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Pengfei
  • Member for 13 years, 4 months
  • Last seen more than a week ago
13 votes
2 answers
3k views

Bounds of the derivatives of the mollifier function

11 votes
2 answers
242 views

Absolute convergence when all the rotated series converge

9 votes
3 answers
310 views

Intersection of two 'huge' sets in the plane

8 votes
1 answer
3k views

Jacobian of a smooth flow on a smooth manifold

7 votes
1 answer
1k views

Can we infer from the support function of a convex domain $Q$ when the boundary $\partial Q$ admits nonvanishing curvature?

5 votes
1 answer
4k views

Centers of the osculating circles along an ellipse

4 votes
1 answer
455 views

Short proof of Seidel-Stern theorem on continued fractions

4 votes
1 answer
3k views

A point of infinite curvature on a curve

3 votes
2 answers
430 views

When could an uncountable union be reduced to a countable union?

3 votes
3 answers
469 views

How to find: $\int_{-d}^d \frac{z}{2\sqrt{z+c}\ \cdot \sqrt{d^2-z^2}} dz$

3 votes
0 answers
953 views

Examples of fundamental group of mapping torus

3 votes
1 answer
789 views

the restriction of a homeomorphism on a subset

3 votes
2 answers
947 views

When does an embedded $2$-torus bound a solid torus in $3$-manifolds?

3 votes
2 answers
382 views

Second category but not locally residual

3 votes
2 answers
458 views

After Whitney embedding

2 votes
1 answer
930 views

Limsup of continuous functions between metric spaces

2 votes
1 answer
235 views

How to find $\int_{-\pi/2}^{\pi/2} \frac{\sin y}{\sqrt{\sin y+c}}\ \text{d}y$?

1 vote
1 answer
248 views

Two sticks between two concentric circles

1 vote
1 answer
190 views

Any explicit pictures of root datum

1 vote
2 answers
424 views

Convergence of $\sum_{k=1}^n(1-k/n)a_k$

1 vote
1 answer
223 views

Continued fraction with alternative signs

1 vote
1 answer
79 views

Projections of lines in $\mathbb{R}^n$ to the torus $\mathbb{T}^n$

0 votes
1 answer
267 views

Sufficient condition for compact embedding between Banach spaces