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17:12
Is there a way to directly equate any single operator of a product variable to a factorial?
like if I did \prod sin(k) is there a way to turn that into sin(k)! or anything like that?
oh btw the log thing has 6 stars now
17:28
@SteamyRoot Underrated comic there. Really underrated.
@DaneJoe definitely not.
the case that Balarka did amounted to the observation that 6=1*2*3=1+2+3, i.e. 6 is a perfect number.
in general there's no relation like that, and certainly not for anything like the sine function
@Semiclassical Well there's already special cases where it's true, I'm just wondering if there's a general case. I wouldn't be so sure about the "definitely" part. There's definitely for sure relationships that use the product of the sine function.
Product of two sines, yes.
You're asking for products of arbitrarily many sines.
mm no I'm thinking more of the gamma function
but anyway, as I said I'm not talking specifically only prod sin(k) = sin(k)!
that statement obviously isn't true
You're looking for relations of the form $f(\Gamma(x))=\Gamma(f(x))$?
17:32
I'm just wondering about cases with a form like that
like sin(k!) or (-1)^kk!
actually, what I just wrote isn't very sensible
so like any formula that comes to mind that "looks" like that
but not limited to that
something more like $\prod_{k=1}^n f(k)=f(n!)$.
but no more like prod f(x) = f(k!)
that's the ideal case
but obviously the real case would be more complicated than that
well, suppose you take logs of both sides
17:34
right then you have the sum
then that becomes $\sum_{k=1}^n \log f(k)=\log f(n!)$
big whoop
id like to keep it as a product however
or a factorial
so if you let $g(x)=\log f(x)$ then that's equivalently $\sum_{k=1}^n g(k) = g(n!)$.
the main advantage being that the left-hand side is additive rather than multiplicative, and that $g(k)=k$ is now a solution.
yeah I was thinking about that but there's something that doesn't quite work
but it could be the indeces im using
ill try it again
oh right
here's the problem I see. for $n=1$, that becomes $g(1)=g(1)$ which is always true. for $n=2$, it's $g(1)+g(2)=g(2!)=g(2)$. so $g(1)=0$.
17:36
you didn't transform the boundaries of summation
at all
but neither did I
and they shouldn't.
seems like they should
no. $\log(f_1f_2\cdots f_n)=\log f_1+\log f_2+\cdots +\log f_n$.
taking the log changes the product to a sum but does nothing to the relevant indices.
17:37
if you do a sum from k=1 to n, but k turns into log(k), then it seems like you'd have log(k)=1 to log(n) or something along those lines
again, no.
that's entirely not true.
there's a lot of implications if you really actually say it's "no"
in fact you'd be the greatest mathematician of the century
no, I'd be anyone who understands that the log of an n-fold product is the n-fold sum of the logs.
you still don't see the general implication of that generalized case, so I'll leave and come back later and see if anything changes
Listen to Semi, he knows stuff.
17:39
i wish he did but i already tried the method he's suggesting, and it didn't work
and it was an ideal assumption
$\log \left(\prod_{k=1}^n f_k\right) = \sum_{k=1}^n \log f_k$, full stop.
(assuming all the $f$'s are positive etc.)
The log of the product is the sum of the logs, what's so hard about that? And yes, period, on the other side of the Atlantic.
Semi's American
Yes, I know, and what I said still holds, full stop.
Also, lol, period.
17:42
I do like the fact that all American sentences end in menstruation
Am I accidentally using the British expression instead of the American one? That'd be kinda funny.
(Well, excluding questions and exclamations)
British say full stop and Americans say period.
(and also 99% of my posts here)
17:43
anyone can clarify the "0.999... = 1" statement?
If they were different there'd be something between them.
sure. multiply both sides by 10. what do you get?
Not another recurring decimal question, lol.
@Semiclassical well... more the part, when is this statement true and when is this statement false
It's always true.
17:44
for example
the question was "get a random number"
where "a random number" is literally ANY number
The thing is, 0.999... is 1, and one will have to invoke the decimal expansion construction of the real numbers for that.
what is the chance to get the number 5?
well, that is 1 / inf
Yeah so when there are infinitely many possibilities, "probability 0" does not mean "impossible"
I wouldn't say there's even a meaningful probability in that case.
which is written down as 0.000... or 0.000...1
17:45
There is the dedekind cut construction, the cauchy sequence construction, the decimal expansion construction, and a few others.
