We prove RE-completeness of the quantum homomorphism problem parameterised by families of graphs derived from the classic metric association schemes. These include Kneser graphs, $q$-Kneser graphs, and the complements of Johnson, Grassmann, and Hamming graphs. Our proof develops a spectral method for establishing non-c...
Lorenzo Ciardo, Iris Hebbeker, Gideo Joubert et al.· 0 citations
We use a Gröbner basis technique first introduced by Knutson, Miller and Yong to study the interplay between properties of a graph [Formula: see text] and algebraic properties of the toric ideal that it defines. We first recover a well-known height formula for the toric ideal of a graph [Formula: see text] and demonstr...
Sergio Da Silva, Emma Naguit, Jenna Rajchgot· Journal of Algebra and its A...· 0 citations
We provide a counterexample to the Pierce-Birkhoff conjecture: a continuous function that is piecewise quadratic on a finite collection of semialgebraic sets that partition $\mathbb{R}^n$ but that cannot be expressed as a finite lattice combination of polynomials. The counterexample was found with the assistance of our...
We show that every faithful, transitive, and generically $(n+2)$-transitive action of a connected group $G$ on an irreducible variety $X$ of dimension $n>0$, all defined over an algebraically closed field $F$, is isomorphic to the natural action of the projective linear group $PGL_{n+1}(F)$ on the projective space $\ma...
Abstract Carvajal-Rojas, Schwede and Tucker asked whether the mod 𝑝 reductions of a complex klt type singularity have uniformly positive 𝐹-signature for all but finitely many primes 𝑝. In this paper, we give an affirmative answer to this conjecture for pure subrings of regular local rings, including reductive quotient...
S. Takagi, Tatsuki Yamaguchi· Journal für die Reine und An...· 5 citations· ⚡1
For simple, nonelementary C*-algebras, we show uniform density of functions realized as ranks of operators. It follows that strict comparison by traces forces almost divisibility, and hence pureness. As an application, we show that strict comparison implies $\mathcal{Z}$-stability for separable, simple, nonelementary C...
Hannes Thiel· 0 citations
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