Tuesday, 10 June 2025
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14:15 |
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Kosmologie und Elementarteilchenphysik |
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Astrid Eichhorn |
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Asymptotic safety meets Horndeski gravity |
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Institut für Theoretische Physik, Phil19 |
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Asymptotic safety can render quantum field theories ultraviolet complete and predictive. There is good evidence that quantum gravity may be asymptotically safe. After presenting the main idea and reviewing some of the evidence for it, I will focus on scalar-tensor theories and discuss results on asymptotically safe scalar-tensor theories from the perspective of Horndeski gravity. In particular, I will explain how the predictive power of asymptotic safety constrains terms in a Horndeski Lagrangian and how asymptotic safety could serve as a theoretical selection principle for dynamical dark energy models, both in and beyond Horndeski. |
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16:30 |
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Heidelberg Joint Astronomical Colloquium |
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Anna de Graaff |
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A new view of the red and distant Universe from JWST/NIRSpec |
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In its three years of science operations, JWST has revolutionized our understanding of the early Universe. Arguably the most impressive leap forward has come from the NIRSpec instrument, providing a detailed view of the physical processes  star formation, feedback, and the growth of massive black holes  that shaped the faintest, reddest, and most distant galaxies. Among a wealth of discoveries, one overarching surprise has emerged: galaxies in the early Universe formed and matured extremely fast. Massive galaxies with old stellar populations exist already in the first billion years of the Universe, with some showing morphologies reminiscent of our own Milky Way, while others host unexpectedly massive black holes. The potential implications on galaxy formation models are profound, as current models struggle to reproduce such rapid galaxy assembly. I will present an overview of key extragalactic surveys from JWST/NIRSpec, focusing on the major discoveries that they have enabled and the challenges that remain. |
Wednesday, 11 June 2025
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09:30 |
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Seminar Dynamik und Struktur von Atomen und Molekülen |
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Carlo Kleine; Excited atoms & molecules in strong fields |
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Intensity Dependencies in Nonlinear Frequency Upconversion and Bright Nonclassical Light |
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Zentraler Seminarraum / Central seminar room (library) |
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11:15 |
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Bothe-Kolloquium |
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Dr. Lukas Bruder; Universität Freiburg |
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Pushing nonlinear spectroscopy and coherent control towards highly dilute samples and the extreme ultraviolet spectral domain |
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Central seminar room, library building |
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We develop nonlinear spectroscopy and coherent control techniques in the gas phase at visible wavelengths and push boundaries towards applications in the extreme ultraviolet (XUV) spectral domain. In the first part of my talk, I will report about high-resolution two-dimensional spectroscopy in the gas phase to study the structure and ultrafast dynamics of molecular nanosystems isolated from environmental perturbations. The nanosystems consist of atomic clusters doped with individual molecules which provide handy systems to explore solute-solvent interactions and effects of nano confinement. In the second part of my talk, I will introduce our methods for coherent manipulation of XUV pulses and discuss applications. We use phase-modulated XUV pulses for Fourier transform spectroscopy and spectral phase shaping to control strong-field processes. |
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14:15 |
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Kosmologie und Elementarteilchenphysik |
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Laura Herold |
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TBA |
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Institut für Theoretische Physik, Online; Note unusual date (Tunch schedule) |
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TBA |
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15:30 |
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Seminar Stored and Cooled Ions |
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Dr. Tim Lellinger, CERN/MPIK |
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First laser-spectroscopy measurements across N = 32 in the calcium isotopic chain at the COLLAPS setup at ISOLDE/CERN |
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Hybrid seminar: central seminar room, library building + Zoom: Meeting-ID: 915 1204 2752 Passcode: 758933 |
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PLEASE NOTE THE UNUSUAL TIME! |
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16:30 |
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Zentrum für Quantendynamik Kolloquium |
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Dr. Sylvain Ravets |
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Synthetic Polariton Matter: Hamiltonian Tomography and Optical Nonlinearities |
