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.

У оквиру семинара Групе за гравитацију, честице и поља Института за физику у Београду, у петак, 02. фебруара 2024. године у 11 часова, на Институту за физику, у сали 360, Душан Ђорђевић (Физички факултет, Универзитет у Београду) одржаће предавање:

Massless minimally coupled scalar field in dS space-time

САЖЕТАК:

In this talk, we will review the quantisation of scalar fields in de-Sitter spacetime. We will discuss the differences between the case of minimally coupled massive and minimally coupled massless scalar fields, as well as the possibility of obtaining, in the massless case, a vacuum state that is invariant under the full SO(4,1) group. The talk will be based on the following papers:

Kirsten, Garriga, arXiv:gr-qc/9305013
Tolley, Turok, arXiv:hep-th/0108119