microseminar
informal seminar of Doppler Institute
on quantum theory and related topics and methods,
usually on Thursdays, usually at 10.45 a.m., usually 20 minutes + discussion
usually in the
briefing room of the Faculty of Science
on the fourth floor
of the Sbuilding
of the University of Hradec Kralove
occasionally also in hybrid form using
Zoom
alternatively also in the seminar room (second floor) of the
Department of Theoretical Physics
of the
Nuclear Physics Institute in Rez
note:
interested speakers
are always warmly
welcome.
FORTHCOMING SESSIONS:
Place:  briefing room of the Faculty of Science (Sbuilding of UHK as usual, but on the fourth floor) 
Remark:  hybrid form (connection by Zoom will be available as usual) 
Date:  
Time:  11:45 a.m. (duration: 20 minutes + questions) 
Speaker: 

Title: 

Abstract:  In a recent paper (A. Fring and T. Frith, Phys. Rev A 100, 101102 (2019)), Dyson’s scheme to deal with density matrix of non Hermitian Hamiltonians has been used to investigate the entanglement of states of a PTsymmetric bosonic system. They found that von Neumann entropy can show a different behavior in the broken and unbroken regime. We show that their results can be recast in terms of an abstract model of pseudoHermitian random matrices. It is found however that, although the formalism is practically the same, the entanglement is not of Fock states but of Bell states. 
Place:  briefing room of the Faculty of Science (Sbuilding of UHK as usual, but on the fourth floor) 
Remark:  hybrid form (connection by Zoom will be available as usual) 
Date:  
Time:  10:45 a.m. (duration: 40 minutes + questions) 
Speaker: 

Title: 

Abstract:  The RayleighBe'nard convection problem deals with the motion of a compressible fluid in a tunnel heated from below and cooled from above. In this context, the socalled Boussinesq relation is used, claiming that the density deviation from a constant reference value is a linear function of the temperature. These density and temperature deviations then satisfy the socalled OberbeckBoussinesq equations. The rigorous derivation of this system from the full compressible NavierStokesFourier system was done by Feireisl and Novotny' for conservative boundary conditions on the fluid's velocity and temperature. In this talk, we investigate the derivation for Dirichlet boundary conditions, and show that differently to the case of conservative boundary conditions, the limiting system contains an unexpected nonlocal temperature term. Joint work with Peter Bella (TU Dortmund) and Eduard Feireisl (CAS). 
ARCHIVE:
Place:  lecture hall S2 of the Department of Physics (UHK) in Hradec Kralove 
Form:  Zoom connection was not available this time 
Date and time: 
Monday, September 12th, 2022,
11:45 a.m.  12:45 p.m.

Speaker:  Ali Mostafazadeh (Koc University, Istanbul) 
Title and abstract: 
Renormalization of point scatterers in two and three
dimensions and its coincidentlimit problem

In two and three dimensions, the standard treatment of the scattering problem for a multideltafunction potential, ??(??)=????? ??(??????),??1 leads to divergent terms. Regularization of these terms and renormalization of the coupling constants ???? give rise to a finite expression for the scattering amplitude, but this expression has an important shortcoming; in the limit where the centers ???? of the delta functions coincide, it does not reproduce the formula for the scattering amplitude of a singledeltafunction potential, i.e., it seems to have a wrong coincidence limit. We provide a critical assessment of the standard treatment of these potentials, offer a resolution of its coincidencelimit problem, and reveal its inability to determine the dependence of the scattering amplitude on the distances between the centers of the delta functions. This is in sharp contrast to the treatment of this problem offered by a recently proposed dynamical formulation of stationary scattering (DFSS). For cases where the centers of the delta functions lie on a straight line, this formulation avoids singularities of the standard approach and yields an expression for the scattering amplitude which has the correct coincidence limit. 
Place:  lecture hall S2 of the Department of Physics (UHK) in Hradec Kralove 
Form:  hybrid form: onsite plus Zoom 
Date and time: 
Thursday, May 19th, 2022,
10:45 a.m.

Speaker:  Iveta Semoradova (NPI Rez) 
Title and abstract: 
Diverging eigenvalues in domain truncations of Schroedinger operators with complex potentials.

Domain truncations of Schroedinger operators with complex potentials are known to be spectrally exact. However, several examples suggest that additional eigenvalues escaping to infinity seem to be a generic feature. We find conditions on the presence of such eigenvalues and obtain their asymptotic expansions. Our approach also yields asymptotic formulas for diverging eigenvalues in a strong coupling regime for the imaginary part of the potential.
The talk was based on joint work with P. Siegl (Graz).  
Remark: 
participants

Place:  communicated, by Zoom, from the Department of Physics (UHK) in Hradec Kralove 
Form:  online only 
Date and time: 
Thursday, April 28th, 2022,
10:45 a.m.

