Institut für Theoretische Physik, PI, Goldene Box & Online via Zoom
A heavy impurity moving in a superfluid has remarkable properties. The medium dresses the impurity into a polaronic quasiparticle, and at strong binding the polaron can substantially deform the surrounding medium. When there are two or more polarons, fluctuations of the medium induce a Casimir interaction between polarons. We investigate this induced interaction using the Gross-Pitaevskii equation and effective field theory (EFT) and find regimes of scale invariance, Yukawa and power-law scaling.
16:30
Particle and Astroparticle Theory Seminar
Dr. Juraj Klaric (Louvain)
Non-perturbative production of fermionic dark matter from fast preheating
Seminar room Lindner 339, Gentner lab, 2nd floor
In this talk we will discuss non-perturbative production of fermionic dark matter in the early universe, during the transition between inflation and radiation domination known as (p)-reheating. Specifically, I will focus on the gravitational production mechanism accompanied by the coupling of fermions to the background inflaton field. The latter leads to the variation of effective fermion mass during preheating and makes the resulting spectrum and abundance sensitive to its parameters. Assuming fast preheating that completes in less than the inflationary Hubble time and no oscillations of the inflaton field after inflation, we find an abundant production of particles with energies ranging from the inflationary Hubble rate to the inverse duration of preheating. The produced fermions can account for all observed dark matter in a broad range of parameters. As an application, we discuss the non-perturbative production of heavy Majorana neutrinos in the model of Palatini Higgs inflation.
Tuesday, 12 December 2023
14:15
Kosmologie und Elementarteilchenphysik
Guillermo Martínez Somonte
Bayesian inference methodology for Primordial Power Spectrum reconstructions from Galaxy Clustering Surveys
Institut für Theoretische Physik, Online
We develop a non-parametric method to reconstruct the primordial power spectrum PR(k) from Large Scale Structure (LSS) data through Bayesian inference and nested sampling. The performance of the method is studied by applying it to simulations of the clustering of two different object catalogues, low-z (ELGs) and high-z (QSOs), with two different photometric errors. These object clusterings are derived from different templates of the primordial power spectrum motivated by models of inflation: the Standard Model (SM) power law characterized by the two parameters As and ns; a local feature template; and a global oscillatory template. Our reconstruction method involves sampling N knots in the log {k,PR(k)} plane. We use two statistical tests to examine the reconstructions for signs of primordial features: a global test comparing the evidences and a novel local test quantifying the power of the hypothesis test between the power law model and the marginalized probability over N-knots model. Scenarios with different redshift bins, photometric errors, feature amplitudes and detection levels are discussed. The method shows good performance in all scenarios considered. In particular, the tests show no feature detection for the SM. The method is able to detect deviations from the power law power spectrum for all considered features with amplitude above a given threshold, and the best sensitivity is reached when combining several redshift bins of low-z or high-z objects. In addition, we include a first application to real data from the Sloan Digital Sky Survey Luminous Red Galaxy Data Release 4 (SDSS LRG 04), finding no preference for deviations from the primordial power law. The method is flexible and model independent, and progress on varying the cosmological parameters is being made to improve the completeness of the approach. Applications and forecasts for upcoming LSS catalogues, as Euclid, BOSS or J-PAS, are expected.
16:30
Heidelberg Joint Astronomical Colloquium
Dr Roberto Decarli
The early growth of quasars and their host galaxies
Philosophenweg 12, Main Lecture hall (gHS)
Since their first discovery about 60 years ago, quasars have been at the forefront of our understanding of the distant universe. We now know >400 quasars at redshift z>6, when the Universe was < 1 Gyr old. Their mere presence poses a challenge to models of the formation and early growth not only of their massive black holes, but also of their host galaxies, their dust content, and the large-scale structures where they reside. In the last few years, however, we have witnessed transformational leaps in our understanding of the properties of early quasars, thanks to unprecedented observational achievements, in particular with ALMA and JWST. We have now accurate black hole mass estimates in quasars up to z~7.6; we have mapped the gas and dust distribution in the quasar host galaxies down to 100 pc resolution, and quantified their star formation rate, metallicity, and other properties (gas density, photoionization conditions, etc); and we have secured a census of tens of spectroscopically-confirmed galaxies in the environment of quasars at z>6. These observational results allow us to sketch a novel picture on the formation of some of the most massive astrophysical sources in the early Universe. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr Decarli is available for meetings by arrangement with his host, Kathryn Kreckel (kathryn.kreckel@uni-heidelberg.de)
Wednesday, 13 December 2023
09:30
Seminar Dynamik und Struktur von Atomen und Molekülen
Moto Togawa
QED tests of Li-like ions with synchrotron radiation
Zentraler Seminarraum / Central seminar room (library)
Thursday, 14 December 2023
11:15
ARI Institute Colloquium
Ulrich Bastian
Gaia's "Focused Product Release" of October 2023
ARI, Moenchhofstrasse 12-14, Seminarraum 1.OG
As an interim between Gaia DR3 (2022) and DR4 (2026), ESA and the science consortium have published five new data sets derived from Gaia observations, including four entirely new data types, and one drastically improved data set. Contrary to the main releases, which address almost any area of astronomy, these data sets are more specialized. In the talk I will briefly describe them: Drastically improved minor-planet orbits, newly discovered gravitational lenses (multiple images of quasars), half a million additional Gaia stars in the core of omega Centauri, the three-dimensional distribution of diffuse interstellar bands in stellar spectra, the radial-velocity variations of long-period pulsating variables. Gaia DR4 will present a large number of new data types, and strong improvements in many of the already established ones. The present data sets are partly meant to enable follow-on work prior to DR4, and partly as "appetizers" for things to come in 2026.
