From Institution to Inspiration: Why the Friars Minor Became Franciscans

Medieval religious institutions, such as the papacy or the religious orders, tend to designate a saint as their founding inspiration. For the papacy, this has been St Peter; for the religious orders, saints such as St Benedict, St Dominic or St Francis. While it might appear logical to think of these inspiring founders as preceding the establishment of such institutions, in reality the latter are almost entirely responsible for the making, maintaining and circulating of the image of a founding saint. Hence it is necessary to approach historiographical narratives with great caution in which an institution is thought to be diverging from the founder's path, falling short of the founder's ideals or deliberately distorting the image of a founder to justify their evolution. If such a discrepancy between the initial ideal and later practice is observed, the central point of investigation should focus on why the hagiographical and liturgical records regarding the founding saint included elements in conflict with the institutional practice. This article will investigate the medieval evidence and the historiographical narratives pertaining to the Order of Friars Minor.

Bialynicki-Birula schemes in higher dimensional Hilbert schemes of points and monic functors

The Bialynicki-Birula strata on the Hilbert scheme $H^n(\mathbb{A}^d)$ are smooth in dimension $d=2$. We prove that there is a schematic structure in higher dimensions, the Bialynicki-Birula scheme, which is natural in the sense that it represents a functor. Let $\rho_i:H^n(\mathbb{A}^d)\rightarrow {\rm Sym}^n(\mathbb{A}^1)$ be the Hilbert-Chow morphism of the ${i}^{th}$ coordinate. We prove that a Bialynicki-Birula scheme associated with an action of a torus $T$ is schematically included in the fiber $\rho_i^{-1}(0)$ if the ${i}^{th}$ weight of $T$ is non-positive. We prove that the monic functors parametrizing families of ideals with a prescribed initial ideal are representable. Comment: Final version

Full-Rank Valuations and Toric Initial Ideals

Let $V(I)$ be a polarized projective variety or a subvariety of a product of projective spaces, and let $A$ be its (multi-)homogeneous coordinate ring. To a full-rank valuation ${\mathfrak{v}}$ on $A$ we associate a weight vector $w_{\mathfrak{v}}$. Our main result is that the value semi-group of ${\mathfrak{v}}$ is generated by the images of the generators of $A$ if and only if the initial ideal of $I$ with respect to $w_{\mathfrak{v}}$ is prime. As application, we prove a conjecture by [ 7] connecting the Minkowski property of string polytopes to the tropical flag variety. For Rietsch-Williams’ valuation for Grassmannians, we identify a class of plabic graphs with non-integral associated Newton–Okounkov polytope (for ${\operatorname *{Gr}}_k(\mathbb C^n)$ with $n\ge 6$ and $k\ge 3$).

Betti numbers of toric ideals of graphs: A case study

We compute the graded Betti numbers for the toric ideal of a family of graphs constructed by adjoining a cycle to a complete bipartite graph. The key observation is that this family admits an initial ideal which has linear quotients. As a corollary, we compute the Hilbert series and [Formula: see text]-vector for all the toric ideals of graphs in this family.

Rational Complexity-One $\boldsymbol{T}$-Varieties Are Well-Poised

Given an affine rational complexity-one $T$-variety $X$, we construct an explicit embedding of $X$ in affine space ${\mathbb{A}}^n$. We show that this embedding is well-poised, that is, every initial ideal of $I_X$ is a prime ideal, and we determine the tropicalization ${\mathrm{Trop}}(X^\circ)$. We then study valuations of the coordinate ring $R_X$ of $X$ which respect the torus action, showing that for full rank valuations, the natural generators of $R_X$ form a Khovanskii basis. This allows us to determine Newton–Okounkov bodies of rational projective complexity-one $T$-varieties, partially recovering (and generalizing) results of Petersen. We apply our results to describe all integral special fibres of ${\mathbb{K}}^*\times T$-equivariant degenerations of rational projective complexity-one $T$-varieties, generalizing a result of Süß and Ilten.

NONCROSSING SETS AND A GRASSMANN ASSOCIAHEDRON

We study a natural generalization of the noncrossing relation between pairs of elements in$[n]$to$k$-tuples in$[n]$that was first considered by Petersenet al.[J. Algebra324(5) (2010), 951–969]. We give an alternative approach to their result that the flag simplicial complex on$\binom{[n]}{k}$induced by this relation is a regular, unimodular and flag triangulation of the order polytope of the poset given by the product$[k]\times [n-k]$of two chains (also called Gelfand–Tsetlin polytope), and that it is the join of a simplex and a sphere (that is, it is a Gorenstein triangulation). We then observe that this already implies the existence of a flag simplicial polytope generalizing the dual associahedron, whose Stanley–Reisner ideal is an initial ideal of the Grassmann–Plücker ideal, while previous constructions of such a polytope did not guarantee flagness nor reduced to the dual associahedron for$k=2$. On our way we provide general results about order polytopes and their triangulations. We call the simplicial complex thenoncrossing complex, and the polytope derived from it the dualGrassmann associahedron. We extend results of Petersenet al.[J. Algebra324(5) (2010), 951–969] showing that the noncrossing complex and the Grassmann associahedron naturally reflect the relations between Grassmannians with different parameters, in particular the isomorphism$G_{k,n}\cong G_{n-k,n}$. Moreover, our approach allows us to show that the adjacency graph of the noncrossing complex admits a natural acyclic orientation that allows us to define aGrassmann–Tamari orderon maximal noncrossing families. Finally, we look at the precise relation of the noncrossing complex and the weak separability complex of Leclerc and Zelevinsky [Amer. Math. Soc. Transl.181(2) (1998), 85–108]; see also Scott [J. Algebra290(1) (2005), 204–220] among others. We show that the weak separability complex is not only a subcomplex of the noncrossing complex as noted by Petersenet al.[J. Algebra324(5) (2010), 951–969] but actually its cyclically invariant part.

On the binomial edge ideals of block graphs

We find a class of block graphs whose binomial edge ideals have minimal regularity. As a consequence, we characterize the trees whose binomial edge ideals have minimal regularity. Also, we show that the binomial edge ideal of a block graph has the same depth as its initial ideal.