Welcome !

The Workshop on Operator Theory and Krein Spaces aims at bringing together mathematicians working on spectral theory, Krein spaces, and related fields. Subjects will range from geometry of indefinite inner product spaces and operator theory to classical analysis of ordinary and partial differential equations.

Please use the links on this website to obtain more information.

Registration (deadline September 22, 2019) and submission of abstracts (deadline November 30, 2019) should be done through this website. The registration fee is € 150. This fee covers conference material, the conference dinner for participants, and coffee breaks. Accompanying persons should pay € 50 to attend the conference dinner.

If you have special requests which are not answered by the information on this site, please use the conference email address otind(at)asc.tuwien.ac.at.

This meeting is dedicated to the memory of our colleague and friend Hagen Neidhardt (20.11.1950 - 23.3.2019). Hagen is well known in the mathematical community for his various contributions to spectral and scattering theory. During the conference some of his main collaborators will report on their common projects. Some photos of Hagen which were shown by the speakers can be found here.

This event is co-organised with COST Action CA18232 "Mathematical models for interacting dynamics on networks", and contains a special session devoted to the topics of the action.

With best regards, the Organizing Committee,

Jussi Behrndt (TU Graz. www)
Aleksey Kostenko (University of Vienna. www)
Raphael Pruckner (Vienna University of Technology)
Harald Woracek (Vienna University of Technology. www)



He will always stay in our thoughts


        


Here are some photos presented by the speakers of the workshop.

We thank Pavel Exner, Takashi Ichinose, and Valentin Zagrebnov for providing pictures from their archives.


     

     

     

     

  

  

  

     

  

  



Travel


By plane

Vienna can comfortably be reached by plane from many destinations. The Vienna International Airport is served by many regular airlines and also by several low-cost carriers. See the website of the Vienna International Airport for detailed information.

Some low-cost carriers offer flights to Bratislava airport. See Bratislava Airport for detailed information. There are regular bus services running between Vienna downtown and Bratislava airport (several companies; 1 to 1 1/2 hours journey).

By long-distance train

Especially if you come from not so far, it is worth to check train connections. There are frequent and fast connections from Zurich, Frankfurt, Munich, Prague, Budapest and other destinations. For the train schedules see the journey planner of the Austrian Federal Railways (OEBB).

How to get to town from the Vienna airport

The airport is conveniently connected to the city in several ways.
  1. By train.

    There are regular train services to Vienna Main Railway Station (Wien Hauptbahnhof) with long-distance trains (RJX, RJ; 15 minutes journey), and to the station Wien Mitte with regional or suburban trains (S, R, 20-25 minutes journey).
    -- Costs: 4.20 Euro (one way).

    Tickets can be bought online from the website of the Austrian Federal Railways (OEBB), or upon arrival at the airport from a counter in the arrival hall or machines in the hall before the platforms. Tickets for long distance trains can also be bought from the conductor in the train (slightly more expensive), for regional and suburban trains it is obligatory to get a ticket before entering the train.

    Another possibility is the City Airport Train (CAT) which runs between the airport and the station Wien Mitte. Among locals this service is known as the heavily advertised overpriced tourist trap. If one travels with a lot of heavy luggage, it may still be worth considering when leaving Vienna since it offers the possibility to check in the luggage for the flight already at Wien Mitte. For schedule and prices see here.

  2. By taxi.

    Several companies offer taxi service from/to the airport. Order a taxi in advance from Airport Drivers, or Vienna Airport Cab, or taxi31300. Especially if you travel in a small group or have more luggage this is a comfortable option.
    -- Costs: Between 30 and 50 Euro (one way) depending on the number of passengers.

    Grab a taxi in front of the airport building (not recommended). This is usually expensive, and it may happen that there are no taxis available.

  3. By bus.

    Vienna Airport Bus (Flughafenbus) runs several bus lines. Buses depart from platforms in front of the airport building. For a detailed schedule and their lines see here.
    -- Costs: 8 Euro (one way), 13 Euro (return trip).
    Tickets can be purchased online or from the driver.



Accomodation

There is a wide range of hotels of all categories and price ranges. You can use any common booking engine like booking.com or budgetplaces.com to look for a place to stay.

