---
title: Differential Geometry
tags: teaching
---
# Differential Geometry
## Unit 1: Review (2 weeks)
:page_with_curl: 2 homeworks
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**Linear algebra**: Subspaces, inner products, cross products, orientations
- Week 1, [time=Jan 30 and Feb 1]
**Read:** Sections 1-1 and 1-3.
> may be that _general_ inner products are not really review, matrix $(g_{ij})$ likely not review
> Orientations might not be review
**HW 1 due on Feb 6.**
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#### Outline of topics
* Vector spaces
* Linear independence, basis & dimension
* Inner products and Cauchy-Schwarz inequality
* Orthonormal bases
* $g=(g_{ij})$ matrix
* Orientations
* Linear transformations (_might extend into Week 2_)
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**Calculus (and some _analytic geometry_)**
- Week 2, [time=Feb 6 and 8, and part of Feb 13]
**Read:** Sections: 1-4, 1-5.
**HW 2 due on Feb 15.**
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#### Outline of topics
* Lines, planes, ~~spheres~~ (in $\mathbb R^3$)
* Parameterization
* Vector calculus
* Chain rule in this setting
* Product rules for inner products, and the cross product
## Unit 2: Regular curves (4-5 weeks)
> Mostly, curves will be in $\mathbb R^3$ ("space curves")
:page_with_curl: 4 homeworks (3 local theory, 1 global theory)
### Begin with _local theory_.
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**Definitions & examples**
- Week 3, [time=Feb 13 and 15]
**Read:** Sections 2-1, 2-2.
**HW 3 due on Feb 22.**
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#### Outline of topics
* Regular space curves, examples
* Reparameterizations
* Arclength (_discussion of section, e.g. unit speed curves, extends to Week 4_)
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**Arc length parameterized curves & Curvature**
- Weeks 4 and 5, [time=Feb 20, 22, and Feb 27]
**Read:** Sections 2-3.
**HW 4 due on Mar 1.**
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**The Frenet-Serret apparatus**
- Second part of Week 5, [time=Mar 1]
**Read:** Section 2-3.
**HW 5 (on curvature, torsion and Frenet-Serret) due on Mar 8.**
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#### Outline of topics
* Using a.l.p. curves (unit speed curves)
* The curvature, $\kappa$, of a regular curve
* The Frenet-Serret apparatus $\{\kappa, \tau, \bf T, N, B\}$
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**Frenet-Serret equations & Planes related to curves, Non-arclength formulae**
- Week 6, [time=Mar 6 and 8]
**Read:** Section 2-4, 2-6.
**HW 6 due on Mar. 13.**
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#### Outline of topics
* The Frenet-Serret equations (Theorem 4.2)
* The osculating plane and normal plane of a space curve
* Calculations with curves that are not a.l.p.
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**Test 1, Mar. 13 in class.** On Chap. 1 (not 1-2), Sections 2-1 through 2-4, and Section 2-6.
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### Some _global theory_.
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**Line integrals, plane curvature, rotation index.**
- during Week 7, [time=Mar 15]
**Read:** Sections 3-1 and 3-2.
**HW 7 due on Mar. 27.**
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#### Outline of topics
* Green's Theorem
* Simple closed curves in the plane
* Plane curvature
* Hopf's Umlaufsatz and Rotation index
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**The isoperimetric inequality**
> Might skip this topic
>
- Week 8 (?), [time=Mar 27]
**Read:** Section 3-4.
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#### Outline of topics
* Proving the isoperimetric inequality
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## Unit 3: Surfaces
:page_with_curl: 4 homeworks
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**Open sets in $\mathbb R^2$**
- Week 8, [time=Oct 21]
**Read:** Section 4-1.
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**Coordinate patches, coordinate transformations**
- Week 9, [time=Oct 26 and 28]
**Read:** Section 4-1.
**HW 6: due on Nov. 2**
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#### Outline of topics
* Definition of a _coordinate patch_ (a _simple surface_) and examples
* _Coordinate transformations_ (analogue of reparameterizations, but for surfaces)
* The _tangent plane_ to simple surface at a point
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**Regular surfaces & Metric coefficients and First Fundamental Form**
- Week 10, [time=Nov 2 and 4]
**Read:** Sections 4-2 and 4-3.
**HW 7: due Nov 11.**
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#### Outline of topics
* Definition of _regular surface_, some discussion of examples (incl. surfaces of revolution)
* The metric coefficients of a coordinate patch, computing arclength of curves on surface with metric coefficients.
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**Normal & Geodesic Curvature**
- Week 11, [time=Nov 9 and 11]
**Read:** Section 4-4.
**HW 8: due on Nov 23.**
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#### Outline of topics
* Definition of _geodesic curvature_ and _normal curvature_. Some examples.
* Coefficients of the Second Fundamental Form.
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**Christoffel Symbols, Gauss's formulas**
- Week 12 (and Tues before Thanksgiving), [time=Nov 16 and 23]
**Read:** More from Section 4-4.
**Exam 2 on Nov 18:** On Sections 2-6, 3-1,3-2,3-4, and 4-1 through 4-4.
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#### Outline of topics
* Christoffel symbols, Gauss' Formulas
* The Christoffel symbols are intrinsic; geodesic curvature is intrinsic.
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**Geodesics, the Second Fundamental form**
- Week 13, [time=Nov 30 and Dec 2]
**Read:** Section 4-5 and 4-7.
**HW 9: due on Dec 7**
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#### Outline of topics
* Geodesics of surfaces of revolution
* Distance minimizers are geodesics
* The second fundamental form & Weingarten map - introduction.
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**Principal and Gaussian curvature & Gauss' Theorem Egregium**
- Week 14, [time=Dec 7 and Dec 9]
**Read:** Sections 4-8 and 4-9.
**HW 10 (short): due on Dec 9**
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#### Outline of topics
* Eigenvalues of the Weingarten map - Principal curvatures.
* Gaussian curvature
* Riemannian curvature tensor and Gauss' Theorem Egregium: Gaussian curvature is intrinsic.
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