SearcharxivSearch

arXiv subjects

Kengo Miyamoto

Publications and source records attributed to Kengo Miyamoto.

14 recordsLinked to original sources

Frobenius--Perron dimension and tensor products of algebras

In this paper, we study how the Frobenius--Perron dimension of finite-dimensional algebras behaves under tensor products and related constructions. We prove that Frobenius--Perron dimension is super-additive under tensor products and is additive whenever one tensor factor is local. In particular every non-negative integer occurs as a Frobenius--Perron dimension. We further show that the invariant equals $1$ for every representation-infinite cycle-finite algebra, such as a tame concealed or tubular algebra, and we determine it on the grids $\mathsf{k} A_m\otimes_{\mathsf{k}}\mathsf{k} A_n$, where it is $0$, $1$, or $\infty$ according to representation type. Finally we treat skew group algebras of local algebras, for which a McKay quiver computation gives a lower bound and shows that the dimension can jump from finite to infinite.

math.RT

Defect Spaces and Gram Operators for Tensor-Valued Incidence Maps

We study vector-valued incidence maps obtained from ordinary graph incidence maps by linear observation of the free vertex space. Let $\mathbb{F}$ be a field, $D = (X, E, s, t)$ a finite directed multigraph, $U$ an $\mathbb{F}$-vector space, and $\phi : X \to U$ a vertex labeling with $\mathbb{F}$-linear extension $\hat{\phi} : \mathbb{F}^X \to U$. The vector-valued incidence map $\partial_\phi : \mathbb{F}^E \to U$, $\partial_\phi(\mathbf{1}_e) = \phi(t(e)) - \phi(s(e))$, factors as $\partial_\phi = \hat{\phi} \circ B_D$, where $B_D$ is the classical incidence map of $D$. We prove the formula $\dim_{\mathbb{F}} \mathrm{Ker}(\partial_\phi) = |E| - |X| + c(D) + \delta_\phi,$ where $c(D)$ is the number of weakly connected components of $D$ and $\delta_\phi := \dim_{\mathbb{F}}(\mathrm{Im}(B_D) \cap \mathrm{Ker}(\hat{\phi}))$ is the defect invariant. We apply this framework to directed tensor-labeled hypergraphs $\mathcal{H} = (Q_0, Q_1, \beta)$, in which each hyperedge carries a pair of boundary tensors $(A_e, B_e)$ in the tensor algebra $T(\mathbb{F}^{Q_0})$, and prove that $\delta(\mathcal{H}) = 0$ over any field for each of the six standard constructions, including symmetric encodings that degenerate in positive characteristic. Over $\mathbb{F} = \mathbb{R}$, the edge Gram operator $\mathcal{L} = \partial_\beta^* \partial_\beta$ has rank $|V_{\mathrm{macro}}| - c_{\mathrm{macro}} - \delta(\mathcal{H})$, and its degree-truncated operators form a Loewner-monotone filtration whose rank increments equal the decrements of the defect filtration. We further realize the cycle space of every oriented hypergraph (in the sense of Reff--Rusnak) as $\mathrm{Ker}(\partial_\beta)$ within this framework, and exhibit a four-edge inclusion--exclusion example with $\delta(\mathcal{H}) = 1$.

