Title: Matrix Rigidity Abstract: A matrix is called rigid if one must change many of its entries before it becomes a low-rank matrix. Leslie Valiant introduced the notion in 1977 as a tool to prove lower bounds on the number of arithmetic operations needed to compute linear transformations like the discrete Fourier transform. Since then, […]

Title: Symmetries of manifolds Abstract: Whenever one studies a mathematical object one ought also to study its symmetries. Manifolds are the central objects of study in topology and geometry, and their groups of symmetries come in many flavours (isometries, diffeomorphisms, homeomorphisms, …). I will discuss some classical and recent results about the spaces of all symmetries […]

Special time, location: Tue. Feb. 27, 4:10-5:25pm, 407 Math Title: Universally counting curves in Calabi–Yau threefolds Abstract: Statements such as “there is a unique line between any pair of distinct points in the plane” and “there are 27 lines on any cubic surface” have given rise to the modern theory of enumerative geometry. To define […]

Title: Curvature blow up at big bang singularities Abstract: Singularities have been accepted as a natural feature in general relativity since the appearance of the singularity theorems of Hawking and Penrose. But these theorems do not say much concerning the nature of singularities. Do the gravitational fields become unbounded? Can the spacetime be extended through […]

Title: On High Girth Steiner-Triple Systems and Subspace Designs Abstract: We discuss the recent resolutions of the 1973 conjecture of Erdős on the existence of high girth Steiner triple systems and the existence of subspace designs. The talk will focus on placing these results within the context of classical design theory and within recent advances in the […]

Title: Dieudonné theory: from classical to modern Abstract: Dieudonné theory gives a classification in terms of “semi-linear algebra” of finite flat commutative group schemes of p-power order over a perfect field of characteristic p > 0. Over the years, Dieudonné theory has evolved in many forms (crystalline, prismatic) and recently V. Drinfeld has proposed various “Shimurian” generalizations […]

Title: Fourier uniformity of multiplicative functions Abstract: The Fourier uniformity conjecture seeks tounderstand what multiplicative functions can have large Fourier coefficients onmany short intervals. We will discuss recent progress on this problem andexplain its connection with the distribution of prime numbers and with othercentral problems about the behaviour of multiplicative functions, such as theChowla and Sarnak conjectures.

Title: Random lattices with symmetries

Title: Generalizing Lie theory to higher dimensions – the De Rham theorem on simplices and cubes