Received: from mail-gw0-f61.google.com ([74.125.83.61]) by chain.digitalkingdom.org with esmtp (Exim 4.72) (envelope-from ) id 1OwNHB-000564-Mf; Thu, 16 Sep 2010 15:50:02 -0700 Received: by gwb11 with SMTP id 11sf1635333gwb.16 for ; Thu, 16 Sep 2010 15:49:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlegroups.com; s=beta; h=domainkey-signature:received:x-beenthere:received:received:received :received:received-spf:received:mime-version:received:received :in-reply-to:references:date:message-id:subject:from:to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:list-post:list-help:list-archive :sender:list-subscribe:list-unsubscribe:content-type; bh=t+N6bT2C8jR2UAAnSmq2x/tuqrNs++H1XSa+KDFvmAo=; b=C6NFiR+ZHKsLwjn7cwhQubvmqfchxrt9wBoyAXsvYoPWZIUIoxR+P01vqjziV1iGaI H2kPQ2T7SjAsfQhlGPhWLtNPijO39tQa3vU846LMRFcunNP7v2dP/TU9qx//g0RnINym tAwvAtLJ8MWpNVCY+y+cP6vWQl13GwXP4//hc= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlegroups.com; s=beta; h=x-beenthere:received-spf:mime-version:in-reply-to:references:date :message-id:subject:from:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:sender:list-subscribe :list-unsubscribe:content-type; b=vZ2aC/FyT9ulMa/Ypl2FoUdMk9MpS6WfFuq57vqKGwKxox+4wKgkl4i7sD97E1HVtv KkmrWqgreBBYvqXnbUIf/Qe++nfRiAny67d37ZnxNlir5Dne2JCkQeuEUQ02UvvwQTQ3 lf1XU4g4IheM9YDyzhJDu5L9u/7rMlndzWHec= Received: by 10.91.209.16 with SMTP id l16mr549911agq.1.1284677367364; Thu, 16 Sep 2010 15:49:27 -0700 (PDT) X-BeenThere: lojban-beginners@googlegroups.com Received: by 10.231.193.98 with SMTP id dt34ls991834ibb.0.p; Thu, 16 Sep 2010 15:49:26 -0700 (PDT) Received: by 10.231.182.66 with SMTP id cb2mr508207ibb.4.1284677366487; Thu, 16 Sep 2010 15:49:26 -0700 (PDT) Received: by 10.231.182.66 with SMTP id cb2mr508206ibb.4.1284677366435; Thu, 16 Sep 2010 15:49:26 -0700 (PDT) Received: from mail-iw0-f173.google.com (mail-iw0-f173.google.com [209.85.214.173]) by gmr-mx.google.com with ESMTP id db12si2264230ibb.1.2010.09.16.15.49.25; Thu, 16 Sep 2010 15:49:25 -0700 (PDT) Received-SPF: pass (google.com: domain of oges007@gmail.com designates 209.85.214.173 as permitted sender) client-ip=209.85.214.173; Received: by mail-iw0-f173.google.com with SMTP id 38so2128568iwn.18 for ; Thu, 16 Sep 2010 15:49:25 -0700 (PDT) MIME-Version: 1.0 Received: by 10.231.14.5 with SMTP id e5mr3902515iba.175.1284677365243; Thu, 16 Sep 2010 15:49:25 -0700 (PDT) Received: by 10.231.30.195 with HTTP; Thu, 16 Sep 2010 15:49:25 -0700 (PDT) In-Reply-To: References: <201009152248.22472.phma@phma.optus.nu> Date: Fri, 17 Sep 2010 08:49:25 +1000 Message-ID: Subject: Re: [lojban-beginners] Cauchy sequences From: Ross Ogilvie To: lojban-beginners X-Original-Sender: oges007@gmail.com X-Original-Authentication-Results: gmr-mx.google.com; spf=pass (google.com: domain of oges007@gmail.com designates 209.85.214.173 as permitted sender) smtp.mail=oges007@gmail.com; dkim=pass (test mode) header.i=@gmail.com Reply-To: lojban-beginners@googlegroups.com Precedence: list Mailing-list: list lojban-beginners@googlegroups.com; contact lojban-beginners+owners@googlegroups.com List-ID: List-Post: , List-Help: , List-Archive: Sender: lojban-beginners@googlegroups.com List-Subscribe: , List-Unsubscribe: , Content-Type: multipart/alternative; boundary=0003255762de01a2e30490684220 Content-Length: 15788 --0003255762de01a2e30490684220 Content-Type: text/plain; charset=ISO-8859-1 Given xorxes' word for convergence, I'd translate "{x_k} is a Cauchy sequence representing a real number x" as {x_k} jbize'a x Because in your context of real analysis all convergent sequences are Cauchy sequences (and vice versa). In a more general metric space context "{x_k} is a Cauchy sequence in metric space Y with limit x" {x_k} pornkoci Y fi'o jbize'a x And to answer your maths question. Consider the space of rational numbers. Then there are sequences of rational numbers that converge to irrational numbers. So considered in Q alone, they are Cauchy sequences (because all the terms get closer and closer together) but they fail to have a limit (they converge to a point outside the set). However the rationals are archimedean. This is basically because Cauchy sequences are powerful enough to find 'holes' in the space (for this example, you can find holes in the rationals where you would normally have the irrationals) Ross On Fri, Sep 17, 2010 at 3:31 AM, Ian Johnson wrote: > Now you're past my analysis level; are systems in which Cauchy sequences > don't converge to a limit necessarily not Archimedean? > > Regardless, in the sentence "{x_k} is a Cauchy sequence representing a real > number x", how many predicates would you use? It's