A few decent, resonably priced, and well located places are
  • Hotel Admiral, Karl Schweighofer-Gasse 7, 1070 Wien (website).
  • Carlton Opera Hotel, Schikanedergasse 4, 1040 Wien (website).
  • Hotel Terminus, Fillgradergasse 4, 1060 Wien (website).
  • Motel One, Elisabethstrasse 5, 1010 Wien (website).
When you plan your trip, please take into account that the time before X-mas is a popular and quite busy tourist period. Hence hotels tend to be fully booked quite some time in advance.

Public Transport in Vienna

The public transport system in Vienna is well-developed. To give you an overview, it includes suburban trains (S-Bahn, numbered "S1", "S2", etc.), underground lines (numbered "U1", "U2", etc.), trams (numbered "1", "2", etc., a few exceptional numberings like "D"), and buses (numbered "1A", "13A", etc.).

A map of public transport lines.

Tickets can be bought from machines at every train/underground station or ordered online in advance. There are tickets for various possible time ranges, for example:
  • a single journey (the notion one journey includes changes of lines),
  • 24h, 48h, 72h,
  • 8 days (not necessarily consequtive),
  • weekly (monday-sunday).
Tickets should be stamped at the beginning of their validity period. Depending on the type of ticket, this period can be one single journey, one day, one week, etc. Machines (little boxes) to stamp tickets are located
  • for S-Bahn/underground generally in the hall before getting to the platforms, latest at the platform,
  • inside trams and buses.
Single tickets can also be bought from machines inside trams and buses (not in S-Bahn or underground trains). However, unless necessary, this is not recommended (sometimes these machines don't work, sometimes one doen't have coins, etc.). Detailed information can be found at the website of the Wiener Linien, see here (english version available). This site includes a practical interactive journey planner (click the Journey button on the site).


Source: https://www.wienerlinien.at.

About food


Restaurants

There are nearly infinitely many places to have lunch or dinner, and many are close to the university. Here are a few restaurants which are not ''just the usual stuff''.
  • Umar (incredible fish and seafood).
    Naschmarkt (stand 76-79)
    http://www.umarfisch.at/index2.shtml
    Sunday closed
    Reservation necessary: call +43 1 5870456

  • Ubl (charming Viennese restaurant; a typical ''Beisl'')
    Pressgasse 26

  • Artner auf der Wieden (somewhat more sophisticated)
    Floragasse 6
    http://www.artner.co.at/wieden/

  • Beograd (Serbian)
    Schikanedergasse 7
    https://restaurant-beograd.at/

  • Figlmüller Wollzeile (despite being advertised already at the airport, the Schnitzel is indeed great and the atmosphere is surprisingly typical -- at least in their place in Wollzeile)
    Wollzeile 5
    https://www.figlmueller.at/en/
    Reservation necessary: online or call +43 1 5126177

  • Ostwind (quite original chinese restaurant)
    Lindengasse 24
    www.ostwindwien.at
    Reservation necessary: call +43 1 5234182

  • I Ragazzi (Italian)
    Burggasse 6-8
    http://www.iragazzi.at
    Reservation recommended: call +43 1 5226325

  • Kojiro 2 (Japanese).
    Kühnplatz 4
    Sunday closed
    Reservations: call +43 1 5855428

  • Amacord (Restaurant)
    Rechte Wienzeile 15
    http://www.amacord-cafe.at

  • Amerlingbeisl (nice place in a nice area for going out).
    Stiftgasse 8
    http://www.amerlingbeisl.at
    Reservations: call +43 1 5261660

Coffee Houses

Coffee houses have a great tradition in Vienna. They are also good to get lunch or dinner; cooked dishes are usually served for reasonable prices. Again we list only a few of the many places.
  • Cafe Prückel (go and eat Apfelstrudel)
    Stubenring 24
    http://www.prueckel.at/

  • Cafe Jelinek (take the time to forget about time)
    Otto-Bauer-Gasse 5
    http://cafejelinek.steman.at/

  • Cafe Sperl (beautiful interior)
    Gumpendorferstrasse 11
    http://www.cafesperl.at/

  • Cafe Bräunerhof
    Stallburggasse 2
    http://www.braeunerhof.at/

In the TU Vienna

Though it may not quite match the title of this page, one should mention that in the university building there are
  • University canteen
    Freihaus building, yellow area, 1st floor
    Saturday/Sunday closed

  • Cafe Schrödinger
    Freihaus building, green area, ground floor (entrance from the street)
    Saturday/Sunday closed

Christmas markets

Naturally, there are many X-mas markets. We recommend two.
  • The market in front of the town hall (Rathausplatz)
    Big and quite touristic, but the town hall and the park is very beautiful.

