Zhengwei LiuYau Mathematical Sciences Center and Department of Mathematics, Tsinghua University, Beijing, 100084, China; Beijing Institute of Mathematical Sciences and Applications, Huairou District, Beijing, 101408, ChinaSebastien PalcouxBeijing Institute of Mathematical Sciences and Applications, Huairou District, Beijing, 101408, ChinaJinsong WuInstitute for Advanced Study in Mathematics, Harbin Institute of Technology, Harbin, 150001, China
Category TheoryFunctional AnalysisQuantum AlgebraRings and AlgebrasSpectral Theory and Operator Algebramathscidoc:2207.04003
We introduce fusion bialgebras and their duals and systematically study their Fourier analysis. As an application, we discover new efficient analytic obstructions on the unitary categorification of fusion rings. We prove the Hausdorff-Young inequality, uncertainty principles for fusion bialgebras and their duals. We show that the Schur product property, Young's inequality and the sum-set estimate hold for fusion bialgebras, but not always on their duals. If the fusion ring is the Grothendieck ring of a unitary fusion category, then these inequalities hold on the duals. Therefore, these inequalities are analytic obstructions of categorification. We classify simple integral fusion rings of Frobenius type up to rank 8 and of Frobenius-Perron dimension less than 4080. We find 34 ones, 4 of which are group-like and 28 of which can be eliminated by applying the Schur product property on the dual. In general, these inequalities are obstructions to subfactorize fusion bialgebras.
The classical de Finetti theorem in probability theory relates symmetry under the permutation group with the independence of random variables. This result has application in quantum information. Here we study states that are invariant with respect to a natural action of the braid group, and we emphasize the pictorial formulation and interpretation of our results. We prove a new type of de Finetti theorem for the four-string, double-braid group acting on the parafermion algebra to braid qudits, a natural symmetry in the quon language for quantum information. We prove that a braid-invariant state is extremal if and only if it is a product state. Furthermore, we provide an explicit characterization of braid-invariant states on the parafermion algebra, including finding a distinction that depends on whether the order of the parafermion algebra is square free. We characterize the extremal nature of product states (an inverse de Finetti theorem).
Yong LinDepartment of Mathematics, Renmin University of China, Beijing 100872, ChinaShuang LiuYau Mathematical Sciences Center, Tsinghua University, Beijing 100084, ChinaHongye SongDepartment of Mathematics, Renmin University of China, Beijing 100872, China; Beijing International Studies University, Beijing 100024, China
We prove the equivalence between some functional inequalities and the ultracontractivity property of the heat semigroup on infinite graphs. These functional inequalities include Sobolev inequalities, Nash inequalities, Faber–Krahn inequalities, and log-Sobolev inequalities. We also show that, under the assumptions of volume growth and CDE(n, 0), which is regarded as the natural notion of curvature on graphs, these four functional inequalities and the ultracontractivity property of the heat semigroup are all true on graphs.
Dachun YangDepartment of Mathematics, Beijing Normal University, Beijing 100875, People’s Republic of ChinaYong LinDepartment of Mathematics, Information School, Renmin (People) University of China, Beijing 100872, People’s Republic of China
Proceedings of the Edinburgh Mathematical Society, 47, (3), 709-752, 2004.11
New spaces of Lipschitz type on metric-measure spaces are introduced and they are shown to be just the well-known Besov spaces or Triebel–Lizorkin spaces when the smooth index is less than 1. These theorems also hold in the setting of spaces of homogeneous type, which include Euclidean spaces, Riemannian manifolds and some self-similar fractals. Moreover, the relationships amongst these Lipschitz-type spaces, Hajłasz–Sobolev spaces, Korevaar–Schoen–Sobolev spaces, Newtonian Sobolev space and Cheeger–Sobolev spaces on metric-measure spaces are clarified, showing that they are the same space with equivalence of norms. Furthermore, a Sobolev embedding theorem, namely that the Lipschitz-type spaces with large orders of smoothness can be embedded in Lipschitz spaces, is proved. For metric-measure spaces with heat kernels, a Hardy–Littlewood–Sobolev theorem is establish, and hence it is proved that Lipschitz-type spaces with small orders of smoothness can be embedded in Lebesgue spaces.
Zhengwei LiuDepartment of Mathematics and Department of Physics Harvard University, Cambridge, MA, U.S.A.Jinsong WuInstitute for Advanced Study in Mathematics Harbin Institute of Technology, Harbin, 150001, China
Pacific Journal of Mathematics, 295, (1), 103-121, 2018.3
In this paper, we prove a sum set estimate and the exact sum set theorem for unimodular Kac algebras. Combining the characterization of minimizers of the Donoso–Stark uncertainty principle and the Hirschman–Beckner uncertainty principle, we characterize the extremal pairs of Young’s inequality and extremal operators of the Hausdorff–Young inequality for unimodular Kac algebras.