Graduate Seminar, 15th April

Speaker: Artur Miroszewski

Title: Early universe cosmology and the coherent states

Abstract: The theory of General Relativity seems to be a well chosen tool to describe the evolution of the universe. Starting from very simplified model of the universe, Friedmann-Lemaître-Robertson-Walker spacetime, we are able to explain most of the observable phenomena on the cosmic scale. On the other hand the cosmological solutions in GR tend to contain past-incomplete geodesics, also know as singularities. The singularities occur in the very early universe regimes, where apart from the GR we should take into account quantum effects. Although the theory of Quantum Gravity seems to be far from invented and understood, the semi-classical approach may be able to point us to some features of it. During my talk I will present the semi-classical approach based on the coherent states, leading to the Big Bang singularity avoidance scenario- the Big Bounce.

Graduate Seminar, 8th April

Author: Chetan Bavdhankar

Title: Peculiar Velocities – a very important probe of cosmology

Abstract: Peculiar velocity of galaxies is one of the very important probes of the cosmological model (Strauss and Willick (1995)). Since peculiar velocities are induced by gravity only, they can be used to obtain various cosmological parameters such as mean matter density or the growth of structure (Nusser and Davis (2011)). The large-scale fluctuations of the matter distribution can be determined using bulk flows where a given volume of the sample shows the net peculiar motion of galaxies. To study these velocity dependent properties, I have started with estimating observers motion using the radial peculiar velocities of the galaxies in observers frame. In this analysis, I have simulated 1000 galaxies in a volume of a sphere of radius 350Mpc. These galaxies have peculiar velocities in random directions with gaussian magnitudes. Then we try to recover the observer’s motion from the observer frame updated data using chi-squared analysis. With real data, this type of analyses can be used to estimate the motion of the Local Group, bulk flows in at different scales, local voids, etc.

Graduate Seminar, 1st April

Speaker: Jakub Sierchuła

Title: Determination of the liquid eutectic metal fuel Dual Fluid Reactor (DFRm) design – steady state calculations

Abstract: The Dual Fluid Reactor (DFR) is a novel concept of a very high-temperature (fast) reactor which falls-off the classification of Generation IV International Forum (GIF). DFR makes best of the two previous designs: Molten Salt Reactor (MSR) and Lead-cooled Fast Reactor (LFR). During the presentation a novel reactor design (DFRm) with the liquid eutectic U-Cr metal fuel composition and the lead coolant will be present. By performing the first steady state neutronic calculations for such a reactor it will be shown that this 250 MWth reactor is critical, and that it can operate almost 20 years without refuelling. The geometry (reflector thickness, fuel tubes pin pitch) was optimise with respect to the multiplication factor. The optimisation together with some other opportunities for the liquid metal fuel design (e.g the use of electromagnetic pumps to circulate the medium) allows DFRm to be of a small size. This rises economy of the construction as expressed nicely in terms of the Energy Return on Invested (EROI) factor which is even higher than for the molten salt fuel design (DFRs). Last but not least, DFRm has all the (fuel, coolant, reflector) temperature coefficients negative, which is an important factor of the passive safety.

Graduate Seminar, 25th March

Speaker: Szymon Nakoneczny

Title: Catalog of quasars from the Kilo-Degree Survey Data Release 3

Abstract: Broad spectroscopic lines, large redshift range and variety of properties make quasar detection in photometric surveys a particularly difficult task. I will present a quasar detection method based on photometric ugri data in Kilo-Degree Survey (KIDS) – an imaging deep and wide field survey covering 447 sq. deg. on the sky. The KiDS third data release contains 49 millions of sources among which, however, a vast majority does not have any spectroscopically confirmed identification. We successfully trained a Random Forest classifier based on the KIDS data and a set of known quasars identified by the SDSS spectroscopic survey. The presented catalog consists of 190,000 quasar candidates, and its training purity equals 91%. Additional validation of the catalog was made by the means of comparison with GAIA second data release, other already existing quasar catalogs and WISE photometric data.

