#question about point at infinity
666 messages · Page 1 of 1 (latest)
It's constant in that it would be a single value
but is it constant in that 1/0 + k doesnt equal 1/0
a property of all vaules that are constant is that adding/subtracting another constant must not equal the orignial value
like inf is not constnat because inf + 1 = inf
Where are you getting this?
I saw it one time ill try to find it again
oh way idk maybe its just something I came up with
nvm then
but I think that should also be trivial right?
if a is constant and k is another constnat than a + k cant equal a
but if a is not constant and k is a constant than a + k can equal a
or perhaps you cant maintuplate a value that is constnat to be nonconstnat
since 0 is a constant the reciprical must also be constant
maybe
look up field axioms
we don't consider infinity a real number or complex number since they're both fields, including infinity violates one of the axioms
right
but what about when 1/0 is deifned as a point at infinity
is it a constant?
what set are we working in here
okay what do you mean by constant?
also you might wanna check out the Riemann sphere since that seems relevant
yes
it can only ever be its self
or like
1/0 + another constant doesnt equal 1/0
actually this is only true from the perspective of 1/0
or "locally" although Im probably using that math term wrong
It's hard to make sense of (1/0) unless you define it rigorously
ohh
or projective number line
1/0 is used the same in both
reiamm sphere is just the projective number line but complex
I still don't exactly know what you mean by constant in this context
only exists at one point
as opposed to?
infintity which doesnt exist at only one point
like?
like on the projective number line
any value thats not at the point at 0 or 1/0 has a value of inf or - inf right?
becuase every location is infinitly far away from 0 on the projective real number line
not include the location of 0 or 1/0
actually this is my assumption I could be wrong
This is for Riemann sphere
it's implied by the definition
oh okay
z+inf=inf
ah
substitute z+inf for inf and you get inf=inf lol
right right
but also
like
okay imagine if you zoom into 1/0
from this perspecitve 0 is infinitly far away
so from that perspective using the same logic that inf + z = inf
0 + z = 0 since all finite number are equally infinitly far away
but we know 0 to be constant so perhaps 1/0 is also
I don't know if this answers your question but on the Riemann sphere z/0 is always infinity regardless of z
(unless z is 0)
this is my understanding not rigoursly defined
meaning 1/0=2/0
yes I agree
thats what I thought
hmm
ya idk
wait do you understand
that like
what I was trying to ask like does 1/0 exist at only one point compared to that inf can exist at any point on an infinitly long line projected into a finite distance
becuase all points are infinitly far away
What else would it be? When is a value ever something besides itself?
0/0
can be anything
does 3 only exist at one point? I'm still confused lol
so I was just making sure that 1/0 is always its self
yes
sorry its becuase im bad at communicating rigoursly and often assume what I say intutivily makes sense haha
my bad
I havent been taught/learned proofs or logic yet
so
oh wait are you confused because some infinities are different sizes (in reference to cardinality)
um
well
not in the context of this
ok cool nvm lol
ya ya
in the context of cardinality could "different" 1/0 have different sizes?
not really
unless 1/0 doesnt mean anything in that context
that doesn't really make sense lol
No you're reaching the same problem here. If you define 0/0 to be something, then it's going to be just that.
ignore my comment on cardinality
oh you know I also that that 1/0 is a numerical represntation for uncountable infinity?
i think this might be wrong though idk
0/0 is undefined because division by zero with finite numbers does not work if you want to keep all the field axioms
wait really
right
If you don't care about the field axioms, then you can define 0/0 to be any value you want without issue
we're throwing out field axioms here this is about the projective real line I think
wait does any model define 0/0 to be meaningful?
Same with 1/0
Not that i am aware of, no
before trying to think of 1/0 as something that could exist people said 0/0 and 1/0 equally dont exist but I always felt 1/0 to have more signifciance and be more consistient
are you trying to say like "are all 1/0s equal to all other 1/0s?"
does this make sense or nah lmaoo
im pretty sure this should be the cast
case*
since all 0s should also be equal to all other zeros righ
In the riemann sphere that's the case
you cant have a smaller magnitude than zero thats like saying how do you get closer to something your touching or how do you move slower than standing still
right
does this make sense?
