21 research outputs found
Conceptual Maps and Integrated Experiments for Teaching/Learning Physics of Photonic Devices
AbstractThis paper presents the experimental approach and an example of using conceptual maps as a method based on constructivist mode of learning, teaching and researching knowledge of quantum Physics, using photonic devices. Understanding the Planck relationship, which links energy and frequency as a result of quantification of the energy, is a crucial step. It is one of the most famous examples of the corpuscular nature of light, which led to the development of quantum mechanics in the early 20th century, and whose explanation is still the standard in teaching Physics in high school. The paper also presents the verification of Einstein's theory and determination of Planck's constant using electroluminescent phenomenon for LEDs of different colours. Conceptual maps are a powerful tool not only for perceiving, representing and achieving knowledge, but also for creating new knowledge. It is essential helping students to understand that all concepts are somehow related to each other. Selecting cross-links as specific as possible and identifying the most appropriate linking words to connect concepts are crucial aims. CmapTools software tool can serve as a basis for a new kind of integration of Internet resources and all classroom experiences, inside Physics laboratories, and outside them. If it is used in conjunction with conceptual maps designed to support learning, it provides a new educational model
Cosmic void exclusion models and their impact on the distance scale measurements from large scale structure
Baryonic Acoustic Oscillations (BAOs) studies based on the clustering of
voids and matter tracers provide important constraints on cosmological
parameters related to the expansion of the Universe. However, modelling the
void exclusion effect is an important challenge for fully exploiting the
potential of these kind of analyses. We thus develop two numerical methods to
describe the clustering of cosmic voids. Neither model requires additional
cosmological information beyond that assumed within the galaxy de-wiggled
model. The models consist in power spectra whose performance we assess in
comparison to a parabolic model on both Patchy boxes and light-cones. Moreover,
we test their robustness against systematic effects and the reconstruction
technique. The void model power spectra and the parabolic model with a fixed
parameter provide strongly correlated values for the Alcock-Paczynski
() parameter, for boxes and light-cones likewise. The resulting
values - for all three models - are unbiased and their uncertainties
are correctly estimated. However, the numerical models show less variation with
the fitting range compared to the parabolic one. The Bayesian evidence suggests
that the numerical techniques are often favoured compared to the parabolic
model. Moreover, the void model power spectra computed on boxes can describe
the void clustering from light-cones as well as from boxes. The same void model
power spectra can be used for the study of pre- and post-reconstructed
data-sets. Lastly, the two numerical techniques are resilient against the
studied systematic effects. Consequently, using either of the two new void
models, one can more robustly measure cosmological parameters.Comment: 18 pages, 24 figure
Cosmic Void Baryon Acoustic Oscillation Measurement: Evaluation of Sensitivity to Selection Effects
Cosmic voids defined as a subset of Delaunay Triangulation (DT) circumspheres
have been used to measure the Baryon Acoustic Oscillations (BAO) scale;
providing tighter constraints on cosmological parameters when combined with
matter tracers. These voids are defined as spheres larger than a given radius
threshold, which is constant over the survey volume. However, the response of
these void tracers to observational systematics has not yet been studied. In
this work we analyse the response of void clustering to selection effects. We
find for the case of moderate (<20 per cent) incompleteness, void selection
based on a constant radius cut yields robust measurements. This is particularly
true for BAO-reconstructed galaxy samples, where large-scale void exclusion
effects are mitigated. Moreover, we observe for the case of severe (up to 90
per cent) incompleteness -- such as can be found at the edges of the radial
selection function -- that an accurate estimation of the void distribution is
necessary for unbiased clustering measurements. In addition, we find that
without reconstruction, using a constant threshold under these conditions
produces a stronger void exclusion effect that can affect the clustering on
large scales. A new void selection criteria dependent on the (local) observed
tracer density that maximises the BAO peak significance prevents the
