## Research Grants of the Combinatorics Group

### Asymptotic properties of graphs on a surface

Since the foundation of the theory of random graphs by Erdős and Rényi five decades ago, various random graphs have been introduced and studied. One example is random graphs on a surface, in particular random planar graphs. Graphs on a 2-dimensional surface and related objects (e.g. planar graphs, triangulations) have been among the most studied objects in graph theory, enumerative combinatorics, discrete probability theory, and statistical physics. The main objectives of this project are to study the asymptotic properties and limit behaviour of random graphs on a surface (e.g. evolution, phase transition, critical behaviour, component size distribution) and to investigate enumerative and algorithmic aspects of unlabelled graphs on a surface (e.g. connectivity, symmetry, decomposition, random generation).

- Supported by Austrian Science Fund (FWF), Grant no. P27290, 01.06.2015-31.03.2019
- Group members in this project:
- Christopher Dowden
- Mihyun Kang (PI)
- Michael Moßhammer
- Philipp Sprüssel (Co-PI)

- Project website

### Doctoral Program "Discrete Mathematics"

The Combinatorics Group takes actively part in the Doctoral Program "Discrete Mathematics", which offers an advanced PhD training and research program.

- Supported by Austrian Science Fund (FWF), Grant no. W1230 II (2015-2019)
- Group members in this project:
- Oliver Cooley (Postdoc Mentor)
- Christopher Dowden (Postdoc Mentor)
- Nicola Del Giudice (Doctoral Student)
- Mihyun Kang (PI of Project 14)
- Christoph Koch (Associated Doctoral Student until December 2016)
- Rigorosum: on 25.11.2016
- Reviewers: Mihyun Kang (TU Graz), Michael Krivelevich (Tel Aviv University), Angelika Steger (ETH Zürich)
- Examiners: Angelika Steger, Wolfgang Woess
- Michael Moßhammer (Associated Doctoral Student)
- Philipp Sprüssel (Postdoc Mentor)

- Project website

### Random recursive structures of small diameters

Austrian-Taiwanese Joint Project FWF-MOST 2015

- Supported by Austrian Science Fund (FWF), Grant no. I2309-N35, 01.03.2016-28.02.2019
- Group members in this project:
- Mihyun Kang (Co-PI)
- Wenjie Fang

- Members at partner institution TU Wien:
- Bernhard Gittenberger (PI)
- Michael Drmota (Co-PI)

- Members at partner institutions in Taiwan:
- Michael Fuchs (PI)
- Hsien-Kuei Hwang (Co-PI)
- Young-Nan Yeh (Co-PI)

- Project website

## Research Grants -- Completed

### Phase transitions and critical phenomena in random graphs

Random graph models that this project focuses on are random graph processes and random hypergraphs. The constraints imposed on these random graph models (in particular random graph processes) lead to difficulties in the analysis of their asymptotic behaviour, due to the long-term and/or global dependence between edges. To overcome these difficulties, new approaches have to be found. The main objective of this project is to advance analytic and probabilistic approaches and to apply them to analyse asymptotic behaviour of such complex random graph models. The scientific program of this project consists of two main themes, which are closely related in that both themes deal with phase transitions and critical phenomena.

- Supported by Austrian Science Fund (FWF), Grant no. P26826, 01.05.2014-31.12.2017
- Group members in this project:
- Oliver Cooley
- Christopher Dowden
- Mihyun Kang (PI)
- Christoph Koch
- Tamas Makai

- Project website

### Random graphs defined geometrically

OeAD Scientific & Technological Agreement with Slovenia 2016-17

- Supported by Austrian Agency for International Cooperation in Education and Research (OeAD), Grant no. SI 12/2016, 01.01.2016-31.12.2017
- Group members in this project: Oliver Cooley, Mihyun Kang (PI), Michael Moßhammer, Philipp Sprüssel
- Members at partner institution in Slovenia : Sergio Cabello (PI), David Gajser, Sandi Klavzar, Bojan Mohar

### Phase Transitions in Random Graphs and Random Graph Processes

The objectives of this project are to study the phase transitions in random graphs and random graph processes with constraints such as degree distribution, forbidden substructures, genus. The phase transition is a phenomenon observed in many fundamental problems from statistical physics, mathematics and theoretical computer science, including Potts models, graph colourings and satisfiability problem. The phase transition observed in the plethora of different random graph models refers to a phenomenon that there is a critical value of edge density such that adding a small number of edges around the critical value results in a dramatic change in the size of the largest components. It is our aim to further develop and apply new analytic approaches combined with counting and probabilistic methods, e.g. singularity analysis, differential equations method, to the study of the phase transitions in random graphs and random graph processes.

- Supported by German Research Foundation (DFG), Grant no. KA 2748/3-1, 01.10.2011-30.11.2014
- Group members in this project: Mihyun Kang (PI), Tamas Makai, Angélica Pachón