An intriguing tension in the measurements of the Hubble constant H0, which sets the expansion rate of the Universe, has emerged in recent years. Independent determinations of H0 are important to assess the tension, which if verified, would imply new physics beyond the standard cosmological model. I will illustrate strong gravitational lenses with measured time delays between the multiple...

Strong gravitational lensing has advanced as a standard probe to map mass densities of cosmic structures or to try and infer parameters of the cosmological concordance model, like the Hubble Constant. Almost all approaches use a global assumption of the light-deflecting mass distribution at a specific redshift and fit the observed data to this model. With increasing data quality, the parameter...

Previous studies of galaxy formation have shown that only 10 per cent of the cosmic baryons are in stars and galaxies, while 90 per cent of them are missing. In this talk, I will present three observational studies that coherently find significant evidences of the missing baryons. The first is the cross-correlation between the kinetic Sunyaev-Zeldovich maps from Planck with the linear...

Einstein's field equations allow various different black hole solutions. Among these solutions the most famous are most likely the Schwarzschild and the Kerr spacetimes, which are both special cases of the so-called Plebanski-Demianski spacetime. Besides the Schwarzschild and Kerr spacetimes the Plebanski-Demianski spacetime also includes other solutions as special cases, among them the...

I will first review the current status of extrasolar planet discoveries with graviational microlensing, and then discuss the future aspects with space missions such as the Earth 2.0 satellite.

Thanks to extreme gravitational lensing magnification factors realized near the lensing caustics cast by galaxy cluster lenses, the most massive and short-lived stars in the Universe can be individually observed at cosmological distances. In this talk, I will demystify the phenomenology of these highly magnified stars, in particular the effect of intracluster microlensing. Additionally, I will...

The past decades have witnessed a lot of progress in gravitational lensing with two main targets: stars and galaxies (with active galactic nuclei). The success is partially attributed to the continuous luminescence of these sources making the detection and monitoring relatively easy. With the running of ongoing and upcoming large facilities/surveys in various electromagnetic and...

Motivated by detecting Earth twins in extreme precise radial velocity data, PEXO is a package aiming for extremely high-precision modeling of the motion of single stars or stars in a system. PEXO is general enough to account for binary motion and stellar reflex motions induced by dark companions and is precise enough to treat various relativistic effects both in the solar system and in the...

SuperBIT telescope was carried to the top of the Earth's atmosphere in April/May 2023, by a helium balloon the size of a sports stadium. For 40 days and 45 nights it circumnavigated the Southern hemisphere 5.5 times. Using image stabilisation, it achieved diffraction-limited UV and optical imaging. We mapped the weak gravitational lensing signal of merging galaxy clusters like the Bullet...

With the fast development of high-precision large photometric surveys, weak lensing (WL) effects have become one of the major probes in cosmology. While the two-point shear correlations are the most extensively employed analyses, other statistics beyond that are desired because of the non-Gaussian nature of cosmic structures. In this presentation, I will discuss the cosmological application of...

Weak gravitational lensing induces flux dependent fluctuations in the observed galaxy number density distribution. This cosmic magnification (magnification bias) effect in principle enables lensing reconstruction alternative and independent to cosmic shear and CMB lensing. However, the intrinsic galaxy clustering overwhelms the lensing signal, and hindered its application. We developed...

Precision cosmology is a very important target for the coming Stage IV weak lensing studies. It is also hard to achieve due to multiple systematical errors. In this talk, we present systematics mitigation performed in 2 published papers and some ongoing works. More specifically, we present intrinsic alignment mitigation with KiDS data, and shear bias removal as well as redshift error...

Cosmic shear statistics, such as the two-point correlation function (2PCF), can be evaluated with the PDF-SYM method instead of the traditional weighted-sum approach. It makes use of the full PDF information of the shear estimators, and does not require weightings on the shear estimators, which can in principle introduce additional systematic biases. This work presents our constraints on $S_8$...