CASUS Institute Seminar, Prof. Alexander Zhuk, Astronomical Observatory, Odessa, I.I. Mechnikov National University, Odessa, Ukraine

Alexander is a specialist in theoretical physics, cosmology and high energy physics. He graduated from the Moscow Engineering Physical Institute, received his PhD while being at the P.N. Lebedev Physical Institute (Moscow), and defended his Diploma of Doctor of Sciences (habilitation) at the N.N. Bogolyubov Institute for Theoretical Physics (Kiev, Ukraine). Alexander was Visiting Professor at Cambridge University (where he worked for one year under the supervision of Prof. S. Hawking), Princeton University, Columbia University, and at  universities in Berlin, Cologne, Istanbul, Munich, Madrid, Lisbon, Covilha, etc. He has been a Senior Associate at ICTP in Trieste (12 years) and a visiting scientist at CERN (for last 12 years).

Thanks to modern telescopes, it was discovered that the universe is filled with a cosmic web which is composed of interconnected filaments of galaxies separated by giant voids. The emergence of this large-scale structure is one of the major challenges of modern cosmology. Alexander’s team studies this phenomenon with the help of relativistic N-body cosmological simulation based on general relativity. It is well known that gravity is the main force responsible for the structure formation in the universe.

In the first part of the talk, Alexander will demonstrate that in the cosmological setting gravitational interaction undergoes an exponential cutoff at large cosmological scales. This effect is called cosmic screening. It arises due to the interaction of the gravitational field with the background matter. Then, he compares two competing relativistic approaches to the N-body simulation of the universe large-scale structure: “gevolution” vs. “screening”.

To this end, employing the corresponding alternative computer codes, he demonstrates that the corresponding power spectra are in very good agreement between the compared schemes. However, since the perturbed Einstein equations have much simpler form in the “screening” approach, the simulation with this code consumes less computational time, saving almost 40% of CPU hours.

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