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Documents authored by Hainzl, Eva-Maria

Document
DOI: 10.4230/LIPIcs.AofA.2026.17
Singularly Perturbed Discrete Differential Equations and Pattern Counts in Simple Triangulations

Authors: Michael Drmota and Eva-Maria Hainzl

Published in: LIPIcs, Volume 381, 37th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2026)

Abstract
Discrete differential equations of order k are of the form R(z,u,F(z,u),Δ F(z,u),…,Δ^kF(z,u)) = 0, where Δ F(z,u) = (F(z,u)-F(z,0))/u and Δ^k F(z,u) = Δ(Δ^{k-1} F(z,u)) for k ≥ 2. Such equations appear most prominently in planar map enumeration but also in several other contexts such as statistical mechanics, lattice path enumeration, pattern avoiding permutations or stack-sortable permutations. Mostly, one is interested in the function F(z,0) that is usually the corresponding counting generating function. In this work, we consider discrete differential equations with an additional parameter x, where the order of the equation is 1 for x = 1 but k > 1 for x ≠ 1. We call such equations singularly perturbed. The solution theory of higher order discrete differential equations is much more involved than for degree 1 and it is a priori not clear that there is a smooth transition from x = 1 to x ≠ 1. The main contribution of this work is to show that there is actually a smooth transition under certain natural assumptions. As an application of this result we consider pattern counts in triangular planar maps and derive a central limit theorem for these counts.
Cite as

Michael Drmota and Eva-Maria Hainzl. Singularly Perturbed Discrete Differential Equations and Pattern Counts in Simple Triangulations. In 37th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 381, pp. 17:1-17:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{drmota_et_al:LIPIcs.AofA.2026.17,
  author =	{Drmota, Michael and Hainzl, Eva-Maria},
  title =	{{Singularly Perturbed Discrete Differential Equations and Pattern Counts in Simple Triangulations}},
  booktitle =	{37th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2026)},
  pages =	{17:1--17:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-435-2},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{381},
  editor =	{Panagiotou, Konstantinos},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AofA.2026.17},
  URN =		{urn:nbn:de:0030-drops-262880},
  doi =		{10.4230/LIPIcs.AofA.2026.17},
  annote =	{Keywords: Discrete differential equations, catalytic equations, generating functions}
}
Document
DOI: 10.4230/LIPIcs.AofA.2026.20
Formulas and Asymptotics of Hypergraph Catalan Numbers

Authors: Eva-Maria Hainzl

Published in: LIPIcs, Volume 381, 37th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2026)

Abstract
Tree walks are a class of closed walks on a complete graph constrained to span trees. They appear in the computation of moments of the spectral measure of various random matrix models, most prominently in the spectral distribution of random graphs. In this work, we focus on a special subclass called k-tours, which were introduced by Gunnells [Gunnels, 2021] after studying another random matrix model. They are enumerated by the so-called hypergraph Catalan numbers c_n^(k). Gunnells conjectured an asymptotic formula for c_n^(k), which we confirm through an alternative approach to their enumeration. As it turns out, the asymptotic growth is governed by the number of k-tours on star-like trees.
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Eva-Maria Hainzl. Formulas and Asymptotics of Hypergraph Catalan Numbers. In 37th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 381, pp. 20:1-20:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{hainzl:LIPIcs.AofA.2026.20,
  author =	{Hainzl, Eva-Maria},
  title =	{{Formulas and Asymptotics of Hypergraph Catalan Numbers}},
  booktitle =	{37th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2026)},
  pages =	{20:1--20:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-435-2},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{381},
  editor =	{Panagiotou, Konstantinos},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AofA.2026.20},
  URN =		{urn:nbn:de:0030-drops-262918},
  doi =		{10.4230/LIPIcs.AofA.2026.20},
  annote =	{Keywords: generating functions, trees, tree walks, catalan numbers}
}
Document
DOI: 10.4230/LIPIcs.AofA.2024.11
Tree Walks and the Spectrum of Random Graphs

Authors: Eva-Maria Hainzl and Élie de Panafieu

Published in: LIPIcs, Volume 302, 35th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2024)

Abstract
It is a classic result in spectral theory that the limit distribution of the spectral measure of random graphs G(n,p) converges to the semicircle law in case np tends to infinity with n. The spectral measure for random graphs G(n,c/n) however is less understood. In this work, we combine and extend two combinatorial approaches by Bauer and Golinelli (2001) and Enriquez and Menard (2016) and approximate the moments of the spectral measure by counting walks that span trees.
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Eva-Maria Hainzl and Élie de Panafieu. Tree Walks and the Spectrum of Random Graphs. In 35th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 302, pp. 11:1-11:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{hainzl_et_al:LIPIcs.AofA.2024.11,
  author =	{Hainzl, Eva-Maria and de Panafieu, \'{E}lie},
  title =	{{Tree Walks and the Spectrum of Random Graphs}},
  booktitle =	{35th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2024)},
  pages =	{11:1--11:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-329-4},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{302},
  editor =	{Mailler, C\'{e}cile and Wild, Sebastian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AofA.2024.11},
  URN =		{urn:nbn:de:0030-drops-204466},
  doi =		{10.4230/LIPIcs.AofA.2024.11},
  annote =	{Keywords: Spectrum of random matrices, generating functions}
}
Document
DOI: 10.4230/LIPIcs.AofA.2022.7
Universal Properties of Catalytic Variable Equations

Authors: Michael Drmota and Eva-Maria Hainzl

Published in: LIPIcs, Volume 225, 33rd International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2022)

Abstract
Catalytic equations appear in several combinatorial applications, most notably in the enumeration of lattice paths and in the enumeration of planar maps. The main purpose of this paper is to show that under certain positivity assumptions the dominant singularity of the solution function has a universal behavior. We have to distinguish between linear catalytic equations, where a dominating square-root singularity appears, and non-linear catalytic equations, where we - usually - have a singularity of type 3/2.
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Michael Drmota and Eva-Maria Hainzl. Universal Properties of Catalytic Variable Equations. In 33rd International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 225, pp. 7:1-7:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{drmota_et_al:LIPIcs.AofA.2022.7,
  author =	{Drmota, Michael and Hainzl, Eva-Maria},
  title =	{{Universal Properties of Catalytic Variable Equations}},
  booktitle =	{33rd International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2022)},
  pages =	{7:1--7:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-230-3},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{225},
  editor =	{Ward, Mark Daniel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AofA.2022.7},
  URN =		{urn:nbn:de:0030-drops-160930},
  doi =		{10.4230/LIPIcs.AofA.2022.7},
  annote =	{Keywords: catalytic equation, singular expansion, univeral asymptotics}
}
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