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- 17.02., Marco Turchetta (IFY, NTNU): Searches and characterisation of optical and X-ray pulsations from candidate millisecond pulsars
Abstract: In recent years three transitional millisecond pulsars (tMSPs) have been identified, showing transitions between rotation and accretion-powered pulsar state. In 2016 the SiFAP2/TNG (INAF) optical photometer unveiled for the first time optical pulsations from one of these systems, PSR J1023 + 0038 (J1023). The issues in explaining this phenomenon in terms of emission fed by either rotation or accretion power have fostered the formulation of new models, in which both the two mechanisms conspire to yield the emission of optical pulsations. During this talk I will present the results obtained in my master thesis work, which was aimed to gain insight into the nature of these optical pulsations. At this purpose, I have performed periodicity searches in optical and X-ray band from five candidate tMSPs, all showing the same multi-wavelength emission features observed in both the two states of J1023. - 21.02., Patrick Reichherzer (RUB Bochum): !postponed! Influence of diffusive cosmic-ray transport on multimessenger observables
Abstract: Cosmic-ray transport in astrophysical environments is often dominated by diffusion in a magnetic field with a turbulent component. The diffusion properties of charged particles directly influence observable properties, such as the spectrum of cosmic rays and their secondaries produced in interactions. In many diffusion scenarios, the simplified assumption of fully resonant Kolmogorov diffusion in the quasi-linear limit results in a parallel diffusion coefficient D ~ E^(1/3). A quantitative investigation of the scattering regimes, however, shows that the diffusion coefficient tensor can deviate significantly from this behaviour. In this talk, the complex dependencies of charged particle diffusion on the turbulence level of the magnetic field are presented. Examples of how this affects observational signatures will be shown in the context of galaxies or the transient sky, i.e., flaring Blazars.
- 10.03., Petter Taule (TU Munich): Non-linear structure formation in cosmologies with non-trivial time- and scale-dependence
Abstract: Mapping out the large-scale structure (LSS) of the Universe is one of the key advances driving precision cosmology. Current and near-future large-scale surveys offers the prospect of testing deviations of the LambdaCDM model, such as measuring the absolute neutrino mass scale or probing properties of dark energy or dark matter. Major efforts have been devoted to describing non-linear scales perturbatively, and in this talk I discuss a framework for computing loop corrections in cosmological perturbation theory for cosmologies with non-trivial time- and scale-dependence. I apply this framework to cosmologies with massive neutrinos taking neutrino perturbations beyond the linear level into account. Finally, I discuss the bispectrum in the context of the effective field theory of LSS, going to next-to-next-to-leading order in perturbation theory.
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- 07.04. Inga Strumke (AI Lab, NTNU): Introduction to machine learning - a guided tour with examples from particle physics
Abstract: Inga will give us a crash course in machine learning, how it's done and which forms exist. She will take us through a a few examples from HEPP, demonstrating current applications and their challenges. Finally, the million dollar question of how to explain machine learning models - also referred to as the "black box problem" - is disseminated and an overview of the status of explainable AI (XAI) is given. The talk is open for everybody, and intellectually available to anyone comfortable with arithmetic and the existence of the Higgs boson :-)
slides
- 12.05., Patrick Reichherzer (RUB Bochum): Influence of diffusive cosmic-ray transport on multimessenger observables
Abstract: Cosmic-ray transport in astrophysical environments is often dominated by diffusion in a magnetic field with a turbulent component. The diffusion properties of charged particles directly influence observable properties, such as the spectrum of cosmic rays and their secondaries produced in interactions. In many diffusion scenarios, the simplified assumption of fully resonant Kolmogorov diffusion in the quasi-linear limit results in a parallel diffusion coefficient D ~ E^(1/3). A quantitative investigation of the scattering regimes, however, shows that the diffusion coefficient tensor can deviate significantly from this behaviour. In this talk, the complex dependencies of charged particle diffusion on the turbulence level of the magnetic field are presented. Examples of how this affects observational signatures will be shown in the context of galaxies or the transient sky, i.e., flaring Blazars.
- 19.5. Sven Heinemeyer (IFT (CSIC), Madrid): New Physics around the corner?!
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