• Boundary Conditions for Scalar Curvature 

      [OWP-2021-01] Bär, Christian; Hanke, Bernhard (Mathematisches Forschungsinstitut Oberwolfach, 2021-01-04)
      Based on the Atiyah-Patodi-Singer index formula, we construct an obstruction to positive scalar curvature metrics with mean convex boundaries on spin manifolds of infinite $K$-area. We also characterize the extremal case. ...
    • Lifting Spectral Triples to Noncommutative Principal Bundles 

      [OWP-2021-02] Schwieger, Kay; Wagner, Stefan (Mathematisches Forschungsinstitut Oberwolfach, 2021-01-11)
      Given a free action of a compact Lie group $G$ on a unital C*-algebra $\mathcal{A}$ and a spectral triple on the corresponding fixed point algebra $\mathcal{A}^G$, we present a systematic and in-depth construction of ...
    • Amorphic Complexity of Group Actions with Applications to Quasicrystals 

      [OWP-2021-03] Fuhrmann, Gabriel; Gröger, Maik; Jäger, Tobias; Kwietniak, Dominik (Mathematisches Forschungsinstitut Oberwolfach, 2021-02-02)
      In this article, we define amorphic complexity for actions of locally compact $\sigma$-compact amenable groups on compact metric spaces. Amorphic complexity, originally introduced for $\mathbb Z$-actions, is a topological ...
    • The C-Map as a Functor on Certain Variations of Hodge Structure 

      [OWP-2021-04] Mantegazza, Mauro; Saha, Arpan (Mathematisches Forschungsinstitut Oberwolfach, 2021-03-15)
      We give a new manifestly natural presentation of the supergravity c-map. We achieve this by giving a more explicit description of the correspondence between projective special Kähler manifolds and variations of Hodge ...
    • The Elser Nuclei Sum Revisited 

      [OWP-2021-05] Grinberg, Darij (Mathematisches Forschungsinstitut Oberwolfach, 2021-03-16)
      Fix a finite undirected graph $\Gamma$ and a vertex $v$ of $\Gamma$. Let $E$ be the set of edges of $\Gamma$. We call a subset $F$ of $E$ \textit{pandemic} if each edge of $\Gamma$ has at least one endpoint that can be ...
    • On the Computational Content of the Theory of Borel Equivalence Relations 

      [OWP-2021-06] Bazhenov, Nikolay; Monin, Benoit; San Mauro, Luca; Zamora, Rafael (Mathematisches Forschungsinstitut Oberwolfach, 2021-03-17)
      This preprint offers computational insights into the theory of Borel equivalence relations. Specifically, we classify equivalence relations on the Cantor space up to computable reductions, i.e., reductions induced by Turing ...
    • Diophantine Approximation in Metric Space 

      [OWP-2021-07] Fraser, Jonathan M.; Koivusalo, Henna; Ramírez, Felipe A. (Mathematisches Forschungsinstitut Oberwolfach, 2021-06-14)
      Diophantine approximation is traditionally the study of how well real numbers are approximated by rationals. We propose a model for studying Diophantine approximation in an arbitrary totally bounded metric space where the ...
    • Weak*-Continuity of Invariant Means on Spaces of Matrix Coefficients 

      [OWP-2021-08] de Laat, Tim; Zadeh, Safoura (Mathematisches Forschungsinstitut Oberwolfach, 2021-07-13)
      With every locally compact group $G$, one can associate several interesting bi-invariant subspaces $X(G)$ of the weakly almost periodic functions $\mathrm{WAP}(G)$ on $G$, each of which captures parts of the representation ...