  • The Spittelberg market (Spittelberggasse and neighbouring streets)
    Nice area, nice market, not too touristic. Also good for getting some small presents.


Copyright: Freytag-Berndt u. Artaria KG, 1230 Vienna, Austria, Europe.

The Vienna University of Technology

  1. Map of all TU Vienna buildings.

    The conference takes place in the Freihaus building, shown on the map as the part of D including the numbers 4,5,12. The main entrance is marked with "i" (because inside the building you find doormen who you may ask for information).

    The address is Wiedner Hauptstrasse 8-10, Vienna 1040.

  2. The Freihaus building itself is structured into three vertical areas: red, yellow, and green.
    Upon entering you find yourself in the red area.

    In each area there are elevators, a main staircase, and small staircases. The main staircases lead from the ground floor up to the 2nd floor (ground floor = floor 0). Small staircases (and, naturally, elevators) lead further up. The different areas are connected; you can pass from one to another on every floor.

  3. All rooms used for the conference are in the green area.

    Talks take place in three lecture rooms.
    • Morning session: FH HS 5 (stands for Freihaus Hörsaal 5) on 2nd floor. This is a large lecture hall.
    • Afternoon sessions: ZS 3 (stands for Zeichensaal 3) on 7th floor and ZS 1 on 8th floor. These are medium size lecture halls.
    These rooms (FH HS 5, ZS 3, ZS 1) are equipped with blackboards and projector+computer. They are open only for the lectures and will be locked during breaks.

    Further we use the following rooms.
    • Coffee Breaks: Sem 03 A (stands for Seminarraum 03 A) on 3rd floor.
    • Rooms for discussion/work: Sem 03 C on 3rd floor and Former Library (Institutsbibliothek) on 6th floor. These are smaller rooms.
    These rooms (Sem 03 A, Sem 03 C, Former Library) will always be open to ensure constant supply with coffee, chalk and blackboard.

    Here are maps of different floors indicating relevant places.

  4. Registration takes place Thursday 9'30-10'00 and 11'00-11'45 in front of FH HS 5. Participants who arrive later, are asked to personally contact one of the organisers who will then take care of the registration.



Conference Dinner

The Conference Dinner takes place Friday 20.12.2019, 19'00 in the Zwölf-Apostelkeller. This restaurant is located in the very heart of the city (Sonnenfelsgasse 3; see this map of the inner city, where we also marked coffee houses). They offer a buffet with traditional Austrian dishes and some vegetarian dishes.

We shall gather after the last talk in front of the main lecture hall (FH HS 5, 2nd floor, green area), and depart at 18'30 to walk there together (about 20 minutes walk through the inner city). Of course you can also get there on your own.

The buffet, non-alcoholic drinks, and beer/wine up to a reasonable amount is covered.

Program

Click on the title of a talk to obtain the abstract.
Program and abstracts are available as pdf in the download area.

Thursday 19.12.2019

Morning session: FH HS 5 (2nd floor)
9'30 Registration
10'00 Christiane Tretter:
Everything is possible for the domain intersection of an operator and its adjoint
10'30 Roman Romanov:
Canonical systems in ideals of compact operators
Coffee Break (Sem 03 A, 3rd floor) / Late registration (in FH HS 5)
11'45 Jonathan Eckhardt:
Continued fraction expansions and generalized indefinite strings
12'15 Vladimir Lotoreichik:
Optimization of lowest Robin eigenvalues on 2-manifolds and unbounded cones
Afternoon session A: ZS 3 (7th floor)
15'00 Igor Sheipak:
On embedding constants in Sobolev spaces. Application to spectral problems with coefficients-distributions.
15'30 Alexander Motovilov:
Equivalence between the complex-rotation and scattering-matrix resonances in the Friedrichs-Faddeev model
Coffee Break (Sem 03 A, 3rd floor)
16'45 Sergey Simonov:
Wave model of symmetric operators
17'15 Vadim Mogilevskii:
Compressions of self-adjoint extensions of a symmetric operator in a Hilbert space
Afternoon session B: ZS 1 (8th floor)
15'00 Seppo Hassi:
Stieltjes and inverse Stieltjes families of linear relations in Hilbert spaces and their representations
15'30 Rudi Wietsma:
Factorizations, invariant subspaces and multi-valency
Coffee Break (Sem 03 A, 3rd floor)
16'45 Lassi Lilleberg:
Minimal passive realizations of generalized Schur functions in Pontryagin spaces
17'15 Annemarie Luger:
Quasi-Herglotz functions

