Please join us in congratulating Professor Duong H. Phong on his recent election to the National Academy of Sciences!
Print this page|
Welcome to the 2024 cohort of graduate students! A list of our new PhD students can be found here. Print this pageIt is with deep sadness and heavy hearts that we inform you of the death of our colleague and friend, Lars Tyge Nielsen. Nielsen joined the Columbia University Department of Mathematics in 2012 as the Director of the Mathematics of Finance MA Program. During his time in the department, he was deeply committed to teaching and investing in students’ academic growth and professional development. Through the years, Nielsen attracted an impressive lineup of practitioners to teach and interact with students in the program and constantly worked on improving the curriculum to align with the changing world of mathematical finance. Nielsen was a great colleague, always kind and positive, treating everyone with respect. In his free time, Nielsen loved reading about world history and traveling to Denmark, where he was born and raised. A funeral service will be held on Wednesday, May 1st at 3:00pm at Holy Trinity Lutheran Church on 3 West 65th Street, New York, NY, 10023. All are welcome. There will be a reception afterwards at the church, refreshments and finger food. The family would like to get an estimate of the number of participants. For this reason, if you are planning to attend, please fill out the form: https://forms.gle/qfJzv8YUT9uqqu5s9.
Print this pageTitle: 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, many connections have been demonstrated between matrix rigidity and other topics in the theory of computation.
Unfortunately, proving that matrices of interest are rigid has shown to be a major challenge. In fact, it remains an open problem to prove that any explicit family of matrices is rigid. By contrast, it is known that a random matrix is rigid with high probability.
In this talk, I’ll give a brief overview of matrix rigidity and its uses in computer science. I’ll then discuss some recent results, including proofs that matrices like Hadamard and Fourier matrices, which were previously conjectured to be rigid, are in fact not rigid. The talk will not assume the audience has a background in computer science.
Time and location: tbd, 4:30-5:30pm, Math 520. Tea will be served in the Math lounge at 4pm.
Print this pageTitle: 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 of certain simple manifolds, and report on an emerging conjectural picture.
Time and location: Wed. Apr. 17, 4:30-5:30pm, Math 520. Tea will be served in the Math lounge at 4pm.
Print this pageSpecial 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. Print this pageCongratulations to Elena Giorgi, an Assistant Professor in the Department of Mathematics, who was recently awarded a prestigious Sloan Fellowship! Sloan Fellowship are awarded to “the most promising scientific researchers working today. Their achievements and potential place them among the next generation of scientific leaders in the U.S. and Canada..” For more information on the fellowship please visit: https://sloan.org/fellowships The full list of 2024 recipients, including two other Columbia faculty, is available at https://sloan.org/fellowships/2024-Fellows, and an official press release from Columbia can be read here https://news.columbia.edu/news/three-columbia-faculty-members-named-sloan-research-fellows. Print this pageTitle: 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 the singularity? Recently, many results demonstrating the stability of spatially homogeneous solutions with big bang singularities have appeared. As a consequence, there is an open set of initial data yielding big bang singularities with curvature blow up. However, the purpose of the talk is to illustrate that it is possible to go beyond stability results. In fact, I will present a new result (joint work with Hans Oude Groeniger and Oliver Petersen) in which we identify a general condition on initial data ensuring big bang formation. The solutions need, in this case, not be close to symmetric background solutions. Moreover, the result reproduces previous results in the Einstein-scalar field and Einstein-vacuum settings. Finally, the result is in the Einstein-non-linear scalar field setting, and therefore yields future and past global non-linear stability of large classes of spatially locally homogeneous solutions.
Time and location: Wed. Feb. 28, 4:30-5:30pm, Math 520. Tea will be served in the Math lounge at 4pm.
Print this pageSpeaker: Blaine Lawson (Stony Brook) 2/15 – First Lecture: On compact minimal surfaces in S^3 Abstract: I will present a construction of compact minimal surfaces in the Euclidean three-sphere. In the orientable case, surfaces of every genus can be minimally embedded. In the non-orientable case, every surface but the real projective plane can be minimally immersed. For the projective plane, no such immersion exists. These surfaces have some charm, and they also relate to the general topic of singularities of minimal three-folds in four dimensional spaces. This work was inspired many years ago by Professor Eugenio Calabi. 2/16 – Second Lecture: Nonlinear PDE’s and Potential Theories
These questions arose in my work with Reese Harvey. We discovered that while calibrated manifolds do not usually have analogues of the holomorphic functions that exist in the Kähler case, they do have analogues of plurisubharmonic functions. This started a long investigation. I will discuss various highlights of that work, and also some responses to these questions. Thursday, February 15, 2024 @ 4:30 PM (407 MATH) Friday, February 16 , 2024 @ 2:00 PM (312 MATH) Print this pageSpecial Colloquium Speaker: Toby Gee (Imperial College London) Date and Time: Tuesday, February 6, 4:30 PM Print this page |
Department of Mathematics
Columbia University
Room 509, MC 4406
2990 Broadway
New York, NY 10027
Phone: (212) 854-4112
Fax: (212) 854-8962
Web Design by
Matthew Kressel @ Sunray Computer