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Events
Conferences, Research Colloquia & Seminars,
Defenses, and other events
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April 2024
Su Mo Tu We Th Fr Sa
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Geometry Seminar
This is the research seminar of the group and focuses
on recent research in (differential) geometry;
during the semester the seminar is usually scheduled
to take place on Wednesday at 16:00 in the
Zeichensaal 1
or online.
If you are interested in giving a talk, please contact
the organizers:
Ivan Izmestiev
Student Seminars
These seminars are usually part of the assessment
and are open to the public,
in particular, to interested students;
topics typically focus on geometry but cover a wider range
of areas, depending on the students' and the advisor's
interests.
Presentations are often delivered in German.
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Summer term 2023 |
Talks in the geometry seminar
(hover/tap name or title to view more information)
- 31 May 2023: Geometry seminar
- Gunter Weiss (TU Wien & TU Dresden):
Der Satz von Miquel und seine Brüder
Abstract
Der elementargeometrische Satz von Miquel geht von einem Dreieck
$ABC$ und Punkten $R, S, T$ auf dessen Seiten aus und behauptet,
dass die drei Kreise $\bigcirc ART$, $\bigcirc BRS$, $\bigcirc CST$ einen Punkt, den
"Miquel-Punkt" $M$, gemeinsam haben. Für $M$ hat man die
Dreiecksebene, also eine zweiparametrige Menge, von
Möglichkeiten, sodass es zu jedem $M$ eine einparametrige Menge
von Tripeln $R, S, T$ geben muss. Wählt man $R, S, T$ speziell
und/oder voneinander abhängig, so ergeben sich das
"Bierdeckel-Theorem", die Sätze von Brocard und
Simson-Wallace als Spezialfälle des Satzes von Miquel. Dabei
ergeben sich auch überraschende "merkwürdige Inzidenzen"
und Zusammenhänge mit anderen elementar-geometrischen Sätzen.
Der Satz von Miquel erlaubt auch eine direkte
3D-Verallgemeinerung, während etwa die Satzgruppe von Brocard
nur mit Modifikationen ins Dreidimensionale übertragbar ist.
- 03 May 2023: Geometry seminar
- Mohammad Ivaki (TU Wien):
Firey's worn stones are round
Abstract
I will talk about the Gauss curvature flow, which in $R^3$ was
proposed by Firey as a model for the changing shape of smooth,
strictly convex stones as they tumble on a beach. I'll give a
summary of the results on this flow from its inception to its
complete resolution.
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Winter term 2022/23
Hans Havlicek with participants, 9 Dec 2022
photograph © Gunter Weiß
Hellmuth Stachel, 18 Nov 2022
photograph © Georg Glaeser
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Festkolloquia
- 09 Dez 2022, Zeichensaal 3: Festkolloquium
- zum 70. Geburtstag von Hans Havlicek
Programm
- 13:30 - 14:30
- Silvia Pianta (Universita Cattolica del Sacre Cuore, Brescia):
1984, and beyond ... through joint Hanswers around parallelisms
- 14:30 - 15:30
- Markus Stroppel (Universität Stuttgart):
Projective geometry in an algebraist's toolbox
- 15:30 - 16:00
- Kaffeepause
- 16:00 - 17:00
- Mark Pankov (University Warmia and Mazury, Olsztyn):
One result of Hans and a non-bijective version of Wigner theorem
- 17:00 - 18:00
- Corrado Zanella (Universita di Padova):
Incidence properties of algebraic varieties
- 18 Nov 2022, Zeichensaal 3: Festkolloquium
- zum 80. Geburtstag von Hellmuth Stachel
Programm
- 13:15 - 14:00
- Eröffnung und Laudatio von Otto Röschel
- 14:00 - 15:00
- Johannes Wallner (TU Graz):
Flexible nets and discrete differential geometry
- 15:00 - 16:00
- Georg Glaeser (Universität für angewandte Kunst Wien):
Forty years between descriptive and computational geometry:
the universe of spatial imagination
- 16:00 - 16:30
- Kaffeepause
- 16:30 - 17:30
- Hans-Peter Schröcker (Universität Innsbruck):
Devil in paradise II - recent results in motion factorization
- 17:30 - 18:30
- Giorgio Figliolini (Universität Cassino):
Kinematics of mechanisms with higher-pairs:
fundamentals and applications
- 19:00
- Abendessen im Restaurant Waldviertlerhof,
Schönbrunnerstr. 20, 1050 Wien
Talks in the geometry seminar
(hover/tap name or title to view more information)
- 21 Feb 2023: Geometry seminar 15:00, ZS1
- Alex Fairley (TU Berlin): Circular nets with spherical parameter lines
Abstract
In the context of discrete differential geometry, circular nets
provide a discretisation of curvature line parametrisations. In
this talk, we will present incidence theorems to construct
circular nets with spherical parameter lines. And we will
present geometric properties of circular nets with spherical
parameter lines. We will compare them with the classical
properties of surfaces with spherical curvature lines. These are
classical surfaces that were intensely studied in the 19th
century.
