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Blogs about: Mathdg

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The concept of mass in General Relativity and its applications

matheuscmss wrote 1 month ago: Hi! Today I’m posting an expanded version of an informal talk (directed to PhD students at IMP … more →

Tags: Expository, mathematics, ADM mass, Differential Geometry, General Relativity, positive mass theorem, Richard Schoen, Yamabe problem

Differential Geometry

camnc wrote 6 months ago: At the time of this posting, there is still a question on the boards without a single solution.  Tha … more →

What is a gauge?18 comments

Terence Tao wrote 1 year ago: “Gauge theory” is a term which has connotations of being a fearsomely complicated part o … more →

Tags: Expository, math.AP, math.CO, math.DS, math.MP, Connections, curvature, fibre bundles, gauge fixing

Classification of Almost Quarter-Pinched Manifolds4 comments

Terence Tao wrote 1 year ago: Peter Petersen and I have just uploaded to the arXiv our paper, “Classification of Almost Quar … more →

Tags: paper, exotic spheres, quarter-pinching, Ricci flow, sphere theorem

Bohm and Wilking's method of deformation of Ricci flow invariant curvature conditions

matheuscmss wrote 1 year ago: In a previous post about the proof of the differentiable sphere theorem (due to S. Brendle and R. Sc … more →

Tags: mathematics, Expository, Ricci flow, Brendle and Schoen, Ricci flow invariant curvature conditions, Bohm and Wilking, spherical space-forms, pinching family of cones, positive curvature operators

Global regularity of wave maps IV. Absence of stationary or self-similar solutions in the energy class9 comments

Terence Tao wrote 1 year ago: I have just uploaded to the arXiv the second installment of my “heatwave” project, entit … more →

Tags: math.AP, paper, caloric gauge, harmonic map heat flow, harmonic maps, orthonormal frames, project heatwave, wave maps

The differentiable sphere theorem of Brendle and Schoen

matheuscmss wrote 1 year ago: A fundamental problem in Differential Geometry is the following: Problem. Determine the topology of … more →

Tags: Expository, mathematics, Bohm and Wilking, Brendle and Schoen, isotropic curvature, Ricci flow, Ricci flow invariant curvature conditions, sphere theorem

285G, Lecture 19: The structure of Ricci flow at the singular time, surgery, and the Poincaré conjecture9 comments

Terence Tao wrote 1 year ago: In the previous lecture, we studied high curvature regions of Ricci flows on some time interval , an … more →

Tags: math.AT, 285G - poincare conjecture, Surgery, canonical neighbourhoods, standard solution, horns

285G, Lecture 18: The structure of high-curvature regions of Ricci flow1 comment

Terence Tao wrote 1 year ago: Having characterised the structure of -solutions, we now use them to describe the structure of high … more →

Tags: 285G - poincare conjecture, canonical neighbourhoods, concentration and compactness, geometric limits, necks, Ricci flows, soul theorem

285G, Lecture 17: The structure of κ-solutions2 comments

Terence Tao wrote 1 year ago: Having classified all asymptotic gradient shrinking solitons in three and fewer dimensions in the pr … more →

Tags: 285G - poincare conjecture, kappa-solutions, compactness and contradiction, gradient shrinking solitons, geometric limits, necks

285G, Lecture 16: Classification of asymptotic gradient shrinking solitons1 comment

Terence Tao wrote 1 year ago: In the previous lecture, we showed that every -solution generated at least one asymptotic gradient s … more →

Tags: 285G - poincare conjecture, gradient shrinking solitons, geometric limits, Cheeger-Gromoll splitting theorem, Toponogov theory, Hamilton's rounding theorem

285G, Lecture 15: Geometric limits of Ricci flows, and asymptotic gradient shrinking solitons13 comments

Terence Tao wrote 1 year ago: We now begin using the theory established in the last two lectures to rigorously extract an asymptot … more →

Tags: math.CA, math.AP, 285G - poincare conjecture, Distributions, geometric limits, gradient shrinking solitons, kappa-solutions, parabolic regularity

285G, Lecture 14: Stationary points of Perelman entropy or reduced volume are gradient shrinking solitons4 comments

Terence Tao wrote 1 year ago: We continue our study of -solutions. In the previous lecture we primarily exploited the non-negative … more →

Tags: 285G - poincare conjecture, gradient shrinking solitons, Perelman entropy, reduced volume, Ricci flow

285G, Lecture 12: High curvature regions of Ricci flow and κ-solutions9 comments

Terence Tao wrote 1 year ago: In previous lectures, we have established (modulo some technical details) two significant components … more →

Tags: 285G - poincare conjecture, kappa-solutions, canonical neighbourhoods, compactness and contradiction, gradient shrinking solitons

285G, Lecture 11: κ-noncollapsing via Perelman reduced volume9 comments

Terence Tao wrote 1 year ago: Having established the monotonicity of the Perelman reduced volume in the previous lecture (after fi … more →

Tags: 285G - poincare conjecture, Entropy, non-collapsing, reduced volume, Ricci flow

285G, Lecture 10: Variation of L-geodesics, and monotonicity of Perelman reduced volume12 comments

Terence Tao wrote 1 year ago: Having completed a heuristic derivation of the monotonicity of Perelman reduced volume (Conjecture 1 … more →

Tags: 285G - poincare conjecture, variation formulae, Perelman reduced volume, Perelman reduced length, geodesics, Bishop-Gromov comparison inequality

285G, Lecture 9: Comparison geometry, the high-dimensional limit, and Perelman reduced volume19 comments

Terence Tao wrote 1 year ago: We now turn to Perelman’s second scale-invariant monotone quantity for Ricci flow, now known a … more →

Tags: 285G - poincare conjecture, Perelman reduced volume, Perelman reduced length, Bishop-Gromov inequality, high-dimensional limit

285G, Lecture 8: Ricci flow as a gradient flow, log-Sobolev inequalities, and Perelman entropy9 comments

Terence Tao wrote 1 year ago: It is well known that the heat equation (1) on a compact Riemannian manifold (M,g) (with metric g st … more →

Tags: 285G - poincare conjecture, math.AP, math.CA, Perelman entropy, Nash entropy, least eigenvalue, semigroup method, log-Sobolev inequality, Poincare inequality

285G, Lecture 7: Rescaling of Ricci flows and κ-noncollapsing13 comments

Terence Tao wrote 1 year ago: We now set aside our discussion of the finite time extinction results for Ricci flow with surgery (T … more →

Tags: math.AP, 285G - poincare conjecture, scale invariance, Criticality, coercivity, noncollapsing, comparison geometry


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