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00:07
@usukidoll If $A$ is the empty set, then $A\times B$ is the empty set no matter what set $B$ is. :)
@TedShifrin hey
01:07
@LeakyNun hey
Would you say that the matrix associated to a bilinear map $f$ is the matrix $A$ such that (a) $f(v,w) = v^TAw$, or (b) $f(v,w) = (vA)^Tw$?
On one hand I like (a). On the other hand, I like $f(v,w) = \langle Av,w\rangle$.
I think (a) is the common one.
01:26
@anakhro obviously $f(v,w) = \langle v,Aw \rangle$
OBVIOUSLY
alternatively, all my inner products are symmetric so it doesn't matter
@usukidoll how's it hanging, d00d?
going to hell with my set theory homework. I just don't get ittttt >:\
I'm having trouble with a combinatorics problem. I have 7 people lined up labeled 1-7. I want to find the number of line orders given that some person labeled $n$ must come before either $n+1$ person or $n-1$ (unless they are the last person in line). Not sure how to proceed really x(
01:38
@usukidoll go ahead and ask anything about it.
Especially...this...since I can't use the Foundation Axiom. Ok so what I have is... Prove that there is not set $V$ such that $x \in V$ for every set $x$ (shows that $\{x \mid x=x \}$ is not a set ). Can not use the FOundation Axiom. I feel like contradicting this like suppose there exists a set such that $\{ x \mid x=x }\$
Extensionality Axiom save me :\ I know that we have two sets A and B that are equal
this seems like x=x so it's equal by that Axiom
@usukidoll what axioms do you have?
like for a set $A$ and $ B$ since $x \in A$ and $x \in B$, then by the Extensionality it's equal so such a set exists ...
the ZFC
but you don't have foundation
so you have everything except foundation?
like empty, extensionality, pairing, union, power set, comprehension scheme, infinity axiom, replacement scheme, foundation (can not use this -_-) , and axiom of choice
problem says do not use foundation axiom dahhh!!!!
01:43
do you want a vague hint or a hint?
regular hint
reconstruct Russell's paradox
that will be like the whole x is not in x or x not equal to x when it is false
@krauser126 I feel your pain
01:44
@krauser126 it's a finite problem so it can be solved in finite time
(is there any admissible order starting with $2$?)
and I have yet to figure out what the power set of omega... then I can probably do the equivlence relation problem. I got the definitions
Lol that doesn't really help me. @LeakyNun Any hints?
try to make one starting with $2$
There are so many orders to test tho. There must be a way that doesn't involve listing them out
ok let's start with $2$, so we have $(2,-,-,-,-,-,-)$
what can the second position be?
01:49
@LeakyNun Any of the other 6 numbers? The numbers dont have to proceed (n+1) or (n-1) immediately.
wait what are the rules again?
I need a second hint... I feel like this should be straightforward so I am not sure what the heck is going on :\ Unless we can not have a set that is equal to itself hmmm...
Person n must come in line before person (n+1) or person (n-1) although not necessarily immediately. Unless person n is that last in line.
@usukidoll what does Russell's paradox say?
@krauser126 oh I misinterpreted then
I found one definition...Like If we let $\mathcal{A}$ be the set of all sets which do not contain themselves be $\{S \mid S \notin S \}$ from a pdf file...
01:58
and how does ZFC solve this issue?
hmmmm like we need sets that contain something including the empty set???? :\
or there`s an unique choice function by the Axiom of Choice??
how can you study axiomatic set theory (ZFC) without knowing its motivation lol
motivation is so important
ZFC solves this issue by not having Russell's set $\{ S \mid S \notin S \}$ be a set
by using restricted comprehension $\{ x \in S \mid \varphi(x) \}$ instead of unrestricted comprehension $\{ x \mid \varphi(x) \}$
the problem of naive set theory is unrestricted comprehension
well I am over due for lunch -_-! That is the Foundation Axiom which unfortunately I can not use for this particular problem... It said to do another proof that does not use the foundation axiom so I
no that is not the foundation axiom
am like use the Axiom of Choice or the Extensionality one
