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bio website github.com/sw1sh
location Moscow, Russia
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visits member for 1 year, 6 months
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You Should Do The Matasano Crypto Challenges. I did and they are awesome.


Feb
25
awarded  Nice Question
Nov
17
awarded  Popular Question
Nov
7
comment What are some examples of notation that really improved mathematics?
@NateEldredge I think it is an improvement. Compare vector expressed as a series in usual notation $\sum \langle x,\phi \rangle \phi$ and in bra-ket notation $\sum \langle \phi | x \rangle |\phi\rangle$. The bra-ket notation also can be read not just as sum of vectors with coefficients but also as matrix-vector multiplication just by swapping things around. Also we can treat $\sum |\phi\rangle\langle\phi |$ as an identity and it gives rise to a bunch of useful algebraic manipulations.
Nov
7
answered What are some examples of notation that really improved mathematics?
Nov
7
comment What are some examples of notation that really improved mathematics?
Einstein's notation is indeed the power of math at its finest! I would add Kronecker and Levi-Civita symbols to this answer.
Nov
7
awarded  Nice Answer
Nov
7
comment How to put 9 pigs into 4 pens so that there are an odd number of pigs in each pen?
@kriss Thx, next to last was wrong indeed (also the second one), counting to five is hard! Fixed it and also colored the pens for more clearity.
Nov
7
revised How to put 9 pigs into 4 pens so that there are an odd number of pigs in each pen?
added 2 characters in body
Nov
7
answered How to put 9 pigs into 4 pens so that there are an odd number of pigs in each pen?
Nov
2
comment When written in decimal notation, every square number has at most 1000 digits that are not 0 or 1. True or false?
[silly]$2^2 = 3.9999999...$ have clearly more than 1000 nines, so it's false[/silly]
Oct
27
comment Counting backwards from $\infty$ and negative cardinality
Who said about any problem? Isn't it just cool?
Oct
27
comment Counting backwards from $\infty$ and negative cardinality
@AsafKaragila I don't understand if there is a correspondence why I can't say they are the same? If size of a set don't behave like a number, I just invent a new type of number and make up an algebra for it to behave it like I want.
Oct
27
comment Counting backwards from $\infty$ and negative cardinality
@AsafKaragila You can call it whatever you want. I just concerned about the meaning of these objects.
Oct
27
comment Counting backwards from $\infty$ and negative cardinality
@AsafKaragila Because it's negative cardinalities.
Oct
27
comment Counting backwards from $\infty$ and negative cardinality
@EuYu It still behaves like infinity in the sum.
Oct
27
revised Counting backwards from $\infty$ and negative cardinality
edited title
Oct
27
revised Counting backwards from $\infty$ and negative cardinality
edited title
Oct
27
comment Counting backwards from $\infty$ and negative cardinality
@AsafKaragila I'm not necessarily talk about the cardinal numbers. I'm not too familiar with them, but this seems like completely different infinity. I have $\#(\infty-1)=-1$ and not $\#(\infty-1)=\aleph_0$.
Oct
27
asked Counting backwards from $\infty$ and negative cardinality
Oct
1
awarded  Yearling