The probability is 0.
0.000....1 is not the same as 1-0.9....
so the probability is not 0% right?
this question is ill-posed, without specifying a probability distribution you're choosing the numbers with
It is. @Wietlol
17:46
Check out different books for the different constructions then.
0.000...001 only makes sense if there's finitely many 0s there.
but 0% is never occurring
that is the definition of 0%
When there are infinitely many possibilities, "probability 0" does not mean "impossible" @Wietlol
there is no such then as 0.0000...0001 with an infinite number of zeros in between.
on the other hand, we can revert the maths, 0 * inf = ... uhm... 0?
17:47
no.
0*inf is not determinate.
0*anything = 0
@AkivaWeinberger That depends on the definition of impossible, lol.
basic math rules
again, no. not if you're doing infinite
there is no determinate meaning to 0*infty
What is a point? A point doesn't really exist, because no matter how small we draw a dot, it can be made even smaller.
17:48
but infinitly many zeroes summed up is still 0
I'm late to the game, are we talking limits or probability?
That's a good point. There are other reasons for leaving 0*infinity undefined.
Probability.
(Set theory supports the idea that it's zero, in that the Cartesian product of the empty set with an infinite set is the empty set.)
What number is in between 1.000... and 0.999...? @Wietlol
17:49
the way I'd say it: If 0.000...001 means that there's a finite number of zeros between the decimal and 1, then this is nonzero and positive.
on another side, for any non-neutral number 'n' "a / n * n = a" is correct right?
There is no such thing as 0.000...0001 actually.
@skullpatrol $0.(9)$ (i.e $0.99999...$) is $1$
@skullpatrol 0.(0)1
but if one intends it as an infinite number of zeros, then to the extent that that is meaningful then it's just 0.
17:50
Because you cannot have infinite number of zeroes followed by one.
Here's a quick argument. Suppose 0.9999... < 1.
@Wietlol What's 0.000...1 divided by 10
any inequality is preserved under multiplication by a positive constant. so let's multiply both sides by 10:
9.999.... < 10.
What's 0.000...1 divided by 2? Or 0.000...1 multiplied by 5? @Wietlol
17:52
...ah, dang. this approach doesn't work.
@Semiclassical it does work
but i dont agree with the next step
@Semiclassical Subtract 0.9999...<1 from both sides?
@Semiclassical What are you trying to prove?
Worthiness.
ow wait, it doesnt work :D
17:52
Recall "..." means "and so on". It never ends.
$a<b$ and $c<d$ doesn't imply anything about $a-c$ or $b-d$.
yet again, i know all those proofs, but i dont think they are always valid
they are.
@AkivaWeinberger NaN
NaN / 2 = NaN, NaN * 5 = NaN
I mean 0.000...1 is "Not a Number" as well
17:53
just like inf is not a number
its comparable to 1/3
it's not a number, and yet you're trying to do arithmetic like it is a number
1/3 is a number. confused
1/3 = 0.(3) but 0.(3) != 1/3
0.(3) does equal 1/3
In any case, there are two relevant facts. (a) The real number system has no infinitesimals. (b) There do exist systems with infinitesimals, but these usually will have more than one infinitesimal.
So if you want 0.000...1 to be a thing you'd want to specify which infinitesimal it is.
@Semiclassical well... the arithmetics werent there at all
17:54
you wrote NaN/2= NaN. that's arithmetic.
moreover, if it's not a number, you can't say it's greater than or less than another number.
just someone trying to say
> 100% / inf = 0.(0)
> 0.(0)% = 0%
> 0% * inf = 0%
> 100% = 0%
I mean if you asked a computer to computer NaN/2 that's probably what it'd return
@Wietlol Yeah so the usual resolution to this is to say that most of those operations aren't defined
a / n * n = a (given n is not 0)
and given a is a number.
yes
but that is completely irrelevant
in most examples, a would be 1 or 100
17:57
If everything were defined, math would be so much simpler. As in, more boring. I think a lot of the structure in math comes from the fact that certain things we'd want to work don't.
here's a fairly concrete example. pick a random real number between 0 and 1 (not including the endpoints)
what's the probability that you pick 1/2 ?