So, Russell's set is not considered a set at all by the ZFC Axioms -- most likely by the Foundation Axiom
02:04
I just told you which axiom
Russell's set is constructed using unrestricted comprehension
ZFC views unrestricted comprehension as the source of the contradiction
so ZFC replaces it with restricted comprehension
Do you understand it better now?
so ZFC is like the rules of set theory
@usukidoll well ZFC is one set of rules, there are other people who use other axiomatic systems for set theory
but ZFC is mainstream
so I use the FOundation Axiom...to show that we can not have a set like that
use comprehension
to construct Russell's set using $V$
02:13
OH! Use the Comprehension Scheme to reconstruct RUssel's paradox to show that no such set exists
just stumbled across this old answer: math.stackexchange.com/a/2186880/137524
on the one hand, i'm not convinced that'd be a good way to generate a -uniform- distribution
on the other: bahahaha
@LeakyNun
@krauser126 it seems like starting from the last position you should be able to see some tricks
Like {7,-,-,-,-,-,-} ?
no, like $(-,-,-,-,-,-,3)$
then you can choose the position of $1$ and $2$
as long as $1$ is before $2$
so $(-,1,-,-,2,-,3)$
02:26
If you're getting lost in the numbers, maybe start with a simpler example like 3 people
then it must be $(7,1,6,5,2,4,3)$
and then consider what happens for 4, etc
@Semiclassical I think 7 is a good starting point
the simplification is to have $2$ to be the last number instead
or even $1$
@krauser126 how many possibilities are there ending with $1$?
Including our constraint?
02:29
Im not really sure.
2 can go in any of the remaining 6 positions.
But i feel like depending on which spot we pick, itll dictate the possible line ups that are within our constraint
start from the last
54 mins ago, by krauser126
I'm having trouble with a combinatorics problem. I have 7 people lined up labeled 1-7. I want to find the number of line orders given that some person labeled $n$ must come before either $n+1$ person or $n-1$ (unless they are the last person in line). Not sure how to proceed really x(
wait
I think I messed up again, give me a minute
I dont think I messed up
$(-,-,-,-,-,\color{red}{-},1)$
For example: 6,7,1,2,3,4,5 is not a possible line up
what can the red blank be?
Because 7 doesnt come before 6
The red can be 2
right
go on
02:34
But it can also be 3
(7,6,5,4,2,3,1) is not valid
3 must come before 2 or 4
Oh wait
Yea youre right
So 3 must be next?
02:40
Thats weird, using this logic would there only be 1 possibility thats decrementing from 7,6,5...1
But that clearly cant be right
yeah that's right
combinatorics is weird
I may have found a rule but I'm not sure. Maybe Im missing something. If it ends in 1: there is only 1 possibility. (7,6,5,...). But if it ends in 2, there are other possibilities. If 2 is the last number, the 2nd to last number must be 1 (since it must come before 2). Then the number before that must be 3 (Since 3 has to come before iether 2 or 4). Then before that must be 4 (same logic) then ...
no there are two choices for the 6th number if the 7th number is 2
your first observation will be that if you start at the last, there are at most two options for each position
Oh right it can be either 1 or 3
If we choose 3, then our next options are either 4 or 1
correct
02:49
Hmm this is interesting
you'll see a > sign if you're "logicing" correctly
the descending chain determines the queue
there is a descending chain and an ascending chain
What do you mean by that?
(why is there a > sign?)
Whats the significance of that shape though? Wouldn't any ordering create a descending chain?
depending on how we look at it
i'm saying any queue satisfying this constraint gives rise to a > shape
try swapping 2 and 1
(i'm placing each number at its height)
7,1,6,5,2,4,3 is a queue satisfying your constraint
02:55
Oooh okay. My mistake. I was reading that ">" as "greater than", not as its shape haha
Right, I see that an order of 3765412 (incorrect) produces a sideways "z" like shape
03:23
I am starting to wonder whether incompleteness implies infinite
Can there be incomplete finite objects?
4
Q: Incomplete measure space that is not sigma-finite

