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Eunghyun Lee

Publications and source records attributed to Eunghyun Lee.

17 recordsLinked to original sources
arXiv2026

Integrability of Multispecies Long-Range Swap Models with Species-Dependent Interpolation

We introduce a class of multispecies exclusion processes with long-range swap interactions, incorporating species-dependent interpolation between TASEP-type and drop--push-type dynamics: each species $i$ is assigned a parameter $μ_i$ governing same-species interactions, resulting in a heterogeneous system in which different species follow distinct microscopic interaction mechanisms. In contrast to previously studied integrable multispecies models, where species dependence typically enters through jump rates, the present framework allows the interaction mechanism itself to depend on the species. Our main result establishes integrability of the model in the binary parameter regime $μ_i \in \{0,1\}$ for arbitrary species compositions. In the continuous parameter regime $μ_i \in (0,1)$, we identify several nontrivial classes of species compositions for which integrability is preserved. We further extend the model to include bidirectional motion, going beyond totally asymmetric dynamics. Using the coordinate Bethe ansatz, we prove two-particle reducibility and derive the associated scattering matrix, which is shown to satisfy the Yang--Baxter equation. The resulting scattering matrix exhibits genuinely species-dependent diagonal entries.

math.PR↗
arXiv2025

Integrable multispecies totally asymmetric stochastic interacting particle systems with homogeneous rates

We study one dimensional stochastic particle systems with exclusion interaction that each site can be occupied by at most one particle, and homogeneous jumping rates. Alimohammadi and Ahmadi previously classified 28 Yang-Baxter integrable two-particle interaction rules for the two species models with homogeneous rates. In this work, we show that 7 of these 28 cases can be naturally extended to integrable models with an arbitrary number of species $N \geq 2$. Moreover, we discover new integrable models with one or two parameters that generalize these 7 cases. For 8 of the remaining 21 cases, we propose an alternative extension scheme that yields integrable $N$ species models.

math-ph↗
arXiv2025

Multispecies totally asymmetric simple exclusion process with long-range swap

We introduce the multispecies totally asymmetric simple exclusion process (mTASEP) with long-range swap, a new interacting particle system combining the backward-push rule with the forward-jump rule. Although governed by local dynamics, the model induces effective long-range particle exchanges. We establish its integrability by proving two-particle reducibility and showing that the associated scattering matrix satisfies the Yang-Baxter equation. In addition, we derive explicit contour integral formulas for transition probabilities. These results position the long-range swap model as a novel exactly solvable multispecies process, characterized by distinctive algebraic features and opening new directions for further study in integrable probability and statistical mechanics.

math-ph↗
arXiv2024

Integrability of the multi-species ASEP with long-range jumps on $\mathbb{Z}$

Let us consider a two-sided multi-species stochastic particle model with finitely many particles on $\mathbb{Z}$ defined as follows. Suppose that each particle is labelled by a positive integer $l$ and waits a random time exponentially distributed with rate $1$. It then chooses the right direction to jump with probability $p$ or the left direction with probability $q=1-p$. If the particle chooses the right direction, it jumps to the nearest site occupied by a particle $l'<l$ (with the convention that an empty site is considered as a particle with labelled $0$). If the particle chooses the left direction, it follows the rule of the multi-species totally asymmetric simple exclusion process (mTASEP). We show that this model is integrable and provide the exact formula of the transition probability using the Bethe ansatz.

math.PR↗
arXiv2023

Distribution of a second-class particle's position in the two-species ASEP with a special initial configuration

In this paper, we consider the two-species asymmetric simple exclusion process consisting of $N-1$ first-class particles and one second-class particle. We assume that the second-class particle is the rightmost particle at t=0. We provide an alternative method to Tracy and Widom's method in [J. Phys. A, 42, 425002, (2009)] to find the probability distribution of the second-class particle's position.

math.PR↗
arXiv2022

Simplified Forms of the Transition Probabilities of the Two-Species ASEP with Some Initial Orders of Particles

