Cosmology

The current progress in gravitational wave detection opened a new exciting window in cosmology. It is natural to ask ourselves how we can best use this new tool to explore physics beyond the standard model. With this idea in mind, my collaborators and I asked what we could learn from Cosmological Gravitational Wave Backgrounds if they were to be detected to a certain accuracy. By drawing comparison to the cosmic microwave background, we investigate the impact of elastic scattering on any cosmological background. Specifically, we focus on quantifying spectral distortions in the energy density spectrum of CGWB attributed to interaction with beyond-the-standard-model particles. We will also explore the effect that elastic scattering of graviton of Primordial Black holes would have on CGWB in the regime where PBHs account for all the dark matter.

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Zoom link https://pitp.zoom.us/j/98460268383?pwd=RytzWHd5dU1lenRhWG1NYXM3OVJpQT09

In this talk, I will discuss two lines of research revolving around the study of weak gravitational lensing in our Universe. First, I will present a pipeline that has been in development to model the matter power spectrum from large to small scales, focusing on stage-IV photometric galaxy surveys. I will discuss the fundamental ingredients of this pipeline, the consistency checks performed to validate it, and how this new tool fares when performing a full Bayesian parameter estimation analysis with an LSST-like survey. In the second part of this talk, I will present a new and exciting methodology to study weakly-lensed gravitational waves in the wave-optics regime.

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Zoom link https://pitp.zoom.us/j/98447653523?pwd=QjFDdk1LZ25LeDd6Nk5iRCtGbFNYQT09

Future surveys will map the cosmic microwave background (CMB) with unprecedented precision. The high fidelity of the data will present new opportunities to extract deep insights about the history, contents, and evolution of our universe.  However, new tools and techniques will be required to maximize the potential of the forthcoming data.  I will describe the techniques necessary to address the emerging challenges and to harness the exciting opportunities provided by future CMB observations.

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Zoom link https://pitp.zoom.us/j/92999899446?pwd=YTNEUkMrV2RXOWE0Mk11b2tDQ2Q0Zz09

Linear cosmological observables, like the cosmic microwave background (CMB), 
offer a unique avenue to investigate the elusive properties of dark matter 
(DM) through its interactions with Standard Model (SM) particles. The 
precision of contemporary experiments has reached sub-percent-level accuracy 
(<1%), necessitating theoretical formalism of definitive accuracy to extract 
meaningful constraints on DM-SM interactions.
I will highlight theoretical assumptions made ubiquitously in deriving most 
constraints on DM-SM scattering interactions, which could potentially induce 
order ~1 errors--- a large margin of uncertainty for precision-cosmology. I 
will discuss the progress we have made toward finding better alternatives by 
developing the first exact implementations in well-defined, cosmologically 
relevant regions of parameter space to mitigate the errors induced by two 
widely adopted theoretical assumptions.
Our exact results provide points of reference that can help determine the 
regimes where current DM-SM scattering constraints can be trusted, and where 
we need better methods going forward. I will end by motivating a higher-order 
statistical formalism for DM-SM scattering with up to 100x greater 
sensitivity.

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Zoom link https://pitp.zoom.us/j/95952209469?pwd=TERqVlZsMVhvbzJqU1hsalhiUVYxdz09

Deep learning (DL) methods have demonstrated great potential for extracting rich non-linear information from cosmological fields, a challenge that traditional summary statistics struggle to address. Most of these DL methods are discriminative models, i.e., they directly learn the posterior constraints of cosmological parameters. In this talk, I will make the argument that learning the field-level likelihood function using generative modeling approaches such as Normalizing Flows usually leads to more effective extraction of cosmological information. This approach also enables anomaly detection to improve the robustness of the analysis. To scale the modeling to high dimensional data and improve its generalization capabilities, we further incorporate physical inductive biases, such as symmetries and multiscale structure, into the architecture of the normalizing flow models. On mock weak lensing maps, I will show that the model leads to significant improvement in constraining power compared to power spectrum and alternative DL models. I will also show that it is able to detect domain shifts between training simulations and test data, such as noise miscalibration and baryonic effect, which, if left unaddressed, could introduce systematic biases in parameter constraints. Finally, I will talk about our ongoing work on applying this model to the field-level cosmic shear analysis for HSC.

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Zoom link https://pitp.zoom.us/j/97478701784?pwd=UVg4TVp1WFArcXNETG5ITGd0S0NuZz09

Abstract TBA

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Zoom link https://pitp.zoom.us/j/96982969023?pwd=MjgzaU5mZUVuV3pNVG11dHM2WUd4UT09

Major improvements in the theoretical aspects of Cosmology have been possible in recent years due to QFT-inspired methods, such as the effective field theory of large-scale structure (EFTofLSS). In this talk, I will explore further connections between high-energy physics and cosmology. I will present a systematic approach to renormalizing the galaxy bias parameters using path integrals and a finite cutoff scale Λ. I will derive the differential equations of the Wilson-Polchinski renormalization group that describe the evolution of the finite-scale bias parameters with Λ, analogous to the β-function running in QFT. I will then discuss how the RG-flow of EFTofLSS can lead to improvements in the extraction of cosmological parameters and also serve as a tool for sanity checks.

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Zoom link https://pitp.zoom.us/j/93248279658?pwd=Z1M1UnI3eVh3NTZ3NCt4NUtGaW5idz09

The current ΛCDM concordance model has been widely successful in describing our Universe. However, crucial questions, such as the H0 tension, remain unanswered and are becoming increasingly critical with the continuous release of high-precision cosmological data. This has led to the exploration of modified ΛCDM models, one of them being the coupled quintessence, or Coupled Dark Energy (CDE) model.  Here, we perform for the first time a tomographic analysis of coupled dark energy, where the coupling strength is parametrised and constrained in different redshift bins. We employ cosmic microwave background data from Planck, ACT and SPT, showing the impact of different choices that can be made in combining these datasets. Then, we use a range of low redshift probes to test CDE cosmologies, both for a constant and a tomographic coupling. In particular, we use for the first time data from weak lensing, galaxy clustering, and 3x2pt galaxy-galaxy lensing cross-correlation data. For CMB and background datasets, a tomographic coupling allows for β values up to one order of magnitude larger than in previous works, in particular at z < 1. The use of 3x2pt analysis then becomes important to constrain β at low redshifts, even when coupling is allowed to vary: for 3x2pt we find, at 0.5 < z < 1, β = 0.018+0.007 −0.011, comparable to what CMB and background datasets would give for a constant coupling. This makes upcoming galaxy surveys potentially powerful probes to test CDE models at low redshifts. 

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Zoom link https://pitp.zoom.us/j/94442666279?pwd=OTgrMTZ5dTRzZmc2WFhuMkF3ekJzdz09