Pop-up SLAM: Semantic Monocular Plane SLAM for Low-texture Environments

Existing simultaneous localization and mapping (SLAM) algorithms are not robust in challenging low-texture environments because there are only few salient features. The resulting sparse or semi-dense map also conveys little information for motion planning. Though some work utilize plane or scene layout for dense map regularization, they require decent state estimation from other sources. In this paper, we propose real-time monocular plane SLAM to demonstrate that scene understanding could improve both state estimation and dense mapping especially in low-texture environments. The plane measurements come from a pop-up 3D plane model applied to each single image. We also combine planes with point based SLAM to improve robustness. On a public TUM dataset, our algorithm generates a dense semantic 3D model with pixel depth error of 6.2 cm while existing SLAM algorithms fail. On a 60 m long dataset with loops, our method creates a much better 3D model with state estimation error of 0.67%.Comment: International Conference on Intelligent Robots and Systems (IROS) 201

Measuring the impact of social cash transfers on poverty and inequality in Namibia

This paper reviews the system for social cash transfers in Namibia, a middle-income country with a long experience in making available a universal and non-contributory old age pension, child grants using means-testing and quasi-conditionalities and other cash transfers. The paper traces the origins of the cash transfers back to the country’s past annexation into apartheid South Africa and shows how Namibia’s system is now faced with a set of distinct challenges that are particularly pertinent as the authorities are rapidly scaling-up access. Notably, in the years after the remaining elements of racial discrimination were eliminated, and the value of the transfers were equalised across the ethnic groups, new discrepancies have developed in the values of the different grants. Moreover, using newly available household data the paper finds inefficiencies in the means-testing for the child grants – especially when compared to South Africa. In spite of these challenges the paper also shows that social cash transfers have a large effect on poverty reduction and that the effects are particularly positive for the poorest of the poor. The transfers also tend to reduce inequality but this impact is more limited. Simulations indicate the fiscal sustainability of an expanded system of social cash transfers and highlight the potential cost-savings that would accrue from a more effective means-test of the child grants. In the analysis the effects of using income and expenditure data as the basis for the welfare variable are discerned.Namibia, Sub-Saharan Africa, Social protection, Social transfers, Old age pension, Disability grants, Child grants

Static impurities in a supersolid of interacting hard-core bosons on a triangular lattice

We study the effect of impurities in a supersolid phase in comparison to the behavior in the solid and superfluid phases. A supersolid phase has been established for interacting hardcore bosons on a triangular lattice which may be realizable by ultracold atomic gases. Static vacancies are considered in this model which always lower the magnitude of the order parameter in the solid or superfluid phases. In the supersolid phase, however, the impurities directly affect both order parameters simultaneously and thereby reveal an interesting interplay between them. In particular the solid order may be enhanced at the cost of a strong reduction of the superfluidity, which shows that the two order parameters cannot be in a simple superposition. We also observe an unusual impurity pinning effect in the solid ordered phase, which results in two distinct states separated by a first-order transition.Comment: 5 pages, 5 figures, final version. More information at http://www.physik.uni-kl.de/eggert/papers/index.htm

Long spin coherence times in the ground state and an optically excited state of 167^{167}Er3+^{3+}:Y2_2SiO5_5 at zero magnetic field

Spins in solids are an ideal candidate to act as a memory and interface with superconducting qubits due to their long coherence times. We spectroscopically investigate erbium-167-doped yttrium orthosilicate as a possible microwave-addressed memory employing its microwave frequency transitions that occur without applying an external magnetic field. We obtain coherence times of 380 $\mu$s in a ground state spin transition and 1.48 ms in an excited state spin transition. This is 28 times longer compared to previous zero field measurements, as well as 200 times longer than a previous microwave memory demonstration in the same material. These long coherence times show that erbium-167-doped yttrium orthosilicate has potential as a microwave-addressed quantum memory.Comment: 9 pages, 7 figures. The paper has been expanded compared to the previous version on arXiv, and the title has change

Parton distribution amplitudes of light vector mesons

A rainbow-ladder truncation of QCD's Dyson-Schwinger equations is used to calculate rho- and phi-meson valence-quark (twist-two parton) distribution amplitudes (PDAs) via a light-front projection of their Bethe-Salpeter wave functions, which possess S- and D-wave components of comparable size in the meson rest frame. All computed PDAs are broad concave functions, whose dilation with respect to the asymptotic distribution is an expression of dynamical chiral symmetry breaking. The PDAs can be used to define an ordering of valence-quark light-front spatial-extent within mesons: this size is smallest within the pion and increases through the perp-polarisation to the parallel-polarisation of the vector mesons; effects associated with the breaking of SU(3)-flavour symmetry are significantly smaller than those associated with altering the polarisation of vector mesons. Notably, the predicted pointwise behaviour of the rho-meson PDAs is in quantitative agreement with that inferred recently via an analysis of diffractive vector-meson photoproduction experiments.Comment: 13 pages, 4 figures, 4 table