Article Instance

HTTP 200 OK
Allow: GET
Content-Type: application/json
Vary: Accept

{
    "pk": 64800,
    "title": "Counting quadrant walks via Tutte's invariant method",
    "subtitle": null,
    "abstract": "In the 1970s, William Tutte developed a clever algebraic approach, based on certain \"invariants\", to solve a functional equation that arises in the enumeration of properly colored triangulations. The enumeration of plane lattice walks confined to the first quadrant is governed by similar equations, and has led in the past 20 years to a rich collection of attractive results dealing with the nature (algebraic, D-finite or not) of the associated generating function, depending on the set of allowed steps, taken in $\\{-1, 0,1\\}^2$.\nWe first adapt Tutte's approach to prove (or reprove) the algebraicity of all quadrant models known or conjectured to be algebraic. This includes Gessel's famous model, and the first proof ever found for one model with weighted steps. To be applicable, the method requires the existence of two rational functions called invariant and decoupling function respectively. When they exist, algebraicity follows almost automatically.\nThen, we move to a complex analytic viewpoint that has already proved very powerful, leading in particular to integral expressions for the generating function in the non-D-finite cases, as well as to proofs of non-D-finiteness. We develop in this context a weaker notion of invariant. Now all quadrant models have invariants, and for those that have in addition a decoupling function, we obtain integral-free expressions for the generating function, and a proof that this series is D-algebraic (that is, satisfies polynomial differential equations).\nKeywords: Lattice walks, enumeration, differentially algebraic series, conformal mappings.\nMathematics Subject Classifications: 05A15, 34K06, 39A06, 30C20, 30D05",
    "language": "en",
    "license": {
        "name": "Creative Commons Attribution 4.0",
        "short_name": "CC BY 4.0",
        "text": "Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.\n\nNo additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.",
        "url": "https://creativecommons.org/licenses/by/4.0"
    },
    "keywords": [],
    "section": "Research Articles",
    "is_remote": true,
    "remote_url": "https://escholarship.org/uc/item/7k6841md",
    "frozenauthors": [
        {
            "first_name": "Olivier",
            "middle_name": "",
            "last_name": "Bernardi",
            "name_suffix": "",
            "institution": "Brandeis University, Department of Mathematics, 415 South Street, Waltham, MA 02453, U.S.A.",
            "department": ""
        },
        {
            "first_name": "Mireille",
            "middle_name": "",
            "last_name": "Bousquet-Mélou",
            "name_suffix": "",
            "institution": "CNRS, LaBRI, Université de Bordeaux, 351 cours de la Libération, 33405 Talence Cedex, France",
            "department": ""
        },
        {
            "first_name": "Kilian",
            "middle_name": "",
            "last_name": "Raschel",
            "name_suffix": "",
            "institution": "CNRS, Institut Denis Poisson, Université de Tours et Université d'Orléans, Parc de Grandmont, 37200 Tours, France",
            "department": ""
        }
    ],
    "date_submitted": "2021-11-11T16:42:50Z",
    "date_accepted": "2021-11-11T16:42:50Z",
    "date_published": "2021-12-15T08:00:00Z",
    "render_galley": null,
    "galleys": [
        {
            "label": "",
            "type": "pdf",
            "path": "https://journalpub.escholarship.org/combinatorial_theory/article/64800/galley/49610/download/"
        }
    ]
}