4,399 research outputs found
Higher order initial conditions with massive neutrinos
No full textThe discovery that neutrinos have mass has important consequences for cosmology. The main effect of massive neutrinos is to suppress the growth of cosmic structure on small scales. Such growth can be accurately modelled using cosmological N-body simulations, but doing so requires accurate initial conditions (ICs). There is a trade-off, especially with first-order ICs, between truncation errors for late starts and discreteness and relativistic errors for early starts. Errors can be minimized by starting simulations at late times using higher order ICs. In this paper, we show that neutrino effects can be absorbed into scale-independent coefficients in higher order Lagrangian perturbation theory (LPT). This clears the way for the use of higher order ICs for massive neutrino simulations. We demonstrate that going to higher order substantially improves the accuracy of simulations. To match the sensitivity of surveys like DESI and Euclid, errors in the matter power spectrum should be well below 1 per cent. However, we find that first-order Zel’dovich ICs lead to much larger errors, even when starting as early as z = 127, exceeding 1 per cent at z = 0 for k > 0.5 Mpc^−1 for the power spectrum and k > 0.1 Mpc^−1 for the equilateral bispectrum in our simulations. Ratios of power spectra with different neutrino masses are more robust than absolute statistics, but still depend on the choice of ICs. For all statistics considered, we obtain 1 per cent agreement between 2LPT and 3LPT at z = 0.The discovery that neutrinos have mass has important consequences for cosmology. The main effect of massive neutrinos is to suppress the growth of cosmic structure on small scales. Such growth can be accurately modelled using cosmological -body simulations, but doing so requires accurate initial conditions (ICs). There is a trade-off, especially with first-order ICs, between truncation errors for late starts and discreteness and relativistic errors for early starts. Errors can be minimized by starting simulations at late times using higher-order ICs. In this paper, we show that neutrino effects can be absorbed into scale-independent coefficients in higher-order Lagrangian perturbation theory (LPT). This clears the way for the use of higher-order ICs for massive neutrino simulations. We demonstrate that going to higher order substantially improves the accuracy of simulations. To match the sensitivity of surveys like DESI and Euclid, errors in the matter power spectrum should be well below 1%. However, we find that first-order Zel'dovich ICs lead to much larger errors, even when starting as early as , exceeding 1% at for for the power spectrum and for the equilateral bispectrum in our simulations. Ratios of power spectra with different neutrino masses are more robust than absolute statistics, but still depend on the choice of ICs. For all statistics considered, we obtain 1% agreement between 2LPT and 3LPT at
A Physical Distance Indicator for Spiral Galaxies and the Determination of H0
No full textWe consider the effect of dark matter on the Tully-Fisher relation for spiral galaxies. We show that a significant fraction of the scatter in this relation could stem from a systematic dependence of the ratio of dark to luminous mass on luminosity. The dynamical effect of the dark matter can be accounted for once a mass decomposition procedure, based on photometry and rotation curve data, has been carried out. We show that the contribution to the circular velocity from the luminous disc alone correlates better with luminosity than does the total velocity, which contains an additional contribution from the dark halo. This correlation is closer to a linear law, has less scatter, and is subject to fewer biases than the conventional Tully-Fisher relation. As an illustration, we use two different sets of distance moduli for a sample of local galaxies to calibrate our relation. Applying Teerikorpi's prescription to correct for Malmquist bias, we then derive values of the Hubble constant of H0 = 61 +/- 5 and 66 +/- 6 km s-1 Mpc-1 for our two sets of calibrators respectively
PiLa-CS Professional Learning Community - Workshop 2 Resources
No full textDuring the Summer of 2021 and 2022, the Participating in Literacies and Computer Science (PiLa-CS) Research Practice Partnership convened and supported a community of practice to learn more about how to enable better CS teaching for emergent bilinguals. These are materials from Workshop 2 of the PLC.Sponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
Translanguaging Pedagogy in CS Ed
No full textEpisode 3: Translanguaging pedagogy in CS Education
This video looks at how multilingual students already use translanguaging in their computer science classes and discusses how CS educators can further support them with translanguaging pedagogy, a framework that prompts teachers to consider their stance, design, and shifts.
Featuring team members from Participating in Literacies and Computer Science (PiLa-CS), https://www.pila-cs.orgEpisode 3: Translanguaging pedagogy in CS Education
This video looks at how multilingual students already use translanguaging in their computer science classes and discusses how CS educators can further support them with translanguaging pedagogy, a framework that prompts teachers to consider their stance, design, and shifts.