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Physikalisches Institut, INF 226, K 1-3 |
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Exciton-polaritons are hybrid quasiparticles arising from strong coupling between cavity photons and excitons in semiconductor quantum wells [1]. They offer a versatile platform for engineering synthetic photonic materials with tailored properties. In this talk, I will present recent progress in the design and characterization of polariton lattices, where microcavity pillars are arranged into 1D or 2D arrays to implement tight-binding Hamiltonians. I will first present a method for Hamiltonian engineering based on the patterning of coupled microcavities, and explain how this allows full control over the lattice geometry and hopping parameters. I will focus on a recently developed measurement technique that enables full reconstruction of the Bloch Hamiltonian, by analyzing the momentum-resolved emission spectra from the lattice. This optical tomography technique provides access to every Bloch mode across the entire Brillouin zone, and enables us to experimentally explore the quantum geometry and topology of polariton lattices. In the second part of the talk, I will explore how polariton-polariton interactions can be harnessed in such systems [1]. By exploiting the matter component of polaritons, we introduce interaction-induced control over the onsite energies. I will show how this enables the all-optical introduction of a vacancy in a SuÂSchriefferÂHeeger (SSH) chain, creating a nonlinear interface for Bogoliubov excitations [2]. This result illustrates how interactions can lead to the emergence of new nonlinear topological phases in driven-dissipative systems [3]. These advances demonstrate the potential of polariton platforms to probe and control synthetic photonic materials. [1] I. Carusotto, and C. Ciuti, Rev. Mod. Phys. 85, 299 (2013) [2] Nicolas Pernet, et al., Nature Physics 18, 678 (2022) [3] D. Solnyshkov, et al., Optical Materials Express 11, Issue 4, 1119 (2021) Figure: FIG. 1. a. SEM image of a polariton honeycomb lattice, implementing a Âphotonic h-BN latticeÂ. b. Measured band structure, and c. experimentally reconstructed Berry curvature. Sylvain Ravets is a CNRS research scientist at the Centre for Nanosciences and Nanotechnology (C2N, CNRS / Université Paris-Saclay, France). His work explores hybrid light-matter systems, with a focus on engineering exciton-polaritons in semiconductor microcavities to study topological and quantum phenomena in synthetic photonic lattices. He earned his Ph.D. in physics in 2014 through a joint program between the Joint Quantum Institute (University of Maryland) and the Institut dÂOptique, working on quantum engineering with cold atoms. He then joined ETH Zurich as a postdoctoral fellow, where he investigated solid-state quantum optics in the Institute of Quantum Electronics. Since joining CNRS in 2018, he has led an experimental program at the intersection of nanophotonics and quantum materials. He was awarded an ERC Starting Grant in 2020. |
Thursday, 12 June 2025
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11:15 |
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Teekolloquium |
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Dr. David Lucas, University of Oxford, Department of Physics |
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Quantum networking and computing with trapped ions |
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Grosser Hoersaal/Big Lecture Hall (library) |
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ARI Institute Colloquium |
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Geraint Lewis |
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Confronting the Cosmological Principle: How secure are the foundations of the cosmos? |
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ARI, Moenchhofstrasse 12-14, Seminarraum 1.OG |
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I will present our recent work using quasars and radio galaxies to challenge the cosmological principle  the foundation of modern cosmology. This principle asserts that the universe is isotropic and homogeneous, yet the Cosmic Microwave Background (CMB) reveals a strong dipole, attributed to our motion relative to the local Hubble flow. This motion should be imprinted on other observables, and I identify a dipole in large-scale surveys of cosmological sources. Whilst there is general agreement in the dipole direction, the amplitude remains at odds with expectations from the CMB. I will explore possible explanations for these tensions and consider whether a fundamental shift in our cosmological understanding is on the horizon. |
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16:15 |
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Teilchen-Tee |
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Aqeel Ahmed |
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Primordial Leptogenesis |
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Institut für Theoretische Physik, Phil12, SR106 |
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In this talk, I will present a framework that provides a mechanism to generate the baryon asymmetry of the universe through inflationary dynamics. I will introduce a minimal model where lepton and baryon asymmetries are generated during a reheating phase through the asymmetric decay of the inflaton field into SM Higgs bosons. This primordial lepton asymmetry is then converted to the baryon asymmetry through the electroweak sphaleron processes. Our mechanism offers an elegant UV completion of Dirac Leptogenesis. |
Friday, 13 June 2025
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17:00 |
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Physikalisches Kolloquium |
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Prof. Dr. Erwin Frey |
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Emergence and Self-Organisation in Biological Systems |