aforementioned exclusion features from contaminating the BAO signal. Finally,
we verify, with large simulations including light cone evolution, that both
void sample definitions (local and constant) yield unbiased and consistent BAO
scale measurements.Comment: 16 pages, 16 figures. Accepted by MNRA
The completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological implications from multi-tracer BAO analysis with galaxies and voids
We construct cosmic void catalogues with the DIVE void finder upon SDSS BOSS
DR12 and eBOSS DR16 galaxy samples with BAO reconstruction applied, and perform
a joint BAO analysis using different types of galaxies and the corresponding
voids. The BAO peak is evident for the galaxy-galaxy, galaxy-void, and
void-void correlation functions of all datasets, including the ones cross
correlating luminous red galaxy and emission line galaxy samples. Two
multi-tracer BAO fitting schemes are then tested, one combining the galaxy and
void correlation functions with a weight applied to voids, and the other using
a single BAO dilation parameter for all clustering measurements of different
tracers. Both methods produce consistent results with mock catalogues, and on
average ~10 per cent improvements of the BAO statistical uncertainties are
observed for all samples, compared to the results from galaxies alone. By
combining the clustering of galaxies and voids, the uncertainties of BAO
measurements from the SDSS data are reduced by 5 to 15 per cent, yielding 0.9,
0.8, 1.1, 2.3, and 2.9 per cent constraints on the distance ,
at effective redshifts of 0.38, 0.51, 0.70, 0.77, and 0.85, respectively. When
combined with BAO measurements from SDSS MGS, QSO, and Ly samples, as
well as the BBN results, we obtain , , and
in the flat-CDM framework,
where the 1 uncertainties are around 6, 6, and 17 per cent smaller
respectively, compared to constraints from the corresponding anisotropic BAO
measurements without voids and LRG-ELG cross correlations.Comment: 33 pages, 30 figures, submitted to MNRA
DESI mock challenge: constructing DESI galaxy catalogues based on FastPM simulations
Together with larger spectroscopic surveys such as the Dark Energy Spectroscopic Instrument (DESI), the precision of large scale structure studies and thus the constraints on the cosmological parameters are rapidly improving. Therefore, one must buildrealistic simulations and robust covariance matrices. We build galaxy catalogues by applying a halo occupation distribution(HOD) model upon the FASTPM simulations, such that the resulting galaxy clustering reproduces high-resolution N-bodysimulations. While the resolution and halo finder are different from the reference simulations, we reproduce the reference galaxytwo-point clustering measurements – monopole and quadrupole – to a precision required by the DESI Year 1 emission line galaxysample down to non-linear scales, i.e. k 10 Mpc h−1. Furthermore, we compute covariance matrices basedon the resulting FASTPM galaxy clustering – monopole and quadrupole. We study for the first time the effect of fitting on Fourierconjugate (e.g. power spectrum) on the covariance matrix of the Fourier counterpart (e.g. correlation function). We estimate theuncertainties of the two parameters of a simple clustering model and observe a maximum variation of 20 per cent for the differentcovariance matrices. Nevertheless, for most studied scales the scatter is between 2 and 10 per cent. Consequently, using thecurrent pipeline we can precisely reproduce the clustering of N-body simulations and the resulting covariance matrices providerobust uncertainty estimations against HOD fitting scenarios. We expect our methodology will be useful for the coming DESIdata analyses and their extension for other studies
Void BAO measurements on quasars from eBOSS
We present the clustering of voids based on the quasar (QSO) sample of the extended Baryon Oscillation Spectroscopic Survey Data Release 16 in configuration space. We define voids as overlapping empty circumspheres computed by Delaunay tetrahedra spanned by quartets of quasars, allowing for an estimate of the depth of underdense regions. To maximise the BAO signal-to-noise ratio, we consider only voids with radii larger than 36Mpc. Our analysis shows a negative BAO peak in the cross-correlation of QSOs and voids. The joint BAO measurement of the QSO auto-correlation and the corresponding cross-correlation with voids shows an improvement in 70 of the QSO mocks with an average improvement of . However, on the SDSS data, we find no improvement compatible with cosmic variance. For both mocks and data, adding voids does not introduce any bias. We find under the flat CDM assumption, a distance joint measurement on data at the effective redshift of . A forecast of a DESI-like survey with 1000 boxes with a similar effective volume recovers the same results as for light-cone mocks with an average of 4.8 improvement in 68 of the boxes
