Of all the mass in our Universe, 80% is thought to consist of a hypothetical and invisible substance called dark matter (DM).

One of the most important correlation functions in physics, especially in cosmology, is the energy density, which describes how much energy is present at each point in spacetime due to matter fields. A key contribution to the energy density of the primordial universe comes from gravitational waves (GWs),…

The first direct detection of gravitational waves opened the possibility of mapping the Universe via this new and independent messenger.

Promotor: K. Kuijken, Co-Promotor: H. Hoekstra

We explored the Universe using weak gravitational lensing, a phenomenon that occurs when light from distant galaxies is bent by the gravitational fields of closer cosmic objects, much like how a lens distorts light.

For centuries astronomers studied the Universe by collecting light. Nowadays, we are living in times of great technological advancements, which allow us to explore our Universe in a new way - though gravitational wave radiation.

In this thesis we study the landscape of gravitational models which modify GR by introducing an additional scalar degree of freedom (d.o.f.) to source Cosmic Acceleration.

In this work, I explore the creation of new methods that optimize simulations of the gravitational N-body problem. Specifically, I take advantage of the recent popularity of Machine Learning methods to find tools that can suit this problem.

The high velocity tail of the total velocity distribution of stars provides essential insight into fundamental properties of the Galaxy.

In astronomy, the interpration of observations and measurements plays a crucial role: we rely purely and fundamentally on the information that reaches us as observers. And 80% of all matter in the universe is undetectable directly.

Learning about My meaningful Way through life and profession.

Leiden My Way is een co-curriculair persoonlijk ontwikkelprogramma uitgevoerd aan de Faculteit der Sociale Wetenschappen.

Promotor: Prof.dr. M. de Jong

Promotor: P. T. de Zeeuw, Co-promotor: N. Neumayer; G. van de Ven

Promotor: K.H. Kuijken

The Sun and all the stars in the night sky reside in the Milky Way galaxy. In the at-rest reference frame of the Galaxy, typical stars travel with velocities of about 100-200 kilometres per second.

Three major cosmology-focused missions are planned for the next decade: the Euclid space telescope, the Vera C. Rubin Observatory in Chile, and the Nancy Grace Roman Space Telescope.

At the largest scales, two ingredients dictate the distribution of matter in the Universe. The first is dark matter, acting as an invisible scaffolding held together by gravitational forces.

This thesis investigates the structural evolution and assembly of galaxies since the first few billions years after the big bang.

Promotor: Prof.dr. A.G.G.M. Tielens

The physical origin of the dozens of stellar-mass binaries, the mergers of which have been detected by the LIGO-Virgo-KAGRA collaboration via gravitational waves, is still unknown.

Op 29 april 2020 verdedigde Beth Van Schaack haar proefschrift 'Imagining Justice for Syria: Water Always Finds Its Way'. Het promotieonderzoek is begeleid door promotor prof.dr. C. Stahn.

Promotor: Prof.dr. H. J. A. Röttgering, Co-Promotor: M. Haverkorn

Galaxy intrinsic alignments induce a major astrophysical contamination to weak gravitational lensing measurements and need to be modelled and mitigated when extracting cosmological information from such measurements.

The ultimate goal of cosmologists is to find a cosmological model able to explain the current observational data.

Promotor: Koen Kuijken Co-promotor: Henk Hoekstra

Galaxies form and live inside dark matter haloes. As a consequence, they are exposed to the tidal fields generated by the surrounding matter distribution: this imprints a preferential direction to the galaxy shapes, which leads to a coherent alignment on physically close galaxies, called intrinsic a…

In this thesis, the research focuses on the properties of dark matter and dark matter haloes and how they connect with the galaxies we can observe in the Universe.

Supervisor: S.F. Portegies Zwart Co-Supervisor: A.G.A. Brown

The formation of stars and planets happens over multiple scales, which can interact. In particular, planet formation happens in the dense, complex environment of star forming regions.

In this project, researchers from computer science, law, psychology, and public administration research in practice how artificial intelligence (AI) can be leveraged to make decision-making in the security domain more effective, while also keeping it safe and accountable.

This thesis is a (biased) journey through very different topics in astrophysics: quasars and new populations of active galactic nuclei, gravitational waves from merging black holes, and protoplanetary discs around young stars.

A brief review essay on some of the work that has been recently published in the emergent field of digital ethnography.

Promotor: Prof.dr. J. Schaye, Co-promotor: Marcello Cacciato

The radio sky harbours both galactic and extragalactic sources of arcminute- to degree-scale emission of various physical origins. To discover extragalactic diffuse emission in the Cosmic Web beyond galaxy clusters, one must image low–surface brightness structures amidst a sea of brighter compact fore-…

Valetudo, zo hebben de astronomen het nieuw ontdekte Jupitermaantje genoemd. Het is een weerbarstig exemplaar dat dwars tegen haar soortgenoten in beweegt. In de Volkskrant reageert Leidse astronoom Simon Portegies Zwart op de bijzondere ontdekking.

What physics controls the properties of quantum matter, such as how electrons flow inside high-temperature superconductors? This question has captivated the physics community and industry for decades, in part due to the great technological potential such materials have, but also because they have resisted…

Improvements of weak gravitational lensing shape measurements are presented and some used for data analysis.

Astronomen onder leiding van Simon Portegies Zwart gebruikten simulaties om te reconstrueren hoe drie sterren 60.000 jaar geleden uit de sterrenhoop R136 werden geslingerd. Uit de analyse blijkt dat er vijf sterren betrokken waren bij de gebeurtenis in de Tarantulanevel.

This thesis is dedicated to the exploration of the primordial dark ages: unknown physics during the earliest stages of the Universe’s expansion that have not yet been directly probed by observations. Cosmic inflation is a burst of exponential expansion of space after the “Big Bang”.

De meeste Learning My Way-modules hebben een vergelijkbare structuur: voorbereiding, seminar, integratie.

If mankind wants to survive into the 22nd century, we will need to change the way we live drastically. The human impact on our planet is everywhere, we are changing the atmosphere, the oceans and the land, leading to global warming, climate change, loss of biodiversity and pervasive pollution. There…

Wat is de invloed van de Internationale Verdragen ICCPR en ICESCR? Hoe kan hun toekomstige rol in de bescherming van de mensenrechten verder worden verbeterd? Dit is een kleine greep uit de vragen die worden gesteld tijdens de conferentie ter ere van de 50ste verjaardag van het ICCPR en ICESCR.

De Learning My Way-methodologie is afgelopen 10 jaar ontwikkeld en geperfectioneerd. Begonnen in experimentele vorm in het FSW Honours College, is LMW al snel door verschillende instellingen opgepakt in opleidingen en voor HRM-doeleinden.

The focus of the dissertation

Promotor: Jelle S. Kaastra Co-promotor: Jelle de Plaa

There are many interpretations of quantum mechanics, and ultimately experiments are needed to verify or falsify these interpretations.

Learning My Way wordt gebruikt in een breed scala aan onderwijscontexten. Daarbij wordt altijd een blended learning en flipped classroom-benadering toegepast om optimale integratie van persoonlijke inzichten in dagelijks leven en gedrag mogelijk te maken.

Promotores: G.R. de Snoo, W.T. de Groot, Co-promotor: C.J.M. Musters