# Seminar details

Date: 10.10.2023

**Suhani Gupta (CFT PAN Warsaw)**

*Non-linear density fields in modified gravity cosmologies*

Abstract:*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.
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Bio
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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