Correction: SISSA algebraic geometry online seminars - Matteo GALLET

Alessandro Nobile anobile at
Wed Oct 28 16:03:29 CET 2020

The seminar of Matteo GALLET will be held tomorrow 29 OCTOBER, not as
erroneously stated before on 29 November. 

Sorry for the spam. 


Dear all,
    this is to announce the first seminar of the group of algebraic
geometry in SISSA. 

SPEAKER:    Matteo GALLET - SISSA  and  

TITLE:      Zero-sum cycles in flexible polyhedra 

WHEN:       Thursday, November 29 at 5.00pm (Rome) 

WHERE:      Link Zoom:
            ID riunione: 828 8248 3158
            Passcode: 446989

ABSTRACT:   We show that if a polyhedron in the three-dimensional affine
space with triangular faces is flexible, i.e., can be continuously
deformed preserving the shape of its faces, then there is a cycle of
edges whose lengths sum up to zero once suitably weighted by 1 and -1.
We do this via elementary combinatorial considerations, made possible by
a well-known compactification of the three-dimensional affine space as a
quadric in the four-dimensional projective space. The compactification
is related to the Euclidean metric, and allows us to use a simple
degeneration technique that reduces the problem to its one-dimensional
analogue, which is trivial to solve. This is a joint work with G.
Grasegger, J. Legerský, and J. Schicho. 

Best regards,

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