math.CO

Arithmetic on $q$-deformed rational numbers

Recently, Morier-Genoud and Ovsienko introduced a $q$-deformation of rational numbers. More precisely, for an irreducible fraction $\frac{r}s>0$, they constructed coprime polynomials $\mathcal{R}_{\frac{r}s}(q),~ \mathcal{S}_{\frac{r}s}(q) \in {\mathbb Z}[q]$ with $\mathcal{R}_{\frac{r}s}(1)=r,~\mathcal{S}_{\frac{r}s}(1)=s$. Their theory has a rich background and many applications. By definition, if $r \equiv r' \pmod{s}$, then $\mathcal{S}_{\frac{r}s}(q)=\mathcal{S}_{\frac{r'}s}(q)$. We show that $rr'{\equiv} -1 \pmod{s}$ implies $\mathcal{S}_{\frac{r}s}(q)=\mathcal{S}_{\frac{r'}s}(q)$, and it is conjectured that the converse holds if $s$ is prime (and $r \not \equiv r' \pmod{s}$). We also show that $s$ is a multiple of 3 (resp. 4) if and only if $\mathcal{S}_{\frac{r}s}(ζ)=0$ for $ζ=(-1+\sqrt{-3})/2$ (resp. $ζ=i$). We give applications to the representation theory of quivers of type $A$ and the Jones polynomials of rational links.

math.CO

On $τ$-tilting finiteness of symmetric algebras of polynomial growth

In this paper, we report on the $τ$-tilting finiteness of some classes of finite-dimensional algebras over an algebraically closed field, including symmetric algebras of polynomial growth, $0$-Hecke algebras and $0$-Schur algebras. Consequently, we find that derived equivalence preserves the $τ$-tilting finiteness over symmetric algebras of polynomial growth, and self-injective cellular algebras of polynomial growth are $τ$-tilting finite. Furthermore, the representation-finiteness and $τ$-tilting finiteness over $0$-Hecke algebras and $0$-Schur algebras (with few exceptions) coincide.

math.RT

Uniform Cyclic Group Factorizations of Finite Groups

In this paper, we introduce a kind of decomposition of a finite group called a uniform group factorization, as a generalization of exact factorizations of a finite group. A group $G$ is said to admit a uniform group factorization if there exist subgroups $H_1, H_2, \ldots, H_k$ such that $G = H_1 H_2 \cdots H_k$ and the number of ways to represent any element $g \in G$ as $g = h_1 h_2 \cdots h_k$ ($h_i \in H_i$) does not depend on the choice of $g$. Moreover, a uniform group factorization consisting of cyclic subgroups is called a uniform cyclic group factorization. First, we show that any finite solvable group admits a uniform cyclic group factorization. Second, we show that whether all finite groups admit uniform cyclic group factorizations or not is equivalent to whether all finite simple groups admit uniform group factorizations or not. Lastly, we give some concrete examples of such factorizations.

math.GR

On periodic stable Auslander-Reiten components containing Heller lattices over the symmetric Kronecker algebra

Let $\mathcal{O}$ be a complete discrete valuation ring, $\mathcal{K}$ its quotient field, and $A$ the symmetric Kronecker algebra over $\mathcal{O}$. We consider the full subcategory of the category of $A$-lattices whose objects are $A$-lattices $M$ such that $M\otimes_{\mathcal{O}}\mathcal{K}$ is projective $A\otimes_{\mathcal{O}}\mathcal{K}$-modules. In this paper, we study Heller lattices of indecomposable periodic modules over $A$. As a main result, we determine the shapes of stable Auslander--Reiten components containing Heller lattices of indecomposable periodic modules over $A$.

math.RT

Automorphism Shuffles for Graphs and Hypergraphs and Its Applications

In card-based cryptography, a deck of physical cards is used to achieve secure computation. A shuffle, which randomly permutes a card-sequence along with some probability distribution, ensures the security of a card-based protocol. The authors proposed a new class of shuffles called graph shuffles, which randomly permutes a card-sequence by an automorphism of a directed graph (New Generation Computing 2022). For a directed graph $G$ with $n$ vertices and $m$ edges, such a shuffle could be implemented with pile-scramble shuffles with $2(n+m)$ cards. In this paper, we study graph shuffles and give an implementation, an application, and a slight generalization of them. First, we propose a new protocol for graph shuffles with $2n+m$ cards. Second, as a new application of graph shuffles, we show that any cyclic group shuffle, which is a shuffle over a cyclic group, is a graph shuffle associated with some graph. Third, we define a hypergraph shuffle, which is a shuffle by an automorphism of a hypergraph, and show that any hypergraph shuffle can also be implemented with pile-scramble shuffles.

