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Didier

A cold place

I have been called an "autocratic teacher or professor who are blindly driving his/her students along the bloody path of his/her interest" once. But I prefer "Didier", which is shorter.

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27
An example of an open ball whose closure is strictly between it and the corresponding closed ball
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14
What's the "best" place for working in Manifolds/Surfaces?
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13
Why are we interested in Einstein metrics?
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13
If $M$ is a compact Riemannian manifold and $g$ and $\tilde{g}$ are metrics on $M$, then $\frac{1}{C} g \leq \tilde{g} \leq C g$ for $C > 1$
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13
Example of a function that is continuous at $c$ whose inverse is discontinuous at $f(c)$
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13
Isn't a differential curve with corners contradictory?
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12
What is the arc length formula in a metric space?
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10
Can someone explain me the following statement about the covariant derivatives?
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10
Prove that $f: \mathbb{R} \to \mathbb{R}, f(x) = x^\frac{1}{9}$ is not a differentiable function
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10
Examples of rings that are Noetherian but not finitely generated?
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9
Orthonormal Frames don't imply Orthnormal Coordinate Frames
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9
Prove that there's no ordered basis $E$ in which $T{x\choose y}={0\choose y}$ can be represented as $1\ 2\choose 2\ 4$
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9
Distance between antipodal points in a geodesic ball
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8
Basis of the space of vector fields on smooth manifolds
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7
The hyperbolic space is a conformally compact Einstein manifold
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7
Diagonalization of the Ricci curvature tensor in dimension 3
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6
Proposition 3.6 part 1 - Do Carmo's Riemannian Geometry
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6
If two vectors are orthogonal, then is their covariant derivative 0?
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6
Geodesics under Levi-Civita connection
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6
Example of manifold with geodesic having infinite exit time and finite negative exit time.
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6
adjoint operator of divergence operator with respect to $L^2$-norm
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6
Is the product of embedded submanifolds still an embedded submanifold?
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6
Let $(M, g) = (\mathbb{R}^n , ds^2 = dr^2 +f^2(r)d\theta^2)$. Determine the Riemannian volume form of $M$.
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6
Derivation of geodesic on $m$-sphere $\gamma : \mathbb{R} \rightarrow S^m$ is given by $\gamma(t) = \cos(t |v|)p \ + \frac{\sin(t |v|)}{|v|} v$
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6
Prove (or confute): distance between a point and a set
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6
Commutation relations between covariant and Lie derivatives
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6
Question about Riemannian metrics
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6
Computing curvatures of $M:=S^n(1) \times S^m(1)$
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5
Since every subset is open, every subset is also closed
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5
Intuitive understanding of inward and outward vector definitions
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