16:15
Particle and Astroparticle Theory Seminar
Dr. Saereh Najjari (MPIK)
Tba.
Seminar room 106, Philosophenweg 12.
Joint Seminar with ITP Heidelberg; Teilchentee
Teilchen-Tee
Saereh Najjari
Dark Matter and Neutrino Masses from Light hidden sectors (joint Teilchentee with MPIK)
Institut für Theoretische Physik, Phil12, SR106
We consider a class of models in which the hidden sector is conformal in the ultraviolet, and the conformal breaking/compositeness scale lies at or below the weak scale. The interaction between the hidden sector and the Standard Model occurs through the neutrino portal. Within this framework, the lightest stable composite state of the hidden sector is identified as dark matter. When the hidden sector is in thermal equilibrium with the Standard Model, the relic abundance of dark matter is produced through the freeze-out mechanism, involving dark matter annihilation into final states containing neutrinos. Conversely, when the hidden sector is out of equilibrium with the Standard Model, dark matter is produced through the freeze-in mechanism. Remarkably, the neutrino portal not only connects dark matter to the Standard Model but also leads to the generation of neutrino masses via the inverse seesaw mechanism, where composite hidden sector states assume the role of singlet neutrinos. To provide a concrete realization of this framework, we construct a holographic model based on a five-dimensional warped geometry and study its phenomenological implications.
Friday, 15 December 2023
17:00
Physikalisches Kolloquium
Prof. Dr. Metin Tolan
Geschüttelt, nicht gerührt: James Bond im Visier der Physik
INF 308, Hörsaal 1
Jeder kennt James Bond, den smarten Geheimagenten, der von Q mit kleinen Gadgets versorgt wird, um seine Abenteuer zu bestehen. Doch wie viel Realität steckt hinter den Erfindungen von Tüftler Q? Funktionieren die Uhren von 007 wirklich? Wie schafft es Bond immer wieder, tödliche Situationen zu überleben? Kann sich ein Auto wirklich sieben Mal überschlagen? Muss James Bond Physiker sein, damit er seine waghalsigen Stunts überlebt? Im Vortrag wird diesen Fragen anhand von vielen Szenen aus den beliebten Filmen nachgegangen und am Ende die Frage aller Fragen geklärt: Warum trinkt 007 seinen Wodka-Martini geschüttelt und nicht gerührt?
Tuesday, 19 December 2023
14:15
Kosmologie und Elementarteilchenphysik
Pavel Kroupa
TBA
Institut für Theoretische Physik, Online
TBA
17:00
Particle Colloquium
Nicolo Jacazio
ALICE looks at the sky
Physikalisches Institut INF 226, Konferenzraum 1-3 (Room 00.101 bis 00.103)
Wednesday, 20 December 2023
11:15
Gentner Colloquium for Astroparticle Physics
Dr. Christian Buck (MPIK, HD)
Neutrino detection at nuclear reactors
Central seminar room, library building
Abstract:
The inverse beta decay in organic liquid scintillators is the basis for antineutrino detection in many experiments at nuclear reactors. The development of highly stable gadolinium loaded scintillators contributed to the success of recent experiments determining neutrino oscillation parameters and searching for sterile neutrinos. New scintillator developments based on opaque, gel-like and safe materials might find applications in the upcoming generation of detectors. Another detection channel is the coherent elastic neutrino nucleus scattering as studied in the CONUS experiment using germanium detectors with very low energy thresholds. This interaction has the advantage of a larger cross section offering the possibility for more compact neutrino detectors.
