THE SPACES OF LAURENT POLYNOMIALS, P 1-ORBIFOLDS, AND INTEGRABLE HIERARCHIES
THE SPACES OF LAURENT POLYNOMIALS, P 1-ORBIFOLDS, AND INTEGRABLE HIERARCHIES
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发表时间:
2006
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通讯作者:
Hsian-Hua Tseng
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作者:
Hsian-Hua Tseng
Let Mk,m be the space of Laurent polynomials in one variable x + t1x k−1 + . . . tk+mx , where k, m ≥ 1 are fixed integers and tk+m 6= 0. According to B. Dubrovin [D], Mk,m can be equipped with a semi-simple Frobenius structure. In this paper we prove that the corresponding descendant and ancestor potentials of Mk,m (defined as in [G1]) satisfy Hirota quadratic equations (HQE for short). Let Ck,m be the orbifold obtained from P by cutting small discs D1 ∼= {|z| ≤ ǫ} and D2 ∼= {|z−1| ≤ ǫ} around z = 0 and z = ∞ and gluing back the orbifolds D1/Zk and D2/Zm in the obvious way. We show that the orbifold quantum cohomology of Ck,m coincides with Mk,m as Frobenius manifolds. Modulo some yet-to-be-clarified details, this implies that the descendant (respectively the ancestor) potential of Mk,m is a generating function for the descendant (respectively ancestor) orbifold Gromov–Witten invariants of Ck,m. There is a certain similarity between our HQE and the Lax operators of the Extended bi-graded Toda hierarchy, introduced by G. Carlet in [Car]. Therefore, it is plausible that our HQE characterize the tau-functions of this hierarchy and we expect that the Extended bi-graded Toda hierarchy governs the Gromov–Witten theory of Ck,m.