Near-extremizers of Young's inequality for discrete groups

Those functions which nearly extremize Young's convolution inequality are characterized for discrete groups which have no nontrivial finite subgroups. Near-extremizers of the Hausdorff-Young inequality are characterized for Z^d

Singular locus of instanton sheaves on P3\mathbb{P}^3

We prove that the singular locus of a rank 2 instanton sheaf $E$ on $\mathbb{P}^3$ which is not locally free has pure dimension 1. Moreover, we also show that the dual and double dual of $E$ are isomorphic locally free instanton sheaves, and that the sheaves \mathcal{E}xt^1(E,\mathcal{O}_{\mathbb{P}^3) and $E^{\vee\vee}/E$ are rank $0$ instantons. We also provide explicit examples of instanton sheaves of rank $3$ and $4$ illustrating that all of these claims are false for higher rank instanton sheaves.Comment: 14 page

CompLex: A New Corpus for Lexical Complexity Prediction from Likert Scale Data

Predicting which words are considered hard to understand for a given target population is a vital step in many NLP applications such as text simplification. This task is commonly referred to as Complex Word Identification (CWI). With a few exceptions, previous studies have approached the task as a binary classification task in which systems predict a complexity value (complex vs. non-complex) for a set of target words in a text. This choice is motivated by the fact that all CWI datasets compiled so far have been annotated using a binary annotation scheme. Our paper addresses this limitation by presenting the first English dataset for continuous lexical complexity prediction. We use a 5-point Likert scale scheme to annotate complex words in texts from three sources/domains: the Bible, Europarl, and biomedical texts. This resulted in a corpus of 9,476 sentences each annotated by around 7 annotators.Comment: Proceedings of the 1st Workshop on Tools and Resources to Empower People with REAding DIfficulties (READI). pp. 57-6

Fostering Computational Thinking

Students taking introductory physics are rarely exposed to computational modeling. In a one-semester large lecture introductory calculus-based mechanics course at Georgia Tech, students learned to solve physics problems using the VPython programming environment. During the term 1357 students in this course solved a suite of fourteen computational modeling homework questions delivered using an online commercial course management system. Their proficiency with computational modeling was evaluated in a proctored environment using a novel central force problem. The majority of students (60.4%) successfully completed the evaluation. Analysis of erroneous student-submitted programs indicated that a small set of student errors explained why most programs failed. We discuss the design and implementation of the computational modeling homework and evaluation, the results from the evaluation and the implications for instruction in computational modeling in introductory STEM courses.Comment: 4 pages, 1 figure, Accepted to Proceedings of the 2011 Physics Education Research Conferenc

A Case Study: Novel Group Interactions through Introductory Computational Physics

With the advent of high-level programming languages capable of quickly rendering three-dimensional simulations, the inclusion of computers as a learning tool in the classroom has become more prevalent. Although work has begun to study the patterns seen in implementing and assessing computation in introductory physics, more insight is needed to understand the observed effects of blending computation with physics in a group setting. In a newly adopted format of introductory calculus-based mechanics, called Projects and Practices in Physics, groups of students work on short modeling projects -- which make use of a novel inquiry-based approach -- to develop their understanding of both physics content and practice. Preliminary analyses of observational data of groups engaging with computation, coupled with synchronized computer screencast, has revealed a unique group interaction afforded by the practices specific to computational physics -- problem debugging

Teaching Computation in Introductory Physics using Complex Problems

Computation is a central aspect of modern science and engineering work, and yet, computational instruction has yet to fully pervade university STEM curricula. In physics, we have begun to integrate computation into our courses in a variety of ways. Here, we discuss a method for integrating computation into calculus-based mechanics where the lecture and laboratory for the course are decoupled. At Michigan State University, we have developed a "lecture" course, called "Projects and Practices in Physics", where science and engineering students solve complex problems in groups of four using analytical and computational techniques. In this paper, we provide details on the computational instruction, activities, and assessment used to teach these introductory students how to model motion using VPython.Comment: 10 pages, 3 figure

Tuning the electronic hybridization in the heavy fermion cage compound YbFe2_{2}Zn20_{20} with Cd-doping