el_tenedorI am looking for an example of an incomplete measure space with a measure that is not sigma-finite. All the measures which are not sigma-finite which I have come across so far are the following: counting measure on a set that is not countable (e.g. on the measurable space $(\mathbb{R},\mathca...

Also an open set is incomplete by definition: It does not contain any of its limit points
03:43
actually correction: It only contains limit points that are part of its interior
Thus it is intuitively "open" in the sense that for every point you are in, there is always a neighbourhood that contains some other points not in the set
In contrast, a closed set contains all its limit points, meaning you cannot fall outside the set by moving to limit points
A neither set is then something that is a hybrid of the two: It does not contain all its limit points, meaning there exists some net consists of points in the set that can lead you to fall out of the set. The rationals in the real line with the usual topology is an example
As for a clopen set...
It is a closed set such that all limit points are located in its interior
Alternately, it is an open set such that the union of its neighbourhoods are its interior
The whole set is clopen because there is no boundary to speak of
The empty set is clopen because there are no points, thus it is vacuously true that it contains all its limit points and all of them are in the interior
04:13
TFW you realize you've just accidentally rediscovered something obscure that you remember seeing in a 100-year old paper
i'm not sure whether to be pleased or put out
04:38
@Semiclassical is there a deleted comment?
A sequence is oscillatory if the intersection of all its tails are in a set of cardinality > 1
Is $\partial_t \nabla \phi = \nabla \partial_t \phi$?
A sequence is divergent but with decreasing pairwise difference if the intersection of all its tails are empty
is there any way to verify my boolean algebra is simplese after resucing it using boolean algebra?
04:54
@LeakyNun it's the "do your own hw" bit i'm gigglign at
it's not nice, but i like people flipping the proverbial bird at choosing beggars
@user76284 As long $\phi$ is twice differentiable, yes
I once asked whether it is possible to have a electric field that shaped like the windmill surface
and my electromagnetism teacher said, nature tend to smooth things a lot to avoid that happen
Jan 31 '18 at 10:53, by Secret
@LeakyNun The "Windmill saddle" above is one example where mixed derivatives exists but not equal
typo: I mean second derivative of $\phi$ are continuous
Thing is, for $\partial_t \nabla \phi \neq \nabla \partial_t \phi$, $\phi$ will have very abrupt behaviour near that cusp
and there exists no known physical phenomenon near Planck time scale that can switch that fast
@Semiclassical actually, do you know of any physics function in experiment scenarios that has no continuous 2nd derivatives?
not off the top of my head, no
 
3 hours later…
08:05
morning guys
08:45
Alright, so, I'm given this equation $ln(E(e^{aX}))/a$ and I'm supposed to find the value when $X$ is an exponential random variable. Does that mean I just evaluate $E(e^{aX})$ or am I looking at $E(e^{a(\lambda e^{-\lambda x})})$?
Also, $a=\alpha\lambda$ for $0<\alpha<1$.
(Where $\lambda$ is the parameter of the exponential variable, in case that isn't clear.)
09:03
Ok, so I actually need to dive into the Cohen model first as this paper only gave instructions on how to force out a dedekind finite borel set
09:42
@Secret Are you free enough to solve a dumb doubt related to partial fractions ? :/
10:24
how would you interpret the following notation: $u\in\mathcal{L}^1(\mathcal{G})$ where $\mathcal{G}$ is a sigma algebra? Does it means that the function $u$ is integrable (with respect to some measure) on the sigma algebra $\mathcal{G}$?
11:11
@Tanuj What is the question?
11:55
On the article on implicit curves (en.m.wikipedia.org/wiki/Implicit_curve), why is the fifth example, $\sin{(x+y)}+\cos{(xy)}-1=0$, not an algebraic curve? Is it not an equation of two variables on the form $F(x,y)=0$?
@schn $F$ is not a polynomial
> If $F(x,y)$ is a polynomial in two variables, the corresponding curve is called an algebraic curve, and specific methods are available for studying it.
@LeakyNun Thanks!
12:23
in Basic Mathematics, 9 mins ago, by user21820
A classical first-order theory whose axioms capture a crazy religion would prove crazy theorems, but that has no implication to anyone's actions in the real world unless they start interpreting those theorems as prescribing what they should do. But to do so would be illogical.
An example where one must distinguish between system and meta system interpretations
Failure to do so you might actually end up killing people without knowing you have lost reason
Hi chat
12:38
@Secret How do I make partial fractions for $$\frac{1}{(1-2x)^2}$$ ?
Should it be $$\frac{1}{(1-2x)^2}=\frac{a}{(1-2x)}+\frac{b}{(1-2x)^2}$$ ?
you have a typo
(1-2x) no square
@Secret for the second term ?
actually wait, I have not touched this for a while, let me think
the second point
14
Q: The logic behind partial fraction decomposition

