82,700 research outputs found
Photo-z optimization for measurements of the BAO radial scale
No full textBaryon Acoustic Oscillations (BAO) in the radial direction offer a method to directly measure the Universe expansion history, and to set limits to space curvature when combined to the angular BAO signal. In addition to spectroscopic surveys, radial BAO might be measured from accurate enough photometric redshifts obtained with narrow-band filters. We explore the requirements for a photometric survey using Luminous Red Galaxies (LRG) to competitively measure the radial BAO signal and discuss the possible systematic errors of this approach. Using the LRG spectra obtained from SDSS, we find that the optimal system consists of similar to 30 filters of width Delta lambda/lambda similar to 0:02. A S/N > 20 is generally necessary at the filters on the red side of the Balmer-break to reach the target photometric accuracy sigma(z) = 0.003(1 + z) for measuring radial BAO. The presence of outliers can significantly degrade this: in any practical application, being able to efficiently remove outliers may require ancillary observations. We estimate that a 5-year survey in a dedicated telescope with etendue in excess of 60 m(2) deg(2) would be necessary to obtain a high enough density of galaxies to measure the radial BAO with shot noise smaller than cosmic variance upto z = 0.85. We conclude that spectroscopic surveys have a superior performance than photometric ones for measuring BAO in the radial direction
Obtenção, caracterização físico química de vidros e vitro-cerâmicos baseados no sistema Li2-ZrO2-BaO-SiO2
Full text linkDissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Curso de Pós-Graduação em QuímicaNeste trabalho encontra-se descrita a preparação de vidros e vitro-cerâmicos de composição 29 % Li2O - 1% ZrO2 - x% BaO - (70 - x %) SiO2, onde x = 0, 2, 3, 5, e 6 % em mol de BaO, obtidos pelo método clássico de fusão. Os materiais foram caracterizados por Difração de Raios-X, Espectroscopia Raman, Espectroscopia no Infravermelho, Espectroscopia de Fotoelétrons Excitados por Raio-X, Microscopia Eletrônica de Varredura e Análise Térmica Diferencial. Determinaram-se o mecanismo e a cinética de cristalização dos vidros, além das propriedades físico-químicas microdureza e durabilidade química
A New Probe of the High-z BAO scale: BAO tomography With CMB LIM-Nulling Convergence
Full text linkStandard rulers such as the baryon acoustic oscillation (BAO) scale serve as
workhorses for precision tests of cosmology, enabling distance measurements
that probe the geometry and expansion history of our Universe. Aside from BAO
measurements from the cosmic microwave background (CMB), most standard ruler
techniques operate at relatively low redshifts and depend on biased tracers of
the matter density field. In a companion paper, we explored the scientific
reach of nulling estimators, where CMB lensing convergence maps are
cross-correlated with linear combinations of similar maps from line intensity
mapping (LIM) to precisely null out the low-redshift contributions to CMB
lensing. We showed that nulling estimators can be used to constrain the high
redshift matter power spectrum and showed that this spectrum exhibits
discernible BAO features. Here we propose using these features as a standard
ruler at high redshifts that does not rely on biased tracers. Forecasting such
a measurement at , we find that next-generation instruments will be
able to constrain the BAO scale to percent-level precision at , while
our futuristic observing scenario can constrain the BAO scale to
precision. This constitutes a fundamentally new kind of BAO measurement during
early epochs in our cosmic history.Comment: 6 pages, 4 figures. arXiv admin note: text overlap with
arXiv:2309.0647
Manifolds associated with (Z(2))(n+1)-colored regular graphs
No full textIn this article we describe a canonical way to expand a certain kind of (Z(2))(n+1)-colored regular graphs into closed n-manifolds by adding cells determined by the edge-colorings inductively. We show that every closed combinatorial n-manifold can be obtained in this way. When n <= 3, we give simple equivalent conditions for a colored graph to admit an expansion. In addition, we show that if a (Z(2))(n+1)-colored regular graph admits an n-skeletal expansion, then it is realizable as the induced graph of an (n + 1)-dimensional closed (Z(2))(n+1)-manifold.Mathematics, AppliedMathematicsSCI(E)1ARTICLE1121-1492
Estudo da cristalização de vitro-cerâmicos em sistema LhO-BaO-SIO2 na presença de diferentes agentes nucleantes
Full text linkTCC (graduação) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Curso de Química.A preparação e caracterização de vitro-cerâmicos de composição 30Li20 : 5BaO : (6 -xA )Si02, onde AN = agente nucIeante, sendo utilizados os seguintes óxidos: Zr02 (x = 1 %) Nb20 S (x = 1 %), V20 S (x = 2%) e Ti02 (x = 5%) em massa, é descrita. Os vitro-cerâmicos foram fundidos em cadinhos de alumina à 1100C por três horas e submetidos a um tratamento térmico á temperatura de 550, 650 e 750°C por uma hora. A caracterização foi feita por análise Térmica Diferencial (DTA), Difração de raio-X (DRX), Microscopia Eletrônica de varredura (MEV), Espectroscopia Raman e no Infravermelho, sendo também determinadas propriedade como Microdureza, Densidade e Volume Molar. Os resultados experimentais mostraram que uma mudança no agente nucleante (Zr02,Nb20 S V20 s e Ti02) confere ao material propriedades distintas. Essas diferenças podem ser encontradas na dureza, nos tipos de fases cristalinas, morfologia, densidade, temperatura de transição vítrea e de cristalização dos sólidos estudados. Ao submeter as diferentes amostras ao tratamento térmico observa-se uma maior dureza das mesmas, sendo que a amostra que apresentou melhor resultado com relação a dureza foi a que usou Nb20 S como AN. Os valores de microdureza estão relacionados com as fase cri talin s presentes nos materiais e a presença de Li2Si03, observados por DRX, contribuiu para o aum nto da dureza do material. A morfologia da superfície das amostras pode ser observada por MEV onde nota-se a presença de fases cristalinas distintas nas amostras GC-Nb e GC-Ti
