## Is it easier to find half a needle than a full needle in a random network?

Common sense tells us that objects of comparable size should be equally hard to find. Yet, when searching inside a random network, surprises are awaiting . . .

## New breakthrough about Ramsey numbers?

In a seminar talk in Cambridge this week, Julian Sahasrabudhe announced that he, together with his colleagues Marcelo Campos, Simon Griffiths and Rob Morris, had obtained an exponential improvement to the upper bound for Ramsey's theorem.

## AI thinks my dog is a Pig! Want to know why?

Applications of machine learning models are everywhere, with many online platforms and major science fields using tools relying on machine learning. Take, for example, image recognition and computer vision. But did you know that the results of supposedly perfect and accurate machine learning models can be deceived by slight perturbations in the data?

## Imaginary numbers are a reality

It is undeniable that natural, integer, rational and real numbers are necessary to explain what happens in our daily life, but in high school some of us also hear about some weird objects called imaginary numbers, also known as complex numbers. What do we need these numbers for?

## Playing with Colors Part 2: An open problem related to graph colouring

Mathematicians often enjoy playing around with the concept of infinity and in the following, I will describe a problem defined on an infinite graph!

## Playing with Colors

Part 1: Learn about applied and theoretical aspects of graph coloring: a tool that helps us design exam schedules or even solve Sudoku!

## Start to jet lag behind. Moving to fairer competitions.

It is safe to say that traveling impacts the peak performance of teams and athletes in general - studies have been done across all kinds of sports that confirm this intuitive idea. Thus, to avoid unfair- and unhappiness, an organizer should aim to minimize the effect of travel time disparities.

## Eigenvalues to the rescue

On a quiet afternoon, professor Meth is working in her office in Leiden on some tantalizing mathematics problems. Suddenly, someone knocking on her door nervously disrupts the silence.

## What have Donald Trump, an epidemiologist and a rock in common?

In this article, dear reader, I am going to show you in which way the development of your opinion during the last political issue, the spread of a virus among your acquaintances during the current pandemic, and the alignment of some particles lying inside the device from which you are reading this article are extremely comparable phenomena.

## How do you decide who is the most important?

Imagine you’re in a remote village and only have a limited number of vaccines to distribute to protect the community from a deadly virus, who do you vaccinate?

A difficult decision, but necessary. Assuming that the disease is just as deadly for everyone in the community, the best way to prevent deaths is to contain the spread of the virus.