Francesco Sica

603 reputation

bio	website	francescosica.org
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visits	member for	1 year, 1 month
	seen	Oct 27 '12 at 16:39
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	603 reputation	bio	website	francescosica.org	visits	member for	1 year, 1 month
35 badges		location			seen	Oct 27 '12 at 16:39

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Apr 23	awarded	Yearling
Sep 6	comment	Inequality. $ab^2+bc^2+ca^2 \geq a+b+c.$ Iuli's proof is substantially correct and you can prove the second displayed equation using rearrangements. This method doesn't necessarily have to prove symmetric inequalities. You just have to take the correct permutation to get $y^2z+z^2x+x^2y$. For instance, supposing that $y\geq x\geq z$, the same inequality can be proved.
Sep 5	revised	Inequality. $ab^2+bc^2+ca^2 \geq a+b+c.$ Typo in the exponent of the first displayed equation. Typo in second equation. Removed the rest, now useless.
Sep 5	suggested	suggested edit on Inequality. $ab^2+bc^2+ca^2 \geq a+b+c.$
Aug 28	awarded	Good Answer
Aug 14	comment	Primes Not Dividing $\binom{2n}{n}$ Any such prime appears exactly twice both in the numerator and the denominator of $\binom{2n}{n}= \frac{(2n)!}{(n!)^2}$.
Jun 8	awarded	Constituent
Jun 8	awarded	Caucus
Jun 1	comment	How to show that if $x_1,\ldots,x_n$ are real numbers, then $\|x_1\|\ldots\|x_n\| \le \|x_1\|^2 + \cdots + \|x_n\|^2$ The right kind of such inequalities should be homogeneous of the same degree on both sides. Here, it is homogeneous of degree $n$ on the left and $2$ on the right.
May 14	comment	Exercise: continuity of a function of two variables Hint: Use uniform continuity of $\phi$ on compact sets.
May 12	answered	UPDATE: How to find the order of elliptic curve over finite field extension
May 11	awarded	Editor
May 11	revised	Cyclic Group Questions added 16 characters in body
May 11	comment	Cyclic Group Questions You're right, I forgot when there are no $2$'s at all. I will edit the answer. Thanks!
May 11	answered	Cyclic Group Questions
May 10	comment	calculating the amplitude of a cosine function Why the notation $\\| A \\|$ etc. in the first displayed formula?
May 10	comment	When did Fubini's name get applied to the theorem without measures? Look at the wikipedia entry for Fubini's theorem. I will just add that in Italian universities, the theorem is known as the theorem of Fubini-Tonelli (and pay attention to the spelling, one 'n').
May 10	awarded	Supporter
May 5	answered	The power series $\sum\limits_{n=1}^{\infty} \frac {z^{n} }{ n^{2}} \ $
May 2	comment	Importance of rigor It is Littlewood, not Landau, who proved that $\mathrm{li}(x) - \pi(x)$ changes sign infinitely often. The first one to give an upper bound on the range of $x$ when this first happens is Skewes.