I don't think the question makes sense by itself, you need to state what set/system you're working in. There could be some system where 1/0≠1/0
hmmm
if we're working in real numbers it doesn't make sense either way so we don't even consider it
do you know of any?
same with complex numbers
Riemann sphere
no but 1/0 does = 1/0
ohh
cause its only a single point
I mean I could come up with one right now lmao
just like 1=1 or 2=2
all things that equal 1 or 2 must exist at the exact same point
do it
actually nvm lmao
that'd contradict deeper axioms I don't know enough about to talk about
but I could define a set where 1/0≠2/0
hmm
are you trying to say 1/0 < 2/0?
I feel like we're getting off track
i mean idk Im okay with it
as opposed to the Riemann sphere which defines anything/0 as infinity
it does relate I think
right
oh also did you know the infinity it uses is a "nuetral" infinity
neither postive nor negative
which is pretty cool
sure
I think its becuase the sign of 1/a is the same sign as a and since 0 is neither postive or negative 1/0 must also be
not necessarily
how
you're thinking with limits rn
no
im not
there is no general limit of 1/0
but 1/0 its self is neutral
I think
well you're applying field algebra rules to things that aren't fields
but can it still be an explation?
i think it can
we don't like to rely on intuition in pure math
I know
oh ya
hm
but I think its still rigours like that
here
on a line
the closer you get to zero
the reciprical of that value would be inversly farther from zero
as the denominator gets closer to zero right?
my point is I could say 1/0 is -infinity and it'd still work the exact same way
you could but it would be redundant
+1/0 = -1/0 the same way +0 = -0
becuaes there is no positve or negative
which works exactly like what used to be "infinity"
this is part of why you can't rely on intuition here lol
okay okay
what?
then its not equal to 1/0
so shouuldnt it not be a valid comparrison?
1/0=-infinity
um
z/0=-infinity for all z
sure
but this would be a differnet defintion and a diffenretion set
so my intution could still be correct becuase im strictly using an explation to descirbe the behvior in the remiann sphere
wait you're talking specifically about the Riemann sphere?
do you wanna hear the other intutive way of thinking I had
yes
or projective number line
oh that makes things easier lol
its defined in the same way
I literlly already said that 😭
right?
or maybe idk
but ya
on the Riemann sphere infinity is as much of a constant as any other number
like I was thinking as a gets closer to 0 on a number line 1/a would get further but when a is on the same point as 0 "a = 0" its the closest possible distance to 0
so the recipricle of 1/0 would inversely be the maxium distance away from zero
and on the projective real number line the number line is a circle and the maxium distance away from a point on a circle is the point directially above on the other side of the circle 😎
1/0
since 0 isnt on either the postive or negative side of the number line a point directally above would also not be on either side and exactly in the middle
niether postive or negative
when you say projective real number line do you mean the projectively extended real line
yes
OH SHOOT
its also defined that 1/(1/0) equals 0
yoo this is what I thought at the very beggining as well
althought 1/0 * 0 is still undefined
1/0 is as constant as any other number on the projectively extended real line
anything else lol
does this make sense?
and this
you're thinking of it intuitively which is good for brainstorming a proof
but you could draw the set in a different way and your intuition would break
but would it be the same set?
do it
but projecting 2 sets diffentially can sometimes lead to diffenret outcomes right?
as long as you trust me when I say that the set containing every element in this representation is equal to the set of the projectively extended real line, then this is the exact same set but represented differently
I'm not sure what you mean and I haven't taken differential geometry yet
this just kills any intuition you have
obviously the other representation is better since it actually gives you an intuitive understanding of what's going on
this is not the same set
but you can't rely on your intuition to answer a question
intuition can lead you in the right direction
is that 2 diffenret points of infiniy?
two sets are equal if they contain the same elements
but it doesnt mean the model is equal
your values arent following the same defined rules
its not compactified by the point at infinity
so its not the same
right>
it's still compactified but "compact" has a different geometric meaning than what you're used to
I know
also
are you sure
how is it compact
you put points that arent connected to the real number line
so how could they compact it
there doesnt exist a finite subcover
right?
compact doesn't mean points need to be touching in the geometric sense
that's a property of how we usually represent it
i think it doesnt
does*
in the one point compactificaiton
1/0 acts as the finite subcover
negative numbers U positive numbers U 0 U infinity
but in your diagrram 1/0 doesnt touch +inf and -inf
so how can it be the same
surely this doesnt count as one point compactifcaiton
also the line you drew is finite with the ending value being 69 lmao thats not even the real number line
are these the integers?
assume there's nothing between 0 and 1 or 1 and 2 or -1 and -2 etc
what
okay so there is no direction to this line
this isnt a number line
number lines must increase or decrease in a specfic direction correct?
