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7:00 PM
@skullpatrol yes?
 
@robjohn Just wondering when you got your new dog :-)
 
@skullpatrol not too long after Lilly passed away.
 
@robjohn Oh, sorry for bothering you.
 
Did you notice my question today?
 
link please
 
7:03 PM
@skullpatrol not really bothering. I was just commenting on a comment someone had left
 
@MatsGranvik nice
 
@MatsGranvik Did you see Hagen von Eitzen's comment?
@MatsGranvik never mind, wrong question
 
Yes I did.
@robjohn They are related though.
I think that it should not be too hard too justify the claim in the eigenvalue question if one does Exp[Exp[Exp[Exp[Exp[Exp[divisors]]]]]] and Log[Log[Log[Log[Log[Log[eigenvalues]]]]]], infinitely many times. The fastest growing exponentiated number should begin to dominate the the eigenvalues. But I don't know enough about determinants to take the factoring in to account.
In fact I don't know much about eigenvalues.
 
7:24 PM
@MatsGranvik I answered the other question assuming that the product was supposed to start at $n=2$.
which is more interesting :-)
 
@robjohn Yes that was my intention.
I will look up the oeis sequence I have thought about, related to it. Just a minute.
http://oeis.org/A224892
1, -2, -3, -4, -5, 0, -7, 0, -9, 0, -11, 12...
 
@MatsGranvik you know that you can only take a finite number of logs of any real number (before it goes negative)
 
Before it goes negative? Ok, I see. The sequence however is the numerators of the Dirichlet series that converges to zero. I might not have described the generating function correctly at the oeis page. It is the translation between symbolical Zeta function products and matrix multiplication that causes me trouble.
 
@MatsGranvik However, beyond that, I cannot comment on the matrix question. I don't seem to have the proper background to understand what is going on.
 
 
1 hour later…
8:41 PM
@robjohn: Hi rob
 
@BabakS. what's up?
 
@robjohn: How can I delete my account? I mean Babak S? Am I supposed to ask you to do that? Thanks
 
@BabakS. What happened to Somaye?
 
I don't know? @skullpatrol
 
@BabakS. Are you sure? that would affect a lot of other accounts probably. Is this due to a problem with another user?
 
8:51 PM
@BabakS. I also wanted do the same thing but then I thought that my decision would affect lots of users. Maybe it's better to ponder over the matter for a couple of days in order to make the best decision. :-)
 
@robjohn: No dear rob. Sometimes, I get bored of some actions of some users. In these cases, I want to leave the site because I can't write them the proper things and want them think about the right way. I am sorry for my self. :(
@robjohn: I wish here was a switch in which I could turn it up or off exactly the same in Facebook.
 
@BabakS. over 1000 answers ... that means your account is a precious one! Well, to be honest with you, people that don't like us we meet every day in all envirionments. I myself get annoyed sometimes, but I try to go on. You may come here and talk about math if you don't like the main anymore. :-)
There are lots of amazing questions here.
 
@Chris'ssis: Thanks. Your words , both of you, are like pulling water on fire. I don't want to affect others accounts. Thanks rob. I feel I am speaking to my father. Thanks.
 
@BabakS. I agree with Chris's sis. Rather than deleting your account, you can simply choose not to use it until you feel a bit less oppressed by the others, who are really nothing more than faceless typists if they are not nice.
3
 
@BabakS. you know, try to think of those that appreciate your work, and I'm one of those! Many of your answers were really helpful to me, and I plan to retake the study of some of them. :-)
 
9:01 PM
afk brb
 
@BabakS. a graph like this is like 10 proofs! I want it to be there, really :-) math.stackexchange.com/questions/457557/… (+1)
 
@robjohn: Nice suggestion. Thanks Chris's sis. It is very kind of you. I am nothing here in this vast ocean. I am just a child playing alongside it. OK. I obey you.
 
It's just an answer randomly taken. Come on! :-)
@BabakS. hehe, great! :-)
 
@Chris'ssis: :-)
 
:-)
 
9:25 PM
@BabakS. you can't leave, Babak. you're like 50% of my readership.
 
...and I'm the other 50% ;-)
 
@AlexanderGruber: Thanks Alexander. Yes. I have learned much about Groups from your answers.
@skullpatrol: What happened to Somaye? :D
@skullpatrol: I think she left the site.
 
