У оквиру семинара Групе за гравитацију, честице и поља Института за физику у Београду, у петак, 15. марта 2024. године у 11 часова, у сали 360 Института за физику у Београду, Петар Петрашиновић (Институт за физику у Београду) одржаће предавање:

Moore-Penrose inverse of matrix and its application to solving general linear systems

САЖЕТАК:

In linear algebra, the Moore-Penrose inverse stands as a generalization of the conventional matrix inverse, having been independently introduced by E.H. Moore in 1920 and later by Roger Penrose in 1955. The Moore-Penrose inverse is uniquely defined for all matrices whose entries are either real or complex numbers and extends its applicability to rectangular and even singular matrices. The versatility and uniqueness of the Moore-Penrose inverse are the major reasons for its significance (and discovery), which is reflected in solving general linear systems of equations, or tensor systems which can be reshaped into matrix form. In this seminar, I will discuss the properties of the Moore-Penrose inverse, display some of the calculation methods, and demonstrate its practical applications.

У оквиру традиционалног колоквијума Института за физику у Београду, у петак, 8. марта 2024. године, у 12 часова у сали „Звонко Марић“ предавање под насловом:

Einstein Telescope : A look at the dawn of the Universe

одржаће проф. др Фернандо Ферони (Научни институт Gran Sasso и Национални институт за нуклеарну физику (INFN), Италија)

САЖЕТАК:

Gravitational waves were detected in 2016 after 100 years of their prediction. Coalescence of black holes and neutron stars have been studied giving birth to a new way of studying our Universe. The coincidence of the gravitational signal with a gamma-ray burst has been identified as the beginning of multi-messenger astronomy. In order to move from the limited number of events, allowed by the actually running interferometers (LIGO and VIRGO), to a huge sample, a new generation of detectors has to be designed, built and operated. In this talk we will present Einstein Telescope, the project for a third generation detector, supported  by a large European collaboration. It is going to be formed by a combination of a low-frequency cryogenic interferometer and a high-frequency high-laser power interferometer, both located underground in order to minimize the noise. The experiment is going to produce results in several fields of research like astronomy, astrophysics, nuclear physics, and cosmology. It is going to be in competition and cooperation with the US project Cosmic Explorer.

У оквиру семинара Центра за изучавање комплексних система Института за физику у Београду, у четвртак, 7. марта 2024. године у 14 часова, путем Zoom платформе, Никола Савић (Институт за теоријску физику, CEA, Saclay, Gif-sur-Yvette, Француска) одржаће предавање:

Chaos in the S-matrix of highly excited strings

САЖЕТАК:

Investigating the chaotic behavior of black holes provides insight into the dynamics of their interior and hence to the black hole information paradox. The correspondence between black holes and highly excited strings suggests that the scattering of highly excited strings in the weakly coupled regime could probe black hole chaos. In this talk we will discuss the phenomenology of scattering of highly excited (open and closed) bosonic strings, focusing on the systematic chaos analysis of the S-matrix within the framework of random matrix theory [1]. We will comment on some interesting aspects of this dynamics and compare the chaotic behavior found in the behavior of black holes.

[1] N. Savić and M. Čubrović, arXiv:2401.02211 (2024).

Приступите предавању
Meeting ID: 869 6145 0010
Passcode: 916068

У оквиру семинара Групе за гравитацију, честице и поља Института за физику у Београду, у петак, 23. фебруара 2024. године у 11 часова, у сали 360 Института за физику у Београду, др Михаило Чубровић (Институт за физику у Београду) одржаће предавање:

Chaos and factorization beyond classical horizons

САЖЕТАК:

Chaotic dynamics of black holes has proven to be of vital importance for the understanding of the black hole information problem. Within the replica formalism, a related issue is that of nonfactorization of partition functions of wormhole geometries. We consider these questions deep in the stringy regime, described by the BFSS and IKKT matrix models, where the notions of geometry and horizon do not apply anymore. Generic solutions factorize when averaged over the quantum fluctuations, whereas the chaotic properties are non-universal. We argue that the correct notion that characterizes the black hole scrambling is instead that of quantum magic (stabilizer Renyi entropy), which guarantees that the dynamics is complex enough to accommodate the total information on infalling matter.