I'm not sure what the definition of "number line" is but if that's the case then don't call it a number line lol
hm
the point is that this is still the set of integers just represented differently
and represented in a way that kind of deletes your intuition of how integers work
also this isnt equvilent to the remainn sphere cause its not only a set right its also the geomtry
-2 is still smaller than 2, it's just not intuitively implied by this representation
like 2 sets projected diffenretially can be defined as seperate things
yes
becuase its not on a number line
so take away the line
{0,1,-1,2,-2,3,-3,4,-4,5,-5...}
"riemann sphere" refers to the model whereas "extended complex numbers" refers to the set the model is describing
right
but also one more then
thing*
try again with a differnet example
because
this isnt a diffenret projection of the reimmann sphere and since my intution was in the context of the reimann sphere it is not a valid counter argument
its not homo something
homotogical
wait
homological
perhaps
what do you mean by "projection" here
also I thought we were talking about the projectively extended real number line not the riemann sphere
as in
you cant just tear the 2 ends apart of the remainn spehere and still claim it is equvilvant
becuase the reiamman sphere is only unqiue becuase it has connected ends
well the concept of a limit takes a different intuition when you represent it in this way
it's still the exact same set just represented with a different model
infinity still compactifies the real line it's just that "compact" no longer has anything to do with numbers "approaching" other numbers and only really makes sense in the formal definition of a limit
then there would be differnet intution depending on the model right?
yeah exactly
which is why you can't rely on intuiton to prove things (or verify a solution to something)
proofs have nothing to do with models they have to do with what the models actually describe
intuition varies depending on the model you conceptualize
which is why topology is OP lol you can find your way around difficult math questions with basic geometric intuition
oh ya well also LMAO im not trying to "prove" it i know you cant with intution but I already know its proved and am using my own thinking
did it make sense to you?
well but you were trying to find an answer to something
no
its already known
that 1/0 is neither postive or negative
and I think I gave valid explations
although there most likely exists rigours ones
oh
the model most people think of when they think of the projectively extended real line is a good intuitive way to remember that infinity is neither positive nor negative yeah
I thought you were trying to use that model to prove that that's the case
no
I was trying to say 1/0 is neither postive or negative
did you read my intution?
I said 1/0 would exist as a point dirrectionally above 0 and since 0 is neither on the postive or negative side 1/0 would also not be either postive or negative
yeah
I'm saying that's a good way to remember that lol
it's just not a sufficient proof which I now assume isn't your goal here
👍
yaaa
i know
but
does it make sense
yeah that makes sense
nice becuase
did you know this was actually my thinking before I even knew these math concpets existed LMAO
in math class I thought this property existed and I got really lucky that it actually does
that's cool
you could've come up with the projectively extended real line lol
there are other models where that isn't true though
perhaps but only the intuion not the proofs
i know
okay cool lol
for my career path I wanna go into therotical fields and I think i can think abstractly
keep coming up with random shit in math class that's how you get both creative and good at math
im always fasinated by things that people say "dont exist" but sometimes they do
yaaa
but lowkey im behind compared to other math people we werent taught intergrals 😭
and Im defintly belove average in this math discord LMAO
you can literally invent a new field of math by figuring out a way to make something that conventionally "doesn't exist" to make sense
what year/grade are you?
I think if I can learn proofs and logic it will help me a lot becuase i can only make ideas with intution which wont be taken seriouslly or formal
just graduated grade 12
yaaa
what was the last math class you took?
weird
yes
its candain
canadain*
so
I think they had it before but it was too hard for the classmaybe
linear algebra is where that starts for most people
yaaa
might wanna take a proof writing course first though
ohhh ya also I thought of a physics thing as well like if time was plotted on a projective number line
in fact here want a basic proof exercise from my linear algebra textbook lol
then after an infinite amount of time it then loops
so a new universe would begin
and I found out this property also already exist in a theroy 😎
penrose diagrahms
cool
yes
each vertical length of the "universe square" represnet an infinite length of time
idk shit about this lol I need to take differential geometry
this is einstein's field equations right
i dont either I just regonize the looping property lmao
um
i think its derived from it
like its called penrose diagrams
oh
and the curved line in the middle is a therotical path you could take to travel to differnet universes
although it requires a type of negative mass which most likely doesnt exist according to the majority of scientists
does this make sense?
