Using the Big Ideas in Cosmology to Teach College Students

Recent advances in our understanding of the Universe have revolutionized our view of its structure, composition and evolution. However, these new ideas have not necessarily been used to improve the teaching of introductory astronomy students. In this project, we have conducted research into student understanding of cosmological ideas so as to develop effective web-based tools to teach basic concepts important to modern cosmology. The tools are intended for use at the introductory college level. Our research uses several instruments, including open-ended and multiple choice surveys conducted at multiple institutions, as well as interviews and course artifacts at one institution, to ascertain what students know regarding modern cosmological ideas, what common misunderstandings and misconceptions they entertain, and what sorts of materials can most effectively overcome student difficulties in learning this material. These data are being used to create a suite of interactive, web-based tutorials that address the major ideas in cosmology using real data. Having students engage with real data is a powerful means to help students overcome certain misconceptions. Students master the scientific concepts and reasoning processes that lead to our current understanding of the universe through interactive tasks, prediction and reflection, experimentation, and model building.Comment: 2012 Fermi Symposium proceedings - eConf C12102

Expansion, Geometry, and Gravity

In general-relativistic cosmological models, the expansion history, matter content, and geometry are closely intertwined. In this brief paper, we clarify the distinction between the effects of geometry and expansion history on the luminosity distance. We show that the cubic correction to the Hubble law, measured recently with high-redshift supernovae, is the first cosmological measurement, apart from the cosmic microwave background, that probes directly the effects of spatial curvature. We illustrate the distinction between geometry and expansion with a toy model for which the supernova results already indicate a curvature radius larger than the Hubble distance.Comment: 4 pages, 1 color figur

Cosmological Imprint of an Energy Component with General Equation of State

We examine the possibility that a significant component of the energy density of the universe has an equation-of-state different from that of matter, radiation or cosmological constant ($\Lambda$). An example is a cosmic scalar field evolving in a potential, but our treatment is more general. Including this component alters cosmic evolution in a way that fits current observations well. Unlike $\Lambda$, it evolves dynamically and develops fluctuations, leaving a distinctive imprint on the microwave background anisotropy and mass power spectrum.Comment: revised version, with added references, to appear in Phys. Rev. Lett. (4 pages Latex, 2 postscript figures

Observations of the Cosmic Microwave Background and Implications for Cosmology and Large Scale Structure

Observations of the Cosmic Microwave Background (CMB) are discussed, with particular emphasis on current ground-based experiments and on future satellite, balloon and interferometer experiments. Observational techniques and the effects of contaminating foregrounds are highlighted. Recent CMB data is used with large scale structure (LSS) data to constrain cosmological parameters and the complementary nature of CMB, LSS and supernova distance data is emphasized.Comment: 23 pages, 10 figures. Phil. Trans. R. Soc. Lond. A., 1998, in pres

Provenance, protolith and metamorphic ages of jadeite-bearing orthogneiss and host paragneiss at Tavagnasco, the Sesia Zone, Lower Aosta Valley, Italy

An eclogite-facies orthogneiss and host paragneiss from a quarry near Tavagnasco in the Lower Aosta Valley were studied in order to refine the protolith, provenance and metamorphic ages of the Eclogitic Micaschist Complex of the Sesia Zone. The orthogneiss contains jadeite with quartz + phengite + K-feldspar ± garnet + rutile + zircon, whereas the paragneiss hosts garnet + jadeite + phengite ± glaucophane + epidote + rutile + quartz. Phase diagram modeling of two representative samples yields minimum equilibration conditions of 550 ± 50 ∘C and 18 ± 2 kbar. Cathodoluminescence images of zircon from the orthogneiss show oscillatory-zoned cores that are embayed and overgrown by complex, oscillatory-zoned rims. Four concordant secondary ion mass spectrometry analyses from the cores give a weighted mean 206Pb / 238U age of 457 ± 5 Ma. The cores have Th/U = 0.1 and negative Eu anomalies indicative of an igneous protolith, which we interpret to have crystallized in the Ordovician at 780 ∘C, based on Ti-in-zircon measurements. Zircon rims yield a range of 206Pb / 238U dates from 74 to 86 Ma, and four concordant analyses define a weighted mean 206Pb / 238U age of 78 ± 2 Ma. The rims are interpreted to have grown in the eclogite facies based on their lower Th/U (0.01), less negative Eu anomalies and steeper heavy rare earth element (HREE) patterns at &lt;600 ∘C. The paragneiss yielded a detrital zircon population with major peaks at 575–600, 655 and 765 Ma; minor older components; and a maximum depositional age of approximately 570 Ma. The prominent Neoproterozoic zircon population and Ediacaran depositional age suggest derivation from the Gondwana margin. The metamorphic zircon is consistent with the oldest eclogite-facies event in the Sesia Zone; it does not show evidence of multiple periods of rim growth or any pre-Alpine (e.g., Variscan) metamorphism.</p

Effects of Increasing Zn from Zinc Sulfate or Zinc Hydroxychloride on Finishing Pig Growth Performance, Carcass Characteristics, and Economic Return

