication at A&A. Discussion section update

Deep Learning Using Havrda-Charvat Entropy for Classification of Pulmonary Optical Endomicroscopy

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Patch-based potentials for interactive contour extraction

International audienceThe problem of interactive contour extraction of targeted objects of interest in images is challenging and finds many applications in image editing tasks. Several methods have been proposed to address this problem with a common objective: performing an accurate contour extraction with minimum user effort. For minimal paths techniques, achieving this goal depends critically on the ability of the so-called potential map to capture edges. In this context we propose new patch-based potentials designed to have small values at the boundary of the targeted object. To evaluate these potentials, we consider the livewire framework and quantify their abilities in terms of number of needed seed points. Both visual and quantitative results demonstrated the strong capability of our proposed potentials in reducing the user's interaction while preserving a good accuracy of extraction