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Research
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PCA-based Data Reduction for 3x2pt
PCA-based Data Reduction for 3x2pt
Enhancing Parametrized MG Constraints with Principal Components Analysis for Stage-IV 3x2pt Survey data
Enhancing Parametrized MG Constraints with Principal Components Analysis for Stage-IV 3x2pt Survey data
Minimizing information loss
Contour plots for cosmological parameter inference with a dark energy-like modified gravity parametrization Σ=1 (modified lensing) and µ= µ0 (ΩΛ(a)/ΩΛ0) (modified structure growth). The PCA method improves constraints on the modified gravity parametrization parameters. We are using LSST Y1-like noiseless 3x2pt GR simulated data + RSD data.
Minimizing bias
Without including RSD data, our method still removes degeneracy directions between modified gravity parameters and provides good constraints - the blue contours are much smaller than the orange ones!
The blue contours show constraints when using the classical (more conservative) linear method for scale cuts. The orange contours show constraints using the novel data reduction method. We build an informative data reduction matrix with f(R), nDGP and GR linear and non-linear power spectra at each point in the parameter inference analysis.
3D non-linear matter power spectrum in different modified gravity theories
Linear and non-linear boosts (ratio of modified gravity to GR power spectra) for f(R), nDGP and ESS (see Wright et al. 2023). The gray area shows the scales that are excluded from a non-linear analysis to mitigate for biases due to baryonic effects.
Part of my PhD's focus is on improving methods to test whole classes of modified gravity (MG) theories, specifically by leveraging the constraining power of available non-linear observational probes.
The PCA-based data reduction method used in this project allows to create cuts in data space to minimize the bias due to non-linearities in the data while minimizing information loss. We can create our reduction matrix by using a training set of modified gravity non-linear matter power spectra (recovered from emulators of N-body simulations).
Results
Results
Coming soon to the arXiv! In the meantime, here is an animation showing how the PCA data reduction method works:
pca-elltodataspace.mp4Testing 4D Einstein-Gauss-Bonnet Gravity on Cosmological Scales
Testing 4D Einstein-Gauss-Bonnet Gravity on Cosmological Scales
4-Dimensional Einstein-Gauss-Bonnet (4DEGB) gravity has garnered significant attention in the last few years as a phenomenological competitor to general relativity. We consider the theoretical and observational implications of this theory in both the early and late universe, (re-)deriving background and perturbation equations and constraining its characteristic parameters with data from cosmological probes.
Results
Results
We explore consequences of 4DEGB on the sound and particle horizons in the very early universe, and demonstrate that 4DEGB can provide an independent solution to the horizon problem for some values of its characteristic parameter α.
The comoving Hubble radius as a function of scale factor. ae is the transition scale factor between inflation domination and radiation domination. Here λ is an example of a primordial perturbation exiting the horizon during inflation and re-entering during radiation domination. We can see the same effect doesn't occur in 4DEGB.
The 4DEGB solution compared to the inflationary solution to the horizon problem, visualized by looking at distances of interest as a function of conformal time η. The plot assumes the exaggerated value of α = 10-7/ H02 to show the qualitative behaviour of the theory (and to aid the visual distinction between CMB and reheating space-like surfaces).
We constrain an unexplored regime of this theory in the limit of small coupling α (empirically supported in the post-Big Bang Nucleosynthesis era by prior constraints). This version of 4DEGB includes a geometric term that resembles dark radiation at the background level, but whose influence on the perturbed equations is qualitatively distinct from that of standard forms of dark radiation. In this limit, only one beyond-ΛCDM degree of freedom persists (αC2). Using CMB data from ACTPol we constrain αC2 = (-9 ± 6) x 10-6 H02 thereby providing a new constraint of a previously untested sector of 4DEGB. We also incorporate the 4DEGB background and perturbation equations within a bespoke cosmological Boltzmann solver to study the qualitative behaviour of small-α 4DEGB in a perturbed universe.
ACTPol posterior results for a ΛCDM+Neff universe. We map this analysis onto our scenario of interest, with ΛCDM+Neff playing an equivalent role to αC2 in 4DEGB for background-only probes. αC2 is consistent with zero within 1.34σ.
Present-day (z=0) linear matter power spectrum for small-α 4DEGB. The middle (solid black) curve is the power spectrum for a ΛCDM model. The dotted (green) and dash-double dotted (gray) curves show the ΛCDM+Neff model with extra neutrino densities equivalent at the background level to the plotted values of αC2.
Emulators in Modified Gravity
Emulators in Modified Gravity
Gaussian-Process Emulator for the 3D non-linear matter power spectrum in Cubic Galileon Gravity using HiCOLA
Gaussian-Process Emulator for the 3D non-linear matter power spectrum in Cubic Galileon Gravity using HiCOLA
Work completed as as part of a Dark Energy Science Collaboration (DESC) project aimed at the development of an emulator for Cubic Galileon 3D matter power spectra.
Results
Results
Coming soon!
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