R RIn the general case of any function would be interesting but my question is concerning the general case of polynomials with integer powers. I can use the method of partial fractions in the simple case required for an introductory course on integration, but I'm not sure I really understand it or c...

Well, This is much higher level than you need, but the short answer is, you have done the decomposition correctly.
12:54
@Secret This gives absurd result though
I have three equations namely $a+b=1$ , $a=0$ and $4a+2b=0$ , by comparing the coefficients of constant terms , $x^2$ and $x$ both sides
and they are contradictory
$1= a (1-2x) + b$
$a+b=1$
$-2b = 0$
wait
ikr :/
$a + b = 1$
$-2a=0$
yeah
ok now it makes more sense
well you cannot decompose this further obviously
thus partial fraction did nothing to it
12:59
hmm
ok then actually my original question was to find the generic function for the generating function : $$\frac{1}{(1-2x)^2}$$
Do you mean that you want to find the coefficients of such?
I know that the generic function for the following generating function ,$\frac{1}{(1-x)^2}$ is $a_n=n+1$
@Tanuj hi
@JohnRennie hi
@Tanuj ah, OK, you're thinking of example 2 in your list of partial fractions.
13:07
If $(1-x)^{-2}=\sum_{n=0}^\infty a_n x^n$, what does that tell you about $(1-2x)^{-2}$?
@JohnRennie yeah
@Semiclassical idk honestly :/
@Tanuj I guess that makes sense since the two denominators can't be the same otherwise it's just one fraction not a sum of two fractions.
mhm
@Tanuj anyhow I'm afraid I have to go out now. I'll be around later.
Let me make it more abstract: If $f(x)=\sum_{n=0}^\infty a_n x^n$, then $f(2x)=?$
13:11
@JohnRennie alright
$f(2x)=\sum_{n=0}^\infty a_n (2x)^n$
I honestly don't know what's happening though
What do you mean? You’ve got a power series in $x$, and you replace $x\to 2x$
yeah , but how do I go from there to finding the generic function ?
Well, you can also write that as $\sum_{n=0} (2^n a_n)x^n$
So the coefficients of $f(2x)$ will be $a_0,2a_1,4a_2,8a_3,\ldots$
Ugh , feels like I'm shooting arrows in the dark , can you let me know how to find generic functions from a given generating function , like a generalised way ?
In general, that’s not at all straightforward. This is an exception
13:18
Well I dont know what you're doing tbh :/
You have $f(x)=(1-x)^{-2}=\sum_{n=0}^\infty a_n x^n$. Let $g(x)=(1-2x)^{-2}=\sum_{n=0}^\infty b_n x^n$
You want to figure out $b_n$ from $a_n$
Right?
$\sum_{n=0}^\infty a_n x^n$ is this part of some kind of a definition ? Like do you describe a generating function like this ?
@Semiclassical Ok , nvm I got it
what next ?
you’ve got $g(2x)=f(x)$. So that’s $\sum_{n=0} b_n x^n =\sum_{n=0}^\infty a_n (2x)^n$
yep
so the generic function becomes $2^n.(n+1)$
13:26
okay , but
how do we get $(n+1)$ as generic function for $f(x)$
There’s a few ways. First, do you know what it would be for $(1-x)^{-1}$?
actually yes , but I've just memorised these results
