Seminars take place in the lecture room of the Spořilov building (see contacts) unless noted otherwise.

Scheduled seminars

Black Hole Spin and Accretion Disk Properties obtained with a New Method for 750+ Sources

Dr. Ruth Daly

Four types of black hole system will be discussed including stellar-mass and supermassive black holes. All of the black hole systems are active and have powerful collimated outflows. Empirically determined relationships between the outflow beam power, accretion disk luminosity, and black hole mass indicate that the outflows are spin powered. The general equation that describes a spin powered outflow is rewritten in dimensionless separable form allowing a determination of the black hole spin. Accretion disk properties such as the disk magnetic field strength and mass accretion rate can also be determined for each source. Good agreement is found between spin values obtained with the new method and published values obtained with well- established methods. The spin values obtained range from about (0.4 - 1), and are found to be independent of source type. Accretion disk magnetic field strengths for the three AGN samples have similar distributions and mean values of about 10 kG, while those for stellar-mass GBHs have mean values of about 100 MG. The new method is independent of a specific accretion disk model; thus the results can be applied to study and constrain disk models.

Location: Online

Meeting Link: Passcode: 789866 Meeting ID: 950 6830 4093

Chirality, Life and Cosmic Rays

Noemie Globus

While we have not yet reached a consensus on the definition of life, biological homochirality seems to be part of the definition as a necessary step for life’s emergence. The unraveling of its origin require interdisciplinary research, by exploring each of fundamental physics, modern chemistry, astrophysics and biology. In this talk, I will focus on the origin of biological homochirality in the context of astrophysics and particle physics. The weak force, one of the fundamental forces operating in nature, is parity-violating, and has been implicated in biological homochirality since over half a century. Cosmic rays, high energy particles coming from outer space, induce showers of billions of secondary particles when they interact with atoms in the atmosphere. On Earth, at ground level, most of our cosmic radiation dose comes from polarized muons formed in a decay involving the weak force. I will show how the spin-polarization is transmitted in cosmic showers in different environments, how it can induce a chiral preference in the early biological life forms and I will discuss the implications for the search of life in other worlds.

Location: Sporilov Virtual, Meeting ID: 917 8917 3885


Dr. Krista Lynne Smith

Location: Online

Meeting link: Password: 2665 Meeting ID: 85894941430


Mislav Baloković

Location: Online (Zoom)

Meeting ID: 86784992819 Password: 2317 Meeting link:

If you would like to give a seminar, please contact Georgios Loukes-Gerakopoulos or Vladimír Karas.