Szczegóły seminarium

Data: 10.10.2023

Suhani Gupta (CFT PAN Warsaw)

Non-linear density fields in modified gravity cosmologies

Large-scale structures (LSS) form via relentless action of gravitational forces on density perturbations over cosmic length and time scales. Thus, the non-linear regime of LSS formation is sensitive to the underlying theory of gravity, and hence provides estimates for observables that can help distinguish modified gravity effects from the expected standard ΛCDM results. In this work, I focus on two modified gravity (MG) models: namely variants of f(R) and nDGP gravity models. These MG theories offer a very good test bed to explore the freedom of modifying the Einstein-Hilbert action to produce a physical mechanism effectively mimicking the action of the cosmological constant, that would result in cosmic acceleration. These MG models are constructed in such a way that they have negligible consequences at early times and share the same expansion history and cosmological background as ΛCDM. As a result, the effect of these MG models is incorporated in the perturbation equations that govern the gravitational dynamics of LSS, and can potentially impact the formation and evolution of dark matter halos. Thus, the statistical properties of dark matter halos, that form the building blocks of cosmological observables associated with large-scale structures in the universe, offer opportunities for testing modifications to the gravitational forces. In this work, I focus on halo statistics: halo mass function, halo bias and halo density profile, using results generated from MG N-body simulations. We obtain systematic trends in these quantities on comparing MG results with standard GR cases. We further used these trends to compute semi-analytical modelling for these MG cosmologies and make robust estimates for cosmological observables. This will be advantageous as N-body simulations are prohibitively expensive for the case of most nontrivial MG scenarios. An additional strength of our approach is that it is general enough to be quite straightforwardly extended, not only to a wider part of the model parameters space but also, in principle, to other modified large-scale cosmological structure formation models. Additionally, I will also discuss the implications of the cosmic environment on halo properties, and how modifications to the underlying gravity theory impacts these effects.

I am a PhD student at the Centre for Theoretical Physics, Warsaw, Poland. My work mainly focuses on studying the effects of modified gravity on large-scale structure formation. Specifically I am studying how the imprints of modified gravity models can be measured by studying the evolution of large-scale structures, and how it will impact cosmological measurables ( for instance weak lensing). I am developing an analytical framework that can be used to quantify the MG effects on the properties of dark matter halos, and will be a useful tool in the upcoming big cosmological data surveys. Other than this, I am also interested in studying the impact of modified gravity of the large-scale dark matter statistics, and dark matter halo properties in the cosmic web. In my work, I mainly deal with cosmological N-body simulation datasets.

Research interests:
Impact of modified gravity cosmologies on:
Dark matter halo properties
Large-scale dark matter density fields
Cosmological observables (e.g. weak lensing)
Cosmic web:
Impact of cosmic web environment on dark matter halo properties.
Influence of MG effects on different cosmic web environments.

Beyond work: I enjoy travelling, hiking, cooking, reading, biking, dancing, photography and to be amidst nature.

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