kind of yeah
niceee
it'll make more sense after I learn more math I think lol
rightttt well I mean i probably only "think" it maekse sense to me becuase I dont know what I dont know
and dont understand the proofs really
so like
the way I compherend things is kinda of cheating lma
lmao
no that's okay
like a fake compheresion haha
it's not like intuition is useless
ya I know its like not my fault
no it's good to have though
if you can think of problems intuitively it'll lead you in the right direction to proving stuff (most of the time)
its jus the only way for me to do it so its not as good espially when I can only communicate that way becuase others then need to take extra time to decripher my informal methods and stuff
ya thats what I was wonderin
but someone in the server said this
wanna try this proof exercise
oh wiat nvm
oh ya bet
ok I have to explain what a field is
wait I gotta help you? oh bruh im cooked LMAO
no you're not helping me I'm giving you a proof problem
you don't need notation
oh okay
you can use english
a field is just a set with two binary operations (addition and multiplication) such that these properties all hold:
real numbers are a field for example
rational numbers are a field
complex numbers are a field
they're similar
in a ring multiplication doesn't need to be commutative
in a field multiplication is commutative
oh
i dont understand
also what does ring mean
in this contet
like a circular number line?
let's focus on fields for now lol
aight bet
basically if you have a set, and multiplication and addition follow each of these rules in that set, it's a field
an example of a non-field would be the set {1,0} for example, with the traditional definitions of addition and multiplication, since the additive inverse property isn't guaranteed (1 doesn't have an additive inverse in this set)
prove that, if x is a member of a field, -(-x))=x
that's the question
actually here use these axioms instead
they actually explain it a little bit better
{1,0} isn't a set since it violates the additive inverse axiom: there's no additive inverse of 1 in {1,0}; there's no value "-1" such that 1+(-1)=0
if you're stuck I can give you the answer
take a few minutes though
hmm okay lets see
don't use the first axioms I posted use the second image
k
i think I got it
wait
no hold on
lmao
i got it
-(-x)) = x
-1 * (-x) = x
-x = x/-1
-x =-1 * x/1
-x = -1 * x
-x = -x
right?
close
we don't know that -1*x=-x yet
so you'll have to prove that for it to be sufficient
thats what I was thinking
and then also division isn't defined yet, but you can multiply by multiplicative inverses
got it
can i just say that then
yeah so in step 3 you'd have to write -x=x*(-1)^-1 instead
-1 *x = -x
0 = -x + 1 * x
0 = -x +x
this is true as the additive inverseinverse therofore -1 * x = -x
your proof is backwards but yeah that works
ya I thought that lmao
actually wait
but nice did I do it? 😎
this is ALMOST right
if you add the additive inverse of 1x to both sides you get that -(1x)=-x
between step 2 and step 3 (reading it backwards)
so you need to prove that this is equivalent to (-1)*x=-x
got it
1 * x = x
a* (b * c) = (a * b ) * (c)
-1 * (x * 1) = (-1 * x) * 1 = (-1 * x) = -1x
YUHHH 🔥
good job
i am ensiten
ok can I embarass you now lol
come up with an elaborate solution just for someone else to prove it in like 3 steps lmao
thats more simple ha
well ya though right often in new theroies there are first eleborate theroys then simiplifed theroys in the future
just like black hole singularitys
yeah
only recnetly were we able to simplify them
that's called abstraction
hmmm okay
which is kind of controversial for beginning undergraduates lol (like me)
i think my brain thinks longer proof = better/more rigours proof LMFAO
since often it gets rid of intuition
which is wrong
how so?
i was thinking about doing this but I didnt think it was defined in the axioms that you can add something to both sides and it still being equal
oh that's a basic property in all of arithmetic
i know
x=x therefore f(x)=f(x) or f(x,y)=f(x,y)
meaning if we let f(x,y)=x+y, then
x=x
f(x,y)=f(x,y)
x+y=x+y
but so is -1*x = x but I was still asked to prove it
i think this is cheating
nope
there can be a set where -1 isn't even defined
brh
isnt this cheating though cause like this proof doesnt explain that adding something to both sides maintains equvilenace
and you cant say its trivial
that actually got me at first when I started linear algebra
what did
this
well
isnt it?
like sure its simplfied but i mean
it missed a step no?
