Numerical simulations of weak gravitational lensing play an important role in statistical analyses of modern galaxy imaging data.

The bright galaxies comes in different colours and show different activities. Some are red, some blue and others have angry supermassive blackholes. These galaxies acts as the doorway to the cosmological universe we live in. Our understanding of inner working of universe and its mysterious dark components of matter and energy depends on the very large scale structure formed by these bright galaxies.

In the last decade, the astrophysical processes driving galaxy formation in a cosmological context at kpc scales have been incorporated, largely independently, into multiple codes developed by different simulation teams.

In this talk I will lead you through the highlights of a series of papers (Gruen++2018, Friedrich++2018, Friedrich&Uhlemann et al. in prep, Uhlemann&Friedrich et al. in prep) that promote an alternative framework of studying large scale structure data: analysis of the 1-point PDF of density fluctuations. The main difference between the PDF and 2-point correlation functions is readily explained: 2-point functions measure the variance of fluctuations as a function of scale, while the PDF measures all moments of the fluctuations at one scale.

The cosmic microwave background (CMB) provides unparalleled views into the early universe and its later evolution. Recent and ongoing experiments have contributed to our understanding of neutrinos, dark energy, and dark matter through measurements of large scale structure imprinted on the CMB and constrained the conditions in the early universe, tightly restricting inflationary and other cosmological models through measurements of CMB polarization.

Observations from large area photometric surveys like LSST or DES will constrain cosmology to unprecedented precision. Deep wide-area imaging will provide observations for faint galaxy samples, for which traditional redshift calibration using spectroscopic data is very difficult.

The recent tension between early- and late-Universe measurements of the Hubble constant highlights the necessity for independent and precise probes such as the time-delay cosmography. The measured time-delays between the lensed images of a background quasar depend on the absolute physical scales in the lens configuration. Thus, they allow measurement of these scales to infer the Hubble constant, H_0.

Supermassive black hole binaries (SMBHBs) are a natural byproduct of galaxy mergers. Yet, they remain undetectable at small separations. A promising method is to identify quasars with periodic variability. I will discuss candidates identified in time-domain surveys, as well as ongoing efforts to confirm their binary nature.

Massive neutrinos suppress the growth of structure below their free-streaming scale and

The cosmology analyzes of the Year-3 (Y3) data from the Dark Energy Survey (DES) is at full speed ahead. Our preliminary weak lensing sample contains 120 million objects over 4200 square degrees of sky and is the largest shape catalog to date. This statistical power comes at a price: the cosmic shear measurements are more sensitive not only to the signal but also to potential systematics.