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Graduate Seminar, 23rd April

Speaker: Katarzyna Frankiewicz

Title: Search for dark matter induced neutrinos with the Super-Kamiokande detector .

Abstract: Indirect searches for dark matter are performed based on atmospheric neutrino data collected with the Super-Kamiokande (SK) detector in years 1996-2016. The excess of neutrinos from possible dark matter sources such as Earth and Galactic Center, compared to the expected atmospheric neutrino background is searched. Angular distributions and energy spectra as expected for signal and background are taken into account and various dark matter annihilation channels are considered. All event samples (fully-contained, partially-contained along with upward-going muons), including both electron and muon neutrinos, covering a wide range of neutrino energies (GeV to TeV) are used. The allowed number of dark matter induced neutrinos which can be contained in SK data so far is estimated. Obtained limits on dark matter induced neutrino flux from the Earth’s core are related to the limit on spin-independent WIMP-nucleon scattering cross section and compared against the results of direct detection experiments. In case of the Galactic Center analysis, the upper limit on the dark matter self-annihilation cross-section is derived.

Graduate Seminar, 12th March

Speaker:  Chetan Bavdhankar

Title: Our velocity and acceleration in the Universe are in the same direction! (Local Group Motion using Supernova type Ia)

Abstract: Supernova type Ia (SN Ia) are one of the accurate distance indicators which are used to measure the distances to distant galaxies. Using the redshift of the galaxy and it’s distance (estimated from SN Ia) we can measure its peculiar velocity. Nearby galaxies in the Universe are bound gravitationally and these bound systems of galaxies are called galaxy groups. We are part of such group which is called ‘The Local Group’ (LG), Andromeda galaxy is also member of this group. These galaxy groups show motion due to nearby masses such as other groups, clusters and superclusters. Our Local Group is also showing such motion and this motion can be seen in CMB dipole. To estimate the responsible masses for this motion of Local Group, dipole in peculiar velocities is useful. This dipole in peculiar velocities has the information about effective distance that can cause our group’s motion. In my work, I have tried to calculate that distance. As SN Ia are not very frequent events, we don’t have enough data points to get very accurate results so we need to generate artificial data more realistically. I have used velocity fields in the Local Universe to generate such a artificial SN Ia data and got the results which says that ‘Our velocity and acceleration in the Universe are in the same direction!’

Graduate Seminar, 26th February

Speaker: Szymon Nakoneczny

Title: Natural language processing methods in biological activity prediction and quasar detection in large scale photometric surveys.

Abstract: The first part will focus on my master ‘s thesis. Virtual screening is a process in which databases of chemical compounds are searched in order to f ind structures characterized with a high biological activity, possible drug candidates. The goal is to classify active compounds by combining the natural language processing methods with a text representation of compounds. The second part is going to cover an approach of detecting quasars with means of machine learning. Because it is not possible to fully sample extragalactic objects with spectroscopy, quasars analysis requires a proper automated approach based on photometric surveys. We are going to focus on describing a problem and showing preliminary results of our approach.

Graduate Seminar, 23rd October

Speaker: Oleksandr Kovalenko

Title: “Chiral magnetic effect in nucleus-nucleus collisions at LHC energies”.

Abstract: The chiral magnetic effect (charge separation in strong magnetic field) is of great importance for QCD studies as it is a direct consequence of parity violation. Main observables and collision parameters that are used in ultra relativistic heavy ion physics will be presented. The most recent results on the Chiral Magnetic Effect in nucleus-nucleus collisions will be reviewed.

Graduate Seminar, 16th October

Speaker: Erik Kofoed

Title: Chiral Perturbation Theory for Neutron-antineutron Oscillations

Abstract: Neutron-antineutron oscillations is a possible consequence of baryon number violating physics. Transition matrix elements for oscillations can be calculated numerically, up to an overall scale, with lattice simulations. Such simulations contain artefacts such as choice of unphysical pion masses and finite volume effects. In order to estimate the impact of these artefacts we compute the matrix element in Chiral Perturbation Theory in both infinite and finite volume and at a variable pion mass.

Graduate Seminar, 9th October

Speaker:  Artem Poliszczuk

Title: Fuzzy support vector machine application to data mining in sky surveys.

Abstract: The first application of the fuzzy support vector machine (FSVM) algorithm as the automated classification tool for astronomical catalogs will be presented. This new approach allows to perform a more trustable classification of astronomical sources by making use of the measurement uncertainties. The performance of different versions of the SVM algorithm is examined on the AKARI-NEP data and the resultant catalog of infrared-selected galaxies is presented.