arXiv subjects

Shinsuke Iwao

Publications and source records attributed to Shinsuke Iwao.

At least 19 recordsLinked to original sources

arXiv2026

Longest increasing subsequences of dyadic-type chaotic orbits

This paper studies the longest increasing subsequence (LIS) problem for sequences generated by dyadic-type chaotic interval maps. Starting from a single point $x\in[0,1)$ chosen uniformly at random, we form the order pattern of the first $N$ points of its orbit, with the doubling map as the basic model. Let $\lambda_1^{(N)}$ be the LIS length, equivalently the length of the first row of the Young diagram obtained by Schensted's insertion. We show that $\mathbb E[\lambda_1^{(N)}]/\sqrt N\to 2$, matching the leading asymptotics in the classical Ulam--Hammersley problem for uniform random permutations.

math.DS↗

arXiv2026

Stationary Measures and Mean Flux Depending on Multiple Conserved Quantities in a Stochastic Cellular Automaton

We analyze a stochastic 5-neighbor cellular automaton with several conserved quantities, including the particle density. By examining the eigenvalue problem of the associated transition matrix, we derive an explicit formula for the stationary distribution on each irreducible component, in which the weight of each configuration is expressed in terms of the numbers of occurrences of two specific local patterns. This analysis further allows us to theoretically derive the dependence of the mean flux on the conserved quantities. In particular, we recover the mean flux formula in the deterministic case by taking the zero-noise limit of the system.

math-ph↗

arXiv2026

Tetrahedral $L$-operators, tensor Schur polynomials and $q$-deformed loop elementary symmetric functions

We study three-dimensional partition functions constructed from the tetrahedral $L$-operator introduced and studied by Bazhanov-Sergeev and Kuniba-Maruyama-Okado. First, we explore the $q=0$ case, extending the authors' previous results and giving applications by a further analysis on the Zamolodchikov-Faddeev algebra. We introduce a class of partition functions which can be expressed as the tensor Schur polynomials, a class of products of Schur polynomials. As an application, we derive the shuffle formula for the Schur polynomials which is geometrically the pushforward formula by Joźefiak-Pragacz-Lascoux. We also give a derivation and a unification of the Gustafson-Milne and Feh{é}r--N{é}methi--Rim{á}nyi identities, and introduce a family of Laurent polynomials using divided difference operators which imitates the Schubert polynomials from the perspective of our study. We also present an application to the steady state of the multispecies totally asymmetric simple exclusion process. Second, we investigate several classes of partition functions for the generic $q$ case, and determine the explicit forms as deformations of the elementary symmetric functions. One of them can be regarded as (an extension of) a $q$-deformed loop elementary symmetric functions.

math-ph↗

arXiv2026

Relativistic Toda lattice of type B and quantum $K$-theory of type C flag variety

We introduce a classical integrable system associated with the torus-equivariant quantum $K$-theory of type C flag variety. We prove that its conserved quantities coincide with the generators of the defining ideal of the Borel presentation of the quantum $K$-ring obtained by Kouno and Naito. In particular, the Hamiltonian of the system is naturally regarded as a type B analogue of the relativistic Toda lattice introduced by Ruijsenaars. We also construct Bäcklund transformations describing the discrete time evolution of the system. This construction makes explicit the integrable structure underlying the quantum $K$-theory and provides a framework for further studies of the $K$-theoretic Peterson isomorphism.

math.RT↗

arXiv2026

Neutral-Fermion constructions of factorial $gp$-and $gq$-Functions

We develop neutral-fermionic constructions for the factorial $gp$-and $gq$-functions introduced by Nakagawa and Naruse, which are respectively dual to the factorial $GQ$- and $GP$-functions of Ikeda and Naruse. In particular, we realize the factorial $GP$-, $GQ$- and $gq$-functions as vacuum expectation values. As applications, we obtain, Jacobi--Trudi type determinantal formulas for the transition coefficients between functions with different equivariant parameters for $gq$ and its dual $GP$, as well as a Pfaffian formula for the factorial $gq$-functions. We further prove a remarkable coincidence among the transition coefficients for parameter changes for $gp$, $gq$, $GQ$, and $GP$. These coefficients admit a description in terms of factorial Grothendieck polynomials of type A.

