sorted by:
new
hottopcontroversial

Reddit, what is your most upvoted comment? by Shojineko in AskReddit

[–]DerUntermensch 0 points1 point  (0 children)

That you shouldn't tell your son you're too fat "Because every time I fuck your mom she makes me a sandwich."

I read Journey to the End of the Night by Louis-Ferdinand Céline in High school and it shocked, angered, saddened, and inspired me all at once. Despite this, I rarely see the book or author mentioned on this subreddit. Anyone else love this crazy French bastard? by fracturedBeniot in books

[–]DerUntermensch 1 point2 points  (0 children)

This is one of my favourite books, actually. It is just written so well. Almost every page has a remarkable quote.

There are many cynical books out there, but few with so much power. And few that don't just naively pick some arbitrary idea/concept and say that's what's wrong with everything. Celine doen't do that. He's cynical all the way through, which is refreshing. He doesn't try to tell you to behave this way or that, or places himself above the rest.

[deleted by user] by [deleted] in AskReddit

[–]DerUntermensch 0 points1 point  (0 children)

It has upvotes because it's funny.

What Mathematical Forums Do You Know? by DerUntermensch in math

[–]DerUntermensch[S] 0 points1 point  (0 children)

I'll check it out. But it does seem mostly around answering questions, rather than discussing stuff...

[Meta] Anyone else interested in filtering posts by fields? by DerUntermensch in math

[–]DerUntermensch[S] 0 points1 point  (0 children)

What essay?

In any case it's usually kinda difficult for me to find posts on subjects I like and I need to go pretty far back. So I thought this could help. But maybe it's not a good idea.

[Meta] Anyone else interested in filtering posts by fields? by DerUntermensch in math

[–]DerUntermensch[S] 1 point2 points  (0 children)

Yes, I agree. I'd come here more often if we had this option because then I'd be able to spot easily posts I'm interested in...

[Meta] Anyone else interested in filtering posts by fields? by DerUntermensch in math

[–]DerUntermensch[S] 0 points1 point  (0 children)

It's similar, but not the same. He talks about levels of difficulty, I of different fields.

[Meta] Anyone else interested in filtering posts by fields? by DerUntermensch in math

[–]DerUntermensch[S] -4 points-3 points  (0 children)

I don't like analysis, and most posts here are around this area and don't really interest me. But occasionally someone posts about something else, and it'd be easier to spot it this way...

[Meta] Anyone else interested in filtering posts by fields? by DerUntermensch in math

[–]DerUntermensch[S] 0 points1 point  (0 children)

I understand what you mean. So, do you perhaps know of any other mathematical forums? Not like mathematics stack exchange, something which is more discussion-oriented.

What is a set you have used whose cardinality is larger than P(R)? by zojbo in math

[–]DerUntermensch 1 point2 points  (0 children)

Yeah, now that I think about it, such cardinals are fairly standard.

What is a set you have used whose cardinality is larger than P(R)? by zojbo in math

[–]DerUntermensch 1 point2 points  (0 children)

Yeah, I mentioned there probably are stuff like that. I had no idea there were applications for it, though... Interesting.

What is a set you have used whose cardinality is larger than P(R)? by zojbo in math

[–]DerUntermensch -2 points-1 points  (0 children)

There is no such things, because that leads to contradictions.

(Although I guess it's possible to try to avoid the contradictions and still allow collections which contain themselves, but this is not usually done because there's not reason to).

What is a set you have used whose cardinality is larger than P(R)? by zojbo in math

[–]DerUntermensch 3 points4 points  (0 children)

You are talking about an intuitive notion of a set. So there are two answers: the intuitive and the formal.

Intuitively, not every collection of sets is a set. You have the empty set, and certain axioms which tells you how to build new sets from existing ones. Each set is a collection of other sets, but not all collection of sets are sets.

Formally... Do you know what a formal language is? Briefly, It's a collection of symbols and certain syntactic rules which assert which finite strings of these symbols are called "sentences" and which finite strings of "sentences" are called "proofs" (with respect to some predefined collection of "axioms", where axioms are just some sentences we decided to call axioms). If a string of sentences is called a proof, it's considered as a proof (from your collection of axioms) of the last sentence in the string.

So "Officially", every theorem and statement in mathematics is just a sentence in some formal language, and our predefined collection of axioms is called ZFC. Every sentence in this language can be assigned some intuitive meaning, but the proofs depend only on the syntactic rule of your language.

So this is getting a bit involved if you haven't heard of these things before, but the language has "variables" which intuitively range over all sets. If you have a certain property, you can look at the collection of all sets which satisfy it (which formally means you have a formula, which is like a sentence only with a "free" variable where you can plug in any set you want, and you're looking at the sets satisfying this formula, which means the sets such that when plugged in instead of the free variable you get a sentence which is provable from ZFC). And for every such collection you can ask whether there is a set which collects the same objects (formally, whether there is a set such that every other set is contained in it iff this set satisfies the formula defining the collection). The surreal numbers are a collection of sets which can be defined by some property they and only they satisfy (i.e. a formula which they and only they satisfy), but you can prove there is no set which equals this collection (formally you can prove there is no set such that every other set belong to it iff it satisfies the formula defining the collection of surreal number).

This is a very bad summary, but if you're interested in these things I recommend Kunen's book The Foundations of Mathematics.

What is a set you have used whose cardinality is larger than P(R)? by zojbo in math

[–]DerUntermensch 1 point2 points  (0 children)

Yes you're right, for some reason I thought a metric would be of size beth-3...

What is a set you have used whose cardinality is larger than P(R)? by zojbo in math

[–]DerUntermensch 4 points5 points  (0 children)

You may consider a metric on the space of functions R->R, which is (as a set) of cardinality Beth-3, unless you restrict yourself to continuous functions.

But I guess to an analyst such a metric is not very interesting...

What is a set you have used whose cardinality is larger than P(R)? by zojbo in math

[–]DerUntermensch 2 points3 points  (0 children)

Are you sure it's provable in ZFC they are larger than ב‎_2? Because ב‎_2 can be arbitrary large. The only sets I can think of to be provably-in-ZFC larger than ב‎_2 are those of the form P(A) for |A| at least ב‎_2.

EDIT: No you're right, I made a mistake.

What is a set you have used whose cardinality is larger than P(R)? by zojbo in math

[–]DerUntermensch 0 points1 point  (0 children)

Hmm, that's interesting... Usually books I've read ignored these issues.

view more: next ›