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KIP, INF 227, Hörsaal 1 |
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Isolated systems tend to evolve towards thermal equilibrium, a special state that has been a research focus in physics for more than a century. By contrast, most processes studied in living and life-like systems are driven and far from thermal equilibrium. A fundamental overarching hallmark of all these processes is the emergence of structure, order, and information, and we are facing the major challenge of identifying the underlying physical principles. Two exciting problems are the self-organised formation of spatio-temporal patterns and the robust self-assembly of complex structures. In both fields, there have been recent advances in understanding the underlying physics that will be reviewed in this talk. |
Tuesday, 17 June 2025
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14:15 |
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Kosmologie und Elementarteilchenphysik |
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Emille E. O. Ishida |
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TBA |
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Institut für Theoretische Physik, Online |
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TBA |
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16:30 |
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Heidelberg Joint Astronomical Colloquium |
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Jennifer Schober |
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The magnetic history of the Universe |
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Magnetic fields permeate nearly every astrophysical environment, from planets and stars to galaxies and galaxy clusters. In these cosmologically overdense regions, magnetic fields are thought to arise primarily from magnetohydrodynamic (MHD) dynamos. These mechanisms convert turbulent kinetic energy into magnetic energy through the stretching and twisting of field lines. In the first part of this talk, I will present recent advances in our understanding of MHD dynamos. In the second part, I will focus on the vast underdense regions of space, cosmic voids, where blazar observations have revealed the existence of magnetic fields. As voids lack turbulence and therefore the energy source of classical dynamos, these large-scale magnetic fields likely originate in the very early Universe shortly after the Big Bang and therefore offer a unique window into fundamental physics. I will outline key theoretical models of magnetogenesis and present new insights in the pre-recombination evolution of these primordial magnetic fields from state-of-the-art numerical simulations. To arrange a visit with the speaker during the visit, please contact their host: Philipp Girichidis |
Wednesday, 18 June 2025
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09:30 |
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Seminar Dynamik und Struktur von Atomen und Molekülen |
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Jan-Hendrik Oelmann; Highly charged ion dynamics |
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tba |
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Central Seminar Room, library building |
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15:00 |
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Special Seminar |
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Dr. Laura Dreissen, Vrije Universiteit Amsterdam |
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Precision quantum metrology in trapped ions for tests of fundamental physics |
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Zentraler Seminarraum / Central seminar room (library) |
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Abstract:
The Standard Model (SM) of particle physics describes fundamental interactions between the known particles extremely well, but it fails to provide answers for big open questions, e.g. the origin and composition of dark matter or the matter anti-matter asymmetry. Hunting for new physics effects with small cross sections, whether through broken symmetries, new feeble interactions or heavy particles at energies beyond our current reach, requires a high sensitivity. In this talk I will elaborate on how precision quantum metrology in trapped cold ions can be used for competitive tests of the SM and search for new physics [1]. In particular, I will show how isotope shift measurements in trapped ions can be used as a sensitive probe for a possible new boson-mediated fifth force that couple electrons and neutrons [2]. Our latest results in Yb+ ions [4] were used to benchmark ab-initio nuclear theory and put competitive bounds on a new long-range boson. To further push this field forward, my research focusses on novel techniques involving quantum state engineering. With entangled states in Ba+ I aim to become more robust against ambient noise and systematic effects, hereby improving the measurement sensitivity. I will apply these techniques to further explore isotope shift spectroscopy, improve optical clock spectroscopy and investigate atomic parity violation. In this talk, I will give a general overview of my line of research and report on the experimental progress.
[1] M. Safronova et al., Rev. Mod. Phys. 90, 025008 (2018)
[2] J. C. Berengut et al., 413 Phys. Rev. Lett. 120, 091801 (2018)
[3] M. Door et al., Phys. Rev. Lett 134, 063002 (2025). |
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16:15 |
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Teilchen-Tee |
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Stella Tallulah Schindler |
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TBA |
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Institut für Theoretische Physik, Phil12, SR106 |
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TBA |
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