Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 13972

A surface is a generalization of a plane which needs not be flat, that is, the curvature is not necessarily zero. This is analogous to a curve generalizing a straight line

5 votes
Accepted

Asymptotic parametrization for negatively curved surfaces

As asked, the answer to the question is 'no'. The simply-connected cover $f:\mathbb{R}^2\to S$ of Sherck's first surface $S$ (which is defined in $\mathbb{R}^3$ by the equation $\mathrm{e}^{z} \cos x …
Robert Bryant's user avatar
2 votes
Accepted

Parametrization of $k$-ruled submanifold: can we choose the base to be orthogonal to the rul...

The answer is already 'no' in the first nontrivial case: A 3-manifold in $\mathbb{R}^d$ (where $d>3$) that is ruled by lines (i.e., $k=1$). One can see this as follows: As the OP notes, one can writ …
Robert Bryant's user avatar
18 votes
Accepted

When does the shape operator commute with a derivative?

The question is essentially equivalent to the following classical question: Given a smooth surface $S$ and a bundle map $L:TS\to TS$, when does there exist an immersion $x:S\to \mathbb{R}^3$ such tha …
Robert Bryant's user avatar
3 votes
Accepted

Requirement of parametrization of surfaces

You can always do this, but it's not as simple as using some kind of ODE (such a flow of vector fields) to construct such charts. First, assume that your surface is connected and simply-connected. Th …
Robert Bryant's user avatar
3 votes
Accepted

Planar curves in $M^{m}$ vs curves in $M^{2}$

Here are some comments about the OP's question that don't give a definitive answer to the final question (although the answer may well be 'no', see below), but do provide more information, at least in …
Robert Bryant's user avatar
6 votes
Accepted

Can every smooth space curve be realized as an origami curved crease?

Note: I'm revising my answer to make the argument/construction more transparent. In the previous version, I stated an existence result about flat surfaces, but didn't indicate a proof (because, at th …
Robert Bryant's user avatar
3 votes
Accepted

Classes of curves closed under Minkowsky sum

There are lots of finite dimensional curve families that are closed under Minkowski sum with circular disks. Here's a way to construct examples: First, choose a finite dimensional space $\mathcal{C}$ …
Robert Bryant's user avatar
5 votes
Accepted

When does a spherical curve equal its tangent indicatrix?

Your question is not very clearly phrased, which may explain why you didn't get any answers on MSE. When you say, "spherical curve $\gamma$ whose tangent indicatrix is the same as the original curve, …
Robert Bryant's user avatar
7 votes

If a triangle can be displaced without distortion, must the surface have constant curvature?

This is sort of an answer and sort of not. I'll let you be the judge: Suppose you formulate the question, not in terms of 'motion' (which you left vague) but terms of 'freely copying' a triangle $T$ …
Robert Bryant's user avatar
19 votes

A necessary and sufficient condition for a space curve to lie on a ellipsoid

There is a straightforward way to deduce necessary conditions for a space curve to lie on an ellipsoid, and it's really a matter of calculation to make these conditions explicit in terms of the curvat …
Robert Bryant's user avatar
8 votes
Accepted

homogeneous surface in $\mathbb{R}^4$

I'm rearranging my answer a little bit because I realized that I overlooked an apparent possibility (that turns out not to occur), and I didn't want my answer to be misleading: If the surface in Eucl …
Robert Bryant's user avatar
7 votes
Accepted

Construction of a linear Weingarten surface from a space curve

You'll find a discussion of the analysis of linear Weingarten surfaces via exterior differential systems in these lecture notes of mine. Particularly look at Section 5.1, where it is discussed at len …
Robert Bryant's user avatar
14 votes
Accepted

A variant of the Monge-Cayley-Salmon theorem?

Setting aside the assumption that $\phi$ be a polynomial mapping for the moment (however, see below for a construction of a large family of polynomial solutions), if one makes the 'nondegeneracy' assu …
Robert Bryant's user avatar
4 votes
Accepted

Umbilic points on Euclidean hypersurfaces

Because people have asked for it, I thought I would supply an example of what I mentioned in my comment above, an immersion of the $3$-sphere into $\mathbb{R}^4$ that has three distinct principal curv …
Robert Bryant's user avatar
16 votes
Accepted

Are there some intrinsic invariants of surfaces other than Gaussian curvature?

As others have pointed out, it's not hard to show that any function $F(\kappa_1,\kappa_2)$ that is intrinsic to the surface metric must be a function of $K = \kappa_1\kappa_2$, so that settles what on …
Robert Bryant's user avatar

15 30 50 per page