On optimality of kernels for approximate Bayesian computation using sequential Monte Carlo

Approximate Bayesian computation (ABC) has gained popularity over the past few years for the analysis of complex models arising in population genetics, epidemiology and system biology. Sequential Monte Carlo (SMC) approaches have become work-horses in ABC. Here we discuss how to construct the perturbation kernels that are required in ABC SMC approaches, in order to construct a sequence of distributions that start out from a suitably defined prior and converge towards the unknown posterior. We derive optimality criteria for different kernels, which are based on the Kullback-Leibler divergence between a distribution and the distribution of the perturbed particles. We will show that for many complicated posterior distributions, locally adapted kernels tend to show the best performance. We find that the added moderate cost of adapting kernel functions is easily regained in terms of the higher acceptance rate. We demonstrate the computational efficiency gains in a range of toy examples which illustrate some of the challenges faced in real-world applications of ABC, before turning to two demanding parameter inference problems in molecular biology, which highlight the huge increases in efficiency that can be gained from choice of optimal kernels. We conclude with a general discussion of the rational choice of perturbation kernels in ABC SMC settings

Options for the SELEX state D_{s\J}^+(2632)

We consider possible assignments for the D_{s\J}^+(2632), which was recently reported in D$_s^+\eta$ and D$^0$K$^+$ final states by the SELEX Collaboration at Fermilab. The most plausible quark model assignment for this state is the first radial excitation ($2^3\S_1$) of the $c\bar s$ D$_s^*(2112)$, although the predicted mass and strong decay branching fractions for this assignment are not in agreement with the SELEX data. The reported dominance of D$_s\eta$ over DK appears especially problematic. An intriguing similarity to the K$^*(1414)$ is noted. $2^3\S_1$--^3\D_1 configuration mixing is also considered, and we find that this effect is unlikely to resolve the branching fraction discrepancy. Other interpretations as a $c\bar s$-hybrid or a two-meson molecule are also considered, but appear unlikely. Thus, if this state is confirmed, it will require reconsideration of the systematics of charmed meson spectroscopy and strong decays.Comment: 6 revtex4 pages, 2 eps figure

Hyperspherical entanglement entropy

The coefficient of the log term in the entanglement entropy associated with hyperspherical surfaces in flat space-time is shown to equal the conformal anomaly by conformally transforming Euclideanised space--time to a sphere and using already existing formulae for the relevant heat--kernel coefficients after cyclic factoring. The analytical reason for the result is that the conformal anomaly on the lune has an extremum at the ordinary sphere limit. A proof is given. Agreement with a recent evaluation of the coefficient is found.Comment: 7 pages. Final revision. Historical comments amended. Minor remarks adde

Contextual-based Image Inpainting: Infer, Match, and Translate

We study the task of image inpainting, which is to fill in the missing region of an incomplete image with plausible contents. To this end, we propose a learning-based approach to generate visually coherent completion given a high-resolution image with missing components. In order to overcome the difficulty to directly learn the distribution of high-dimensional image data, we divide the task into inference and translation as two separate steps and model each step with a deep neural network. We also use simple heuristics to guide the propagation of local textures from the boundary to the hole. We show that, by using such techniques, inpainting reduces to the problem of learning two image-feature translation functions in much smaller space and hence easier to train. We evaluate our method on several public datasets and show that we generate results of better visual quality than previous state-of-the-art methods.Comment: ECCV 2018 camera read

Charmonium-Nucleon Dissociation Cross Sections in the Quark Model

Charmonium dissociation cross sections due to flavor-exchange charmonium-baryon scattering are computed in the constituent quark model. We present results for inelastic $J/\psi N$ and $\eta_c N$ scattering amplitudes and cross sections into 46 final channels, including final states composed of various combinations of $D$, $D^*$, $\Sigma_c$, and $\Lambda_c$. These results are relevant to experimental searches for the deconfined phase of quark matter, and may be useful in identifying the contribution of initial $c\bar c$ production to the open-charm final states observed at RHIC through the characteristic flavor ratios of certain channels. These results are also of interest to possible charmonium-nucleon bound states.Comment: 10 pages, 5 eps figures, revte

Effects of Extreme Obliquity Variations on the Habitability of Exoplanets

We explore the impact of obliquity variations on planetary habitability in hypothetical systems with high mutual inclination. We show that large amplitude, high frequency obliquity oscillations on Earth-like exoplanets can suppress the ice-albedo feedback, increasing the outer edge of the habitable zone. We restrict our exploration to hypothetical systems consisting of a solar-mass star, an Earth-mass planet at 1 AU, and 1 or 2 larger planets. We verify that these systems are stable for $10^8$ years with N-body simulations, and calculate the obliquity variations induced by the orbital evolution of the Earth-mass planet and a torque from the host star. We run a simplified energy balance model on the terrestrial planet to assess surface temperature and ice coverage on the planet's surface, and we calculate differences in the outer edge of the habitable zone for planets with rapid obliquity variations. For each hypothetical system, we calculate the outer edge of habitability for two conditions: 1) the full evolution of the planetary spin and orbit, and 2) the eccentricity and obliquity fixed at their average values. We recover previous results that higher values of fixed obliquity and eccentricity expand the habitable zone, but also find that obliquity oscillations further expand habitable orbits in all cases. Terrestrial planets near the outer edge of the habitable zone may be more likely to support life in systems that induce rapid obliquity oscillations as opposed to fixed-spin planets. Such planets may be the easiest to directly characterize with space-borne telescopes.Comment: 46 pages, 12 Figures, 5 Table

The use of ICT in the assessment of modern languages: the English context and European viewpoints

The ever increasing explosion of highly attractive multimedia resources on offer has boosted the use of information and communication technology (ICT) in the teaching and learning of modern languages. The use of ICT to assess languages is less frequent, however, although online testing is starting to develop. This paper examines the national context for the assessment of modern foreign language proficiency in England, outlines the kinds of assessment currently available and the development of electronic forms of assessment and compares the above with the survey results of a European Union (EU) funded project on current good practice in online assessment of languages in other European countries. The findings indicate that speaking is inadequately served by online testing as tests currently focus primarily on receptive language skills. The implications for future successful online testing include the incorporation of interactive skills and effective formative feedback