mm-225 === Subject: Re: Homeomorpsms and compactness Adjunct Assistant Professor at the University of Montana.>I have a small question wch I have been unable to solve on my own. I>know that if f: M->N is a homeomorpsm, thenK compact in M <=> f(K) compact in Nand I'd like to know if the opposite way holds, that is, if f is>bijective andK compact in M <=> f(K) compact in Nis f then a homeomorpsm? I have proven ts to be true for locally>compact spaces, but I would like to know whether the result holds>generally.Any help?I feel dumb. Here's a counterexample if your definition ofcompactness includes the separation axiom.Let M and N both have as underlying sets the 2 elements set {x,y}. LetM be given the indiscrete topology, and let N be given the Sierpinskytopology: the open sets are the empty set, the total set, and {x}.Every subset satisfies the finite subcover property. But the onlysubsets that satisfy the separation axioms are the empty set and theone element sets, in both M and N. Therefore, any bijection between Mand N will satisfy that K compact in M if and only if f(K) is === H#SM:U1U-/6#NN83s6?Die557~]Dfifz~-|V:wSKGL6T-|!qk{U4/M7+k5Py!-{ q=2Q/%0@ E29yc_kQC&^> Actually, 10000!! is easy, using Mathematica. The !! notation> represents the double factorial function, such that n!! => n*(n-2)*(n-4)*....I wasn't aware of that usage.> I tnk you meant (10000!)!,I did indeed.> wch is a bit larger.Several bits.-- J.97n Fairbairn === initials Adjunct Assistant Professor at the University of Montana.> The concept of free speech encompasses the right of people to say stupid >> and hateful tngs. The Supreme Court said you can burn the American >> ßag or claim that Falwell had sex with s mother in an outhouse, >> and that those tngs are protected speech. I for one defend your right >> to say whatever the hell you want.You can burn the ßag, but you have no right to say that Falwell>had sex with s mother in an outhouse (unless it's true). There are>libel laws.->Context<-. Fishfry's presentation is indeed way too superficial. The case in question, wch ->did<- involve a claim that Falwell had had sex with s mother in an outhouse, and a suit forlibel against Hustler magazine, Hustler Magazine v. Falwell, 485U.S. 46 (1988)http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=us &vol=485&invol=46decided 8-0, with Cef Justice Rehnquist writing the opinion for theCourt, involved Hustler magazine's parody of a Campari liquor adabout first times. The opinion states in part: We conclude that public figures and public officials may not recover for the tort of intentional inßiction of emotional distress by reason of publications such as the one here at issue without showing in addition that the publication contains a false statement of fact wch was made with actual malice, i. e., with knowledge that the statement was false or with reckless disregard as to whether or not it was true. [...] Here it is clear that respondent Falwell is a public figure for purposes of First Amendment law. 5 The jury found against respondent on s libel claim when it decided that the Hustler ad parody could not reasonably be understood as describing actual facts about [respondent] or actual events in wch [he] participated. App. to Pet. for Cert. C1. The Court of Appeals interpreted the jury's finding to be that the ad parody was not reasonably believable, 797 F.2d, at 1278, and in accordance with our custom we accept ts finding. Respondent is thus relegated to s claim for damages awarded by the jury for the intentional inßiction of emotional distress by outrageous conduct. But for reasons heretofore stated ts claim cannot, consistently with the First Amendment, form a basis for the award of damages when the conduct in question is the publication of a caricature such as the ad parody involved === function >I have a second order transfer function that looks like ts: >P(s) = k/((tau1*s+1)*(tau2*s+1)) * exp(-td*s) >In order to reverse laplace transform ts I will have to multiply P(s) with >1/s >The resulting Laplace transform will be: > >p(t)=k*(1+tau1*exp(-(t-td)/tau1)/(tau2-tau1)-tau2*exp(-(t-td) /tau2)/(tau2-tau1) >) >When tau1, tau2 and td are known it is possible to construct the curve p(t). >Ts is not difficult. >However, imagine that you have ts curve, but do not know the values of tau1, >tau2 and td that constructed the curve. > > In my field ts is the problem that I have. I have a second order system that >generates a curve p(t) as output when a step function is input into the system. >The problem is that I do not know the time constants (tau1 and tau2) nor the >dead time (td). I want to analyse the curve and based on ts find the values >of tau1, tau2 and td. But, I have no idea how to do ts. The general solution >for p(t), presented above, doesn't allow me to solve for t. >For a first order system it is all much easier as it will be possible to >linearize the function for t and then it is just a question of solving a system >of linear equations. Ts does not seem to be possible for a second order >system. >How do I find tau1, tau2 and td given a curve with values for t and p(t)? > in advance, >-- >Someone >given a dataset (t(i),p(t(i)) you want to get td, tau1, tau2 such that the above equations holds on the dataset as good as possible:a typical job for nonlinear least squares.look athttp://plato.la.asu.edu/topics/problems/nlolsq.html for codes for doing ts (for example ELSUNC would be a good candidate for ts).you write a function program for computing the residual left hand side minus right hand side for a givenparameter set x in the code, for example x(1)=td, x(2)=-tau1, x(3)=tau2 and the optimizer will give you the good parameters.but you should provide reasonable initial guesses for them, otherwsie the outcomemight be a fault. === there?http://www.giganews.com/info/dmca.html>How many continuous functions are there from R to R?It seems it must be same as the number of reals, since a continuous>function is determined by its value at the rationals, and c ^ a_0 =>(2 ^ a_0) ^ a_0 = 2 ^ (a_0 * a_0) = 2 ^ a_0 = c.Is that right?Yes.>-- Richard-- >Spam filter: to mail me from a .com/.net site, put my surname in the headers.FreeBSD === > My main point is to show that the writer of that book is not a fraud. > s methods can be very useful, as opposed to current methods taught> in schools. If current methods are indeed useless, how did people build the Golden > Gate Bridge or the Queen Mary?I did not expect ts sort of response from you, Ranjit. Ts sort I> expect from the type of Mr Singh & Co.I never mentioned in any post that the current methods are useless; I> said that ts Vedic method is better. That did *not* imply that the> current methods are *useless*. You are twisting my words, the same way> Mr Singh does.If Mr. Singh were to use your wording and say, methods taught inschools can be very useful, as opposed to Vedic methods, would youunderstand that he never mentioned that Vedic methods are useless butthat he merely said methods taught in schools were better? The arebetter implication would have been clear only if you had saidsometng along the lines of s methods are more useful than currentmethods taught in schools.> As for your question, people built the Golden Gate Bridge and the> Queen Mary the same way the Egyptian built pyramids. It is generally> understood that the ancient Egyptians did not know trigonometry, or> any modern mathematics.FYI, people designed the bridge and sp in question WITH theapplication of trigonometry and mathematics, not without it. So, theydid not === Re: JSH: My use of my initials Adjunct Assistant Professor at the University of Montana.> I see, thx. I wasn't clear on who was firing at who :) But JSH does>> sometimes threaten people with litigation, and he had somebody in court one>> time, for calling m a crank. The case was quickly tossed.I don't tnk there was any such incident.He has threatened on occasion; but I tnk Mr. Hammick may be gettingconfused with the case where Underwood Dudley ->was<- sued for callingsomeone a crank. Dilworth v. Dudley:http://www.law.emory.edu/7circuit/jan96/95-2282.htmlThe === functions are there?> How many continuous functions are there from R to R?It seems it must be same as the number of reals, since a continuous> function is determined by its value at the rationals, and c ^ a_0 => (2 ^ a_0) ^ a_0 = 2 ^ (a_0 * a_0) = 2 ^ a_0 = c.Is that right?-- Richard> It's essentially right. The only error in it is that at the moment you've only shown that the cardinality is at most c - not every possible function from Q to R extends to a continuous function. However it's easy to check that the cardinality is at least c, so you have the cardinality is exactly c. (I would prefer to tnk of it in terms of injections of functions and apply schroeder-bernstein, but it doesn't really matter - wchever === want to do your new students a favor you can show them ts simple new proof of the fundamental theorem of the calculus and then they will know what they are learning. Its at: === letters of recommendation> I provided each professor with a labelled envelope, tYeah, that's about the extent of it. You want to make their job as easyas possible, but there is tto much variation. But I write my letters inWord (heresy!) anyway, so with cut and paste that part is not too muchtrouble. You might offer to send them the addresses over email so thatthey can cut/paste that if they write the letters electronically.V.