Friday 20.12.2019

Morning session: FH HS 5 (2nd floor)
Dedicated to the memory of Hagen Neidhardt
9'00 Pavel Exner:
Spectral gaps of periodic quantum graphs
9'45 Takashi Ichinose:
Magnetic Relativistic Schrödinger Operators and Kato's Inequality
10'30 Vadim Adamyan:
Close singular perturbations of selfadjoint operators
Coffee Break (Sem 03 A, 3rd floor)
12'00 Mark Malamud:
Scattering matrices, perturbation determinants, and trace formulas in the works of Hagen Neidhardt
12'45 Valentin Zagrebnov:
The Howland-Evans-Neidhardt approach to approximation of propagators
Afternoon session A: ZS 3 (7th floor)
15'30 Artur Stephan:
On evolution semigroups and Trotter product operator-norm estimates
16'00 Anton Boitsev:
A model of several point-like windows in the resonator boundary with the Dirichlet boundary condition
Coffee Break (Sem 03 A, 3rd floor)
17'15 Nadezhda Rautian:
Semigroups for integro-differential equations with convolution memory terms
17'45 Victor Vlasov:
Spectral analysis and representation of solutions of Volterra integro-differential equations with fractional exponential kernels
Afternoon session B: ZS 1 (8th floor)
15'30 Noema Nicolussi:
Self-adjoint extensions of infinite quantum graphs
16'00 Jakob Reiffenstein:
Theorem of Hermite-Biehler for matrix-valued entire functions
Coffee Break (Sem 03 A, 3rd floor)
17'15 Sergey Belyi:
Perturbations of L-systems
17'45 Samuel Mohr:
Eigenvalues of Graphs
Sem 03 C (3rd floor)
15'30 Core Group Metting COST Action CA18232
Zwölf-Apostelkeller (Sonnenfelsgasse 3)
19'00 Conference Dinner

Saturday 20.12.2019

Morning session: FH HS 5 (2nd floor)
Mathematical models for interacting dynamics on networks
(COST Action CA18232)
10'00 Marjeta Kramar-Fijavz:
Bi-Continuous Operator Semigroups for Flows in Infinite Networks
10'30 Pavel Kurasov:
Inverse Problem for Quantum Graphs: Complete Solution using Magnetic Control
Coffee Break (Sem 03 A, 3rd floor)
11'45 Ivica Nakic:
Optimal control of parabolic equations using spectral calculus
12'15 Petra Csomos:
Trotter-Kato Product Formula in Viewpoint of Numerical Analysis
Afternoon session A: ZS 3 (7th floor)
15'00 Petru Cojuhari:
On spectral analysis of Dirac operators
15'30 Alexander Makin:
On the basis property of root functions systems of Dirac operators with regular boundary conditions
Coffee Break (Sem 03 A, 3rd floor)
16'45 Andrii Khrabustovskyi:
Geometric approximations of point interactions
17'15 Alexander Sakhnovich:
Discrete Dirac system and Arov--Krein entropy
Afternoon session B: ZS 1 (8th floor)
15'00 Andrea Posilicano:
The semi-classical limit with delta potentials
15'30 Luka Grubisic:
Contour integration methods for self adjoint operators
Coffee Break (Sem 03 A, 3rd floor)
16'45 Jaroslav Dittrich:
Scattering along a curve in the plane
17'15 Nikos Yannakakis:
The angle along a curve and range-kernel complementarity

Sunday 22.12.2019

Morning session: FH HS 5 (2nd floor)
10'00 Rostyslav Hryniv:
Inverse scattering for reflectionless Schroedinger operators and generalized KdV solitons
10'30 Matthias Langer:
Canonical systems whose Weyl coefficients have regularly varying asymptotics
Coffee Break (Sem 03 A, 3rd floor)
11'45 Volodymyr Derkach:
De Branges-Pontryagin spaces and embedding of de Branges matrices with negative squares in generalized J-inner matrices
12'15 Felix Schwenninger:
From input-to-state stability to semigroup perturbations
Closing

