Deep Learning of Geometric Constellation Shaping including Fiber Nonlinearities

A new geometric shaping method is proposed, leveraging unsupervised machine learning to optimize the constellation design. The learned constellation mitigates nonlinear effects with gains up to 0.13 bit/4D when trained with a simplified fiber channel model.Comment: 3 pages, 6 figures, submitted to ECOC 201

Dust in the Photospheric Environment II. Effect on the Near Infrared Spectra of L and T Dwarfs

We report an attempt to interpret the spectra of L and T dwarfs with the use of the Unified Cloudy Model (UCM). For this purpose, we extend the grid of the UCMs to the cases of log g = 4.5 and 5.5. The dust column density relative to the gas column density in the observable photosphere is larger at the higher gravities, and molecular line intensity is generally smaller at the higher gravities. The overall spectral energy distributions (SEDs) are f_{J} < f_{H} < f_{K} in middle and late L dwarfs, f_{J} f_{K} in early T dwarfs (L/T transition objects), and finally f_{J} > f_{H} > f_{K} in middle and late T dwarfs, where f_{J}, f_{H}, and f_{K} are the peak fluxes at J, H, and K bands, respectively, in f_{nu} unit. This tendency is the opposite to what is expected for the temperature effect, but can be accounted for as the effect of thin dust clouds formed deep in the photosphere together with the effect of the gaseous opacities including H_2 (CIA), H_2O, CH_4, and K I. Although the UCMs are semi-empirical models based on a simple assumption that thin dust clouds form in the region of T_{cr} < T < T_{cond} (T_{cr} = 1800K is an only empirical parameter while T_{cond} about 2000K is fixed by the thermodynamical data), the major observations including the overall SEDs as well as the strengths of the major spectral features are consistently accounted for throughout L and T dwarfs. In view of the formidable complexities of the cloud formation, we hope that our UCM can be of some use as a guide for future modelings of the ultracool dwarfs as well as for interpretation of observed data of L and T dwarfs.Comment: 43 pages, 13 figures, to appear in Astrophys. J. (May 20, 2004) Some minor corrections including the address of our web site, which is now read

An adversarial optimization approach to efficient outlier removal

This paper proposes a novel adversarial optimization approach to efficient outlier removal in computer vision. We characterize the outlier removal problem as a game that involves two players of conflicting interests, namely, optimizer and outlier. Such an adversarial view not only brings new insights into various existing methods, but also gives rise to a general optimization framework that provably unifies them. Under the proposed framework, we develop a new outlier removal approach that is able to offer a much needed control over the trade-off between reliability and speed, which is otherwise not available in previous methods. The proposed approach is driven by a mixed-integer minmax (convex-concave) optimization process. Although a minmax problem is generally not amenable to efficient optimization, we show that for some commonly used vision objective functions, an equivalent Linear Program reformulation exists. We demonstrate our method on two representative multiview geometry problems. Experiments on real image data illustrate superior practical performance of our method over recent techniques.Jin Yu, Anders Eriksson, Tat-Jun Chin, David Suterhttp://www.iccv2011.org

The fate of planetesimals formed at planetary gap edges

The presence of rings and gaps in protoplanetary discs are often ascribed to planet-disc interactions, where dust and pebbles are trapped at the edges of planetary induced gas gaps. Recent work has shown that these are likely sites for planetesimal formation via the streaming instability. Given the large amount of planetesimals that potentially form at gap edges, we address the question of their fate and ability to radially transport solids in protoplanetary discs. We perform a series of N-body simulations of planetesimal orbits, taking into account the effect of gas drag and mass loss via ablation. We consider two planetary systems: one akin to the young Solar System, and another one inspired by HL Tau. In both systems, the close proximity to the gap-opening planets results in large orbital excitations, causing the planetesimals to leave their birth locations and spread out across the disc soon after formation. Planetesimals that end up on eccentric orbits interior of 10au experience efficient ablation, and lose all mass before they reach the innermost disc region. In our nominal Solar System simulation with $\dot{M}_0=10^{-7}\, M_{\odot}\, \textrm{yr}^{-1}$ and $\alpha=10^{-2}$, we find that 70% of the initial planetesimal mass has been ablated after 500kyr. The ablation rate in HL Tau is lower, and only 11% of the initial planetesimal mass has been ablated after 1Myr. The ablated material consist of a mixture of solid grains and vaporized ices, where a large fraction of the vaporized ices re-condense to form solid ice. Assuming that the solids grow to pebbles in the disc midplane, this results in a pebble flux of $\sim 10-100\,M_{\oplus}\textrm{Myr}^{-1}$ through the inner disc. Our results demonstrate that scattered planetesimals can carry a significant flux of solids past planetary-induced gaps in young and massive protoplanetary discs.Comment: Accepted for publication in A&

Si/SiGe quantum dot with superconducting single-electron transistor charge sensor

We report a robust process for fabrication of surface-gated Si/SiGe quantum dots (QDs) with an integrated superconducting single-electron transistor (S-SET) charge sensor. A combination of a deep mesa etch and AlOx backfill is used to reduce gate leakage. After the leakage current is suppressed, Coulomb oscillations of the QD and the current-voltage characteristics of the S-SET are observed at a temperature of 0.3 K. Coupling of the S-SET to the QD is confirmed by using the S-SET to perform sensing of the QD charge state.Comment: 4 pages, 3 figure