Graduate Seminar, 11th March

Speaker: Paritosh Verma

Title: Gravitational waves in the Jordan-Brans-Dicke theory

Abstract: I shall talk about gravitational waves in Jordan Brans Dicke (JBD) theory. There are two tensor polarization states in the General theory of relativity but there can also be vector and scalar polarization states in alternative theories of gravity. The JBD theory is one of the attempts to modify general theory of relativity by varying gravitational constant G and it has three polarization states. The first two states are the same as in GR and the third one is the scalar polarization.

Venue: Pasteura 7, Room 404.

Graduate Seminar, 28th January

Speaker: Grzegorz Żarnecki

Title: T2K results on CP violation in the neutrino sector

Abstract: Each of the three flavour states of neutrinos is a superposition of mass eigenstates. The flavour-mass mixing matrix may have an irreducible imaginary component resulting in possible CP symmetry violation in neutrino oscillations, i.e. asymmetries between neutrino and antineutrino oscillations. In the T2K experiment the CP is probed by the measurement of appearance probability of electron (anti)neutrinos originating from accelerator-produced muon (anti)neutrinos beam. Current T2K results indicates CP violation at 2 sigma confidence level.

Graduate Seminar, 14th January 2019

Speaker: Joanna Reszczyńska

Title: Modelling of human cell reactions to ionizing radiation – from a DNA lesion to a cancer growth

Abstract: Understanding the consequences of exposure to low dose ionizing radiation is an important public health concern. It has become clear that cellular responses can be very different at low compared to high radiation doses. Important biological mechanisms may play key role in dose-response at low doses, which has been described by many deterministic and stochastic models, that try to implement current radiobiological knowledge to experimental data. In this talk, I will discuss post-irradiation cellular processes. I will present dose and time-dependent analytic model of responses of cells in the body to ionizing radiation for two exposure categories: acute and protracted. Special emphasis will be dedicated on the new approach of capturing the key dynamics–formation of the tumour.

Graduate Seminar, 17th December

Speaker: Piotr Kalaczyński

Title: EAS simulations with CORSIKA for KM3NeT

Abstract:  In the talk the design, status and physical goals of the KM3NeT experimental infrastructure will be introduced. Structure of the whole KM3NeT simulation chain and functions of its elements will be explained, but the focus will be on the CORSIKA branch. As a natural extension of this work, an analysis aiming at determining the visibility of the atmospheric charmed component was devised and will be sketched.

Graduate Seminar, 26th November 2018

Speaker: Rahul Nair

Title: Study Of Thermalisation Of Quark Gluon Plasma Using Ultra Relativistic Heavy Ion Collisions

Abstract: In this talk, I will discuss the process of thermalisation of QGP formed at ultra relativistic heavy Ion Collisions. A brief overview of a heavy Ion Collision scenario will be presented. The hydrodynamical calculations together with experimental results points towards a rapid thermalisation of the QGP formed in such a collision. The anisotropic elliptic flow is an indicator of such a thermalisation in the medium. This fact will be discussed and demonstrated using results from Hydrodynamics and data from RHIC and ALICE. I will also explain how the dilepton yield can be used to estimate the thermalisation time of the QGP drop.

Graduate Seminar, 19th November

Speaker: Michał Palczewski

Title: Shapes and sizes of high-K states in SHN

Abstract: Superheavy elements are highly unstable systems with extremely low production cross sections. As the creation of new ones is very difficult, as a parallel or additional line of  study one could try a search for new, long-lived metastable states of already known nuclei. It is well known that an enhanced stability may result from the K-isomerism phenomenon which is based mainly on the (partial) conservation of the K-quantum number. To do such studies energies are calculated within the microscopic – macroscopic approach with the deformed Woods-Saxon potential. Configurations are fixed by a standard blocking procedure and their energy found by a subsequent minimization over deformations. Results of blocking for 2 quasiparticle states (nn or pp)as well as for 4 quasiparitcle states (nnpp) will be shown. The relationship between electric quadrupole moments in different isotopes will be discussed next. Especially some of specific deformation parameters for No isotopes – which are experimentally studied now via laser technique will be demonstrated during the talk. Finally, predictions for Rf and some of heavier elements as: Sg, Hs, Ds and Cn – will be shown.