Casimir cosmology
Abstract
Van der Waals forces are essential for life, in protein folding, in the capillary forces giving leaves the water they need for photosynthesis and much more. What has this benevolent force to do with the relentless expansion of the universe? Astronomers have discovered that the expansion of the universe is accelerating. Normally, gravity is attractive and would slow down the cosmic expansion, but Einstein’s cosmological constant has the opposite effect. As it is constant while all other densities are diluted by expansion, it is all that will remain, driving the universe to exponential expansion. Where does it come from? Cosmologists agree that it must originate from the quantum vacuum, because the vacuum is all that is left once matter and radiation is diluted. But how does the vacuum generate the cosmological constant? And is it really constant? Van der Waals forces are also caused by vacuum fluctuations. Is there a connection between the two? This is what the colloquium discusses, which is not an entirely academic problem, as fortunately there is increasing astronomical evidence for the cosmological constant to be varying. We may already have sufficient data to settle the question.
About the speaker
Ulf Leonhardt joined the Weizmann Institute of Science as a Professor of Physics in November 2012 after an international career. He was born in Schlema, in former East Germany, in 1965. He studied physics at Friedrich-Schiller University Jena, Moscow State University, and Humboldt University Berlin, where he received his PhD in 1993. He was a Visiting Scholar at the Oregon Center for Optics in the US, a Habilitation Fellow at the University of Ulm in Germany, and a Göran-Gustafson and Feodor-Lynen fellow at the Royal Institute of Technology in Stockholm, Sweden. From 2000 until 2012, he was the Chair of Theoretical Physics at the University of St Andrews, UK. Ulf Leonhardt also had various visiting positions: in 2008, he was a Visiting Professor at the National University of Singapore; in 2011, at the University of Vienna; in 2012/13 at South China Normal University; and in 2023, at the Technical University of Vienna. In 2025, he is a distinguished visitor at the Institute of Advanced Studies in Luxembourg.
Ulf Leonhardt is the first from former East Germany to receive the Otto Hahn Award from the Max Planck Society. For his PhD thesis, he received the Tiburtius Prize of the Senate of Berlin. In 2006, Scientific American listed him among the top 50 policy, business, and research leaders of the world of that year. In 2008, he received a Royal Society Wolfson Research Merit Award, and in 2009, a Theo Murphy Blue Skies Award of the Royal Society. In 2012, he received a thousand-talent award from China. He is a Fellow of the Institute of Physics and the Royal Society of Edinburgh.
On-site at Campus Limpertsberg, you will have the opportunity to meet the speaker over a walking lunch from noon to all registered participants (Hall Bâtiment des Sciences). The talk will be at 1 PM in BS 0.03.
- Online – through Webex – to allow you to listen to the talk in case you are traveling or cannot make it on-site at Campus Limpertsberg. Here are the details to join the talk online:
https://unilu.webex.com/unilu/j.php?MTID=m546a1d4a3c3b58d9ceabd04cd0290d0e
Meeting number: 2780 314 7750
Meeting password: 7CReGYmGU73
For organizational reasons, please register for lunch by 21 April 2025