**Seminars for the year:**
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**Time: ** 7. February 2020, 11:00h

**Place: ** Institute of Physics, room 360

**Speaker: ** Ljubica Davidovic

**Title: ** T-duality in a weakly curved background

**Abstract:**

We will present a generalized T-dualization procedure which we developed for the bosonic string moving in a coordinate dependent background. The generalized procedure is applicable to an arbitrary coordinate, what enabled the T-dualization along the background field's arguments. We will present the results of a partial T-dualization, by which the T-dualization diagram was formed, connecting all theories obtained by T-dualization along arbitrarily chosen coordinates. We will show the corrections obtained by studying the weakly curved background of the second order. The symmetries of the bosonic string will be discussed, as well as T-duality of an open string with Neumann and mixed boundary conditions.

**Time: ** 31. January 2020, 11:00h

**Place: ** Institute of Physics, room 360

**Speaker: ** Igor Salom

**Title: ** Three-particle hyperspherical harmonics

**Abstract:**

The topic of the lecture will be the three-particle permutation symmetryc O(6) hyperspherical harmonics --- their construction, properties and applications in the context of three-quark bound states. These harmonics represent a natural basis of functions for solving the nonrelativistic three-body Schrodinger equation in three spatial dimensions. First we will show that the mathematically correct construction of three-particle harmonics must be based on the chain of subgroups S_3 X SO(3)_rot \subset O(2) X SO(3)_rot \subset O(6), and then we will demonstrate how these harmonics can be explicitly calculated. Next we will analyze the transformation properties of these harmonics, explain how to calculate their matrix elements, and finally apply all these results to estimate the low energy levels of three-quark bound states for the cases of effective Δ and Y potentials.

**Time: ** 22. January 2020, 11:00h

**Place: ** Faculty of Physics, room 661

**Speaker: ** Dusko Latas

**Title: ** Noncommutative model of cosmology

**Abstract:**

We will present a noncommmutative model of de Sitter space in which the coordinates are defined via the algebra of the de Sitter group SO(1,4). We will discuss the spectrum of these coordinates, with special attention devoted to the time coordinate. It will be demonstrated that the spectrum of the cosmological time is discrete and the radius of the Universe is bounded from below, thereby avoiding the Big Bang singularity.

**Seminars for the year:**
2020
2019
2018
2017
2016
2015
2014
2013
2012
2011
2010
2009
2008
2007