0.1234127346172384617324691823647632798467...
1/inf
Infinity is not a real number.
17:58
@skullpatrol so, what is the answer then?
sniped come on
17:58
Daminarked
by what calculation?
sniped, @Akiva
@BalarkaSen That's what I said
I said sniped before you said daminarked
so you are sniped slash daminarked
its 1 / totalNumberOfOptions
17:59
@Wietlol The probability it's between 0.4999 and 0.5001 is 0.0002, right?
That's applicable if there are finitely many options.
So it's less than 0.0002
That's not how probability is defined for continuous distributions.
yes... sort of
i think
18:00
Similarly it's clearly less than any positive number. So it's zero
probably have to include one of the endpoints to make it correct
TL;DR Probability doesn't work right for infinite options. So we had to step in and fix it
and it works kinda weirdly but it works
but you get weird results sometimes
What one needs to distinguish in probability are: "X occurs with probability zero" and "X never occurs."
but this fights 2 logic rules now
If there's finitely many options, the two are identical.
18:01
In general instead of a probability mass function you have a probability density function $f$ corresponding to the random variable $X$ you are working with and $\Bbb{P}(a \leq X \leq b) = \int_a^b f(x) dx$ by definition.
one, 0% chance should never occur
If there are infinitely many, they are not.
that is why it is 0%
Again, no.
"X occurs with probability zero" = "X almost never occurs"
2
18:02
who made this completely illogical statement?
i want to kill someone
i only deal with logic
and logically 0 = 0
Well, there's two scenarios.
0% chance is 0 successes out of any number of attempts
In mathematics, infinitary combinatorics, or combinatorial set theory, is an extension of ideas in combinatorics to infinite sets. Some of the things studied include continuous graphs and trees, extensions of Ramsey's theorem, and Martin's axiom. Recent developments concern combinatorics of the continuum and combinatorics on successors of singular cardinals. == Ramsey theory for infinite sets == Write κ, λ for ordinals, m for a cardinal number and n for a natural number. ErdÅ‘s & Rado (1956) introduced the notation κ → ( λ ) ...
that is logic
"logic" is overrated these days
18:02
Infinity is weird
i dont strike infinity as weird
i programmed it once
@Wietlol Choose a random number from 0 to 1. A random number in [0, 1]. What are the odds you choose something in [0, 1/2]?
hop in to measure theory to see why {0.5} has measure 0 while [0,1] has measure 1
That is, something between 0 and 1/2
18:03
When you have studied enough mathematics, everything will make sense.
@Wietlol It's not illogical. Just that probability for continuous distributions is not what you think it is.
Things only don't make sense when you have studied only a little.
You programmed something you thought of as infinity into a computer.
thats 50%
Well, there are infinitely many options and infinitely many success events, so
would you say infty/infty??
18:04
user image
3
@Semiclassical and the computer will always say that it is larger than any finite number
See, "success events divided by possibilities" doesn't work for infinity
and every other rule applied on infinity is also applied correctly
I mean, yes, the answer is 50%
infty/infty
also correct
but here you have 2 different infinities
18:05
Is it even possible to use finite amount of computer resource to compute an algebraic element that is larger than any real number?
so, you have to specify their origin
one of them is only half as large as the other
@Secret yes
because all of our definable numbers (infinity included) can be defined in a finite number of steps using predicates
via ZFC axiom schema
The distinction that should be drawn is this. If I pick a random real number from 0 to 1, is 1/2 an allowed possibility? Yes, certainly so.
By comparison, is 2 an allowed possibility? No, certainly not.
18:06
@Wietlol OK, so if we call the first infinity $j$, the second one will be called $j/2$. Is that what you're saying
@LeakyNun Interesting, I did not know that infinity can be defined in a finite number of steps
@Secret if it can't, you won't be able to talk about it
that would be correct
So X=1/2 can occur, but X=2 cannot.
@Wietlol So what kind of number is j?
What's j+1?
18:07
However, I can guarantee that if you ask a random number generator to produce samples from this sequence, you will never ever ever see exactly 1/2.
iDunno
@Wietlol you may want to read about this answer and this answer.
i dont know the value of j
so j+1 = j+1
I don't know why I linked that. Just for the title lol
Hm I actually don't know how to continue this
18:08
It is not logically forbidden for X=1/2 to occur, but the probability of it occuring is 0 because there's only one possible way to succeed but infinitely many ways to fail.
