The theoretical explanation of cosmic acceleration is nowadays one of the biggest puzzles in cosmology.

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

It must be there. We just cannot see it: mysterious dark matter and dark energy in the universe. Henk Hoekstra is one of the many cosmologists who would love to know what exactly these substances consist of. He has received a European research grant of 1.3 euro million to find out.

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”.

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

Henk Hoekstra and Alessandra Silvestri work on the astronomy and theoretical physics in the Euclid mission. These Dutch researchers are part of the mission.

Dark matter is one of the biggest mysteries of the Universe. Its properties cannot be explained with the known laws of physics and elementary particles.

One of the most important puzzles in modern astrophysics is the nature of dark matter.

Promotor: A. Achúcarro Co-promotor: A. Boyarsky

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.

Dark matter. Something invisible that, according to calculations, comprises about 85% of the matter in the universe. With an ERC Advanced Grant of €2.5 million, Professor of Observational Cosmology Henk Hoekstra will map out even more precisely where this dark matter is to be found.

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 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.

It is an established fact that the Standard Model has to be extended to explain the so-called Beyond the Standard Model (BSM) phenomena: dark matter, matter-antimatter asymmetry of the Universe and neutrino flavour oscillations.

The focus of the dissertation

This book provides the answers, presenting clear insights into the current state of affairs and exploring future prospects.

What is Leiden University doing to reduce energy consumption and move away from fossil energy? Where can you find information about energy? And what changes can you make yourself?

This thesis is largely an experimental study on the formation of solid-state simple and complex organic molecules in the H2O-rich and CO-rich ice phases of dense interstellar clouds and dark cores.

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

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

The RIPEET project will support Responsible, Research and Innovation (RRI) policy experimentations for energy transition in three European territories - in Extremadura (ES), Highlands and Islands of Scotland (UK) and Ostrobothnia (FI). The framework conditions, processes, and outcomes of these experiments…

Twenty years from now, the world population is estimated to be around 8.7 billion people, compared to the current 7.3 billion. In combination with the improvements in living standards and the corresponding growth in consumption, this will result in an enormous increase in the demand for food, consumables,…

The transition to new and renewable energy sources should be completed by 2050. Researchers in various disciplines at Leiden University are conducting unique research that will help us make this transition and reduce CO2 emissions.

In this project, we use social network analysis to analyze the behavior of users in online forums and associated marketplaces over time.

For Leiden University’s operations, sustainability is an important topic, especially looking at the CO2-footprint, renewable energy and the greening of buildings.

The energy system is at the heart of two of the greatest challenges of the 21st century: decreasing CO2 emissions to meet the ambitions of the Paris agreement while fulfilling the growing energy demand associated with the economic aspirations of a growing world population.

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

Not only dark matter, but also ordinary matter and dark energy are tracked in the largest ever cosmological computer simulation ever. In the FLAMINGO simulations, you can see virtual galaxies and clusters of galaxies emerging over the course of billions of years. This is no easy task: with more than…

An international team of astronomers has found an unexpected link between dark matter and visible stars in stellar systems. This discovery may even cause us to reconsider our understanding of gravity. They published on their discovery in 'Nature' on 1 October.

The energy transition is a complex transformation process that is not only about technology -moving towards renewable energy sources-, but even more so about societal and institutional change. The energy transition requires and provides opportunities for actors to take on new roles.

The Institute of Environmental Sciences has carried out and participates in several projects that deal with the analysis of energy systems.

How do technological systems impact the environment? And can they be designed in a more sustainable way? The Resources and Energy research program studies the importance of resources and energy for our society and aims to guide the shift towards a sustainable circular economy.

Energy transition will entail the construction of large numbers of new energy installations. Such construction projects may meet with opposition from people living close by. Assistant Professor Bríd Walsh investigated how the local community can best take part in such projects.

An international team of astronomers, including Professor Koen Kuijken, has published a series of online articles presenting the first results of a major search for dark matter. Never before have researchers been able to chart so precisely the characteristics of groups of galaxies and their dark matter.…

We would like to present to you a simple guidebook about living a sustainable life as a student in the cities of Leiden and The Hague. Whether you are a first-year student still trying to find your way around or already doing your masters – students wanting to explore more sustainable options and save…

Promotor: Huub de Groot, Co-promotor: Francesco Buda

Marc Koper’s research focuses on electrocatalysis and electrochemical surface science for sustainable energy and chemistry. Reactions of interest are the redox reactions of the oxygen/hydrogen cycle (water oxidation, hydrogen evolution), the carbon cycle (reduction of carbon dioxide, oxidation of small…

Twenty years from now, the world population is estimated to be around 9 billion people (now 8 billion). In combination with the improvements in living standards and the corresponding growth in consumption, this population will result in an enormous increase in the demand for food, consumables, water…

How can you see something that’s invisible? Well, with Euclid! This future ESA telescope will map the structure of the Universe and teach us more about invisible dark matter and dark energy. Scientific coordinator of Euclid and Leiden astronomer Henk Hoekstra explains how this works.

Research on this theme addresses the systemic risks faced by European societies and affecting the quality of life of European citizens.

The transition from fossil fuels and the practical changes that this entails make many demands on citizens. Emma ter Mors, a psychologist and lecturer at Leiden University, is researching the factors that contribute to public perception and acceptance of new energy technologies.

Understanding how galaxies form, interact, and evolve comes largely from comparing theory predictions with observational data. Numerical simulations of galaxies provide the most accurate approach to testing the theory, as they follow the non-linear evolution of gas and dark matter in great detail and…

We are cosmologists, in other words we use physics to study the Universe, how it started and evolved into the structure that we observe around us.

Astronomer Koen Kuijken and physicist Tjerk Oosterkamp have each been awarded a major subsidy by NWO. The funding will allow them to construct new research facilities.

Examining if large scale application of new energy pathways can be constrained by materials and emissions.

Hetterscheid

Lecture, Tuesday Talks: Science Insights

Chemical reactions go hand-in-hand with an energy exchange with the environment in which they take place. Surfaces offer a variety of energy dissipation channels, constituted by the nuclear and electronic degrees of freedom of the atoms at the interface. Aiming at an improved future harvesting of energy,…