Little Ado About Everything: \eta CDM, a stochastic cosmology from structure formation
Institut für Theoretische Physik, Online
I will present the eta CDM framework, a new cosmological model aimed to cure some drawbacks of the standard Lambda CDM scenario, such as the origin of the accelerated expansion at late times, the cosmic tensions, and the violation of the cosmological principle due to the progressive development of inhomogeneous/anisotropic conditions in the late Universe via structure formation. To this purpose, the model adopts a statistical perspective envisaging a stochastic evolution of large-scale patches in the Universe, which is meant to render our ignorance on the complex processes leading to the formation of the cosmic web. The stochasticity among different patches is technically described via the diverse realizations of a multiplicative noise term (Âa little adoÂ) in the cosmological equations, and the overall background evolution of the Universe is then operationally defined as an average over the patch ensemble. I will highlight that the ensemble-averaged evolution in eta CDM can be described in terms of a spatially flat cosmology and of an Âemergent dark energy with a time-dependent equation of state, able to originate the cosmic acceleration with the right timing and to solve the coincidence problem. I will showcase the extremely good performances of the eta CDM model in confronting the most recent supernova type-Ia, baryon acoustic oscillations and structure growth rate datasets. I will stress that eta CDM is able to alleviate simultaneously both the H0 and the f sigma 8 tensions. Finally, I will propose that the Linders diagnostic test may constitute a helpful tool to better distinguish eta CDM from the standard scenario in the near future via upcoming galaxy surveys at intermediate redshifts such as those being conducted by the Euclid mission.
16:30
Heidelberg Joint Astronomical Colloquium
Timothy Davis
Tracing out the darkness with cold gas: dynamically probing galaxy evolution and black holes
In this talk I will describe how mapping the dynamics of gas clouds in the centre of galaxies can help us to constrain a wide range of astrophysical problems. From the enigmatic relation between galaxies and their supermassive black holes, to the suppression of star-formation in dying galaxies, the dynamics of cold gas provides an ideal probe that can help us make progress. I will show how ~ten parsec resolution ALMA observations can be used to estimate the masses of supermassive black holes in galaxies across the Hubble sequence, both dynamically, and via the newly discovered Âfundamental plane of black hole accretion in the millimetreÂ. I will show that the deep potential wells of massive galaxies change the small-scale structure of the ISM, suppressing star formation, and helping to keep bulge-dominated objects quenched. Finally I will show first results from the KILOGAS project, a new ALMA legacy survey for the resolved extragalactic ISM, that will map molecular gas and star formation across the Hubble sequence in nearly 500 nearby galaxies. To arrange a visit with the speaker during the visit, please contact their host: Dominika Wylezalek
17:00
Particle Colloquium
Prof. Dr. Marc Schumann
Dark Matter and more with XENONnT and XLZD\n
Physikalisches Institut INF 226, Konferenzraum 1-3 (Room 00.101 bis 00.103)
Wednesday, 23 July 2025
09:30
Seminar Dynamik und Struktur von Atomen und Molekülen
André Giraldi; Ultra-cold dynamics and collisions
Towards experimental studies of Interatomic Coulombic Electron Capture
Central Seminar Room, library building
16:30
Zentrum für Quantendynamik Kolloquium
Prof. Zoran Hadzibabic
Nonequilibrium Bose Gas in a Box
Physikalisches Institut, INF 226, K 1-3
Nonequilibrium Bose Gas in a Box Prof. Zoran Hadzibabic Department of Physics, University of Cambridge Compared to the traditionally studied harmonically trapped ultracold atomic gases, the spatially uniform gases produced in optical box traps offer many new possibilities for studies of fundamental many-body physics and comparisons with theory. I will give an overview of our recent experiments on out-of-equilibrium box-trapped Bose gases, including the studies of turbulence [1] and of universal coarsening dynamics [2,3]. [1] L. H. Dogra et al., Nature 620, 521 (2023) [2] M. Gazo et al., arXiv:2312.09248 [3] G. Martirosyan et. al., arXiv:2410.08204
Thursday, 24 July 2025
11:15
ARI Institute Colloquium
Rainer Spurzem
DRAGON star cluster simulations and how to form an intermediate mass black hole
ARI, Moenchhofstrasse 12-14, Seminarraum 1.OG
DRAGON star cluster simulations have provided the first fully realistic long-term simulations of globular star clusters, have reproduced LIGO/Virgo observed binary black hole mergers, and are now entering into the next phase to simulate more massive, young and nuclear star clusters. They are based on the direct N-body simulation code Nbody6++GPU. In the talk an introduction and overview to direct N-body simulation and DRAGON simulations is given. Two current new applications are then shown, first initially very dense star clusters which form quickly an intermediate mass black hole of order 50.000 solar masses, which could be a seed for massive black holes in the early universe. Second, a still ongoing project is discussed, in which an already pre-existing supermassive black hole in a nuclear star cluster is followed, how it tidally disrupts stars, and captures low-mass stars, white dwarfs, neutron stars and stellar mass black holes.
Monday, 28 July 2025
10:00
How to MPIK
Lobby area (red sofas), Library
International Office/Administration
We will answer all kinds of questions about the daily work routine at MPIK. The event is of course intended for new employees, internationals, but also for old employees who have to deal with certain problems with the administration in Germany or at MPIK.
Tuesday, 29 July 2025
14:00
Astrophysics Seminar
Dr. Karol Fulat - University of Wisconsin
The influence of pre-existing turbulence on electron acceleration at collisionless shocks