Tuning of the electronic properties of heavy fermion compounds by chemical substitutions provides excellent opportunities to further understand the physics of hybridized ions in crystal lattices. Here we present an investigation on the effects of Cd doping in flux-grown single crystals of the complex intermetallic cage compound YbFe$_{2}$Zn$_{20}$, that has been described as a heavy fermion with Sommerfeld coefficient of 535 mJ/mol.K$^{2}$. Substitution of Cd for Zn disturbs the system by expanding the unit cell and, in this case, the size of the Zn cages that surround Yb and Fe. With increasing amount of Cd, the hybridization between Yb $4f$ electrons and the conduction electrons is weakened, as evidenced by a decrease in the Sommerfeld coefficient, which should be accompanied by a valence shift of the Yb$^{3+}$ due to the negative chemical pressure effect. This scenario is also supported by the low temperature dc-magnetic susceptibility, that is gradually suppressed and evidences an increment of the Kondo temperature, based on a shift to higher temperatures of the characteristic broad susceptibility peak. Furthermore, the DC resistivity decreases with the isoelectronic Cd substitution for Zn, contrary to the expectation for an increasingly disordered system, and implying that the valence shift is not related to charge carrier doping. The combined results demonstrate excellent complementarity between positive physical pressure and negative chemical pressure, and point to a rich playground for exploring the physics and chemistry of strongly correlated electron systems in the general family of Zn$_{20}$ compounds, despite their structural complexity.Comment: J. Phys.: Cond. Mat. (accepted

Nonperturbative dynamical many-body theory of a Bose-Einstein condensate

A dynamical many-body theory is presented which systematically extends beyond mean-field and perturbative quantum-field theoretical procedures. It allows us to study the dynamics of strongly interacting quantum-degenerate atomic gases. The non-perturbative approximation scheme is based on a systematic expansion of the two-particle irreducible effective action in powers of the inverse number of field components. This yields dynamic equations which contain direct scattering, memory and ``off-shell'' effects that are not captured by the Gross-Pitaevskii equation. This is relevant to account for the dynamics of, e.g., strongly interacting quantum gases atoms near a scattering resonance, or of one-dimensional Bose gases in the Tonks-Girardeau regime. We apply the theory to a homogeneous ultracold Bose gas in one spatial dimension. Considering the time evolution of an initial state far from equilibrium we show that it quickly evolves to a non-equilibrium quasistationary state and discuss the possibility to attribute an effective temperature to it. The approach to thermal equilibrium is found to be extremely slow.Comment: 21 pages RevTeX, 12 figure

Requirements Engineering Practice and Problems in Agile Projects: Results from an International Survey

Requirements engineering (RE) is considerably different in agile development than in more traditional development processes. Yet, there is little empirical knowledge on the state of the practice and contemporary problems in agile RE. As part of a bigger survey initiative (Naming the Pain in Requirements Engineering), we build an empirical basis on such aspects of agile RE. Based on the responses of representatives from 92 different organisations, we found that agile RE concentrates on free-text documentation of requirements elicited with a variety of techniques. Often, traces between requirements and code are explicitly managed and also software testing and RE are aligned. Furthermore, continuous improvement of RE is performed due to intrinsic motivation. Important experienced problems include unclear requirements and communication flaws. Overall, we found that most organisations conduct RE in a way we would expect and that agile RE is in several aspects not so different from RE in other development processes

Anomalies and fluctuations of near-surface air temperature at Tianhuangping (Zhejiang), China, produced by the longest total solar eclipse of the 21st century under cloudy skies

We analyze the near-surface air temperature response, at three different heights over the ground, recorded by the Williams College expedition under meteorological conditions characterized by cloudy skies during the longest total solar eclipse of the 21st century on 22 July 2009, at Tianhuangping (Zhejiang), China. An analysis of the relationship between solar radiation and air temperature was made by applying a study previously published in which we evaluated the cloudiness contribution in estimating the impact on global solar radiation throughout this phenomenon at that site. The analysis of this response includes linear and absolute negative anomalies as well as fluctuations, which was undertaken through a statistical study to get information on the convection activity produced by the latter. The fluctuations generated by turbulence were studied by analyzing variance and residuals. The results, indicating a steady decrease and recovery of both perturbations, were consistent with those published by other studies for this total solar eclipse