Log-gamma directed polymer with fixed endpoints via the replica Bethe Ansatz

Abstract

Abstract. We study the model of a discrete directed polymer (DP) on the square lattice with homogeneous inverse gamma distribution of site random Boltzmann weights, introduced by Seppalainen [1]. The integer moments of the partition sum, Z n , are studied using a transfer matrix formulation, which appears as a generalization of the Lieb-Liniger quantum mechanics of bosons to discrete time and space. In the present case of the inverse gamma distribution the model is integrable in terms of a coordinate Bethe Ansatz, as discovered by Brunet. Using the BrunetBethe eigenstates we obtain an exact expression for the integer moments of Z n for polymers of arbitrary lengths and fixed endpoint positions. Although these moments do not exist for all integer n, we are nevertheless able to construct a generating function which reproduces all existing integer moments, and which takes the form of a Fredholm determinant (FD). This suggests an analytic continuation via a Mellin-Barnes transform and we thereby propose a FD ansatz representation for the probability distribution function (PDF) of Z and its Laplace transform. In the limit of very long DP, this ansatz yields that the distribution of the free energy converges to the Gaussian unitary ensemble (GUE) Tracy-Widom distribution up to a non-trivial average and variance that we calculate. Our asymptotic predictions coincide with a result by Borodin et al. [3] based on a formula obtained by Corwin et al. [2] using the geometric Robinson-Schensted-Knuth (gRSK) correspondence. In addition we obtain the dependence on the endpoint position and the exact elastic coefficient at large time. We argue the equivalence between our formula and the one of Borodin et al. As we discuss, this provides connections between quantum integrability and tropical combinatorics.arXiv:1406.5963v2 [cond-mat.dis-nn]

The Strict-Weak Lattice Polymer

“…Using the below reduction of the true evolution to the free evolution, it is possible to diagonalize the true evolution equation via coordinate Bethe ansatz. We do not pursue this further here, but reference, for example [7,8,16].…”

Point-to-line polymers and orthogonal Whittaker functions

“…In their method they had first to derive a series representation for the half-flat initial condition and then the flat case was deduced from the former via a suitable limit. More recently, [G17] applied the method of Calabrese and Le Doussal and of Thiery and Le Doussal [TLeD14] to study, again at non-rigorous level, the Laplace transform of the loggamma polymer with end point lying free on a line. Ortmann-Quastel-Remenik [OQR16,OQR17] have made a number of steps in the approach of Calabrese and Le Doussal rigorous in the case of the Asymmetric Exclusion Process (see also the earlier work of Lee [Lee10]).…”

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