У оквиру семинара Лабораторије за фотоакустику Института за физику у Београду, у четвртак, 22. фебруара 2024. године у 10 часова у читаоници билиотеке „др Драган Поповић“, проф. др Младен Франко (Лабораторија за животну средину и науке о животу, Универзитет у Новој Горици, Словенија) одржаће предавање:

Effects of Photodegradation in Thermal Lens Spectrometric Measurements and their Mitigation

САЖЕТАК:

Most analytical applications of thermal lens spectrometry (TLS) and related theoretical models consider the absorbance of the sample constant during a single excitation by the pump laser beam. For photolabile analytes, intensive excitation light can cause photodegradation, significantly affecting TLS measurement results. Theoretical models will be presented that account for changes in concentration and consequent changes in absorbance, caused by chemical reactions of different orders [1,2]. Furthermore, TLS signal transients were observed for fast photochemical reactions on a millisecond time scale, and the contributions of photodegradation and molecular diffusion were analyzed in detail [3]. In this presentation, a comparison of theoretical predictions and experimental results will be presented. It will be furthermore demonstrated that the effects of photodegradation can be successfully reduced by performing TLS measurements in flowing systems such as in the case of flow injection analysis (FIA) [4] or
microfluidics [5].

У читаоници библиотеке „др Драган Поповић“ у 11 часова проф. др Младен Франко одржаће предавање:

Applications of Thermal Lens Spectrometry in Photochemistry and Photocatalysis

САЖЕТАК:

The findings on the effects of photochemical reactions on TLS signal were utilized to study the kinetics of chemical reactions [6,7], processes such as photostability of the soybean oil [8] and thermal stability of biodiesel [9], or to improve the sensitivity of TLS detection in case of photolabile analytes [10,11]. Furthermore, in combination with the concept of biomolecular recognition, FIA-TLS was exploited to study the efficiency of degradation and removal of some neurotoxic substances, such as organophosphate insecticides, and has confirmed photocatalysis as a proper method, which prevents the formation of degradation products with higher toxicity than parent compounds, as it was observed for example during ozonation monitored by TLS [12]. The high sensitivity of TLS has enabled discrimination between photocatalytic and photosensitization mechanisms in photocatalytic degradation of textile dyes [13], as well as discrimination between photodegradation and photocatalysis as will be demonstrated by the results of the latest research in this field [14]. will be given by Prof. Dr. Mladen Franko, Laboratory for Environmental and Life Sciences, University of Nova Gorica (https://www.ung.si/en/), Nova Gorica, Slovenia (mladen.franko@ung.si)

References:
[1] M. Franko and C.D. Tran, Rev. Sci. Instrum. 62, 2430-2437 (1991).
[2] M. Franko and C.D. Tran, Rev. Sci. Instrum. 62, 2438-2442 (1991).
[3] P.R.B. Pedreira, L.R. Hirsch, J.R.D. Pereira, A.N. Medina, A.C. Bento, M.L. Baesso, M.C.E. Rollemberg, M. Franko, and J. Shen, J. Appl. Phys. 100, 044906 (2006).
[4] A. Madžgalj, M.L. Baesso, and M. Franko, Eur. Phys. J. Special Topics 156, 503-506 (2008).
[5] M. Liu, S. Malovrh, and M. Franko, Anal. Methods 8, 5053-5060 (2016).
[6] M. Franko and C.D. Tran, Rev. Sci. Instrum. 62, 2438-2442 (1991).
[7] P.R.B. Pedreira, L.R. Hirsch, J.R.D. Pereira, A.N. Medina, A.C. Bento, M.L. Baesso, M.C.E. Rollemberg, M. Franko, and J. Shen, J. Appl. Phys. 100, 044906 (2006).
[8] E.L. Savi, L.C. Malacarne, M.L. Baesso, P.T.M. Pintro, C. Croge, J. Shen, and N.G.C. Astrath, Spectrochim. Acta A 145, 125–129 (2015).
[9] E.L. Savi, L.S. Herculano, G.V.B. Lukasievicz, H.R. Regatieri, A.S. Torquato, L.C. Malacarne, N.G.C. Astrath, Fuel, 217, 404-408 (2018).
[10] A. Madžgalj, M.L. Baesso, and M. Franko, Eur. Phys. J. Special Topics 156, 503-506 (2008).
[11] M. Liu, S. Malovrh, and M. Franko, Anal. Methods 8, 5053-5060 (2016).
[12] M. Bavcon Kralj, P. Trebše, and M. Franko, TrAC, Tends Anal. Chem. 26, 1020-1031 (2007).
[13] Z. Ebrahimpour, M. Abdelhamid, O. Pliekhova, K. Gadejisso-Tossou, H. Cabrera, D. Korte, J. Niemela, U. Lavrenčič Štangar, and M. Franko, Spectrochim. Acta A: Mol. Biomol. Spectrosc. 252, 119481, (2021).
[14] L. Godec, S.N. Sindhu, Research report, University of Nova Gorica, (paper in preparation) 2023.