Ok. Suppose $(1-x)^{-1}=\sum_{n=0}c_n x^n$
okay
Try multiplying both sides by $1-x$
13:30
yeah
The left is trivial. For the right, just multiply it out and look for the pattern
Don’t assume you know what $c_n$ actually is for the moment
what pattern ?
If I tell you it, you won’t have seen it for yourself
I’m asking you to expand out the first few terms of the product $(1-x)(c_0+c_1 x+c_2 x^2+\cdots)$
yeah
Where $c_n$ is some yet-unknown generic function
What are the first few terms?
13:34
$c_0-c_0.x+c_1.x-c_1.x^2...$
Group that by powers of x
That’s what you should always be doing with generating functions
$c_0$
$(c_1-c_0)x$
$(c_2-c_1)x^2$
Ok. Do you see a pattern in those? Go one more if you don’t yet
hmm I do but what does it mean
What’s the pattern you see? This is a trick that you can use a bunch
13:41
the subscripts of $c_i$ differ by one for different powers of $x$
idk what that tells me :/
Ok. So you started with a GF that had coefficients $$c_0,c_1,c_2,c_3,\ldots$$ and got another GF with coefficients $$c_0,c_1-c_0,c_2-c_1,c_3-c_2,\ldots$$
How would you describe the second set of coefficients in relation to the first?
They differ by one in the second set?
I don’t know what you mean by that
I’m not asking you to use any properties of $c_n$ yet
14:02
I can't see it :(
Ok. Each coefficient in the second set is how much the corresponding coefficient in the first set differs from the one before it
yeah
what does that tell me about $c_n$
So the nth coefficient in the second set is $c_n-c_{n-1}$ ( with the understanding that there’s no coefficient before $c_0$, ie $c_{-1}=0$)
yeah
So, let’s wrap back to where we started. We wanted to find $c_n$ such that $(1-x)^{-1}=\sum_{n=0}^\infty c_n x^n$
14:09
yes
And now we’ve established that multiplying the right side by $1-x$ gives $$(1-x)\sum_{n+0}^\infty c_n=c_0+\sum_{n=1}^\infty (c_n-c_{n-1})x^n$$
yes
What do you get when you multiply the left side by $1-x$?
Right. So you have $1=c_0+\sum_{n=1}^\infty (c_n - c_{n-1})x^n$
14:12
yes
What does that tell you about the c’s?
That equation has to be true for all x
idk
they are all 1 ?
okay
So $(1-x)^{-1}=1+x+x^2+\cdots$
Another way to say this is that $1$ itself is the GF with coefficients $1,0,0,0,\ldots$
And that’s what you get from taking consecutive differences of the coefficients $1,1,1,1,\ldots$
To swap those two: $1,1,1,1,\ldots$ constitutes the sequence of partial sums for the sequence $1,0,0,0,\ldots$
14:17
okay suppose I'm doing the same thing for $$\frac{1}{(1-x^2)}$$
Hi! Um I need help understanding some probability stuff in a basic intuitive way, because I don't understand what part of the formula represents what.

The question is as follows (videogame context): You have a material $m$ and you use it to craft/create an item. The creation itself is always $100\%.$

When you are creating the item, you have a $25\%$ chance of getting $m$ back. If you don't get it back, you can instead not complete the item and have a $90\%$ chance of getting $m$ back.