It has been known that the transition probability of the single species ASEP with $N$ particles is expressed as a sum of $N!$ $N$-fold contour integrals which are related to permutations in the symmetric group $S_N$. On other hand, the transition probabilities of the multi-species ASEP, in general, may be expressed as a sum of much more terms than $N!$. In this paper, we show that if the initial order of species is given by $2\cdots 21$, $12\cdots 2$, $1\cdots 12$ or $21\cdots 1$, then the transition probabilities can be expressed as a sum of at most $N!$ contour integrals, and provide their formulas explicitly.

math-ph↗
arXiv2022

Integrability of the multi-species TASEP with species-dependent rates

Assume that each species $l$ has its own jump rate $b_l$ in the multi-species totally asymmetric simple exclusion process. We show that this model is \textit{integrable} in the sense that the Bethe Ansatz method is applicable to obtain the transition probabilities for all possible $N$-particle systems with up to $N$ different species.

math.PR↗
arXiv2018

On the TASEP with Second Class Particles

In this paper we study some conditional probabilities for the totally asymmetric simple exclusion processes (TASEP) with second class particles. To be more specific, we consider a finite system with one first class particle and $N-1$ second class particles, and we assume that the first class particle is initially at the leftmost position. In this case, we find the probability that the first class particle is at $x$ and it is still the leftmost particle at time $t$. In particular, we show that this probability is expressed by the determinant of an $N\times N$ matrix of contour integrals if the initial positions of particles satisfy the step initial condition. The resulting formula is very similar to a known formula in the (usual) TASEP with the step initial condition which was used for asymptotics by Nagao and Sasamoto [Nuclear Phys. B 699 (2004), 487-502].

math.PR↗
arXiv2018

Some conditional probabilities in the TASEP with second class particles

In this paper we consider the TASEP with second class particles with the initial order is such that $k$ first class particles are located to the left of $N-k$ second class particles. Under this assumption of the initial state of order, we find the probability that the first class particles are at $x,x+1,\cdots, x+k-1$ and the first class particles are still located to the left of all second class particles at later time $t$. Moreover, we obtain an explicit formula of this probability for the step initial condition. This probability generalizes a result for $k=1$ in Lee (arXiv:1705.10544).

math.PR↗
arXiv2017

Fredholm determinants in the multiparticle hopping asymmetric diffusion model

In this paper we treat the multiparticle hopping asymmetric diffusion model (MADM) of which initial configuration is such that a single site is occupied by infinitely many particles and all other sites are empty. We show that the probability distribution of the $m^{\textrm{th}}$ leftmost particle's position at time $t$ is represented by a Fredholm determinant. Also, we consider an exclusion process type model of the MADM, which is the (two-sided) PushASEP. For the PushASEP with the step Bernoulli initial condition, we find a Fredholm determinant representation of the probability distribution of the $m^{\textrm{th}}$ leftmost particle's position at $t$.

math.PR↗
arXiv2017

Distributions of a particle's position and their asymptotics in the $q$-deformed totally asymmetric zero range process with site dependent jumping rates

In this paper we study the probability distribution of the position of a tagged particle in the $q$-deformed Totally Asymmetric Zero Range Process ($q$-TAZRP) with site dependent jumping rates. For a finite particle system, it is derived from the transition probability previously obtained by Wang and Waugh. We also provide the probability distribution formula for a tagged particle in the $q$-TAZRP with the so-called step initial condition in which infinitely many particles occupy one single site and all other sites are unoccupied. For the $q$-TAZRP with step initial condition, we provide a Fredholm determinant representation for the probability distribution function of the position of a tagged particle, and moreover we obtain the limiting distribution function as the time goes to infinity. Our asymptotic result for $q$-TAZRP with step initial condition is comparable to the limiting distribution function obtained by Tracy and Widom for the $k$-th leftmost particle in the asymmetric simple exclusion process with step initial condition (Theorem 2 in Commun. Math. Phys. 290, 129--154 (2009)).

math.PR↗
arXiv2013

The transition probability and the probability for the left-most particle's position of the q-TAZRP