Participants

  1. Vadym Adamyan
    (Odessa I.I. Mechnikov National University, Ukraine)
  2. Nausica Aldeghi
    (Stockholm University, Sweden)
  3. Andras Batkai
    (PH Vorarlberg, Austria)
  4. Jussi Behrndt
    (Graz University of Technology, Austria)
  5. Sergey Belyi
    (Troy University, USA)
  6. Anton Boitsev
    (ITMO University, Russia)
  7. Petru Cojuhari
    (AGH University of Science and Technology, Poland)
  8. Petra Csomos
    (Eötvös Lorand University, Hungary)
  9. Vahid Darvish
    (Nanjing University of Information Science and Technology, China)
  10. Volodymyr Derkach
    (Vasyl Stus Donetsk University, Ukraine)
  11. Jaroslav Dittrich
    (Nuclear Physics Institute CAS, Czech Republic)
  12. Jonathan Eckhardt
    (Loughborough University, UK)
  13. Pavel Exner
    (Czech Academy of Sciences, Czech Republic)
  14. Asaf Franco
    (IIMAS-UNAM, Mexico)
  15. Luka Grubisic
    (University of Zagreb, Croatia)
  16. Seppo Hassi
    (University of Vaasa, Finland)
  17. Rostyslav Hryniv
    (Ukrainian Catholic University, Ukraine / University of Rzeszow, Poland)
  18. Markus Holzmann
    (Graz University of Technology, Austria)
  19. Takashi Ichinose
    (Kanazawa University, Japan)
  20. Michael Kaltenbäck
    (Vienna University of Technology, Austria)
  21. James Kennedy
    (University of Lisbon, Portugal)
  22. Andrii Khrabustovskyi
    (Graz University of Technology, Austria / University of Hradec Kralove, Czech Republic)
  23. Werner Kirsch
    (Fernuinversität Hagen, Germany)
  24. Aleksey Kostenko
    (Vienna University of Technology, Austria / University of Ljubljana, Slovenia)
  25. Marjeta Kramar-Fijavz
    (University of Ljubljana, Slovenia)
  26. Pavel Kurasov
    (Stockholm University, Sweden)
  27. Heinz Langer
    (Vienna University of Technology, Austria)
  28. Matthias Langer
    (University of Strathclyde, UK)
  29. Lassi Lilleberg
    (University of Vaasa, Finland)
  30. Vladimir Lotoreichik
    (Czech Academy of Sciences, Czech Republic)
  31. Annemarie Luger
    (Stockholm University, Sweden)
  32. Alexander Makin
    (Russian Technological University, Russia)
  33. Mark Malamud
    (Russian Friendship University, Russia)
  34. Vadim Mogilevskii
    (Poltava V.G. Korolenko National Pedagogical University, Ukraine)
  35. Samuel Mohr
    (TU Ilmenau, Germany)
  36. Alexander Motovilov
    (Bogoliubov Laboratory of Theoretical Physics at the Joint Institute for Nuclear Research, Russia)
  37. Ivica Nakic
    (University of Zagreb, Croatia)
  38. Noema Nicolussi
    (University of Vienna, Austria)
  39. Andrea Posilicano
    (Universita dell'Insubria, Italy)
  40. Olaf Post
    (Universität Trier, Germany)
  41. Aleksandra Puchalska
    (University of Warsaw, Poland)
  42. Raphael Pruckner
    (Vienna University of Technology, Austria)
  43. Nadezhda Rautian
    (Lomonosov Moscow State University, Russia)
  44. Jakob Reiffenstein
    (Vienna University of Technology, Austria)
  45. Roman Romanov
    (St.Petersburg State University, Russia)
  46. Alexander Sakhnovich
    (University of Vienna, Austria)
  47. Felix Schwenninger
    (University of Twente, The Netherlands)
  48. Igor Sheipak
    (Lomonosov Moscow State University, Russia)
  49. Harun Siljak
    (Trinity College Dublin, Ireland)
  50. Sergey Simonov
    (Steklov Mathematical Institute, Russia)
  51. Henk de Snoo
    (University of Groningen, The Netherlands)
  52. Artur Stephan
    (WIAS-Berlin, Germany)
  53. Georg Stenzel
    (Graz University of Technology, Austria)
  54. Dmytro Strelnikov
    (TU Ilmenau, Germany)
  55. Christiane Tretter
    (University of Bern, Switzerland)
  56. Carsten Trunk
    (TU Ilmenau, Germany)
  57. Victor Vlasov
    (Lomonosov Moscow State University, Russia)
  58. Rudi Wietsma
    (University of Vaasa, Finland)
  59. Harald Woracek
    (Vienna University of Technology, Austria)
  60. Nikos Yannakakis
    (National Technical University of Athens, Greece)
  61. Valentin Zagrebnov
    (Institut de Mathematiques de Marseille, France)