cs.CR

Graph Automorphism Shuffles from Pile-Scramble Shuffles

A pile-scramble shuffle is one of the most effective shuffles in card-based cryptography. Indeed, many card-based protocols are constructed from pile-scramble shuffles. This article aims to study the power of pile-scramble shuffles. In particular, for any directed graph $G$, we introduce a new protocol called "a graph shuffle protocol for $G$", and show that it can be implemented by using pile-scramble shuffles only. Our proposed protocol requires $2(n+m)$ cards, where $n$ and $m$ are the numbers of vertices and edges of $G$, respectively. The number of pile-scramble shuffles is $k+1$, where $1 \leq k \leq n$ is the number of distinct degrees of vertices of $G$. As an application, a random cut for $n$ cards, which is also an important shuffle, can be realized by $3n$ cards and two pile-scramble shuffles.

cs.CR

Report on the finiteness of silting objects

We discuss the finiteness of (two-term) silting objects. First, we investigate new triangulated categories without silting object. Second, one studies two classes of $τ$-tilting-finite algebras and give the numbers of their two-term silting objects. Finally, we explore when $τ$-tilting-finiteness implies representatoin-finiteness, and obtain several classes of algebras in which a $τ$-tilting-finite algebra is representation-finite.

math.RT

On the non-periodic stable Auslander--Reiten Heller component for the Kronecker algebra over a complete discrete valuation ring

We consider the Kronecker algebra $A=\mathcal{O}[X, Y]/(X^2, Y^2)$, where $\mathcal{O}$ is a complete discrete valuation ring. Since $A \otimesκ$ is a special biserial algebra, where $κ$ is the residue field of $\mathcal{O}$, one can compute a complete list of indecomposable $A\otimesκ$-modules. For each indecomposable $A\otimesκ$-module, we obtain a special kind of $A$-lattices called "Heller lattices". In this paper, we determine the non-periodic component of a variant of the stable Auslander--Reiten quiver for the category of $A$-lattices that contains "Heller lattices". Moreover, we give the strong restrictions on stable Auslander--Reiten quivers for symmetric orders over a complete discrete valuation ring.

math.RT

On components of stable Auslander-Reiten quivers that contain Heller lattices: the case of truncated polynomial rings

Let $A$ be a truncated polynomial ring over a complete discrete valuation ring $\mathcal{O}$, and we consider the additive category consisting of $A$-lattices $M$ with the property that $M\otimes \mathcal{K}$ is projective as an $A\otimes \mathcal{K}$-module, where $\mathcal{K}$ is the fraction field of $\mathcal{O}$. Then, we may define the stable Auslander-Reiten quiver of the category. We determine the shape of the components of the stable Auslander-Reiten quiver that contain Heller lattices.

math.RA

Self-injective cellular algebras of polynomial growth representation type

We classify Morita equivalence classes of indecomposable self-injective cellular algebras which have polynomial growth representation type, assuming that the base field has an odd characteristic. This assumption on the characteristic is for the cellularity to be a Morita invariant property.

math.RT

Extremely scalable algorithm for 10$^8$-atom quantum material simulation on the full system of the K computer

An extremely scalable linear-algebraic algorithm was developed for quantum material simulation (electronic state calculation) with 10$^8$ atoms or 100-nm-scale materials. The mathematical foundation is generalized shifted linear equations ((zB - A) x = b), instead of conventional generalized eigenvalue equations. The method has a highly parallelizable mathematical structure. The fundamental theory is mathematical and is applicable also to other scientific fields. The benchmark shows an extreme strong scaling and a qualified time-to-solution on the full system of the K computer. The method was demonstrated in a real material research for ultra-flexible (organic) devices, key devices of next-generation IoT products. The present paper shows that an innovative scalable algorithm for a real research can appear by the co-design among application, algorithm and architecture.

cond-mat.mtrl-sci