Now what is the average amount of items made from 1 copy of $m$?
I end up with $1=c_0+c_1.x+\sum_{n=2}^\infty (c_n - c_{n-2})x^n$
Actually, that’d be $(1-x^2)^{-1}$
That's what I said
Oops
But I thought you wanted $(1-x)^{-2}$?
14:21
that too , but this for right now
Fair enough
How do I infer what $c_n$ is for this one ?
start with the first few terms. What are c0 and c1?
$c_0$ should be 1
$c_1$ should be 0
eh idk
Right. And all higher coefficients on the left are zero, so $c_n-c_{n-2}=0$ for n>=2
14:24
yeah
Which means $c_2=c_0=1,c_4=c_2=1,\ldots$
yes
What does this tell you about $c_n$ for even $n$?
its 1 ?
and 0 for odd n ?
14:29
ok doubt
how does it disappear for odd n
You could also have seen it like so:$$\frac{1}{1-x}=1+x+x^2+x^3+\cdots \implies \frac{1}{1-x^2}= 1+x^2+x^4+x^4+\cdots$$
Just by replacing $x\to x^2$ in the first series
Note that the latter still has 1’s for the even terms, but the odd terms have disappeared entirely
ok nvm got it
what's the simplest way to find the solution to the equation $3(\log_2 n)^5 = \sqrt{n}$?
Plot both sides and look for the intersection @anush
@Semiclassical tricky to do that in this case I think
14:33
Trying to solve that analytically is a non-startwr
@Semiclassical what range would you take for $n$?
Since the left side uses log_2, I’d evaluate at powers of 2
And use that to get a sense of what range is a appropriate
@Semiclassical I just tried it.. you never find an answer without the values of integers allowed on a PC
Eg for 2^0, 2^2, 2^4, ... you get 3(0)^5=0, 3(1)^5= 3, 3(2)^5= 96... for the first and 1,sqrt(2)=1.414,2,... on the right
however, from what I know about the log function, the rhs will eventually get bigger than the lhs
So let’s substitute $n=4^p$. (The four is for convenience)
In which case we want to solve $3(2p)^5=2^p$
And that’s definitely got an answer if you pick big enough p
Taking log-2 of both sides and plotting, I get an intersection at about p=32. From WA I get p=31.46 as a better estimate
15:24
user image
3
time
the final frontier of physics
@CowperKettle what book is this in?
RudyRucker book finally finished:
1. A possible form of physical infinity is the indefinite divisibility of spacetime, which in theory is hard to experimentally verify
2. Another sign of physical infinity is if our universe exhibit a recurrence in structure when scaled small enough or enlarged enough, then the universe has to be infinite for that to happen. Simply put, a closed topology of the universe place heavy constraint on its volume
3. Thought process can be infinitely nested, such that it is either incomplete, or that its completion can only be perceived all at once with mystical methods
4. The Absolute infinite is inconceivable, and the reflection principle holds
5. $\omega_1$ is the smallest cardinality of all eventually dominating functions
6. An absolutely continuous line will have absolute infinite number of points, meaning all cardinals and proper classes will be smaller than it
7. Definability is indefinable
8. The Euler spiral can be used to construct a length of $\pi$. Many other transcendentals can be constructed using other curved shapes that are not ellipses
thus it is possible to get some transcendentals in finite number of steps provided you use the correct shape
9. A number that encodes all possible integer sequence cannot be defined using said encoding and hence look random to that encoding
10. Even if some perfectly accurate description U of the universe exists, it seems likely that if we represented U by the clumsy expedient of putting numbers in books, then this representation of U would not fit in the universe. Of course, the most efficient representation of U is the universe itself, so at least one representation of U exists. But could we ever hope to have a desk-top or pocket-sized model of the universe? Only if matter is indefinitely divisible.
This is an interesting point because it is proved in a paper that if our universe is a simulation, and hence have bounded memory and CPU time, the accuracy of simulated black holes in a computer in this simulation will get less accurate the more it is nested
11. If every possible universe exists, then there is no need to account for the special peculiarities of this universe (e.g., the facts that there is an ant crawling up my screen right now, or that there are 79 clover blooms in my backyard, or that sentient beings exist in this universe, or that space has three dimensions). If every possible universe exists, then there is no need to explain any peculiarity.
But anyone who has ever savored the endless diversity of nature must feel–and even hope–that the universe can never be fully captured by any finite schema, and that the pattern of the universe is, in a formal sense, random and unnameable.
12. ii) It is a mistake to let everyday reality condition possibility, and only to imagine the combinings and permutations of physical objects—the mind is capable of directly perceiving infinite sets. iii) The ultimate goal of such thought, and of all philosophy, is the perception of the Absolute.
13. There is no reason why R could not print out his program for us, perhaps in some extremely compact and coded form (compare sperm cells!). But, as was discussed above, we would not be able to understand this program, nor would we be able to prove to our satisfaction that R was consistent. The interesting thing is that even though we cannot understand the program of R, we are able to set up the physical conditions that lead to R’s coming into existence.
16:05
Hello!! Does someone of you have an idea about my question for diagonals?
0
Q: Show that the angles that are created between two consecutive diagonals are all equal