Speaker:  Hassan Hassanabadi (UHK) 
Title and abstract: 
Investigation of the Dunkl oscillator in the position and momentum
representation

In this work, first we introduce Dunkl operator and its properties as well as $\nu$deformed exponential function. Then the DunklHeisenberg relation in the position and momentum representation is obtained by applying the reflection operator for the position and momentum. We then obtain the corresponding eigenfunction and eigenvalue. Based on the $\nu$deformed Hermite polynomials, we derive the energy levels, groundstate wave functions, and excited wave functions. We expand the method to obtain the related coherent states.  
Remark: 
participants

Place:  lecture hall S2 of the Department of Physics (UHK) in Hradec Kralove 
Form:  hybrid form: onsite plus Zoom 
Date and time: 
Thursday, March 24th, 2022,
10:45 a.m.

Speaker:  Petr Siegl (TU Graz) 
Title and abstract: 
The damped wave equation with singular damping

We analyze the spectral properties and peculiar behavior of solutions of a damped wave equation on a finite interval with a singular damping of the form \alpha/x with a positive \alpha. We establish the exponential stability of the semigroup and determine conditions for the spectrum to consist of a finite number of eigenvalues. As a consequence, we fully characterize the set of initial conditions for which there is extinction of solutions in finite time.
The talk was based on joint work with P. Freitas (Lisbon) and N. Hefti (Bern).  
Remark: 
participants

Place:  lecture hall S2 of the Department of Physics (UHK) in Hradec Kralove 
Form:  hybrid form: onsite plus Zoom 
Date and time: 
Thursday, March 3rd, 2022,
10:45 a.m.

Speaker:  Anton Galaev (UHK) 
Title and abstract: 
Holonomy groups and their application

A short introduction to the holonomy groups of linear connections on smooth manifolds will be given. I will explain the classification results for the LeviCivita connection on Riemannian and Lorentzian manifolds as well as for the metric connections with skewsymmetric torsion. The importance of these results is shown by the fact that spaces with a broad class of holonomy groups automatically satisfy the Einstein equation and admit parallel spinor fields (supersymmetries).  
Remark: 
participants

Place:  University of Hradec Kralove, Faculty of Science 
Form:  online talk, presented by Zoom 
Date and time: 
Thursday, February 3rd, 2022,
10:45 a.m.

Speaker:  Jan Kriz (UHK) 
Title and abstract: 
Soft quantum waveguides

A brief review of the theory of planar quantum waveguides will be provided. The recent results concerning socalled soft waveguides will be discussed in more details. Mathematically, we investigate the existence of discrete spectrum of twodimensional Schrodinger operators with an attractive potential in the form of a channel of a fixed profile built along an unbounded curve.  
Remark: 
participants

Place:  University of Hradec Kralove, Faculty of Science, Department of Physics, Building S, lecture hall S2 
Form:  talk presented in the hybrid (i.e., Zoom + onsite) form this time 
Date and time: 
Thursday, January 6th, 2022, 10:45 a.m.

Speaker:  Jiri Lipovsky (UHK) 
Title and abstract: 
Spectral determinants

We introduce a generalization of the notion of the determinant from matrices to operators with infinitely many eigenvalues, which uses the spectral zeta function. We show how to compute it for simple operators and sketch the main difficulties in its definition, especially the dependence of the spectral determinant on the branch cut of the logarithm appearing in the definition of the spectral zeta function.
This is joint work with P. Freitas based on the paper [1]. [1] P. Freitas, J. Lipovsky, Spectral determinant for the damped wave equation on an interval, Acta Physica Polonica A 136 (2019), 817823 [arXiv: 1908.06862 [mathph]]. 
Form:  virtual this time: Jan Kriz (UHK) invited us to join via Zoom 
Date and time: 
Thursday, December 2nd, 2021, 10:45 a.m.