math.CO↗

arXiv2025

Equivariant homology of the symplectic affine Grassmannian and dual affine Schur $P$-functions

We study the torus-equivariant homology $H_*^T(\mathrm{Gr}_G)$ of the affine Grassmannian $\mathrm{Gr}_G$, where $G=\mathrm{Sp}_{2n}(\mathbb{C})$ is the symplectic group. This homology admits a natural ring structure and a Schubert basis, giving rise to a well-defined Schubert calculus. We realize $H_*^T(\mathrm{Gr}_G)$ in terms of symmetric functions. Our first main result introduces a new family of symmetric functions, called the \emph{dual affine Schur $P$-functions}, which represent the Schubert classes. These functions are defined through the action of the affine nil-Hecke algebra, and specialize, in the stable limit as $n\to \infty$, to the dual factorial $P$-functions of Nakagawa and Naruse. Our second main result gives a precise comparison between this symmetric function model and the geometric construction of $H_*^T (\mathrm{Gr}_G)$ due to Ginzburg and Peterson, which identifies it with a coordinate ring of a centralizer family in the Langlands dual group.

math.RT↗

arXiv2025

Free fermionic probability theory and K-theoretic Schubert calculus

For each of the four particle processes given by Dieker and Warren [arXiv:0707.1843], we show the $n$-step transition kernels are given by the (dual) (weak) refined symmetric Grothendieck functions up to a simple overall factor. We do so by encoding the particle dynamics as the basis of free fermions first introduced by the first author, which we translate into deformed Schur operators acting on partitions. We provide a direct combinatorial proof of this relationship in each case, where the defining tableaux naturally describe the particle motions.

math.CO↗

arXiv2025

Bethe roots for periodic TASEP and algebraic curve

We present an algebraic method for solving the Bethe ansatz equations for the periodic totally asymmetric exclusion process (TASEP) with an arbitrary number of sites and particles. The Bethe ansatz equations are realized as an algebraic equation on a certain Riemann surface. While our Riemann surface is essentially the same as the one introduced by Prolhac, we focus on its algebraic realization as a (singular) plane curve. Through a counting argument on the Riemann surface, we establish a rigorous proof that the Bethe ansatz equation has the expected number of solutions when counted with multiplicity. Consequently, under appropriate generic conditions, the completeness of the Bethe ansatz follows. The decomposition of the Riemann surface into connected components determines how often each value of the product of Bethe roots appears. We classify the connected components and their multiplicities using a similar argument to the spectral degeneracy of the Markov matrix discussed by Golinelli-Mallick. As a result, we give an algebro-geometric characterization of Golinelli-Mallick-type spectral degeneracy of the Markov matrix. We also give explicit formulas for the number of connected components, the number of ramification points, and the total genus of the Riemann surface. These formulas recover the table of examples presented by Prolhac. Moreover, we explore applications of the special type of Bethe roots that appear in this case to partition functions of the five-vertex model. We introduce a version of the free energy and evaluate the thermodynamic limit to find the explicit form in terms of the Riemann zeta function.

math-ph↗

arXiv2025

An elementary construction of the ring of dual $K$-$Q$-cancellation property

This paper presents an elementary introduction on $K$-theoretic $Q$-functions, which were introduced by Ikeda and Naruse in 2013. These functions, which serve as $K$-theoretic analogs of Schur $Q$-functions, are known to possess combinatorial and algebraic constructions. In a 2022 paper, the author introduced ``$β$-deformed power-sums" to provide a simpler, more algebraic construction of these functions. Since the original approach relies on fermionic operators and vacuum expectation values, this paper presents a more accessible, purely algebraic treatment, following the exposition of Schur $Q$-functions in Macdonald's standard textbook. We also show that the algebra of dual $Q$-cancellation property with integer coefficients is generated by dual $K$-$Q$-functions associated with an odd row partition.

