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We derive an explicit formula for the connected $(n,m)$-point functions associated to an arbitrary diagonal tau-function $\tau_f(\boldsymbol{t}^+,\boldsymbol{t}^-)$ of the 2d Toda lattice hierarchy using fermionic computations and the…

Exactly Solvable and Integrable Systems · Physics 2023-11-07 Zhiyuan Wang , Chenglang Yang

Spin Hurwitz numbers are related to characters of the Sergeev group, which are the expansion coefficients of the Q Schur functions, depending on odd times and on a subset of all Young diagrams. These characters involve two dual subsets: the…

High Energy Physics - Theory · Physics 2021-02-02 A. Mironov , A. Morozov , S. Natanzon

We elaborate on a construction of quantum LG superpotential associated to a tau-function of the KP hierarchy in the case that resulting quantum spectral curve lies in the quantum two-torus. This construction is applied to Hurwitz numbers,…

Mathematical Physics · Physics 2015-12-11 Jian Zhou

We show that the generating series of some Hodge integrals involving one or two partitions are tau-functions of the KP hierarchy or the 2-Toda hierarchy respectively. We also formulate a conjecture on the connection between relative…

Algebraic Geometry · Mathematics 2007-05-23 Jian Zhou

It is well-known that a BKP tau-function is the square root of a certain KP tau-function, provided one puts the even KP times equal to zero. In this paper we compute for all polynomial BKP tau-function its corresponding KP "square". We also…

Mathematical Physics · Physics 2021-12-22 Johan van de Leur

The CKP hierarchy is one important sub-hierarchy of the KP hierarchy, which is quite special due to its tau function. Here we construct the tau functions for the constrained CKP hierarchy…

Exactly Solvable and Integrable Systems · Physics 2026-05-19 Danqi Chen , Jipeng Cheng , Shen Wang

Polynomial-in-time algorithms for computing classical Hurwitz numbers were given in [4] based on the Pandharipande equation. The paritition function of double Hurwitz numbers was proved [21] to satisfy the 2-Toda hierarchy. In this paper,…

Mathematical Physics · Physics 2026-04-30 Xiang Li

The isomonodromic tau-function for the Hurwitz spaces of branched coverings of genus zero and one are constructed explicitly. Such spaces may be equipped with the structure of a Frobenius manifold and this introduces a flat coordinate…

Mathematical Physics · Physics 2020-12-16 A. Kokotov , I. A. B. Strachan

The quantum spectral curve equation associated to KP $\tau$-functions of hypergeometric type serving as generating functions for rationally weighted Hurwitz numbers is solved by generalized hypergeometric series. The basis elements spanning…

Mathematical Physics · Physics 2021-03-04 M. Bertola , J. Harnad

The construction of hypergeometric 2D Toda $\tau$-functions as generating functions for quantum Hurwitz numbers is extended here to multispecies families. Both the enumerative geometrical significance of these multispecies quantum Hurwitz…

Mathematical Physics · Physics 2016-11-01 J. Harnad

The KP $\tau$-function of hypergeometric type serving as generating function for quantum weighted Hurwitz numbers is used to compute the Baker function and the corresponding adapted basis elements, expressed as absolutely convergent Laurent…

Mathematical Physics · Physics 2021-03-04 J. Harnad , B. Runov

For a tau-function of the KP or BKP hierarchy, we introduce the notion of lifting operator and derive an equation connecting the corresponding fermionic two-point function and fermionic one-point function through the lifting operator. This…

Mathematical Physics · Physics 2025-02-14 Shuai Guo , Ce Ji , Chenglang Yang

We derive a formula for the connected $n$-point functions of a tau-function of the BKP hierarchy in terms of its affine coordinates. This is a BKP-analogue of a formula for KP tau-functions proved by Zhou in [arXiv:1507.01679]. Moreover, we…

Exactly Solvable and Integrable Systems · Physics 2022-07-06 Zhiyuan Wang , Chenglang Yang

We construct all polynomial tau-functions of the BKP, DKP and MDKP hierarches.

Mathematical Physics · Physics 2019-07-24 Victor Kac , Johan van de Leur

We generalize the determinant representation of the KP $\tau$ functions to the case of the 2D Toda $\tau$ functions. The generating functions for the weighted Hurwitz numbers are a parametric family of 2D Toda $\tau$ functions; for which we…

Mathematical Physics · Physics 2023-01-18 Xiang-Mao Ding , Xiang Li

We study spin Hurwitz numbers, which count ramified covers of the Riemann sphere with a sign coming from a theta characteristic. These numbers are known to be related to Gromov-Witten theory of K\"ahler surfaces and to representation theory…

Mathematical Physics · Physics 2024-06-19 Alessandro Giacchetto , Reinier Kramer , Danilo Lewański

We introduce a useful and rather simple class of BKP tau functions which which we shall call "easy tau functions". We consider two versions of BKP hierarchy, one we will call "small BKP hierarchy" (sBKP) related to $O(\infty)$ introduced in…

Mathematical Physics · Physics 2012-01-24 A. Yu. Orlov , T. Shiota , K. Takasaki

We explain how to construct a quantum deformation of a spectral curve to a tau-function of the KP hierarchy. This construction is applied to Witten-Kontsevich tau-function to give a natural explanation of some earlier work. We also apply it…

Mathematical Physics · Physics 2015-11-30 Jian Zhou

The generating function of double Hurwitz numbers is known to become a tau function of the Toda hierarchy. The associated Lax and Orlov-Schulman operators turn out to satisfy a set of generalized string equations. These generalized string…

Mathematical Physics · Physics 2015-05-20 Kanehisa Takasaki

We consider ramified coverings of P^1 with arbitrary ramification type over 0 and infinity and simple ramifications elsewhere and prove that the generating function for the numbers of such coverings is a tau-function for the Toda lattice…

Algebraic Geometry · Mathematics 2007-05-23 Andrei Okounkov