Speaker:  Marzieh Baradaran (UHK) 
Title and abstract: 
Spectrum of a Kagome network

Spectral properties of quantum graphs in the form of a kagome or a triangular lattice
were investigated
assuming that wave functions at the vertices are matched through conditions which are noninvariant with respect to the timereversal. While the positive spectrum consists of an infinite number of bands, the negative one has at most three and two bands, respectively. We discussed, in particular, the highenergy behavior of such systems and the probability that a randomly chosen positive number belongs to the spectrum.
This is joint work with Prof. Pavel Exner based on preprint [1]. [1] M. Baradaran, and P. Exner: arXiv:2106.16019 [mathph] 
Place:  University of Hradec Kralove, Faculty of Science, Department of Physics, Building S, lecture hall S3 
Date and time: 
Thursday, November 4th, 2021, 11:00 a.m.
(triple length: 60 min.) 
Speaker:  Petr Seba (UHK) 
Title and abstract: 
Applications of repetitive ballistographic data

Mathematically processed ballistography signals are used to evaluate various clinically significant markers routinely used in the human diagnostics. 
Place:  University of Hradec Kralove, Faculty of Science, Department of Physics, Building S, laboratory S19 on the second floor 
Date and time:  Tuesday, October 12th, 2021, 10:45 a.m. 
Speaker: 
Andrii Khrabustovskii (UHK) 
Title and abstract:  Construction of selfadjoint differential operators with prescribed spectral properties 
The objective of the talk is to illustrate how one can construct domains or potentials such that the essential or discrete spectrum of Laplace and Schroedingertype operators coincides with a predefined subset of the real line. Another aim is to emphasize that the spectrum of a differential operator on a bounded domain or bounded interval is not necessarily discrete, e.g., eigenvalues of infinite multiplicity or continuous spectrum may be present.
The talk is based on resent works with J. Behrndt (TU Graz). 
Place (unusual!):  University of Hradec Kralove, Faculty of Science, Department of Physics, Building S, ground floor, room Nr. S13 
Date and time:  Thursday, September 16th, 2021, 10:30 a.m. 
Speaker: 
Miloslav Znojil (UHK) 
Title and abstract:  Alice in the wanderland of algebraic geometry, and behind quantum catastrophes 
A compact reparametrization of the Arnold polynomial potentials of arbitrary degree (known from the classical theory of catastrophes) is introduced and shown useful in quantum phenomenology. Main attention is paid to the specific unstablelocalization dynamical regime. In this regime a systematic determination of the observable density distributions proves feasible via 1/N approximation yielding a qualitative classification and approximate description of a new type of quantum phase transitions, tractable as the (avoided) level crossings or, alternatively, as a manifestation of the existence of a fairly close complex exceptional point. 
Place:  University of Hradec Kralove, Faculty of Science, Department of Physics, Building S, 1st floor, room Nr. 72549 
Date and time:  Thursday, June 17th, 2021, 10:30 a.m. 
Speaker: 
Miloslav Znojil (UHK) 
Title and abstract:  From Cizek and Dyson to Bender 
In the first microseminar organized in UHK the Benderinspired formulation of quantum mechanics (a.k.a. PTsymmetric quantum mechanics) will be briefly reviewed. With emphasis on the history of the field, five related paradoxes will be formulated. (1) People never noticed the overlap of the theory with the Jiri Cizek's coupled cluster method in which one calculates the real spectrum using realistic Hamiltonians in nonHermitian representation. (2) Only too late people noticed the overlap of the theory with an analogous Freeman Dyson's recipe. (3) Frequent misunderstandings were evoked by the Bender's claim that his Hamiltonians were nonHermitian. At present, it is clear that they are only nonHermitian in an unphysical, auxiliary, irrelevant Hilbert space. In this sense, their proper name should have been quasiHermitian Hamiltonians. (4) The main inspiration of the Bender's new theory was the Bessis' imaginary cubic interaction model. In 2012, in a paper by Siegl and Krejcirik, this particular model was proved not to fit the theory. (5) Subsequently, the initial orientation of the theory on the so called closed quantum systems has changed. Today, most people apply the concept of PT symmetry to open quantum systems.  
Photo of whiteboard: 
The archive of the older microseminars:
The list of talks during 2016  2020
The list of talks during 2012  2015
The list of talks during 2008  2011
The list of the talks during 2008
A compactified list of the speakers during 2008
The list of the talks during 2007
A compactified list of the speakers during 2007
The list of the talks during 2006
A compactified list of the speakers during 2006
PS: in parallel, nested seminars of the similar type may be also sought on the webpages of our local
microconferences
devoted to the analytic an algebraic methods in physics
Info for interested speakers:
send email to
Miloslav Znojil  
propose a talk (Thursdays on 10.30 or 10:45 are preferable) 

on any subject related to


you should book your term of talk:  not later than 2 or 3 days in advance 
your talk's length should be  20 minutes 
time for subsequent questions:  unlimited 
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