The seminar of the Astro & Theory Section takes place normally on Wednesdays in D5-106, starting at 15. If you would like to suggest a seminar speaker or want to be added to the email list, please contact the organizer (

The (planned) seminars in 2024 are

  • 06.02. Michael Unger  (KIT and IFY, NTNU): News from the Galactic Magntic Field (...and the Origin of the Amaterasu Particle)
    Abstract:  Galaxies are known to be permeated by large-scale magnetic fields with energy densities comparable to the turbulent and thermal energy densities of the interstellar medium. A good knowledge of the global structure of these fields is important to understand their origin and to infer their effect on galactic dynamics and the propagation of charged particles in galaxies.  In this talk I will present new studies of the global structure of the magnetic field of our Galaxy based on the analysis of recent new full-sky data of extragalactic rotation measures and the final polarized intensity maps from WMAP and Planck. The analysis employs the latest models for the thermal electron density tuned to the dispersion measures of Galactic pulsars and state-of-the-art cosmic-ray electrons models, needed to predict the rotation measures and synchrotron emission from the Galaxy, respectively. As a result, I will present a major revision of the widely-used Jannson-Farrar 2012 model of the magnetic field of the Galaxy. In addition to a fiducial magnetic field model, a suite of alternative models was studied that fit the data with similar quality, but use different model assumption.  This suite of models is then used to place a lower limit on the model uncertainties. As an application, I will discuss the uncertainties of the predicted deflection of ultrahigh-energy cosmic rays in the Galaxy, in particular the origin of the extremely energetic "Amaterasu particle" recently reported by the Telescope Array Collaboration.

  • 13.02. Lena Saurenhaus  (MPP Muenchen): Seyfert Galaxies as Astrophysical Neutrino Sources
    Abstract:  Active galactic nuclei (AGNs) are among the most powerful objects in the Universe and are suspected to be sources of astrophysical neutrinos. Recently, the IceCube Collaboration reported an excess of neutrino events with energies between 1.5 and 15 TeV associated with NGC 1068, a nearby Seyfert galaxy with an extraordinarily high intrinsic X-ray flux. The lack of observable gamma rays in this energy range indicates that these neutrinos are likely to be produced in the AGN corona, which is opaque to high-energy gamma rays. I will give an overview over existing neutrino emission models for NGC 1068-like sources and talk about our current project, which explores the prospects of observing other hidden neutrino sources with similar neutrino production mechanisms and aims to constrain their contribution to astrophysical neutrino observations.

  • 05.03. Triantafyllos Kormpakis  (IFY, NTNU): The Particle in Cell method: Theory and astrophysical applications
    Abstract:  The Particle in Cell (PIC) numerical method (first developed in the 1950s) aims to simulate the behavior of plasmas in the presence of electric and magnetic fields. With it's unique architecture, moving particles on a Langrangian frame and depositing their charge and current densities on a fixed eulerian mesh, it tracks the evolution of systems where high densities of charged particles (mainly electron-positron pairs) and/or strong electromagnetic fields are present. In the parameter space where the Force free magnetic field approximation is valid, such as the magnetospheres of pulsars, magnetars and active galactic nuclei (AGN) jets, the PIC scheme accurately simulates features such as magnetic reconnection phenomena, enables the study of shock acceleration, particle flows and emission regions. In this talk I will first give a basic overview of the PIC method, particularly in its implementation on the Zeltron code. This will lead to the discussion of my application and qualitative reproduction of existing results, in magnetic reconnection in ABC magnetic fields (particular eulerian flows with stable as well as chaotic flow regimes). Lastly, I will also describe my application and results of PIC methodology to a test case: an axially symmetric magnetic field, representing a magnetic field topology present in an AGN jet.s.

  • 14.03. Rita C. Anjos  (U Parana): The nature of high-energy multi-messenger sources 
    Abstract:  In this seminar, I will present the main results of high-energy physics, considering charged particles and gamma radiation as multi-messengers. In this context, the primary sources of these particles will be discussed, along with significant challenges in the field and some results from my research group in Brazil. I will also introduce some diversity/outreach initiatives developed by the group to foster the inclusion of children and youth in the subatomic universe. 

  • 19.03. Ellis Owen  (U Osaka): Cosmic Ray feedback in galaxy evolution 
    Abstract:  Cosmic rays go hand-in-hand with violent and energetic astrophysical conditions. They are an active agent within galactic and circumgalactic ecosystems, where they can deposit energy and momentum, modify the circulation of baryons, and even have the potential to regulate star-formation on local and galactic scales. Their influence in galaxies can be probed using observable signatures across the electromagnetic spectrum, with high energy radiation being particularly important to determine their energy budget, feedback power and hydrodynamic effects. In this talk, I will discuss some of the astrophysical impacts hadronic and leptonic cosmic rays can have in and around galaxies, how their influence can be probed using signatures in X-rays and gamma-rays, and the opportunities soon to open-up that will allow us to map-out the multi-scale effects of cosmic rays in galaxies near and far.

  • 21.03. Dmitri Semikoz  (APC Paris): Multi-messenger signatures of astrophysical neutrino sources 
    Abstract:  In this talk I’ll review recent observations of galactic and extragalactic neutrino sources comparing them to the predictions of theoretical models. At multi-TeV energies dominant contribution to the neutrino flux of Milky Way is expected from Galactic Ridge, brightest region of our  Galaxy, where cosmic rays interact with interstellar gas and produce secondary gamma-rays and neutrinos.  In neutrinos first hint of Galactic Ridge  was found in ANTARES in 2022.  In 2023  IceCube detected it in cascade channel with 4 sigma significance.  I’ll discuss perspectives of detection of Galactic Ridge by  future neutrino telescopes and by LHAASO, SWGO and CTA in gamma-rays. Also I’ll review recent gamma-ray and neutrino observations from Pevatron source in Cygnus region.

    For extragalactic neutrino sources I’ll focus on Seyfert galaxies. In addition to well known NGC 1068 only two other sources, based on their  hard X-ray properties,   NGC 4151 and NGC 3079 are expected to be detectable in 10 years of IceCube data.  We find an evidence for neutrino signal from both sources in publicly available ten-year IceCube dataset. The chance coincidence probability to find the observed neutrino count excesses in the directions  of the two out of two expected sources, in addition to the previously reported brightest source, is p<2.6e-7. This corresponds to the detection of Seyfert galaxies as a neutrino source class. 


  • 25.06. Paul Lai  (University College London): Tracking the gas distribution in the Galactic Centre using neutrinos  and Alisha Roberts (IFY, NTNU): Investigating Neutrino Emissions from Blazar 3C 454.3

  • tbd. Jens Oluf  Andersen  (IFY, NTNU): Pion condensation and pion stars
    Abstract:  In this talk I will discuss pion condensation in the context of two and three-flavor chiral perturbation theory. I will present results for quark and pion condensates as functions of the isospin chemical potential. The results compare favorably to those of lattice QCD. As an application,  I will discuss pion condensation in a dense neutrino cloud and the possibility of pion stars. These are compact objects with a mass up to 20 solar masses and radii of  up to 140km.

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