Seminář se koná každé úterý v 10:40 v posluchárně ÚTF MFF UK
v 10. patře katedrové budovy v Tróji, V Holešovičkách 2, Praha 8
We present a new explicit class of black holes in general quadratic gravity with a cosmological constant. These spherically symmetric Schwarzschild–Bach–(anti-)de Sitter geometries form a three-parameter family determined by the black-hole horizon position, the value of the Bach invariant on the horizon, and the cosmological constant. The tidal effects on free test particles and basic thermodynamic quantities are also determined.
The talk will review our present understanding of the physical processes that determine the mechanism how massive stars explode. Neutrinos play a crucial role by providing the explosion energy of the far majority of these stars, and by setting the conditions for the production of heavy chemical elements including radioactive species during the explosion. Both the neutrinos and such nuclei, besides gravitational waves radiated from the generically aspherical, violent origin of the blast wave, can serve as observational probes of the electromagnetically obscured centers of dying stars. A future Galactic supernova is therefore the long-desired target of a growing pool of detection facilities.
The development of laser-driven X-ray sources using a 20 TW titanium-sapphire laser system have been carried out at PALS research center as a preparatory phase for ELI Beamlines facility that is becoming operational. High-order harmonics from gas targets (HHG), X-ray lasers pumped by transient collisional excitation, plasma X-ray sources, or X-ray sources based on relativistic electron beams have been investigated during last few years here. In this contribution we will present new aspects of those sources as well as the status of their implementation with much more powerful laser drivers at ELI Beamlines. Results of first secondary X-ray sources that have been commissioned in 2018 (HHG Beamline, plasma X-ray source) with commercial 1 kHz laser driver will be also discussed.
Recently two, a priori, different branches of physics have started to merge. One is attosecond physics, that deals with, both theoretical and experimentally, the phenomena that take place when ultrashort laser pulses, with durations ranging from the attosecond to the femtosecond time scale, interact with atoms, molecules or solids. The second branch involves the manipulation and engineering of mesoscopic systems, e.g. solids, metals, dielectrics, with nanometric precision, a scale that was only reached recently. In this way, it is possible to design and build bulk matter samples which pave the way to study light-matte interaction in a completely new regime. In this seminar I’ll summarize the theoretical work we have done to tackle the underlying physics of laser-matter processes driven by spatially and temporal synthesized fields, with a main emphasis in above-threshold ionization (ATI) and high-order harmonics generation (HHG) in atoms and molecules induced by plasmonic fields . At the end of the talk I’ll present a brief summary of other current and future projects.
M. F. Ciappina, et al. Attosecond Physics at the nanoscale, Rep. Prog. Phys 80, 054401 (2017)
We present a rigorous method to find the invariant measure of a dynamical system exactly describing Navier-Stokes turbulence in a bounded volume. In particular we derive a system of linear algebraic equations for long-time mean values of variables such as fluid velocity at a point or higher-order moments of such velocity.
Jiří Horáček Jiří Bičák