#extremalcombinatorics — Public Fediverse posts

An email landed in my inbox about some local mathematical news. It somehow prompted me to look up where a paper of one of my former PhD students ended up. This was actually one of his thesis chapters:

https://doi.org/10.1090/jams/1069

Congrats Eoin!

#combinatorics #extremalcombinatorics #ramseynumbers

https://arxiv.org/abs/2603.12358

Here is the *third* manuscript coming out of the "Topics in Ramsey theory" online-only problem-solving session (https://sparse-graphs.mimuw.edu.pl/doku.php?id=sessions:2025sessions:2025session1) of the Sparse (Graphs) Coalition, which took place less than a year ago.

It is still surprising to realise what one can make of such events, if they are set up well.

#combinatorics #remoteconferences #graphtheory #extremalcombinatorics #openscience

RE: https://mastoxiv.page/@arXiv_mathCO_bot/115904052353835071

Here is the second manuscript coming out of the "Topics in Ramsey theory" online-only problem-solving session (https://sparse-graphs.mimuw.edu.pl/doku.php?id=sessions:2025sessions:2025session1) of the Sparse (Graphs) Coalition, which took place less than a year ago.

The first manuscript already came out a couple months earlier (https://arxiv.org/abs/2510.17981).

Both have made serious progress in serious Erdős problems.

#combinatorics #remoteconferences #graphtheory #extremalcombinatorics #erdős

Here's some new work that came from last month's Sparse (Graphs) Coalition session on Ramsey numbers:

https://mathstodon.xyz/@WouterCvB/115418077892309375

#combinatorics #ExtremalCombinatorics #graphtheory #remoteconferences

Just yesterday, I was musing to a (younger) research visitor, "I hope that within my lifetime we will still see another breakthrough on the bounds for R(3,k)"...

https://arxiv.org/abs/2505.13371

I am excited to see what developments follow on from here!

(Also that old adage: just as soon as you publish a survey (https://arxiv.org/abs/2501.03379) it is out of date.)

#math #mathematics #combinatorics #ExtremalCombinatorics #graphtheory #probability

(Just finished writing my laudatio speech.)

Eoin Hurley will defend his PhD on Wednesday.

https://www.uva.nl/en/content/events/2025/05/leave-it-to-chance-random-solutions-to-deterministic-problems-in-discrete-mathematics.html

#combinatorics #graphtheory #ExtremalCombinatorics #probability #algorithms #math

For various (mathematical, meteorological, alimentary) reasons, I usually prefer 2π day.
Nevertheless, today I make the following offering:

http://arxiv.org/abs/2503.10002

Pjotr Buys, @Janvadehe and I used Shearer's induction to address the question:

How few independent sets can a triangle-free graph of average degree d have?

The answer is close to how many a random graph has.
What is perhaps surprising is just *how* close it comes.
(I queried the combinatorial hive mind about this last week.)

#combinatorics #graphtheory #ExtremalCombinatorics #probability #math #mathematics #piDay

Starting out in mathematical research, especially in discrete mathematics, a big focus is problem-solving. It's like a race, and once you've solved one, you set out right away for the next adrenaline rush.

Take for granted a bustling market of open problems (again, especially in discrete mathematics). Scour papers or problem sites. Challenge close colleagues with the ones that eluded you. The harder, the better, right? There is occasionally awkward coffee talk of that intangible `taste' or `judgement', but, come on, less talk and more solving!

(please imagine here a subtly ironic tone in my voice)

(1/3)

#math
#graphtheory
#combinatorics
#ExtremalCombinatorics

A post of @11011110 has reminded me that (after a year and a half lurking here) it's never too late for me to toot and pin an intro here.

I am a Canadian mathematician in the Netherlands, and I have been based at the University of Amsterdam since 2022. I also have some rich and longstanding ties to the UK, France, and Japan.

My interests are somewhere in the nexus of Combinatorics, Probability, and Algorithms. Specifically, I like graph colouring, random graphs, and probabilistic/extremal combinatorics. I have an appreciation for randomised algorithms, graph structure theory, and discrete geometry.

Around 2020, I began taking a more active role in the community, especially in efforts towards improved fairness and openness in science. I am proud to be part of a team that founded the journal, Innovations in Graph Theory (https://igt.centre-mersenne.org/), that launched in 2023. (That is probably the main reason I joined mathstodon!) I have also been a coordinator since 2020 of the informal research network, A Sparse (Graphs) Coalition (https://sparse-graphs.mimuw.edu.pl/), devoted to online collaborative workshops. In 2024, I helped spearhead the MathOA Diamond Open Access Stimulus Fund (https://www.mathoa.org/diamond-open-access-stimulus-fund/).

Until now, my posts have mostly been about scientific publishing and combinatorics.

#introduction
#openscience
#diamondopenaccess
#scientificpublishing
#openaccess
#RemoteConferences
#combinatorics
#graphtheory
#ExtremalCombinatorics
#probability