Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site ucbvax.ARPA Path: utzoo!linus!decvax!decwrl!ucbvax!usenet From: usenet@ucbvax.ARPA (USENET News Administration) Newsgroups: net.math Subject: Re: How Many Continuous Functions Are There Message-ID: <10585@ucbvax.ARPA> Date: Tue, 8-Oct-85 05:30:38 EDT Article-I.D.: ucbvax.10585 Posted: Tue Oct 8 05:30:38 1985 Date-Received: Thu, 10-Oct-85 06:39:40 EDT References: <310@ihnet.UUCP> <10556@ucbvax.ARPA> <3368@pur-ee.UUCP> Reply-To: tedrick@ucbernie.UUCP (Tom Tedrick) Organization: University of California, Berkeley Lines: 28 In article <3368@pur-ee.UUCP> yena@pur-ee.UUCP (Anthony T Yen) writes: > > >> Since the cardinality of the set of polynomials > >> mapping R -> R is C, and any continuous function > >> mapping R -> R is the limit of a sequence of >**>> polynomials (the card of the set of such sequences >**>> again being C), therefore the card of the set of > >> continuous functions is also C. > >Nope. Consider: Each real number is the limit of a sequence of >rational numbers, but reals are uncountable and rationals are. > >The reason is that each limit is (sort of) defined by a countable >subset of (in your case) polynomials, so there are as many limits >as there are countable subsets (actually, there are less, but that >can be taken care of easily [details are left for homework :-) ]). >There are C polynomials ---> there are aleph-0 * C countable subsets. > >Incidentally, C = aleph-1. >( C <= the number of finite subsets of reals = aleph-1 >and C >= the number of reals = aleph-1 --> C = aleph-1) >and so aleph-0 * C = aleph-2. > >================================================ >Hao-Nhien Qui Vu ( pur-ee!vu ) Purdue University I don't understand what is wrong with the original argument. I'm too tired to deal with this now, can someone check this out?