@Semiclassical its only 0 because you follow the rule that 0.(0) = 0
otherwise, the probability would have been 0.(0)
how is $j$ behave like infinity if it cannot absorb finite numbers additively?
Sure. I see no reason why one wouldn't follow that rule.
@Secret it will still remain a relative number
@Semiclassical so, 1/inf = 0 ONLY IF 0.(0) = 0
Again, you're reifying infinity into a quantity that one can do meaningful arithmetic on.
18:11
You need to somehow intoduce a notion that it is larger than all finite numebrs else $j$ is just some algebraic element, not a representation of infinity
then you can choose between following that rule or not
then you have a different situation
@Secret true, j+1 is also infinite
but it is larger than j now
exactly by 1
that will mean $j$ is some ordinal number
so its definition is j+1
@Wietlol are you aware how real numbers are defined?
hearing your question, i assume not
18:12
if it cannot absorb 1 and $j+1 > j$ then the only sensible way to define $j$ is it is some infinite ordinal
even though before you asked it, i would have said yes
@Secret That, uh,
why
Hyperreals have infinite things that don't absorb stuff for example
I was almost going to said that
(surreals...)
9 mins ago, by Leaky Nun
user image
@Secret I don't know how helpful this is to be honest
@LeakyNun That's not even the real graph
Fun fact
18:14
@AkivaWeinberger heh
the more you know
I underestimate my understanding of Dunning–Kruger
@LeakyNun that means that... you are either an idiot or an expert
because im quite confident
or is it about myself?
@Wietlol how did you draw this conclusion seeing that I did not say I am confident?
yes. yes, it does.
Well, suppose $j$ is an infinite hyperreal, what wil that lead us?
18:15
ah, i misread competence
still, then im either an idiot or an expert
Eh whatever I'm out bye
@Wietlol whatever
1
Q: Hyperreal probability density?

user175740I'm fairly new to the subject of hyperreal numbers and I'm wondering if there exists an infinitesimal number $a$ such that (in some reasonable sense) $$\sum_{n=1}^\infty a=1$$ ? In other words: Is there a uniform (hyperreal valued) probability distribution on the natural numbers? I hope the qu...

4
Q: Probability theory with the hyperreals?

Ben Blum-SmithForgive the undoubted ignorance of this question. I am out of my element both in probability and in nonstandard analysis. A mathematically curious layperson friend recently had a conversation with me where he wanted a notion of "pick a random integer" (meaning uniformly random). I told him that ...

knowing i passed that first peak, and knowing that i grew in confidence
im closer to being an expert than an idiot
4
:D
in Algebraic/Transcendence Theory, Dec 26 '16 at 15:03, by DHMO
The natural numbers are the numbers specified by Peano's axioms, denoted by $\Bbb N$.
in Algebraic/Transcendence Theory, Dec 26 '16 at 15:05, by DHMO
The integers are the numbers in $\Bbb N \times \Bbb N$ under the equivalence relationship $(a,b) = (c,d) \iff a+d = b+c$. A natural number $n$ is represented by the equivalence class $[(n,0)]$. They are denoted as $\Bbb Z$.
in Algebraic/Transcendence Theory, Dec 26 '16 at 15:10, by DHMO
The rational numbers are the numbers in $\Bbb Z \times \Bbb Z^+$ under the equivalence relationship $(a,b) = (c,d) \iff ad = bc$. An integer $z$ is represented by the equivalence class $[(z,1)]$. They are denoted as $\Bbb Q$.
in Algebraic/Transcendence Theory, Dec 26 '16 at 15:12, by DHMO
The real numbers are denoted as $\Bbb R$. They are defined in the following two ways:
in Algebraic/Transcendence Theory, Dec 26 '16 at 15:14, by DHMO
1. Real numbers as Cauchy sequences: Let $(a_n)$ be a sequence of real numbers such that for any given $\epsilon > 0$, there is a natural number $N$ such that for all natural numbers which are greater than $m$ and $n$, $|a_m - a_n| < \epsilon$. Then, this sequence is a Cauchy sequence, and its limit is defined as a real number.
in Algebraic/Transcendence Theory, Dec 26 '16 at 15:16, by DHMO
2. Real numbers as Dedekind cuts: a real number is defined a partition of the rational numbers into two sets, the smaller set containing no biggest element. The real number is the supremum of the smaller set (and the infimum of the larger set).
