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DTSTART;TZID=America/New_York:20241004T120000
DTEND;TZID=America/New_York:20241004T130000
DTSTAMP:20260507T194339
CREATED:20240907T183353Z
LAST-MODIFIED:20240930T155114Z
UID:10003464-1728043200-1728046800@cmsa.fas.harvard.edu
SUMMARY:High-dimensional learning of narrow neural networks
DESCRIPTION:Member Seminar \nSpeaker: Hugo Cui\, CMSA \nTitle: High-dimensional learning of narrow neural networks \nAbstract: This talk explores the interplay between neural network architectures and data structure through the lens of high-dimensional asymptotics. We focus on a class of narrow neural networks\, namely networks possessing a finite number of hidden units\, while operating in high dimensions. In the limit of large data dimension and comparably large number of samples\, we derive a tight asymptotic characterization of the learning of these architectures. As an illustration\, we discuss how this characterization enables the analysis of a solvable model of dot-product attention. We show how the latter can learn to implement either a positional attention mechanism (with tokens attending to each other based on their respective positions)\, or a semantic attention mechanism (with tokens attending to each other based on their meaning)\, and evidence a phase transition with sample complexity from positional to semantic learning.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-10424/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Member-Seminar-10.4.24.png
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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241011T120000
DTEND;TZID=America/New_York:20241011T130000
DTSTAMP:20260507T194339
CREATED:20240919T144307Z
LAST-MODIFIED:20241008T132658Z
UID:10003520-1728648000-1728651600@cmsa.fas.harvard.edu
SUMMARY:Scattering Amplitude from a Twistor Point of View
DESCRIPTION:Member Seminar \nSpeaker: Keyou Zeng \nTitle: Scattering Amplitude from a Twistor Point of View \nAbstract: Scattering amplitude is a key quantity in quantum field theory. Although challenging to compute at higher loops and for large particle numbers\, physicists have developed various tools to gain a deeper understanding of amplitudes. In this seminar\, I will introduce a novel approach\, initiated by K. Costello and N. Paquette\, which makes use of twistor correspondence. This approach enables the computation of certain amplitudes using chiral algebra. I will also present an upcoming work that constructs a top-down holography model for computing tree and loop amplitudes of certain non-SUSY theories in various self-dual backgrounds.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-101124/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Member-Seminar-10.11.24.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241018T120000
DTEND;TZID=America/New_York:20241018T130000
DTSTAMP:20260507T194339
CREATED:20240919T144412Z
LAST-MODIFIED:20241015T180358Z
UID:10003521-1729252800-1729256400@cmsa.fas.harvard.edu
SUMMARY:Positive mass and rigidity theorems in Riemannian geometry  
DESCRIPTION:Member Seminar \nSpeaker: Puskar Mondal \nTitle: Positive mass and rigidity theorems in Riemannian geometry \nAbstract: Positive mass theorem proved by Schoen-Yau\, Witten\, Taubes-Parker is one of the most important results in scalar curvature geometry in asymptotically flat settings. Since then several versions have been proven and generalized to other geometries such as asymptotically hyperbolic manifolds. The analogous theorem for strictly positive curvature geometries is absent. There have been counterexamples but a precise quantification does not exist.I prove a scalar curvature rigidity theorem for spheres. In particular\, I prove that $n+1~(n\geq 2)$ dimensional spherical caps with constant positive mean curvature totally umbilic boundaries are rigid under smooth perturbations\, and such rigidity results fail for the hemisphere. The assertion of this result is based on the notion of a real Killing connection and solution of the boundary value problem associated with its Dirac operator. Additionally\, an improved eigenvalue estimate for the Dirac operator on hypersurfaces in positively curved manifolds is obtained.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-101824/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Member-Seminar-10.18.24.png
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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20241025T120000
DTEND;TZID=America/New_York:20241025T130000
DTSTAMP:20260507T194339
CREATED:20240919T144515Z
LAST-MODIFIED:20241022T155009Z
UID:10003522-1729857600-1729861200@cmsa.fas.harvard.edu
SUMMARY:Formality Theorem and Webs
DESCRIPTION:Member Seminar \nSpeaker: Ahsan Khan \nTitle: Formality Theorem and Webs \nAbstract: The “formality theorem” of Kontsevich was a key result that implies that every Poisson manifold admits a deformation quantization. I will review the ideas behind the formality theorem and discuss a potentially novel viewpoint on it involving webs and twisted masses.
URL:https://cmsa.fas.harvard.edu/event/member-seminar-102524/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Member Seminar
ATTACH;FMTTYPE=application/pdf:https://cmsa.fas.harvard.edu/media/CMSA-Member-Seminar-10.25.24.docx.pdf
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