Mary StarFrom a vertex of a n-sided convex polygon we draw the diagonals. I want to show that the angles that are created between two consecutive diagonals are all equal. For that do we have to consider the triangles that created and to show that these have the angles?

14. One/Many problem: There are collection things too large to be a set, or even be considered as one individual object
Inward Way and the Way of Unity are examples of these, and it is said to be one and the same
15. Large cardinals and Godel numbering is taught
16. Now if you were to have a full understanding of how Mh operates, then perhaps you could prove that Mh is consistent. But, as I just mentioned, in the case where h is the mind recipe, the operation of the eventual Mh is incomprehensibly intricate, and we will never be in a position to legitimately claim to know the truth of the sentence Con(h), which asserts that Mh is consistent.
This is, indeed, the content of Gödel’s Second Incompleteness Theorem. Rather than ruling out man-machine equivalence, the theorem places limits on what we can know about machines equivalent to ourselves.
@Mr.Xcoder google seems to think it's Zach Weinsersmith's " Science: Abridged Beyond the Point of Usefulness" (same guy who does SMBC)
16:33
@Semiclassical ah ok, thanks
17:07
$\begin{pmatrix}
e^t&0\\
0&e^{-t}
\end{pmatrix}$
@Semiclassical I got some doubts regarding some problems/statements on mathematical logic.Your help would be greatly appreciated.
how is the trace of a matrix the sum of the eigenvalues?
is it only the complex eigenvalues ?
 
1 hour later…
19:12
Evening all :)
19:45
hello
ABC
ABC
19:58
Hi
guys if I have a reversible cycle with 2 Heat source (source 1 at temperature T1 and source 2 at temperature T2). The cycle is: ibb.co/Vwvjg37.
AB: isochoric
BC: adiabatic
CA: isotherm

If I want know performance of that cycle Can I write Performance=1-T1/T2 ??
this is a question about school physics, thus not something anybody in this chat is likely to know. you should ask at the physics site
20:25
I took thermodynamics for a couple of semesters in college, but I have no idea what "performance" is. (I also never learned the word "isochoric.")
Hi @s.harp and @Ted :)
ABC
ABC
@TedShifrin efficiency*
isochoric transformation mean tranformation with Constant volume
$\chi\omega\rho\alpha$ apparently means space in greek, hence where the word isochoric comes from
apparently the etymology of "ergodic" is contested
either being a combination of ergon and odos or of ergon and eidos
at any rate the word was invented by boltzmann
interesting stuff
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Ok I didn't know that :')
 
1 hour later…
21:39
@s.harp did you seriously spell out the word as chi omega rho alpha
chora
that's like spelling "space" out as ess-pee-ay-see-ee
χώρα
no, it would be like entering the ASCII numbers of the letters to a renderer because you do not have access to a keyboard with those letters
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