Featuring team members from Participating in Literacies and Computer Science (PiLa-CS), https://www.pila-cs.orgSponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
PiLa-CS Professional Learning Community - Design Journal Template
No full textDuring the Summer of 2021 and 2022, the Participating in Literacies and Computer Science (PiLa-CS) Research Practice Partnership convened and supported a community of practice to learn more about how to enable better CS teaching for emergent bilinguals. These are materials from from the PLC for a Design Journal to act as a planing template for teachers.Sponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
Arizona Then and Now: Exploring Arizona's Five Cs Through Photography
No full textabstract: Arizona Then and Now: Exploring Arizona's Five Cs Through Photography is a photographic exploration of the evolution of Arizona's five Cs: cotton, copper, citrus, cattle, and climate. This project first looks to the past to see how these five elements shaped the state of Arizona. Photographs were taken across the valley of these elements, or lack thereof, discovering what Arizona has transformed into in the process. Each chapter of the book begins with a brief history of the element focused on in that chapter, followed by an analytical thought about the photographs taken and how the element has evolved. Each chapter shows two historical photographs followed by a series of photographs taken during the project that the author thought depicted what is seen today. The book ends on a final positive note about how the five Cs are not dead, but soon could be completely taken over. This project was a way for a non-art major to explore the state that she grew up while also challenging herself by more than just taking pictures. The photographs displayed in the book depict a sampling of what the author saw that is left of the five Cs
IR-improved DGLAP-CS QCD parton showers in Pythia8
No full textAbstractWe introduce the recently developed IR-improved DGLAP-CS theory into the showers in Pythia8, as this Monte Carlo event generator is in wide use at LHC. We show that, just as it was true in the IR-improved shower Monte Carlo Herwiri, which realizes the IR-improved DGLAP-CS theory in the Herwig6.5 environment, the soft limit in processes such as single heavy gauge boson production is now more physical in the IR-improved DGLAP-CS theory version of Pythia8. This opens the way to one’s getting a comparison between the actual detector simulations for some of the LHC experiments between IR-improved and unimproved showers as Pythia8 is used in detector simulations at LHC whereas Herwig6.5, the environment of the only other IR-improved DGLAP-CS QCD MC in the literature, Herwiri1.031, is not any longer so used. Our achieving the availability of the IR-improved DGLAP-CS Pythia8 then is an important step in the further development of the LHC precision theory program under development by the author and his collaborators
What CS Ed Can Offer Bi/Multilinguals
No full textEpisode 4: What can CS offer multilingual learners?
This video discusses how computer science education can benefit multilingual learners. You will meet a middle school ENL (English as a New Language) teacher who successfully incorporated both translanguaging pedagogy and CS education into her classroom, leading to a memorable experience for one of her students.
Featuring team members from Participating in Literacies and Computer Science (PiLa-CS), https://www.pila-cs.orgEpisode 4: What can CS offer multilingual learners?
This video discusses how computer science education can benefit multilingual learners. You will meet a middle school ENL (English as a New Language) teacher who successfully incorporated both translanguaging pedagogy and CS education into her classroom, leading to a memorable experience for one of her students.
Featuring team members from Participating in Literacies and Computer Science (PiLa-CS), https://www.pila-cs.orgSponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
The luminosity dependence of clustering and higher order correlations in the PSCz survey
No full textWe investigate the spatial clustering of galaxies in the PSCz galaxy redshift survey, as revealed by the two-point correlation function, the luminosity mark correlations and the moments of counts-in-cells. We construct volume-limited subsamples at different depths and search for a luminosity dependence of the clustering pattern. We find no statistically significant effect in either the two-point correlation function or the mark correlations and so we take each subsample (of different characteristic luminosity) as representing the same statistical process. We then carry out a counts-in-cells analysis of the volume-limited subsamples, including a rigorous error calculation based on the recent theory of Szapudi, Colombi & Bernardeau. In this way, we derive the best estimates to date of the skewness and kurtosis of IRAS galaxies in redshift space. Our results agree well with previous measurements in both the parent angular catalogue and the derived redshift surveys. This is in contrast with smaller, optically selected surveys, where there is a discrepancy between the redshift space and projected measurements. Predictions from cold dark matter theory, obtained using the recent semi-analytical model of galaxy formation of Benson et al., provide an excellent description of our clustering data
Microporous cesium salts of tetravalent Keggin-type polyoxotungstates Cs-4[SiW12O40], Cs-4[PW11O39(Sn-n-C4H9)], and Cs-4[PW11O39(Sn-OH)] and their adsorption properties
No full textMicroporous cesium salts of modified and unmodified tetravalent Keggin-type polyoxometalates, including Cs-4[SiW12O40], Cs-4[PW11O39(Sn-n-C4H9)], and Cs-4[PW11O39(Sn-OH)], were synthesized. The crystalline structures, which had body-centered cubic (bcc) arrangements, the lattice constants, and the pore-size distributions of the three Cs salts were similar, regardless of the presence or absence and types of functional groups introduced. The Cs salts had only micropores and no mesopores. The micropore size distributions were determined from adsorption isotherms of Ar, which showed a sharp peak at 0.59 nm and a shoulder at 0.62 nm. The fractions of the external surface areas to the total surface areas of the Cs salts were less than 6%. It is plausible that the micropores originate from the heteropoly anion defects in the crystallite, which form to avoid mismatches in the Cs+/(heteropoly anion) ratio required for charge balance (=4) and for a bcc structure (=3). The surface of the Cs salt introduced with n-butyl groups was hydrophobic, although the surface density of the n-butyl groups was low. On the other hand, the hydroxyl groups present on the surface of Cs-4[PW11O39(Sn-OH)] had little effect on the adsorption of water, methanol, ethanol, and hexane but a great impact on that for benzene due to the interactions between the -OH groups and the aromatic rings (-OH center dot center dot center dot pi). (C) 2013 Elsevier Inc. All rights reserved
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