math.CO↗

arXiv2025

Relativistic Toda Lattice and Equivariant $K$-Homology of Affine Grassmannian

We investigate the phenomenon known as ''quantum equals affine'' in the setting of $T$-equivariant quantum $K$-theory of the flag variety $G/B$, as established by Kato for any semisimple algebraic group $G$. In particular, we focus on the $K$-Peterson isomorphism between the $T$-equivariant quantum $K$-ring $QK_T(\mathrm{SL}_n(\mathbb{C})/B)$ and the $T$-equivariant $K$-homology ring $K_*^T(\mathrm{Gr}_{\mathrm{SL}_n})$ of the affine Grassmannian, after suitable localizations on both sides. Building on an earlier work by Ikeda, Iwao, and Maeno, we present an explicit algebraic realization of the $K$-Peterson map via a rational substitution that sends the generators of the quantum $K$-theory ring to explicit rational expressions in the fundamental generators of $K_*^T(\mathrm{Gr}_{\mathrm{SL}_n})$, thereby matching the Schubert bases on both sides. Our approach builds on recent developments in the theory of $QK_T(\mathrm{SL}_n(\mathbb{C})/B)$ by Maeno, Naito, and Sagaki, as well as the theory of $K$-theoretic double $k$-Schur functions introduced by Ikeda, Shimozono, and Yamaguchi. This concrete formulation provides new insight into the combinatorial structure of the $K$-Peterson isomorphism in the equivariant setting. As an application, we establish a factorization formula for the $K$-theoretic double $k$-Schur function associated with the maximal $k$-irreducible $k$-bounded partition.

math.RT↗

arXiv2024

Tetrahedron equation and Schur functions

The tetrahedron equation introduced by Zamolodchikov is a three-dimensional generalization of the Yang-Baxter equation. Several types of solutions to the tetrahedron equation that have connections to quantum groups can be viewed as $q$-oscillator valued vertex models with matrix elements of the $L$-operators given by generators of the $q$-oscillator algebra acting on the Fock space. Using one of the $q=0$-oscillator valued vertex models introduced by Bazhanov-Sergeev, we introduce a family of partition functions that admits an explicit algebraic presentation using Schur functions. Our construction is based on the three-dimensional realization of the Zamolodchikov-Faddeev algebra provided by Kuniba-Okado-Maruyama. Furthermore, we investigate an inhomogeneous generalization of the three-dimensional lattice model. We show that the inhomogeneous analog of (a certain subclass of) partition functions can be expressed as loop elementary symmetric functions.

math-ph↗

arXiv2023

Closed $k$-Schur Katalan functions as $K$-homology Schubert representatives of the affine Grassmannian

Recently, Blasiak-Morse-Seelinger introduced symmetric functions called Katalan functions, and proved that the $K$-theoretic $k$-Schur functions due to Lam-Schilling-Shimozono form a subfamily of the Katalan functions. They conjectured that another subfamily of Katalan functions called the closed $k$-Schur Katalan functions are identified with the Schubert structure sheaves in the $K$-homology of the affine Grassmannian. The main result is a proof of the conjecture. We also study a $K$-theoretic Peterson isomorphism that Ikeda, Iwao, and Maeno constructed, in a non-geometric manner, based on the unipotent solution of the relativistic Toda lattice of Ruijsenaars. We prove that the map sends a Schubert class of the quantum $K$-theory ring of the flag variety to a closed $K$-$k$-Schur Katalan function up to an explicit factor related to a translation element with respect to an anti-dominant coroot. In fact, we prove the above map coincides with a map whose existence was conjectured by Lam, Li, Mihalcea, Shimozono, and proved by Kato, and more recently by Chow and Leung.