Talks

  1. Vadym Adamyan:
    Close singular perturbations of selfadjoint operators
  2. Sergey Belyi:
    Perturbations of L-systems
  3. Anton Boitsev:
    A model of several point-like windows in the resonator boundary with the Dirichlet boundary condition
  4. Petru Cojuhari:
    On spectral analysis of Dirac operators
  5. Petra Csomos:
    Trotter-Kato Product Formula in Viewpoint of Numerical Analysis
  6. Volodymyr Derkach:
    De Branges-Pontryagin spaces and embedding of de Branges matrices with negative squares in generalized J-inner matrices
  7. Jaroslav Dittrich:
    Scattering along a curve in the plane
  8. Jonathan Eckhardt:
    Continued fraction expansions and generalized indefinite strings
  9. Pavel Exner:
    Spectral gaps of periodic quantum graphs
  10. Luka Grubisic:
    Convergence of contour integration methods for self adjoint operators
  11. Seppo Hassi:
    Stieltjes and inverse Stieltjes families of linear relations in Hilbert spaces and their representations
  12. Rostyslav Hryniv:
    Inverse scattering for reflectionless Schroedinger operators and generalized KdV solitons
  13. Takashi Ichinose:
    Magnetic Relativistic Schrödinger Operators and Kato's Inequality
  14. Andrii Khrabustovskyi:
    Geometric approximations of point interactions
  15. Marjeta Kramar-Fijavz:
    Bi-Continuous Operator Semigroups for Flows in Infinite Networks
  16. Pavel Kurasov:
    Inverse Problem for Quantum Graphs: Complete Solution using Magnetic Control
  17. Matthias Langer:
    Canonical systems whose Weyl coefficients have regularly varying asymptotics
  18. Lassi Lilleberg:
    Minimal passive realizations of generalized Schur functions in Pontryagin spaces
  19. Vladimir Lotoreichik:
    Optimization of lowest Robin eigenvalues on 2-manifolds and unbounded cones
  20. Annemarie Luger:
    Quasi-Herglotz functions
  21. Alexander Makin:
    On the basis property of root functions systems of Dirac operators with regular boundary conditions
  22. Mark Malamud:
    Scattering matrices, perturbation determinants, and trace formulas in the works of Hagen Neidhardt
  23. Vadim Mogilevskii:
    Compressions of self-adjoint extensions of a symmetric operator in a Hilbert space
  24. Samuel Mohr:
    Eigenvalues of Graphs
  25. Alexander Motovilov:
    Equivalence between the complex-rotation and scattering-matrix resonances in the Friedrichs-Faddeev model
  26. Ivica Nakic:
    Optimal control of parabolic equations using spectral calculus
  27. Noema Nicolussi:
    Self-adjoint extensions of infinite quantum graphs
  28. Andrea Posilicano:
    The semi-classical limit with delta potentials
  29. Nadezhda Rautian and Victor Vlasov (1):
    Semigroups for integro-differential equations with convolution memory terms
  30. Nadezhda Rautian and Victor Vlasov (2):
    Spectral analysis and representation of solutions of Volterra integro-differential equations with fractional exponential kernels
  31. Jakob Reiffenstein:
    Theorem of Hermite-Biehler for matrix-valued entire functions
  32. Roman Romanov:
    Canonical systems in ideals of compact operators
  33. Alexander Sakhnovich:
    Discrete Dirac system and Arov--Krein entropy
  34. Felix Schwenninger:
    From input-to-state stability to semigroup perturbations
  35. Igor Sheipak:
    On embedding constants in Sobolev spaces. Application to spectral problems with coefficients-distributions.
  36. Sergey Simonov:
    Wave model of symmetric operators
  37. Artur Stephan:
    On evolution semigroups and Trotter product operator-norm estimates
  38. Christiane Tretter:
    Everything is possible for the domain intersection of an operator and its adjoint
  39. Rudi Wietsma:
    Factorizations, invariant subspaces and multi-valency
  40. Nikos Yannakakis:
    The angle along a curve and range-kernel complementarity
  41. Valentin Zagrebnov:
    The Howland-Evans-Neidhardt approach to approximation of propagators