@BabakS. She married and is kinda busy atm.
 
9:35 PM
@BabakS. I think she missed too many rainbows...
...in here.
 
@GustavoBandeira: Are u sure? Did she tell you that by any mail?
 
@BabakS. Yes.
Yahoo messenger, actually.
 
@GustavoBandeira: Oh I see. Miss her. ;-)
@GustavoBandeira: Send my best regrds to her if you chat later.
 
@BabakS. Ok. I'll do it. =)
 
@GustavoBandeira Yeah, and tell her skullpatrol is looking for her :-)
 
9:41 PM
@skullpatrol No. You're a hipster.
 
@GustavoBandeira Well, excuuuse me... ;-)
 
@skullpatrol: This is for you.
 
@BabakS. Thanks pal :D
 
@skullpatrol: :D
 
9:47 PM
 
@skullpatrol MAN!
 
@GustavoBandeira I prefer this pal.
 
10:13 PM
lol I got the enlightened badge for pointing out that $+$ and $\max\{\cdot,\cdot\}$ are commutative binary operations.
 
@user1 Heh!
@user1 Sire, are you there?
 
10:53 PM
@AlexanderGruber
@anon
 
> Just ask; don't ask to ask.
I put that in the room description. :-)
 
@anon How are you, stranger?
 
alright
 
Hi Peter, I saw you there, I wanted to ask you a question.
 
@anon I am doing some exercises. I have proven that given two nonzero linear forms in $V^*$, then $\{\varphi_1,\varphi_2\}$ is linearly dependent $\iff$ $\operatorname{ker}\varphi_1=\operatorname{ker}\varphi_2$. Now I am being asked to prove that given $\varphi_1,\ldots,\varphi_r$ linear forms and $\varphi$ another one such that $\bigcap \operatorname{ker}\varphi_i\subseteq \operatorname{ker}\varphi$ then $\varphi\in \langle\varphi_1,\ldots,\varphi_r\rangle$. Here all is finite dimensional.
@julien Go ahead.
 
11:03 PM
@PeterTamaroff See this answer and the comments math.stackexchange.com/a/458097/38053. I would just like to know if I'm alone to get spiteful downvotes in retaliation when I comment to point out a mistake. From this specific user I mean.
 
@julien Hmmm... yikes.
 
@PeterTamaroff That's the third time...
 
I think DonAntonio is not the "friendly" type.
But it is stupid to downvote someone who points out mistakes.
I would just try to ignore it. If this continues and you're certain it's him, just talk to a mod, maybe?
 
@PeterTamaroff Yeah, I think I commented kindly. And I did not even downvote this utterly wrong answer.
 
@julien You're a Linear Algebra Overlord. Mind seeing what I put above?
I'm doing some work on the Dual Space (usually of a finite dimensional vector space)
 
11:08 PM
@PeterTamaroff Hmm, I was about to go for dinner. But I might have two or three minutes. WHere?
 
@julien 7 messages above.
 
@PeterTamaroff Oh yes, that's a good one.
 
@julien I proved the first thing like this.
First suppose $\alpha_1\varphi_1+\alpha_2\varphi_2\equiv 0$. Then choosing $x$ in each kernel yields the double inclusion at once.
 
fix an isomorphism $V\cong V^*$, with $\varphi_i\leftrightarrow\psi_i$. Then $$\bigcap \ker\varphi_i\subseteq\ker\varphi\Leftrightarrow\bigcap \psi_i^\perp=\langle\psi_1,\cdots,\psi_r\rangle^\perp\subseteq\langle \psi\rangle^\perp\Leftrightarrow \langle\psi\rangle\subseteq\langle\psi_1,\cdots\rangle\Leftrightarrow\cdots$$
 
On the other hand if there is some $x$ not in the other kernel, from $\alpha_1\varphi_1+\alpha_2\varphi_2\equiv 0$ evaluting at $x$ one gets say $\alpha_1=0$; and then since the form is nonzero, we get $\alpha_2=0$.
@anon What is that wedge?
 
