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

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.

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

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),…

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.

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

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.

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.

Promotor: T. H. Oosterkamp

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.

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.

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…

Nieuw onderzoek van de National University of Singapore en Leiden laat zien dat chimpansees en bonobo’s net zoveel contrast in hun ogen hebben als mensen, waardoor ze gemakkelijk de richting van iemands blik kunnen volgen.

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.

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.

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

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.

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.

Negentig jonge, pas gepromoveerde wetenschappers kunnen vanaf 1 februari reageren op een postdoc-positie binnen het LEaDing Fellows Postdocs Programma.

Het college van bestuur kan met groot genoegen melden dat per 1 januari 2025 Joanne van der Leun voor de universiteit aan de slag is gegaan als Academic Lead International Affairs.

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

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.

De president van Indonesië, Susilo Bambang Yudhoyono heeft Jan Slikkerveer, hoogleraar Etnobotanische Kennissytemen in Ontwikkelingslanden, persoonlijk uitgenodigd om een lezing te houden op het World Culture Forum. Dat wordt van 24 tot 27 november in Indonesië gehouden.

Prof. Vriesendorp en prof. Wessels zijn opgenomen in de 2020 Lawdragon 500 Leading Global Restructuring & Insolvency Lawyers. Prof. Haentjens is genoemd in de 2020 Lawdragon Leading Global Restructuring Advisors & Consultants.

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.

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”.

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.

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.

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

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-…

Dit team zorgt ervoor dat alle Una Europa activiteiten van de Universiteit Leiden en het LUMC soepel verlopen en biedt ondersteuning aan collega's die direct betrokken zijn bij Una Europa activiteiten.

This Thesis shows discoveries in non-linear astrochemical kinetics as well as a deeper analysis of dark clouds chemistry.

Invasive lobular carcinoma (ILC) is the second most common type of breast cancer.

An objective of this research was to achieve direct, well-defined and non-rate-limiting electron transfer between respiratory enzymes and the electrode surface by means of 'Q-wires'.

Plastics are an intrinsic part of our society. Annually, 400Mt of plastics are produced of which roughly 40% is discarded within a year.

De meeste materie in het heelal is onzichtbaar, vermoeden veel astronomen. Maar hoe weeg je donkere materie die je niet kunt zien? Hoogleraar Henk Hoekstra zoekt naar een oplossing. Oratie op 25 juni.

Promotor: A. Doelman, Co-promotor: J.D.M. Rademacher

Op 21 januari 2020 verdedigde Patrick van Berlo zijn proefschrift 'Human Rights Elephants in an Era of Globalisation: Commodification, Crimmigration, and Human Rights in Confinement'. Het promotieonderzoek is begeleid door promotoren prof.dr. J.P. van der Leun en prof.mr.dr. M.A.H. van der Woude.

Atoms and molecules are the basic units of matter. If we keep dividing a bar of gold or a glass of water into smaller parts, at the end we are left with a single gold atom or a water molecule.

The bacterial cell wall is a nearly universal structure that offers protection and gives the cell its shape. However, environmental stressors, such as cell wall-targeting antibiotics and hyperosmotic conditions, can induce bacteria to shift to a wall-deficient state. It is unknown whether the lack of…

Single-molecule spectroscopy has become a powerful method for using organic fluorescent molecules in numerous applications.

Promotor: C.A.J. Knibbe, Co-promotor: J.J. Boelens, R.G.M. Bredius

According to the amyloid cascade hypothesis, accumulation of beta-amyloid (Aβ) peptides initiates the pathological cascade in Alzheimer's disease (AD).

The role of material production as a driver of environmental impacts is increasing, which calls for a better understanding of global material flows. This thesis explores the role of in-use stocks of products, buildings and infrastructure as a key driver of global material demand and discusses the implications…