math.CO↗

arXiv2023

Free-fermions and canonical Grothendieck polynomials

We give a presentation of refined (dual) canonical Grothendieck polynomials and their skew versions using free-fermions. Using this, we derive a number of identities, including the skew Cauchy identities, branching rules, expansion formulas, and integral formulas.

math.CO↗

arXiv2023

On flagged $K$-theoretic symmetric polynomials

We provide a fermionic description of flagged skew Grothendieck polynomials, which can be seen as a $K$-theoretic counterpart of flagged skew Schur polynomials. Our proof relies on the Jacobi-Trudi type formula established by Matsumura. This result generalizes the author's previous works on a fermionic description of skew Grothendieck polynomials and multi-Schur functions.

math.CO↗

arXiv2023

Generating functions of dual $K$-theoretic $P$- and $Q$-functions and boson-fermion correspondence

In this paper, we present a new algebraic description of Ikeda-Naruse's $K$-theoretic Schur $P$- and $Q$-functions and their dual functions in terms of neutral fermion operators. We introduce four families of ``$\beta$-deformed neutral-fermion operators'' depending on a parameter $\beta$, which reduce to the usual neutral-fermion operators when $\beta$ is zero. Using these operators, we introduce two families of $\beta$-deformed vertex operators, power sums, and boson-fermion correspondences. From commutation relations among these operators, we naturally derive the $K$-theoretic Cauchy kernel of Nakagawa-Naruse. Exploiting this fact, we show that the four $K$-theoretic functions can be realized as vacuum expectation values of certain $\beta$-deformed fermionic operators. This presentation also allows us to derive generating functions for the dual $K$-theoretic $P$-and $Q$-functions, as conjectured by Nakagawa-Naruse.

math.CO↗

arXiv2021

Free fermions and Schur expansions of multi-Schur functions

Multi-Schur functions are symmetric functions that generalize the supersymmetric Schur functions, the flagged Schur functions, and the refined dual Grothendieck functions, which have been intensively studied by Lascoux. In this paper, we give a new free-fermionic presentation of them. The multi-Schur functions are indexed by a partition and two ``tuples of tuples'' of indeterminates. We construct a family of linear bases of the fermionic Fock space that are indexed by such data and prove that they correspond to the multi-Schur functions through the boson-fermion correspondence. By focusing on some special bases, which we call refined bases, we give a straightforward method of expanding a multi-Schur function in the refined dual Grothendieck polynomials. We also present a sufficient condition for a multi-Schur function to have its Hall-dual function in the completed ring of symmetric functions.

math.CO↗

arXiv2021

Neutral-fermionic presentation of the $K$-theoretic $Q$-function

We show a new neutral-fermionic presentation of Ikeda-Naruse's $K$-theoretic $Q$-functions, which represent a Schubert class in the $K$-theory of coherent sheaves on the Lagrangian Grassmannian. Our presentation provides a simple description and yields straightforward proof of two types of Pfaffian formulas for them. We present a dual space of $GΓ$, the vector space generated by all $K$-theoretic $Q$-functions, by constructing a non-degenerate bilinear form that is compatible with the neutral fermionic presentation. We give a new family of dual $K$-theoretic $Q$-functions, their neutral-fermionic presentations, and Pfaffian formulas.

math.RA↗

arXiv2020

Free-fermions and skew stable Grothendieck polynomials

Skew stable Grothendieck polynomials are $K$-theoretic analogues of skew Schur polynomials. We give a free-fermionic presentation of skew stable Grothendieck polynomials and their dual symmetric functions. By using our presentation, we derive a family of determinantal formulas, which are $K$-analogues of the Jacobi-Trudi formula for skew Schur functions. We also introduce a combinatorial method to calculate certain expansions of skew (dual) stable Grothendieck polynomials by using the non-commutative supersymmetric Schur functions.

math.CO↗