18:23
All this can be found in several books.
Read those books for more info. Don't take Math SE as the authority.
@WillHunting I concur
@LeakyNun I just use agree, my vocab is very small, lol.
@WillHunting I agree
Again, I recommend Elliot Mendelson: Number Systems and the Foundations of Analysis for a construction of the real numbers in a few hundred pages.
18:43
Oh yeah I figured out the problem with transcendental numbers
So polynomials of a degree of 5 or more can't have solutions generalized by only algebraic functions...
But transcendental functions are not solutions to polynomials as they are defined
by algebraic functions, you mean elementary ops + taking radicals?
So somehow there's a function that can't be described by algebraic operations, and yet somehow it is not transcendental because it is implied it is the solution tova polynomial
@DaneJoe a number, not a function.
I think this is misleading and I think it results from the fact mathematicians assumed all polynomials could be generalized with radicals before the Abel ruffini theorem
The reason I say this is that the more common definition of "algebraic function" (the one which Wikipedia uses, for instance) is: "In mathematics, an algebraic function is a function that can be defined as the root of a polynomial equation."
18:45
I thought you already figured out that not all roots of polynomials can be written with elementary operations
But remember the discussion
So under that definition the roots are always an algebraic function of the coefficients.
There's a difference between an algenraic number and algebraic.operations
That's where the ambiguity comes from
@DaneJoe yes, there is
Right so that's what I'm saying,
18:46
Under your definitions, yes.
Under the concensus decision you mean
@DaneJoe it's either an equivocation fallacy or an etymological fallacy
Given that Google pings back the Wikipedia definition of "Algebraic function" if you type that in with quotes...no, I wouldn't call yours the consensus definition by any means.
Like I said given how old it is, it would seem the terminology is a misnomer stemming from a period from when mathematicians assumed all polynomials could be generalized by algebraic operators
Only insofar as you insist on "algebraic operators" taking your meaning.
18:48
@DaneJoe you can view it so.
The definition I have is according to multiple sources including wikipedia
So you should be agreeing with me
I don't see the point you're trying to make.
Some algebraic numbers cannot be expressed with algebraic operations. So what?
At least for algebraic operations
Ah. You're using two phrases which sound similar but are distinct.
"algebraic operation" vs. "algebraic operator"
It's a misnomer because algebraic operations are simply radicals and basic operations. But, the solutions to all polynomials must include an operation that is not one of those
18:50
@DaneJoe ok, it's a misnomer, so?
The latter isn't used much, but it does have a determinate meaning and that meaning is more in line with algebraic function, algebraic value, etc.
They should be called "polynomial" operations instead
Yeah, I'd buy that.
So I think from now on if I publish anything related to that I'm going to call them polynomial solutions and polynomial numbers
No. You're conflating things.
18:51
@DaneJoe that is, if you publish anything related to that.
You're correct that the usage of algebraic operations is inconsistent with algebraic number and algebraic function.
But algebraic number is a far more significant concept than algebraic operation.
how to argue that this function is not differentiable at $\frac{n\pi}{4}$ desmos.com/calculator/k32dmnlvas
It's not really conflating, it's updating
@deostroll nice programming skills
@deostroll argue that the left- and the right- derivatives differ
Any argument for "significance" is arbitrary relative to math itself. The terminology comes from an older era, and it's not unheard of to change things. If algebraic numbers are more "significant" the sure people wouldn't mind renaming the group of operators to something like "elementary" or "radical" operators
18:55
@DaneJoe which we did.
I call them elementary operations.
or elementary functions
@LeakyNun thanks
No elementary just means +-/*
It doesn't include radicals
@DaneJoe Of course algebraic numbers are more important than those operations that are called algebraic here (I am not actually sure I have heard them called that before btw)
18:57
I think it would be easier to make a new term than to change a current definition
Elementary can stay as it is, but a new term should be for when it includes radicals

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