-- email: lastname at cs utk eduhomepage: cs === of recommendation Adjunct Assistant Professor at the University of Montana.>I am a senior and I will be needing to fill out applications for graduate>school. My problem is that I am on the quarter system and the quarter is about>to end. We will not resume until the beginning of January. I'm pretty shy and>have not asked any of my professors for letters. I'm just not sure how to ask>them and now that I basically have no time left, I was just wondering how I>should go up to them and ask. I have had the same professors for a lot of>classes in some cases but I'm not sure whether or not lower level classes would>give a professor enough to say anytng about me. Is there any standard way to>go about ts? Most schools seem to want three and for me that is a lot.Asking for letters is about the most uncomfortable tng I've had todo, both when applying for grad school, and now for jobs. The goodnews is that most people are very nice about it.First: do it, and do it SOON. The letters have to be in, and youshould give the professors at least a couple of weeks to do it; as thesemester winds down, a professor's time supply is short. Ask for theletters ts week or next, and don't delay.Pick upper division classes in wch you did well. They don't all haveto be math classes, but at least one (preferably two) should be.Go to the professor, remind m who you are and how he knows you, andsay simply that you are applying for grad school, and since you didwell in s/her class, you would very much appreciate it if he/shecould could write you a letter of recommendation for yourapplication. Take the forms with you, and be ready with informationabout deadlines and so on. Probably the best is to catch them duringtheir regularly scheduled office hours. If the professor only knows you from lower division courses, it isprobably not a good bet for a letter, but if you had m for bothupper and lower divisions, then feel free to go for it.And, keep ts in mind: most professors understand that ts is partof their job. If you did well in the class, they will be === two complex numbersWhy (a,b) x (c,d) = (ac - bd, ad + bc) ? (a,b) x (c,d) = (2ac - bd, ad + bc) also will serve to solve === instantaneous help for you:> It only shows how depesrate you are to attack me in such a cheap way> that you failed to realize how you are revealing how low you are.> >>http://www.virtual-vibrator.com/index-ns.shtml#You're trying to fit your desparation shoes onto my feet?LOLClearly sometng ails you. Feel free to judge with your experience.>The other possibilities> are magintudes worse. Sounds like you are speaking about yourself.> Feel free to tell us. Would you rather not make assumptions .. like you have been doing? Why?I do apologize for name calling; I forgot that you could be mucholder.But..everytng else I said .. stands. You started picking on meafter you assumed that I was a Muslim. Of course you didn't say itexplicitly but your prejudice was obvious; the timing of the offensivepost just after not siding with Hanson's (Hanson cannot tnk with sbrain) plea to be on s side.I remember a professor (he must be almost 60 at the time) who reallylike ts student who doesn't look her typical ethnic group (I meanliking as a person) till he found out the ethnic background.Some people just enjoy being prejudiced. Poor === and so forth only exist insofar as they can demonstrate> their authority. They say they're here to preserve order, but in fact> they'd go absolutely mad if all the criminals of the world went on> strike for only a month. They'd be on their knees waiting for a> crime. That's the only existence they have.William S. Burroughs (American writer)> Guardian, 1966huffyI'm beginning to tnk you're a one-trick pony.--Ron === ts is a curve fitting equation. So what I needto know is given a known value for x I need to predict for y.Jo>Can someone help me solve the following equation for x. Could you>please put all the steps down so I can follow it (idiot's guide!)>y = A1*exp(-x/t1) + A2*exp(-x/t2) + y0Ts looks like a function, not an equation, unless y is supposed to> be a constant. I assume you want to solve y = 0?Huh? An equation is sometng with an equals sign in the middle, > so I'd say ts qualifies as an equation. I assume when the poster > asks for help solving for x, the poster wants the equation solved > for x. Of course, the steps you gave are useful for my interpretation as > well (except that you won't want to set y to zero). But when you > write, A1 z^{t2} + A2 z^{t1} + y0 = 0.If t1, t2 are integers, then ts is a polynomial in z. Solve it by> any of the usual methods, the usual methods are going to be tricky unless t1 & t2 have been > chosen (by whoever set the problem) === two complex numbers Adjunct Assistant Professor at the University of Montana. >Why (a,b) x (c,d) = (ac - bd, ad + bc) ?Because you are tnking of the pair (a,b) as representing a+bi, wherei^2 = 1.