arXiv subjects

Keiichi Shigechi

Publications and source records attributed to Keiichi Shigechi.

28 records · Page 2Linked to original sources

arXiv2017

Ballot tilings and increasing trees

We study enumerations of Dyck and ballot tilings, which are tilings of a region determined by two Dyck or ballot paths. We give bijective proofs to two formulae of enumerations of Dyck tilings through Hermite histories. We show that one of the formulae is equal to a certain Kazhdan--Lusztig polynomial. For a ballot tiling, we establish formulae which are analogues of formulae for Dyck tilings. Especially, the generating functions have factorized expressions. The key tool is a planted plane tree and its increasing labellings. We also introduce a generalized perfect matching which is bijective to an Hermite history for a ballot tiling. By combining these objects, we obtain various expressions of a generating function of ballot tilings with a fixed lower path.

math-ph↗

arXiv2017

Shifted tableaux and products of Schur's symmetric functions

We introduce a new combinatorial object, semistandard increasing decomposition tableau and study its relation to a semistandard decomposition tableau introduced by Kraśkiewicz and developed by Lam and Serrano. We also introduce generalized Littlewood--Richardson coefficients for products of Schur's symmetric functions and give combinatorial descriptions in terms of tableau words. The insertion algorithms play central roles for proofs. A new description of shifted Littlewood--Richardson coefficients is given in terms of semistandard increasing decomposition tableaux. We show that a "big" Schur function is expressed as a sum of products of two Schur $P$-functions, and vice versa. As an application, we derive two Giambelli formulae for big Schur functions: one is a determinant and the other is a Pfaffian.

math-ph↗

arXiv2014

Laurent polynomial solutions of the boundary quantum Knizhnik--Zamolodchikov equation

We construct Laurent polynomial solutions of the boundary quantum Knizhnik--Zamolodchikov equation for $U_{q}(\widehat{\mathfrak{sl}}_{2})$ on the parabolic Kazhdan--Lusztig bases. They are characterized by non-symmetric Koornwinder polynomials with the specialized parameters. As a special case, we obtain the solution of the minimal degree.

math-ph↗

arXiv2014

A Positive integral property on the ground state of the two-boundary Temperley--Lieb Hamiltonian

We study the two-boundary Temperley--Lieb $O(n)$ loop model on Kazhdan--Lusztig bases of type A and B. We obtain explicit expressions of the ground state of the two-boundary Temperley--Lieb Hamiltonian by means of a coideal subalgebra of $U_q(\mathfrak{sl}_2)$. This ground state possesses a positive integral property. We conjecture that some components of the ground state are directly related to an enumeration of binary or permutation matrices.

math-ph↗

arXiv2014

Canonical bases of a coideal subalgebra in $U_q(\mathfrak{sl}_2)$

We consider tensor products of finite-dimensional representations of a coideal subalgebra in $U_{q}(\mathfrak{sl}_2)$. We present an explicit expression for the dual of the canonical bases through a diagrammatic presentation. We show that the decomposition of tensor products of dual canonical bases and the action of the coideal subalgebra have integral and positive properties. As an application, we consider the eigensystem of the generator of the coideal subalgebra on the dual canonical bases. We provide all the eigenvalues and obtain an explicit expression of the eigenfunction for the largest eigenvalue. The sum of the components of this eigenfunction is conjectured to be equal to the total number of arrangements of bishops with a certain symmetry.

math-ph↗

arXiv2014

Kazhdan-Lusztig polynomials for the Hermitian symmetric pair $(B_N,A_{N-1})$

We provide combinatorial rules to compute Kazhdan--Lusztig polynomials for the Hermitian symmetric pair $(B_N,A_{N-1})$ when the Hecke algebra has unequal parameters. They are obtained by filling regions delimited by paths with ballot strips. We also extend the binary tree algorithm introduced by Lascoux and Schützenberger to our case.

math.RT↗

arXiv2009

Exact finite size groundstate of the O(n=1) loop model with open boundaries

We explicitly describe certain components of the finite size groundstate of the inhomogeneous transfer matrix of the O(n=1) loop model on a strip with non-trivial boundaries on both sides. In addition we compute explicitly the groundstate normalisation which is given as a product of four symplectic characters.

math-ph↗

arXiv2007

A_k Generalization of the O(1) Loop Model on a Cylinder: Affine Hecke Algebra, q-KZ Equation and the Sum Rule

We study the A_k generalized model of the O(1) loop model on a cylinder. The affine Hecke algebra associated with the model is characterized by a vanishing condition, the cylindric relation. We present two representations of the algebra: the first one is the spin representation, and the other is in the vector space of states of the A_k generalized model. A state of the model is a natural generalization of a link pattern. We propose a new graphical way of dealing with the Yang-Baxter equation and $q$-symmetrizers by the use of the rhombus tiling. The relation between two representations and the meaning of the cylindric relations are clarified. The sum rule for this model is obtained by solving the q-KZ equation at the Razumov-Stroganov point.

math-ph↗

arXiv2005

Boxed Skew Plane Partition and Integrable Phase Model

We study the relation between the boxed skew plane partition and the integrable phase model. We introduce a generalization of a scalar product of the phase model and calculate it in two ways; the first one in terms of the skew Schur functions, and another one by use of the commutation relations of operators. In both cases, a generalized scalar product is expressed as a determinant. We show that a special choice of the spectral parameters of a generalized scalar product gives the generating function of the boxed skew plane partition.

cond-mat.stat-mech↗

arXiv2004

WDVV equation and Triple-product Relation

We study the relation between the WDVV equations and the $τ$-function of the noncommutative KP (NCKP) hierarchy. WDVV-like equations (Hirota triple-product relation) in the noncommutative context appear as a consequence of the non-trivial equation for $τ$-function of the NC KP hierarchy, while the prepotential in the Seiberg-Witten (SW) theory has been identified to the $τ$-function of the Whitham hierarchy. We show that the spectral curve for the SW theory is the same as the Toda-chain hierarchy. We also show that Whitham hierarchy includes commutative Toda/KP hierarchy as a construction. Further, we comment on the origin of the Hirota triple-product relation in the context of the SW theory.

hep-th↗