A total of 1,008 pigs [TR4 (Fast × L02 PIC; initially 70.6 lb BW)] were used in a 103-d growth study to determine the effects of Zn source and level on finishing pig growth performance, carcass characteristics, and economic return. The 6 dietary treatments were arranged as a 2 × 3 factorial with main effects of Zn source (ZnSO4; Agrium Advance Technology, Loveland, CO, or Zn hydroxychloride; Intellibond-Z®; Micronutrients, Indianapolis, IN) and level (50, 100, or 150 ppm added Zn). The trace mineral premix was formulated to contain no added Zn. There were 21 pigs per pen and 8 pens per treatment. Overall, there was no effect of Zn source for growth performance criteria observed. Increasing added Zn maximized (quadratic, P = 0.007) ADG when diets contained 100 ppm Zn; however, F/G tended to worsen (source × level, linear, P = 0.068) as Zn from Zn hydroxychloride increased, but was relatively unchanged when pigs were fed increasing Zn from ZnSO4. Carcass yield increased (linear, P = 0.027) as Zn level increased. Pigs fed diets with Zn hydroxychloride had heavier (P = 0.041) HCW, and increased HCW ADG (P = 0.036) than those fed ZnSO4. Hot carcass weight and HCW ADG were maximized (quadratic, P ≤ 0.006) when diets contained 100 ppm Zn. There was a tendency for income over feed cost (IOFC) to be maximized when pigs were fed diets with 100 ppm Zn when economic analysis was calculated on both a constant day (quadratic, P = 0.059) and constant carcass weight (quadratic, P = 0.070) basis, respectively.In summary, these results suggest that a total of 100 ppm added Zn is adequate to maximize ADG, HCW, HCW ADG, and IOFC, but F/G worsened as Zn level increased. Zinc source did not affect growth performance; however, pigs fed Zn hydroxychloride had increased HCW and HCW ADG compared to those fed ZnSO4

New CMB Power Spectrum Constraints from MSAMI

We present new cosmic microwave background (CMB) anisotropy results from the combined analysis of the three flights of the first Medium Scale Anisotropy Measurement (MSAM1). This balloon-borne bolometric instrument measured about 10 square degrees of sky at half-degree resolution in 4 frequency bands from 5.2 icm to 20 icm with a high signal-to-noise ratio. Here we present an overview of our analysis methods, compare the results from the three flights, derive new constraints on the CMB power spectrum from the combined data and reduce the data to total-power Wiener-filtered maps of the CMB. A key feature of this new analysis is a determination of the amplitude of CMB fluctuations at $\ell \sim 400$. The analysis technique is described in a companion paper by Knox.Comment: 9 pages, 6 included figure

Anisotropy in the Cosmic Microwave Background at Degree Angular Scales: Python V Results

Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m off-axis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37-45 GHz in two frequency bands. With a 0.91 deg x 1.02 deg beam the instrument fully sampled 598 deg^2 of sky, including fields measured during the previous four seasons of Python observations. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background, we place constraints on the angular power spectrum of fluctuations in eight multipole bands up to l ~ 260. The observed spectrum is consistent with both the COBE experiment and previous Python results. There is no significant contamination from known foregrounds. The results show a discernible rise in the angular power spectrum from large (l ~ 40) to small (l ~ 200) angular scales. The shape of the observed power spectrum is not a simple linear rise but has a sharply increasing slope starting at l ~ 150.Comment: 5 page

Scaling solutions in general non-minimal coupling theories

A class of generalized non-minimal coupling theories is investigated, in search of scaling attractors able to provide an accelerated expansion at the present time. Solutions are found in the strong coupling regime and when the coupling function and the potential verify a simple relation. In such cases, which include power law and exponential functions, the dynamics is independent of the exact form of the coupling and the potential. The constraint from the time variability of $G$, however, limits the fraction of energy in the scalar field to less than 4% of the total energy density, and excludes accelerated solutions at the present.Comment: 10 pages, 3 figures, accepted for publication in Phys. Rev.

Accelerating LSTM-based High-Rate Dynamic System Models

In this paper, we evaluate the use of a trained Long Short-Term Memory (LSTM) network as a surrogate for a Euler-Bernoulli beam model, and then we describe and characterize an FPGA-based deployment of the model for use in real-time structural health monitoring applications. The focus of our efforts is the DROPBEAR (Dynamic Reproduction of Projectiles in Ballistic Environments for Advanced Research) dataset, which was generated as a benchmark for the study of real-time structural modeling applications. The purpose of DROPBEAR is to evaluate models that take vibration data as input and give the initial conditions of the cantilever beam on which the measurements were taken as output. DROPBEAR is meant to serve an exemplar for emerging high-rate "active structures" that can be actively controlled with feedback latencies of less than one microsecond. Although the Euler-Bernoulli beam model is a well-known solution to this modeling problem, its computational cost is prohibitive for the time scales of interest. It has been previously shown that a properly structured LSTM network can achieve comparable accuracy with less workload, but achieving sub-microsecond model latency remains a challenge. Our approach is to deploy the LSTM optimized specifically for latency on FPGA. We designed the model using both high-level synthesis (HLS) and hardware description language (HDL). The lowest latency of 1.42 $\mu$S and the highest throughput of 7.87 Gops/s were achieved on Alveo U55C platform for HDL design.Comment: Accepted at 33rd International Conference on Field-Programmable Logic and Applications (FPL