- 23 Jan 2023: Geometry seminar
- Sergey Agafonov (Sao Paulo State University):
Confocal conics and 4-webs of maximal rank
Abstract
Confocal conics form an orthogonal net. Supplementing this net
with one of the following: 1) the net of Cartesian coordinate
lines aligned along the principal axes of conics, 2) the net of
Apollonian pencils of circles whose foci coincide with the foci
of conics, 3) the net of tangents to a conic of the confocal
family, we get a planar 4-web. We show that each of these 4-webs
is of maximal rank and characterize confocal conics from the web
theory viewpoint.
12 Dec 2022
16 Jan 2023: Geometry seminar- Christian Müller (TU Wien):
The Geometry of Discrete AGAG-Webs in Isotropic 3-Space
Abstract
We investigate webs from the perspective of the geometry of webs
on surfaces in three dimensional space. Our study of AGAG-webs
is motivated by architectural applications of gridshell
structures where four families of manufactured curves on a
curved surface are realizations of asymptotic lines and geodesic
lines. We describe all discrete AGAG-webs in isotropic space and
propose a method to construct them. Furthermore, we prove that
some sub-nets of an AGAG-web are timelike minimal surfaces in
Minkowski space and can be embedded into a one-parameter family
of discrete isotropic Voss nets. This is a joint work with
Helmut Pottman.
- 09 Jan 2023: Geometry seminar
- Jan Gregorovic (TU Wien):
Invariants of curves in conformal manifolds
Abstract
I will talk about invariants that can be assigned to curves in
conformal manifolds of dimension greater than 2. An invariant is
a quantity depending only on the curve and the conformal class
of metrics and in particular, is invariant under all conformal
transformation. The construction of these invariants uses the
description of conformal manifolds via tractor bundles, which I
describe in detail. Using tractor fields instead of vector
fields along the curve allows to construct an analogy of the
Frenet frame and use it to define invariants.
- 28 Nov 2022: Geometry seminar
- Günter Rote (FU Berlin):
Grid peeling and the affine curve-shortening flow
Abstract
Grid Peeling is the process of taking the integer grid points
inside a convex region and repeatedly removing the convex hull
vertices.
It has been observed by Eppstein, Har-Peled, and Nivasch,
that, as the grid is refined, this process converges to
the Affine Curve-Shortening Flow (ACSF), which is defined
as a deformation of a smooth curve.
As part of the M.Ed. thesis of Moritz Rüber, we
have investigated the grid peeling process for special
parabolas, and we could observe some striking phenomena.
This has lead to a conjecture for the value of the constant
that relates the two processes.
- 14 Nov 2022: Geometry seminar
- Karoly Bezdek (University of Calgary):
Ball polyhedra -- old and new
Abstract
We survey a number of metric properties of intersections of
finitely many congruent balls called ball polyhedra in Euclidean
spaces. In particular, our talk is centered around the status of
the shortest billiard conjecture, the global rigidity
conjecture, Hadwiger???s covering conjecture, and the
Gromov-Klee-Wagon volumetric conjecture for ball polyhedra.
- 17 Oct 2022: Geometry seminar
- Group meeting
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Events in former years
External Links
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Technische Universität Wien