Slides

Here you find most presentations given at the conference.

  1. Vadym Adamyan:
    Close singular perturbations of selfadjoint operators
  2. Sergey Belyi:
    Perturbations of L-systems
  3. Anton Boitsev:
    A model of several point-like windows in the resonator boundary with the Dirichlet boundary condition
  4. Petru Cojuhari:
    On spectral analysis of Dirac operators
  5. Volodymyr Derkach:
    De Branges-Pontryagin spaces and embedding of de Branges matrices with negative squares in generalized J-inner matrices
  6. Jaroslav Dittrich:
    Scattering along a curve in the plane
  7. Jonathan Eckhardt:
    Continued fraction expansions and generalized indefinite strings
  8. Pavel Exner:
    Spectral gaps of periodic quantum graphs
  9. Luka Grubisic:
    Convergence of contour integration methods for self adjoint operators
  10. Seppo Hassi:
    Stieltjes and inverse Stieltjes families of linear relations in Hilbert spaces and their representations
  11. Rostyslav Hryniv:
    Inverse scattering for reflectionless Schroedinger operators and generalized KdV solitons
  12. Takashi Ichinose:
    Magnetic Relativistic Schrödinger Operators and Kato's Inequality
  13. Andrii Khrabustovskyi:
    Geometric approximations of point interactions
  14. Pavel Kurasov:
    Inverse Problem for Quantum Graphs: Complete Solution using Magnetic Control
  15. Matthias Langer:
    Canonical systems whose Weyl coefficients have regularly varying asymptotics
  16. Lassi Lilleberg:
    Minimal passive realizations of generalized Schur functions in Pontryagin spaces
  17. Vladimir Lotoreichik:
    Optimization of lowest Robin eigenvalues on 2-manifolds and unbounded cones
  18. Alexander Makin:
    On the basis property of root functions systems of Dirac operators with regular boundary conditions
  19. Mark Malamud:
    Scattering matrices, perturbation determinants, and trace formulas in the works of Hagen Neidhardt
  20. Vadim Mogilevskii:
    Compressions of self-adjoint extensions of a symmetric operator in a Hilbert space
  21. Samuel Mohr:
    Eigenvalues of Graphs
  22. Alexander Motovilov:
    Equivalence between the complex-rotation and scattering-matrix resonances in the Friedrichs-Faddeev model
  23. Ivica Nakic:
    Optimal control of parabolic equations using spectral calculus
  24. Noema Nicolussi:
    Self-adjoint extensions of infinite quantum graphs
  25. Andrea Posilicano:
    The semi-classical limit with delta potentials
  26. Nadezhda Rautian:
    Semigroups for integro-differential equations with convolution memory terms
  27. Roman Romanov:
    Canonical systems in ideals of compact operators
  28. Alexander Sakhnovich:
    Discrete Dirac system and Arov--Krein entropy
  29. Igor Sheipak:
    On embedding constants in Sobolev spaces. Application to spectral problems with coefficients-distributions.
  30. Sergey Simonov:
    Wave model of symmetric operators
  31. Artur Stephan:
    On evolution semigroups and Trotter product operator-norm estimates
  32. Victor Vlasov:
    Spectral analysis and representation of solutions of Volterra integro-differential equations with fractional exponential kernels
  33. Rudi Wietsma:
    Factorizations, invariant subspaces and multi-valency
  34. Nikos Yannakakis:
    The angle along a curve and range-kernel complementarity
  35. Valentin Zagrebnov:
    The Howland-Evans-Neidhardt approach to approximation of propagators


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Operator Theory and Krein Spaces
(dedicated to the memory of Hagen Neidhardt)

Vienna, December 19-22, 2019