> (a,b) x (c,d) = (2ac - bd, ad + bc) also will serve to solve x^2 + 1 = 0.Mostly because it is not associative:[(a,b)x(c,d)] x (e,f) = = (2ac - bd, ad+bc) x (e,f) = (2(2ac-bd)e - (ad+bc)f, (2ac-bd)f + (ad+bc)e ) = (4ace - 2bde - adf - bcf, 2acf - bdf + ade + bce)(a,b) x [(c,d) x (e,f)] = (a,b) x (2ce - df, cf+de) = ( 2a(2ce-df) - b(cf+de), a(cf+de) + b(2ce-df) ) = (4ace - 2adf - bcf - bde, acf + ade + 2bce - bdf)On the other hand, (a,b) x (c,d) = (ac - 2bd, ad+bc)would work, since then you are tnking of (a,b) as === factorization, from basic to advancedIn ts post I'll go from a rather basic factorization to a far more> complicated one, outlining how to use one polynomial to tell you about> the roots of another.You demonstrably cannot balance your checkbook much less performsometng complicated. You are like Sarfatti or Saddam Husseinaimlessly firing into the sky hoping to t sometng. Both of themmelted down their gunbarrels and t notng. All you t is yourselfin the face.http://www.crank.net/harris.html It's not every braying jackass that gets a whole page at crank.net http://b5.sdvc.uwyo.edu/bab5/snds/argcstpd.wavhttp:// w0rli.home.att.net/youare.swfhttp://www.mazepath.com/uncleal/ === for ts series?It needed several try because at first i used the wrong closed form for thegeometric serie, i used (1-A^N)/(1-A) instead of the right one(1-A^(N+1))/(1-A) but at last i found the right expression bydifferentiating and multiplying by A as you suggested.It should be (A-N*A^(N+1)+N*A(N+2)-A^(N+1))/((1-A)^2)It works with several === <87smkswqrm.fsf@pwumbda.org> sha1:/WVc+qrQYi2l0MeVzwEPlv3zd6U=> In another post by huffy, you signed (and clearly spoke as>> Correy). Presumably it wants to avoid killfiling. I have no idea why it> tnks that the opinion of ts late novelist, heroin addict> and wife-murderer is at all relevant though. These huffy posts> are considerably more tedious than the rantings of D S Kabatoff.Posting the exact same quote 47 times is an odd way to avoidkillfiling.-- Jesse HughesBasically there are two angry groups. I am a harsh force ofone. Against me is a society of mathematicians. So far it's been adraw. -- JSH gives another display of keen === recommendation> Is there any standard way to go about ts? I've had students walk into my office with the letter written for me and asking me to sign it. Let's callthat not standard (and not acceptable.)As others have said, professors do ts all the time, andoften for students they barely know, except as a list ofnumbers in a grade book. If you can help make the connectiona bit, that is a good tng. Some students walk in andask for recommendations and then walk out. Later I getsome addresses. OK, I can deal with it, and they get thebest letter I can put together.But other students hand me a little resume of their careers,wch helps me immensely. It reminds me that they were inthat production of Ot I enjoyed so much and that theyare always lying next to me when I'm giving blood at the blood drive and it helps me find their records amongst allmy spreadsheets when they've listed the classes they took.Oh, yeah, she DID win that freshman math contest.It helps keep the letter from looking generic.Plus the fact that the student had it together enough tohand me the resume says sometng in itself. Grad school also takes perserverence, and the letter ought to addressthe student's character if it can. So if I can say sometngpositive that indicates that the student not only has somemathematical talent, but also exbits the academic maturityfor sticking tngs out, then I will. The brief inteview you get when asking for the letter is a quick, but importantchance to demonstrate those characteristics.So, my advice is that wle you're asking for the recommendation,you connect personally with the professor a bit. It's anopportunity to ask m for advice on the choice of grad schoolsor field of study or tips for getting through and it willhelp m write the letter if he knows you a bit === but what about the OP's 10000! ;-)>That's large itself, but it doesn't take long to>compute. computing 10000!! isn't feasible whatever algorithm>you use. True [at least for (10000!)!, as opposed to the Mathematicameaning]. OTOH, its last 10000!