The Colloquium takes place every Wednesday at 11:15 AM - Warsaw Copernicus Astronomical Centre online by means of Zoom platform. The Colloquium is given in English and chaired by dr Stanisław Bajtlik (bajtlik@camk.edu.pl). People from outside of the Copernicus Center are very welcome to participate. For technical detailes please contact Dr. Stanislaw Bajtlik.
Jarosław Duda (Jagiellonian University, Cracow)
While naively laser only excites target, it can also cause its deexcitation – as stimulated emission, SASE (self-amplified spontaneous emission), synchrotron self-absorption, ASE (amplified spontaneous emission), or in Rabi cycle cyclically causing excitation and deexcitation. STED microscopy is a popular application of laser causing deexcitation - I would like to propose and discuss a few more, based on its properties suggested by CPT symmetry. For example, while CT scanner makes 3D maps of absorption coefficient, CPT symmetry suggests how to analogously measure/map emission coefficients, what should have much better transparency thanks to lower concentrations (N2 << N1). Related medical application could be causing deexcitation of autoluminescent molecules like NADH, e.g. to starve cancer tissue. It suggests also how to build new type of telescope - seeing synchrotron radiation, but not thermal. Finally, the original motivation was more symmetric and powerful two-way quantum computers (2WQC), for example with photonic chip between coupled laser resonators.
Professor Gulab Dewangan (Inter-University Centre for Astronomy and Astrophysics, India)
Abstract: Nearly all galaxies harbor supermassive black holes at their cores. In a subset of these galaxies, the accretion of matter onto the central supermassive black hole generates substantial radiation across almost the entire electromagnetic spectrum. These astrophysical objects, known as active galactic nuclei (AGN), are typically persistent and variable sources, serving as cosmic laboratories for studying various physical phenomena, including the effects of strong gravity near the central black hole. Recent observations have unveiled a fascinating category of galactic nuclei that exhibit extreme variability, such as very large amplitude quasi-periodic X-ray eruptions (QPEs), complete transformations in spectral appearance, referred to as changing-look AGNs. Additionally, the tidal disruption of stars by central supermassive black holes can trigger accretion, leading to transient phenomena in otherwise quiescent galactic nuclei. Multi-wavelength observations of these highly variable events and transient phenomena in galactic nuclei are providing an abundance of information, offering new insights and posing significant challenges. The speaker will present an overview of galactic nuclear activity and discuss recent findings, particularly those derived from India's pioneering multi-wavelength space observatory, AstroSat.
Journal Club takes place on Mondays at 11:15 AM in the Seminar Room. The presentation is given in English and is chaired by Journal Club Coordinators. Anyone interested in giving a Journal Club talk is encouraged to contact the email: journalclub(@camk.edu.pl).