Combined tracer analysis for DESI 2024 BAO
No full textInternational audienceThis paper demonstrates how the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1) and future baryon acoustic oscillations (BAO) analyses can optimally combine overlapping tracers (galaxies of distinct types) in the same redshift range. We make a unified catalog of Luminous Red Galaxies (LRGs) and Emission Line Galaxies (ELGs) in the redshift range 0.8 < z < 1.1 and investigate the impact on the BAO constraints. DESI DR1 contains ~30% of the final DESI LRG sample and less than 25% of the final ELG sample, and the combination of LRGs and ELGs increases the number density and reduces the shot noise. We developed a pipeline to merge the overlapping tracers using galaxy bias as an approximately optimal weight and tested the pipeline on a suite of Abacus simulations, calibrated on the final version of the DESI Early Data Release. When applying our pipeline to the DESI DR1 catalog, we find an improvement in the BAO constraints of 11% for and ~7.0% for consistent with our findings in mock catalogs. Our analysis was integrated into the DESI DR1 BAO analysis to produce the LRG+ELG result in the 0.8 < z < 1.1 redshift bin, which provided the most precise BAO measurement from DESI DR1 with a 0.86% constraint on the BAO distance scale and a detection of the isotropic BAO feature
BAO angular scale at
No full textAims. We measure the transverse baryon acoustic oscillations (BAO) signal in the local Universe using a sample of blue galaxies from the Sloan Digital Sky Survey (SDSS) survey as a cosmological tracer.
Methods. The method is weakly dependent on a cosmological model and is suitable for 2D analyses in thin redshift bins to investigate the SDSS data in the interval z ∈ [0.105, 0.115].
Results. We detect the transverse BAO signal θBA
Combined tracer analysis for DESI 2024 BAO
No full textInternational audienceThis paper demonstrates how the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1) and future baryon acoustic oscillations (BAO) analyses can optimally combine overlapping tracers (galaxies of distinct types) in the same redshift range. We make a unified catalog of Luminous Red Galaxies (LRGs) and Emission Line Galaxies (ELGs) in the redshift range 0.8 < z < 1.1 and investigate the impact on the BAO constraints. DESI DR1 contains ~30% of the final DESI LRG sample and less than 25% of the final ELG sample, and the combination of LRGs and ELGs increases the number density and reduces the shot noise. We developed a pipeline to merge the overlapping tracers using galaxy bias as an approximately optimal weight and tested the pipeline on a suite of Abacus simulations, calibrated on the final version of the DESI Early Data Release. When applying our pipeline to the DESI DR1 catalog, we find an improvement in the BAO constraints of 11% for and ~7.0% for consistent with our findings in mock catalogs. Our analysis was integrated into the DESI DR1 BAO analysis to produce the LRG+ELG result in the 0.8 < z < 1.1 redshift bin, which provided the most precise BAO measurement from DESI DR1 with a 0.86% constraint on the BAO distance scale and a detection of the isotropic BAO feature
Combined tracer analysis for DESI 2024 BAO
No full textInternational audienceThis paper demonstrates how the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1) and future baryon acoustic oscillations (BAO) analyses can optimally combine overlapping tracers (galaxies of distinct types) in the same redshift range. We make a unified catalog of Luminous Red Galaxies (LRGs) and Emission Line Galaxies (ELGs) in the redshift range 0.8 < z < 1.1 and investigate the impact on the BAO constraints. DESI DR1 contains ~30% of the final DESI LRG sample and less than 25% of the final ELG sample, and the combination of LRGs and ELGs increases the number density and reduces the shot noise. We developed a pipeline to merge the overlapping tracers using galaxy bias as an approximately optimal weight and tested the pipeline on a suite of Abacus simulations, calibrated on the final version of the DESI Early Data Release. When applying our pipeline to the DESI DR1 catalog, we find an improvement in the BAO constraints of 11% for and ~7.0% for consistent with our findings in mock catalogs. Our analysis was integrated into the DESI DR1 BAO analysis to produce the LRG+ELG result in the 0.8 < z < 1.1 redshift bin, which provided the most precise BAO measurement from DESI DR1 with a 0.86% constraint on the BAO distance scale and a detection of the isotropic BAO feature
Dynamics of space charge distributions in polymer LEDs studied by means of an electro-optic technique
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