The news of Professor Claudi Alsina's death has deeply affected me. A brilliant mathematician, a dedicated public servant, and above all, a teacher and friend who forever shaped my understanding of education, politics, and life, has passed away.

An old and dear friend, Claudi Alsina, has passed away. We met in the mid-1970s in Berkeley. I was teaching, and he, a young mathematics professor at the architecture school, was visiting. We talked about everything, but especially about two subjects that marked his professional and civic life: mathematics and the university. So much so that, fifty years later, he has left us, on the one hand, some forty books on mathematics, both technical monographs—published in English, and some highly awarded—and popular science works—a field in which he had a very special talent and in which he displayed his characteristic humor. I know that in the last week of his life, helped by his beloved Carme and Victoria, he was proofreading galleys of his next—I don't want to say last—book.

Today the world of mathematics and its teaching has suffered a devastating blow. The death of Claudi Alsina leaves an immense void, one that is difficult to fill.

Claudi Alsina Català, professor of mathematics and renowned science communicator, passed away this Sunday at the age of 73. Alsina had received the Creu de Sant Jordi in 2014 in recognition of his academic career and his contribution to science communication in Catalonia. He held a doctorate in mathematics from the University of Barcelona and served as a professor at the Polytechnic University of Catalonia until his retirement in 2016. Throughout his career, he published more than fifty books and hundreds of articles, specializing in functional equations, geometry, and education. He also held important institutional positions, such as Secretary General of the Inter-University Council of Catalonia and Director General of Universities, and coordinated the university entrance exams in Catalonia between 2000 and 2002. His last published book was co-authored with Anton Aubanell and Carme Burgués and is titled Go for it! Spark an interest in learning mathematics.