Sergei Ivanov

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Name Sergei Ivanov
Member for 3 years
Seen 8 hours ago
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Location Saint Petersburg, Russia
Age 40
I am a research fellow at St.Petersburg Department of Steklov Math Institute
22

Questions
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Are fundamental groups of aspherical manifolds Hopfian?

may 20 10 at 17:28 Agol 23.9k●1●33●84

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1k
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What can be tiled by T-tetrominoes?

jun 16 11 at 7:46 fiufhg 1

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1

5
17
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answer
1k
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Is every smooth function Lebesgue-Lebesgue measurable?

mar 26 10 at 22:12 Anton Petrunin 16.5k●41●110

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16
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answers
963
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A set that can be covered by arbitrarily small intervals

jun 16 11 at 16:49 mmm 742●3●8

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14
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1k
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Smoothness of $f(\sqrt x)$

mar 25 at 21:48 Bazin 2,968●2●8

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5
11
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1
answer
405
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Rational approximations on the circle

apr 19 11 at 15:15 GH 15.1k●1●31●53

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206

Answers
votes newest views recent
74
solving f(f(x))=g(x)
65
Is the sphere the only surface all of whose projections are circles? Or: Can we deduce a spherical Earth by observing that its shadows on the Moon are always circular?
41
Is every closed set of Q² the intersection of some connected closed set of R² with Q²
41
Is there a dense subset of the real plane with all pairwise distances rational?
30
How to solve f(f(x)) = cos(x) ?
26
Why are free groups residually finite?
25
Linearity of the inner product using the parallelogram law
24
When factors may be cancelled in homeomorphic products?
22
Smooth functions for which $f(x)$ is rational if and only if $x$ is rational
22
Does every symmetric group S_n have a single element of maximal word norm?
22
An easy proof that S(n) does not embed into A(n+1)?
19
Diameter of m-fold cover
18
Set theory in practice
18
Smoothness of distance function in Riemannian Manifolds
18
Microwaving Cubes
18
Geodesics of bounded length on a Riemannian manifold
18
square root of diffeomorphism of R: does it always exist?
16
Convex Hull of Path Connected sets
16
Double a manifold with boundary
16
Counterexample to Sard Theorem for a not-C1 map
15
The kissing number of a square, cube, hypercube?
15
Can all convex polytopes be realized with vertices on surface of convex body?
15
closed dual of vector fields
15
Do random projections (approximately) preserve convexity?
15
To what extent is convexity a local property?
14
Why is Lebesgue integration taught using positive and negative parts of functions?
14
Point on a line nearest a point in Banach space
14
Algebraicity of Eigenvectors in a Hilbert space
14
Are there unique geodesics in the NIL and SOL geometry?
14
The sum of same powers of all matrices modulo p
1 2 3 4 5 … 7 next

 

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