We treat the $N$-particle ZRP whose jumping rates satisfy a certain condition. This condition is required to use the Bethe ansatz and the resulting model is the $q$-boson model that appeared in [J. Phys. A, \textbf{31} 6057--6071 (1998)] by Sasamoto and Wadati or the $q$-TAZRP in \textit{MacDonald processes} by Borodin and Corwin. We find the explicit formula of the transition probability of the $q$-TAZRP via the Bethe ansatz. By using the transition probability we find the probability distribution of the left-most particle's position at time $t$. To find the probability for the left-most particle's position we find a new identity corresponding to Tracy and Widom's identity for the ASEP in [Commun. Math. Phys., \textbf{279} 815--844 (2008)]. For the initial state that all particles occupy a single site, the probability distribution of the left-most particle's position at time $t$ is represented by the contour integral of a determinant.

math-ph↗
arXiv2013

Symmetric polynomials, generalized Jacobi-Trudi identities and τ-functions

An element [Φ] of the Grassmannian of n-dimensional subspaces of the Hardy space H^2, extended over the field C(x_1,..., x_n), may be associated to any polynomial basis ϕ for C(x). The Plücker coordinates S^ϕ_{λ,n}(x_1,..., x_n) of Φ, labelled by partitions λ, provide an analog of Jacobi's bi-alternant formula, defining a generalization of Schur polynomials. Applying the recursion relations satisfied by the polynomial system to the analog of the complete symmetric functions generates a doubly infinite matrix of symmetric polynomials that determine an element [H] of the Grassmannian. This is shown to coincide with [Φ], implying a set of {\it quantum Jacobi-Trudi identities} that generalize a result obtained by Sergeev and Veselov for the case of orthogonal polynomials. The symmetric polynomials S^ϕ_{λ,n}(x_1,..., x_n) are shown to be KP (Kadomtsev-Petviashvili) tau-functions in terms of the monomial sums [x] in the parameters x_a, viewed as KP flow variables. A fermionic operator representation is derived for these, as well as for the infinite sums \sum_λS_{λ,n}^ϕ([x]) S^θ_{λ,n} ({\bf t}) associated to any pair of polynomial bases (ϕ, θ), which are shown to be 2D Toda lattice τ-functions. A number of applications are given, including classical group character expansions, matrix model partition functions and generators for random processes.

math-ph↗
arXiv2012

The current distribution of the multiparticle hopping asymmetric diffusion model

In this paper we treat the \textit{multiparticle hopping asymmetric diffusion model} (MADM) on $\mathbb{Z}$ introduced by Sasamoto and Wadati in 1998. The transition probability of the MADM with $N$ particles is provided by using the Bethe ansatz. The transition probability is expressed as the sum of $N$-dimensional contour integrals of which contours are circles centered at the origin with restrictions on their radii. By using the transition probability we find $\mathbb{P}(x_m(t) =x)$, the probability that the $m$th particle from the left is at $x$ at time $t$. The probability $\mathbb{P}(x_m(t) =x)$ is expressed as the sum of $|S|$-dimensional contour integrals over all $S \subset \{1,...,N\}$ with $|S| \geq m$, and is used to give the current distribution of the system. The mapping between the MADM and the pushing asymmetric simple exclusion process (PushASEP) is discussed.

math-ph↗
arXiv2011

Transition Probabilities of the Bethe Ansatz Solvable Interacting Particle Systems

This paper presents the exact expressions of the transition probabilities of some non-determinantal Bethe ansatz solvable interacting particle systems: the two-sided PushASEP, the asymmetric avalanche process and the asymmetric zero range process. The time integrated currents of the asymmetric avalanche process and the asymmetric zero range process are immediate from the results of the asymmtric simple exclusion process.

math-ph↗
arXiv2010

Distribution of a particle's position in the ASEP with the {alternating} initial condition

In this paper we give the distribution of the position of the particle in the asymmetric simple exclusion process (ASEP) with the alternating initial condition. That is, we find $\mathbb{P}(X_m(t) \leq x)$ where $X_m(t)$ is the position of the particle at time $t$ which was at $m =2k-1, k \in \mathbb{Z}$ at $t=0.$ As in the ASEP with the step initial condition, there arises a new combinatorial identity for the alternating initial condition, and this identity relates the integrand to a determinantal form together with an extra product.

math-ph↗