Void BAO measurements on quasars from eBOSS
We present the clustering of voids based on the quasar (QSO) sample of the extended Baryon Oscillation Spectroscopic Survey Data Release 16 in configuration space. We define voids as overlapping empty circumspheres computed by Delaunay tetrahedra spanned by quartets of quasars, allowing for an estimate of the depth of underdense regions. To maximise the BAO signal-to-noise ratio, we consider only voids with radii larger than 36Mpc. Our analysis shows a negative BAO peak in the cross-correlation of QSOs and voids. The joint BAO measurement of the QSO auto-correlation and the corresponding cross-correlation with voids shows an improvement in 70 of the QSO mocks with an average improvement of . However, on the SDSS data, we find no improvement compatible with cosmic variance. For both mocks and data, adding voids does not introduce any bias. We find under the flat CDM assumption, a distance joint measurement on data at the effective redshift of . A forecast of a DESI-like survey with 1000 boxes with a similar effective volume recovers the same results as for light-cone mocks with an average of 4.8 improvement in 68 of the boxes
Cosmic void exclusion models and their impact on the distance scale measurements from large scale structure
Baryonic Acoustic Oscillations (BAOs) studies based on the clustering of voids and matter tracers provide important constraints on cosmological parameters related to the expansion of the Universe. However, modelling the void exclusion effect is an important challenge for fully exploiting the potential of these kind of analyses. We thus develop two numerical methods to describe the clustering of cosmic voids. Neither model requires additional cosmological information beyond that assumed within the galaxy de-wiggled model. The models consist in power spectra whose performance we assess in comparison to a parabolic model on both Patchy boxes and light-cones. Moreover, we test their robustness against systematic effects and the reconstruction technique. The void model power spectra and the parabolic model with a fixed parameter provide strongly correlated values for the Alcock-Paczynski () parameter, for boxes and light-cones likewise. The resulting values - for all three models - are unbiased and their uncertainties are correctly estimated. However, the numerical models show less variation with the fitting range compared to the parabolic one. The Bayesian evidence suggests that the numerical techniques are often favoured compared to the parabolic model. Moreover, the void model power spectra computed on boxes can describe the void clustering from light-cones as well as from boxes. The same void model power spectra can be used for the study of pre- and post-reconstructed data-sets. Lastly, the two numerical techniques are resilient against the studied systematic effects. Consequently, using either of the two new void models, one can more robustly measure cosmological parameters
Cosmic void exclusion models and their impact on the distance scale measurements from large scale structure
Baryonic Acoustic Oscillations (BAOs) studies based on the clustering of voids and matter tracers provide important constraints on cosmological parameters related to the expansion of the Universe. However, modelling the void exclusion effect is an important challenge for fully exploiting the potential of these kind of analyses. We thus develop two numerical methods to describe the clustering of cosmic voids. Neither model requires additional cosmological information beyond that assumed within the galaxy de-wiggled model. The models consist in power spectra whose performance we assess in comparison to a parabolic model on both Patchy boxes and light-cones. Moreover, we test their robustness against systematic effects and the reconstruction technique. The void model power spectra and the parabolic model with a fixed parameter provide strongly correlated values for the Alcock-Paczynski () parameter, for boxes and light-cones likewise. The resulting values - for all three models - are unbiased and their uncertainties are correctly estimated. However, the numerical models show less variation with the fitting range compared to the parabolic one. The Bayesian evidence suggests that the numerical techniques are often favoured compared to the parabolic model. Moreover, the void model power spectra computed on boxes can describe the void clustering from light-cones as well as from boxes. The same void model power spectra can be used for the study of pre- and post-reconstructed data-sets. Lastly, the two numerical techniques are resilient against the studied systematic effects. Consequently, using either of the two new void models, one can more robustly measure cosmological parameters