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The observed matter on very large scales in the Universe is distributed into
galaxies, clusters of galaxies and superclusters with large void spaces in between. This
spider-web like pattern of matter is very loosely referred to as large scale structure. This
structure was seeded by tiny fluctuations generated during the inflationary phase of the
Universe's history and was subsequently amplified by gravity to form the bound objects that
we see today. This evolution depends sensitively upon various parameters that describe the
initial conditions and the overall expansion history of the Universe. Indeed many surveys
such as LSST, EUCLID etc. aim to observe and characterize this structure and thereby
constrain the parameters of the model that describes the fate of the Universe.
N-body codes are usually employed to make theoretical predictions to compare with
observations. However, they are computationally expensive and also are limited by shot-
noise. Given the plethora of cosmological models, this feature is prohibitive and alternate
methods are required to gain physical insights. This talk will focus on two such analytical
methods - spherical and triaxial collapse. Some applications of these methods such as
computing observables such as the one-point probability density function (PDF) and
investigating growth in modified gravity models will be discussed. |