11:13 PM
sorry, should be perp
an isomorphism $V\cong V^*$ induces an inner product, so we can speak of complement subspaces
 
@anon Well, I don't have all that at hand... =/
So I cannot follow what you mean.
 
$$\begin{array}{ll} \bigcap \ker \varphi_i \subseteq \ker \varphi & \iff \bigcap \psi_i^\perp = \langle \psi_1 , \cdots , \psi_r \rangle^\perp \subseteq \langle \psi \rangle^\perp \\ & \iff \langle \psi \rangle \subseteq \langle \psi_1 , \cdots , \psi_r \rangle \\ & \iff \langle \varphi \rangle \subseteq \langle \varphi_1 , \cdots , \varphi_r \rangle . \end{array}$$
 
@PeterTamaroff Sorry, I really need to go. Duality is indeed the key. Bye!
 
@anon Should I extend to a basis and consider the dual basis of $\{\varphi_1,\ldots,\varphi_r,\ldots,\varphi_n\}$ in $V$?
 
perhaps
I was going to explain my terms, because I want to
Let $\psi_i$ and $\psi$ be the image of $\varphi_i$ and $\varphi$ under an isomorphism $V^*\xrightarrow{\sim}V$.
Call the isomorphism $\rho:V^*\to V$ and $\tau:V\to V^*$
 
11:20 PM
@anon Go ahead! =)
@anon What are the $\psi$?
 
there is an inner product structure on $V$ given by $\langle v,w\rangle=\tau_v(w)$
 
What does $\tau_v$ mean?
Ah.
The form associated to $v$?
 
@PeterTamaroff $\psi_i=\rho(\varphi_i)$ and $\psi=\rho(\varphi)$; like I said in the comment you're replaying to, $\psi$'s are the images of the $\phi$'s under the isomorphism $V^*\to V$
@PeterTamaroff yes, $\tau:V\to V^*:v\mapsto \tau_v$, where $\tau_v\in V^*$
 
So $\langle v,w\rangle$ is the image of $w$ under the form $\tau(v)$.
 
mmhmm
 
11:22 PM
@anon OK. I see it is bilinear.
But I would need to check the other stuff.
 
fun fact to keep in mind, isomorphisms $V\to V^*$ are in one-to-one correspondence with inner products on $V$
now, with $\tau(v)=v^*\in V^*$, we have $V\supseteq \ker v^*=\{w\in V:0=v^*(w)=\langle v,w\rangle\}=v^\perp$, the complementary subspace of $\langle v\rangle$ relative to the inner product
 
@anon Ah.
 
facts one can check: $\bigcap (X_i^\perp)=(\bigcup X_i)^\perp$ and $A\subseteq B\iff B^\perp\subseteq A^\perp$
both used in my proof
 
@anon Yes, sure.
 
(for any sets $X_i$ and subspaces $A,B$)
 
11:29 PM
@anon Ah, but the statement is an $\iff$? I am asked to prove one direction only.
 
then just use $\implies$s
 
Sure, proving it both ways would be nice.
But maybe the other way is easier?
 
actually I don't think $\Leftarrow$ is correct, hmm
 
@anon You did write $\iff$s, yes?
 
oh nevermind, the other direction is obvious!
silly me, I am not sure why I was doubting myself
(well, I do know why, but whatever)
if $x$ is s.t. $\varphi_i(x)=0$ for each $i$, then surely $\varphi(x)=0$ for all $\varphi\in\langle\varphi_1,\cdots,\varphi_r\rangle$
 
11:35 PM
FYI, this is all that has been proven in the chapter on the Dual Space:
$1.$ For each base there is a unique dual base.

$2.$ If $B=\{v_1,\ldots,v_n\}$ is a base and $B^*=\{\varphi_1,\ldots,\varphi_n\}$ then $(v)_B=(\varphi_1(v),\ldots,\varphi_n(v))$ and $(\varphi)_{B^*}=(\varphi(v_1),\ldots,\varphi(v_n))$.

$3.$ To each base $B_1$ in the dual there is a base $B$ with $B^*=B$.

$4.$ $\dim S^\circ+\dim S=\dim V$

$5.$ $(S+T)^\circ =S^\circ \cap T^\circ$ and $(S\cap T)^\circ=S^\circ+T^\circ$
 
so my understanding is that they only asked you to prove the nontrivial direction of implication
 
@anon Right, that was meh pointz.
 
I am going to go take a shower, later
 
@anon Byes.
 
RGB
lol
 
11:46 PM
@Franklin What is funny?
 
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