4,782 reputation
917
bio website motls.blogspot.com
location Czech Republic
age 40
visits member for 3 years, 6 months
seen Aug 4 at 12:45

Hi, I am a string theorist and a publicist.


Aug
17
awarded  Nice Answer
Jul
21
answered IMO 2011 Problem 5 - Show that $f(m) \mid f(n)$ if $f(m) \leq f(n)$
Jul
9
comment True, false, or meaningless?
I see, so $\forall i\in \{\}: T(i)$ holds for any $T(i)$ because there is no counterexample in an empty set for which $T(i)$ would fail - it holds for everyone (all zero of them). On the other hand, $\exists i\in\{\}: T(i)$ is always untrue because there doesn't exist any $i$ in an empty set that has a property - whatever property - because there's nothing in an empty set even without adjectives.
Jul
9
answered True, false, or meaningless?
Jul
9
answered Closed-form Expression for $\sum_{j=0}^{k-1}(2j+2)\sum_{i=1}^j \frac 1 {i^2}$? (problem with Mathematica)
Jul
9
answered Compositions of prime numbers
Jun
27
comment Validity of $\sum_{i=1}^n(a_i^2+b_i^2+c_i^2+d_i^2)\lambda_i\geq\lambda_1+\lambda_2+\lambda_3+\lambda_4$?
Oh, I see, you're right.
Jun
27
comment Puzzle: $(\Box @)+(\Box @) = (\Box\bigstar\Box$)
Thanks for your care and implicit compliments, @JTL and @Jyrki, but I don't think it's a big issue. Let's be generous, people have the right to vote the way they want.
Jun
27
awarded  Nice Answer
Jun
26
revised Validity of $\sum_{i=1}^n(a_i^2+b_i^2+c_i^2+d_i^2)\lambda_i\geq\lambda_1+\lambda_2+\lambda_3+\lambda_4$?
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Jun
26
revised Puzzle: $(\Box @)+(\Box @) = (\Box\bigstar\Box$)
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Jun
26
revised Validity of $\sum_{i=1}^n(a_i^2+b_i^2+c_i^2+d_i^2)\lambda_i\geq\lambda_1+\lambda_2+\lambda_3+\lambda_4$?
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Jun
26
comment Validity of $\sum_{i=1}^n(a_i^2+b_i^2+c_i^2+d_i^2)\lambda_i\geq\lambda_1+\lambda_2+\lambda_3+\lambda_4$?
Interesting, I jumped on the same intuition as you did - it couldn't be right, I thought, because the RHS didn't have the minimal $\lambda$ anymore. Of course, the catch is that the "generalization" has almost nothing to do with the original inequality.
Jun
26
answered Validity of $\sum_{i=1}^n(a_i^2+b_i^2+c_i^2+d_i^2)\lambda_i\geq\lambda_1+\lambda_2+\lambda_3+\lambda_4$?
Jun
26
comment How to take the inverse of this signal?
You were faster, I erased my answer. ;-)
Jun
26
answered Puzzle: $(\Box @)+(\Box @) = (\Box\bigstar\Box$)
Jun
26
answered Eigenvectors of a normal matrix
Jun
26
answered How common is the use of the term “primitive” to mean “antiderivative”?
Jun
26
comment Plane intersecting line segment
The objects you called $dist$ are not distances in the exact sense. They're inner products which can be both positive and negative. There's no reason to divide the debate to the positive and negative case because all the geometrically natural formulae here are linear, rational, or otherwise analytic and they work uniformly both for positive and negative values of the inner products.
Jun
26
comment Plane intersecting line segment
Dear @PUK, if a line belongs to a plane, then it surely is parallel with it. At any rate, when it is so, the intersection - as in set theory - of the plane and the line is the whole line (the very same one). I don't understand in what sense it would make sense to pick two particular points on the line as "better intersections" than all the other points. Also, I am confused by your separate discussion of negative and positive values of $dist.dist$. A fun about maths and algebra is that one may calculate with negative numbers just like with the positive ones w/o splitting derivations.