sounding like you would > use two. > > > -- > > mi'o bazu klama ti tu zi'o > > On Thu, Sep 16, 2010 at 2:55 AM, Ross Ogilvie wrote: > >> But Cauchy sequences don't necessarily converge to a limit. I would say >> that convergence of a sequence to a limit should be a separate predicate, >> but my vocab isn't up to finding one. You could then indicate the limit of a >> Cauchy sequence with a tagged place. >> >> Ross >> >> On Thu, Sep 16, 2010 at 3:18 PM, Ian Johnson wrote: >> >>> That makes sense, but should that really be the x2? Or should there be >>> another predicate that we use to relate numbers and sequences? For example, >>> we could say: >>> x1 is a Cauchy sequence converging to limit x2 in metric space x3. >>> >>> >>> mi'o bazu klama ti tu zi'o >>> >>> On Wed, Sep 15, 2010 at 10:48 PM, Pierre Abbat wrote: >>> >>>> On Wednesday 15 September 2010 20:01:06 Ian Johnson wrote: >>>> > I found myself being lazy in my analysis class having to repeatedly >>>> write: >>>> > Let x in R. Suppose {x_k} is a Cauchy sequence representing x. >>>> > I was trying to come up with a good word to use to represent this >>>> clunky >>>> > relation, that is: >>>> > x1 is a Cauchy sequence representing the real number x2. >>>> > The thing I came up with first was pretty bad, but I didn't have a >>>> > dictionary on me. It was {listrkoci}. Once I got to a dictionary I >>>> thought >>>> > of {porsrkoci}, which seems a bit better. Does anyone have any better >>>> > ideas? Maybe something that isn't a fu'ivla? >>>> >>>> "porsrkoci" and "pornkoci" are both good, and are different forms of the >>>> same >>>> word (though the Book doesn't say that different rafsi of one gismu are >>>> equivalent, except in lujvo). The alternatives are a lujvo, which would >>>> be >>>> longish, and "kocis.zei.porsi", which is also longish. I'd go >>>> with "pornkoci". >>>> >>>> > To clarify, this should hold, if broda is assigned to this relation: >>>> > li pa ce'o li pa fi'u re ce'o li pa fi'u ci ce'o ... broda li no >>>> > (sorry that I don't know a good way to say "et cetera ad infinitum" in >>>> > lojban.) >>>> >>>> I think the place structure should be "x1 (sequence) is a Cauchy >>>> sequence in >>>> x1 (metric space)". I know a sequence of rational numbers which >>>> converges to >>>> +3 in the real numbers and to -3 in the 2-adic numbers. There are Cauchy >>>> sequences of rational numbers which don't converge to any rational >>>> number, >>>> and there are sequences of rational numbers which are Cauchy sequences >>>> in one >>>> metric but not in another. >>>> >>>> Pierre >>>> -- >>>> li fi'u vu'u fi'u fi'u du li pa >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Lojban Beginners" group. >>>> To post to this group, send email to lojban-beginners@googlegroups.com. >>>> To unsubscribe from this group, send email to >>>> lojban-beginners+unsubscribe@googlegroups.com >>>> . >>>> For more options, visit this group at >>>> http://groups.google.com/group/lojban-beginners?hl=en. >>>> >>>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "Lojban Beginners" group. >>> To post to this group, send email to lojban-beginners@googlegroups.com. >>> To unsubscribe from this group, send email to >>> lojban-beginners+unsubscribe@googlegroups.com >>> . >>> For more options, visit this group at >>> http://groups.google.com/group/lojban-beginners?hl=en. >>> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Lojban Beginners" group. >> To post to this group, send email to lojban-beginners@googlegroups.com. >> To unsubscribe from this group, send email to >> lojban-beginners+unsubscribe@googlegroups.com >> . >> For more options, visit this group at >> http://groups.google.com/group/lojban-beginners?hl=en. >> > > -- > You received this message because you are subscribed to the Google Groups > "Lojban Beginners" group. > To post to this group, send email to lojban-beginners@googlegroups.com. > To unsubscribe from this group, send email to > lojban-beginners+unsubscribe@googlegroups.com > . > For more options, visit this group at > http://groups.google.com/group/lojban-beginners?hl=en. > -- You received this message because you are subscribed to the Google Groups "Lojban Beginners" group. To post to this group, send email to lojban-beginners@googlegroups.com. To unsubscribe from this group, send email to lojban-beginners+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/lojban-beginners?hl=en. --0003255762de01a2e30490684220 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Given xorxe= s' word for convergence, I'd translate "{x_k} is a Cauchy sequ= ence representing a real number x" as
{x_k} jbize'a x

