sci.math Google Group

Re: Why "meta diagonals" are irrelevant

dik.win...@cwi.nl (Dik T. Winter) — Tue, 02 Dec 2008 15:45:30 UT

...
> > > > But if you can not take them all you should state:
> > > > sum{n = 1...oo} 1/(2^n) < 1
> > > > because it can never be 1 as you can not take them all.
> > >
> > > unless all would exist, of course. If all exist, then I get the sum 1.
> >
> > But in your vision all does *not* exist, so the sum is less than 1 and you

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lolekk1...@wp.pl (lolekk1223@wp.pl) — Tue, 02 Dec 2008 15:44:49 UT

[link]

Complexity of Convex Programming

ask_for_mail_address_ple...@invalid.invalid (Patterson) — Tue, 02 Dec 2008 15:17:14 UT

"Convex programs can be solved in polynomial time, up to an
arbitrarily small error." I doubt that this is true in that
generality.
Assume, however, that all functions involved are continuously
differentiable at least two times, and that these derivates are
efficiently computable. Does that make the statement true? Can

Compendium on Mathematical Programming

ask_for_mail_ple...@invalid.invalid (Patterson) — Tue, 02 Dec 2008 11:03:35 UT

Could anyone recommend a _results_ _oriented_ compendium on
mathematical programming? I am especially interested in a list of
program classes that can be solved in polynomial time, ideally
together with references where to find the algorithms or even
implementations.
There exist _huge_ books on, e.g., convex programming. However, I

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Oxyshopping.com introduce gifts for Christmas shopping

diya...@gmail.com (Diya_Smart_Beauty) — Tue, 02 Dec 2008 05:56:48 UT

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love to shop during Christmas.
Dec 01, 2008. Bells of Christmas are about to ring and it will soon
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involved in tons of shopping. Now, you can just do tons and tons of

Expander graphs with minimal eigenvalue gap

pagnu...@htdconnect.com (Lou Pagnucco) — Tue, 02 Dec 2008 05:31:48 UT

Have the d-regular graphs with a given edge expansion constant
with minimal gap between the largest eigenvalue (=d) and the
second largest eigenvalue been characterized?
Are they constructible?

Some doubts (basic field theory)

solrac...@hotmail.com (Carl R.) — Tue, 02 Dec 2008 05:13:50 UT

Let K,E be fields. Then every homomorphism f: K-> E is injective.
Isn't this false because for instance
the trivial homomorphism f(x) = 0 for all x in K has kernel equal K so
its not an injection. Although
I think the statement is correct if we state it as follows: every
*NONTRIVIAL* homomorphism of fields is

JSH: Normalization issue?

jst...@gmail.com (JSH) — Tue, 02 Dec 2008 05:12:54 UT

Here's a case where normalization opens up a huge argument where a
math journal has died over this thing.
I have the special mathematical construction:
7*(175x^2 - 15x + 2) = (5a_1(x) + 7)(5a_2(x)+ 7)
where the a's are roots of
a^2 - (7x-1)a + (49x^2 - 14x) = 0.
(If you doubt the correctness of the construct, multiply everything

Question about construction of vectors

jyab...@nycap.rr.com (Jay R. Yablon) — Tue, 02 Dec 2008 04:30:32 UT

Question:
Let's take a vector of some sort, of some number of dimension, say, (A,
B, C, D), of four dimensions. Let's even say this vector transforms as
such under SU(4), though one can think of this vector more generally as
well.
Clearly, one can form the scalar product A^2+ B^2+C^2+D^2.
Clearly, one can also form a 4x4 tensor which has AB, AC, AD, BC, BD,

T&T

pe...@brains.org (Pekka Malin) — Tue, 02 Dec 2008 04:19:31 UT

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Exponential Series convergence problem?

yedong...@gmail.com (leaf) — Tue, 02 Dec 2008 03:12:05 UT

Does there exist a sequence {a_n} such at:
S=sum(|a_n|) converges and S=sum(|a_n|^p)diverges for any p satisfying
0.5<p<1. Thanks.

Laplace transform - please see if my solution is on the right track

word.dr...@gmail.com — Tue, 02 Dec 2008 02:49:48 UT

i need to find the following laplace transfrom:
f(x) = x sinx e^(x)
here's what i have so far:
L {f(x)} = L {x sinx e^(x)} = L{x sinx} L {e^(x)} = 2s / [(s^2 + 1)^2]
multiplied by 1/s - 1
then its just a matter of simple arithmetic.
comments are very much appreciated.

proper credit was added to site

simon.plou...@gmail.com (plouffe) — Tue, 02 Dec 2008 02:38:18 UT

Hello,
after a brief exchange with Jon Borwein, my name was added
to the site in question :
[link]
This is all I asked, I am satisfied with the proposed solution.
Je remercie Jon Borwein pour s'être montré compréhensif
sur ce sujet.
****************************** ******************************

An exact 1-D integration challenge - 61 - (exp)

v...@cybertester.com (Vladimir Bondarenko) — Tue, 02 Dec 2008 00:56:58 UT

Hello,
int(exp(2*sin(z))*(exp(4*sin(z ))*(2*cos(cos(z))^2-1
)+2*exp(2*sin(z))+2*cos(cos(z) )^2-1)/(exp(4*sin(z))
+2*exp(2*sin(z))*(2*cos(cos(z) )^2-1)+1)^2, z=0..Pi)
?
Cheers,
Vladimir Bondarenko
Co-founder, CEO, Mathematical Director
[link] Cyber Tester Ltd.