ill ask chat gpt and ill see what it says
usually in algebra classes that's automatically assumed since unless you're working in some extremely nonstandard area that's always true in math
at that point you'd have to define what it even means for two things to be equal
in the context you gave me the only things you are allowed to assume are the axioms
and there isnt an axiom in the ones you gave me that claim this
sorry lol
HA so its not my fault
these axioms add to the ZFC axioms
yes
whenever someone asks you a math problem assume you're working in zfc as well lmao
it was just so basic that like i thought you could only assume the axioms were true and nothin else
you might like set theory then lol
you didn't seem to have a problem with dividing both sides by -1 though lol
oh ya
idk
maybe im giving exuces so make me self not feel dumb HA
I don't mean this in a condescending way but get used to feeling dumb in math lol
oh ya
no its okay that makes sense
I thought of this quote
"the more you discover the less you know"
i think somone already said that though
exactly
people always stealing my ideas 😭
lmao just playing
also there will always be moments where you're thinking "what the fuck is happening what does that mean why is that true huh??? etc" when you're learning math
the higher you go the more that happens
"what the fuck is happening what does that mean why is that true huh??? etc" when you're learning math" i had a moment like this were I tried to understand why a harmonic series was divergent
I had to learn to get not hate myself when that happens lol
and I tried with intuion
but i only came to the wrong conclusion becuase someone gave me the wrong awsner for something
otherwise I would have been correct
damn
it was like half a year ago i wasnt as good with math but bassically someone asked does 1 + 1/2 + 1/3 + 1/4 + ...
and I said it converges (incorrrect) but I later made my own intutive proof
this series can be represnt with an infinite number of finite sseries
however the sum of an infinite amount of finite sums is infinite
1 + 1/2 + 1/3 + 1/4 + 1/5 + ...
can be expressed as (1 + 1/2 + 1/4 + 1/16 + ...) + (1/3 + 1/9 + 1/81 + ... ) + (1/4 + 1/16 + 1/256 + ... ) + ...
these are finite sums however it would take an infinite amount of fininite sums to fully represent the intial sum therfore the intial sum is also infinite and divergent
that's an interesting proof lol
is it valid?
I'm not sure
im sure not rigours
I don't know enough about infinite series
does the proof make sense
it does
okay bet
it looks rigorous but I'm not sure if rearranging elements in an infinite series yields the same result
it does
well it doesn't if it's conditionally convergent
In mathematics, the Riemann series theorem, also called the Riemann rearrangement theorem, named after 19th-century German mathematician Bernhard Riemann, says that if an infinite series of real numbers is conditionally convergent, then its terms can be arranged in a permutation so that the new series converges to an arbitrary real number, or di...
oh
which is extremely weird LOL
I haven't really thought about infinite series in a while I'll probably learn more about them in analysis
WHAT
THATS IMPOSSIBLE
HOW DOES IT DO THAT
wait my brain is on to something
but I dont know what its thinking
LMFAO
I THINK
IT
um
i think it stretched out larger values further
which makes it differnt
wait
RAH
my brain is working
okay
hmmm
it doesnt have enough time to converge back maybe to zer
wait no idk
also there's the famous 1+2+3+4+5...=-1/12
fuck that bull shit
i know that
it's not equal to -1/12
but it's a way to give an answer to a divergent series
it shouldnt be aloud to say that
its not in the same way
i have heard
if we can do this 1+2+3+4+5...=-1/12 then we cant ever have a sum that equals anything
righht?
it's not "correct"
it's a way to assign a value to a divergent series
since it's obviously divergent lmao
it just shows that you have to be really careful manipulating infinite series since they act really weird sometimes
okay good
I'm guessing the reason it's "wrong" is because the concept of a limit isn't being used here or theres some rule of limits being broken
oh here btw
I don't know enough about this subject though
this is chat gpt
but i think its accurate
Notice how the partial sums begin to approach a positive value and diverge from zero. This arrangement manipulates the balance between positive and negative terms, causing the series to converge to
ln2 instead of 0
i think in the series the rearrange meant makes it so thats there "more" postive terms
like same thing with a series thats 1-1 +2-2 + 3-3 + 4-4 + 5-5 + 6-6 + 7-7 + ...
but does this series 1 +2 +3 -2 +4 +5 +6 - 3 + 7 +8 +9 +10 -4 also not converge to 0 because I rearranged it
i think i understand
it looks like unconditionally convergent series can be rearranged to get the same answer though
which means I think your proof is correct
wait no it diverges to infinity
yaya
ok I gotta go byebye
same LMFAO
fun math talk lol
sure lol dm me shit
sometimes I be doing comp math questions if you wanna try to figure them out with me sometime
bet bet
solved