Because in your context of real analysis all con= vergent sequences are Cauchy sequences (and vice versa). In a more general = metric space context

"{x_k} is a Cauchy sequence in metric spa= ce Y with limit x"
{x_k} pornkoci Y fi'o jbize'a x

And to answer your maths que= stion. Consider the space of rational numbers. Then there are sequences of = rational numbers that converge to irrational numbers. So considered in Q al= one, they are Cauchy sequences (because all the terms get closer and closer= together) but they fail to have a limit (they converge to a point outside = the set). However the rationals are archimedean. This is basically because = Cauchy sequences are powerful enough to find 'holes' in the space (= for this example, you can find holes in the rationals where you would norma= lly have the irrationals)

Ross

On Fri, Sep 17, 2010 at 3:31 AM,= Ian Johnson <blindbravado@gmail.com> wrote:
Now you're past my analysis level; are systems in which Cauchy sequence= s don't converge to a limit necessarily not Archimedean?

Regardl= ess, in the sentence "{x_k} is a Cauchy sequence representing a real n= umber x", how many predicates would you use? It's sounding like yo= u would use two.


--

mi'o bazu klama ti tu zi'o
On Thu, Sep 16, 20= 10 at 2:55 AM, Ross Ogilvie <oges007@gmail.com> wrote:
<= /div>
But Cauchy sequences don't necessarily converge to a= limit. I would say that convergence of a sequence to a limit should be a s= eparate predicate, but my vocab isn't up to finding one. You could then= indicate the limit of a Cauchy sequence with a tagged place.

Ross

On T= hu, Sep 16, 2010 at 3:18 PM, Ian Johnson <blindbravado@gmail.com&= gt; wrote:
=
That makes sense, but should that really be the x2? Or should there be= another predicate that we use to relate numbers and sequences? For example= , we could say:
x1 is a Cauchy sequence converging to limit x2 in= metric space x3.=A0


mi'o bazu klama ti tu zi'o
=

On Wed, Sep 15, 2010 at 10:48 PM, Pierre Abbat <phma@= phma.optus.nu> wrote:
On Wednesday= 15 September 2010 20:01:06 Ian Johnson wrote:
> I found myself being lazy in my analysis class having to repeatedly wr= ite:
> Let x in R. Suppose {x_k} is a Cauchy sequence representing x.
> I was trying to come up with a good word to use to represent this clun= ky
> relation, that is:
> x1 is a Cauchy sequence representing the real number x2.
> The thing I came up with first was pretty bad, but I didn't have a=
> dictionary on me. It was {listrkoci}. Once I got to a dictionary I tho= ught
> of {porsrkoci}, which seems a bit better. Does anyone have any better<= br> > ideas? Maybe something that isn't a fu'ivla?

"porsrkoci" and "pornkoci" are both good, and are= different forms of the same
word (though the Book doesn't say that different rafsi of one gismu are=
equivalent, except in lujvo). The alternatives are a lujvo, which would be<= br> longish, and "kocis.zei.porsi", which is also longish. I'd go=
with "pornkoci".

> To clarify, this should hold, if broda is assigned to this relation: > li pa ce'o li pa fi'u re ce'o li pa fi'u ci ce'o .= .. broda li no
> (sorry that I don't know a good way to say "et cetera ad infi= nitum" in
> lojban.)

I think the place structure should be "x1 (sequence) is a Cauchy= sequence in
x1 (metric space)". I know a sequence of rational numbers which conver= ges to
+3 in the real numbers and to -3 in the 2-adic numbers. There are Cauchy sequences of rational numbers which don't converge to any rational numb= er,
and there are sequences of rational numbers which are Cauchy sequences in o= ne
metric but not in another.

Pierre
--
li fi'u vu'u fi'u fi'u du li pa

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