/4 or so digits are easy to calculate,at least to base 10, wch gets you part of the way; and so are thefirst few digits. It's just those in the middle that are hard ....-- Andy Walker, School of MathSci., Univ. of Nott'm, === theory> Let q1,q2 algebraic integers such that q1^k=n(integer),q2^k=m(integer) let >> K1=Q(q1),K2=Q(q2),Q:rational field.>> Also suppose that m,n free from k powers and K1=K2. >> Is there any relation of m,n?>>Do you have any examples where m and n are not equal?k=3, m=2, n=4. Then Q(q2) is clearly contained in Q(q1), and > 2^{1/3} = (1/2)(4^{1/3})^2 so you get the reverse inclusion.If k=2, then m must equal n. If k=3, I believe that you must have that all primes that divide m> divide n as well, and vice-versa, and that will be both necessary and> sufficient.>>Is Q(cube root 6) the same field as Q(cube root 12)?Accoreding to Magma, x^3 - 12 is irreducible over Q(cube root of 6),and x^3 - 6 is irreducible over Q(cude root of 12), so the answerwould appear to be no.Derek Holt.>Don't know. I thought about it more, and must take it back (good tng>I said I believe...)The best I could come up with was a sufficient condition, wch I>->tnk<- may be necessary as well:Let P = {positive rational primes}.Define a (set-theoretic) map from the nonzero integers to Z^P as>follows: given a nonzero integer n, let f(n) be the vector in Z^P>wch has ord_p(n) in the p-th coordinate (i.e., the coordinate>corresponding to the prime p).Let k>0. There is a natural map from Z^P to (Z/kZ)^P, and let g(n) be>the image of f(n) under ts map. Then Q(q1) is equal to Q(q2) if the following occurs: (1) If k is even, then either n and m are both positive or else they> are both negative. (2) The cyclic subgroup of (Z/kZ)^P generated by g(n) is equal to> the cyclic subgroup of (Z/kZ)^P generated by what I accept as reality.> --- Calvin (Calvin and === H#SM:U1U-/6#NN83s6?Die557~]Dfifz~-|V:wSKGL6T-|!qk{U4/M7+k5Py!-{ q=2Q/%0@ E29yc_kQC&^>> Yes, but what about the OP's 10000! ;-)>That's large itself, but it doesn't take long to>compute. computing 10000!! isn't feasible whatever algorithm>you use. True [at least for (10000!)!, as opposed to the Mathematica> meaning]. OTOH, its last 10000!/4 or so digits are easy to calculate,> at least to base 10, wch gets you part of the way; and so are the> first few digits. It's just those in the middle that are hard ....I wasn't tnking so much of the difficulty, as where to storethem when you're done.-- J.97n Fairbairn === it yesterday.>In German.>Uhm, did the synchro botch everytng up or is it>a lot of senseless mathbabble already in the original? :-)>-- >Hauke Reddmann <:-EX8 >Private email:fc3a501@math.uni-hamburg.de>For our chemistry anytng elseSaw it too.> The math is not completely senseless: the idea to interpret the> numbers as coordinates is quite obvious, isn't it?> Later on they used the same numbers to describe the path a subcube follows over time. It's not so clear how to do that, although it's> possible.> Then suddenly the property of being a prime power played a role in> identifying those rooms, that are traps. At that point I guess it> was just nonsense. It seems difficult to me to encode two types of> information into the number triplets shown in the movie.HAfter reading ts thread, I bought a copy. When I brought it to the counter:salesgirl: Oh, Cube. It's actually a tesseract, you know. me: What?salesgirl: A tesseract. It's like a square, only three dimensional. me: A cube _is_ threee dimensional.salesgirl: Oh, I meant four dimensional, where each face of the cube is connected to another cube. me: I know what a tesseract is, I'm wondering if you know what it is.At ts point the transaction was complete so I walked away. Didn't want tobe beaten with sticks by those in the queue bend me.If JSH wants to make money, he should become a script writer. s bullstsounds more plausible than that produced by Hollywood. I can see it now:Aliens invade and because of the core error, the mathematical establishment is rendered helpless and only JSH, with s Advanced Polynomial Factorization,can save the === <87znf0wyzo.fsf@pwumbda.org> Discussion, concept of free speech encompasses the right of people to say stupid > and hateful tngs. The Supreme Court said you can burn the American > ßag or claim that Falwell had sex with s mother in an outhouse, > and that those tngs are protected speech. I for one defend your right > to say whatever the hell you want.>>You can burn the ßag, but you have no right to say that Falwell>>had sex with s mother in an outhouse (unless it's true). There are>>libel laws. ->Context<-. Fishfry's presentation is indeed way too superficial. I didn't realize he was referring to an actual case. for thedetails. When you add the fact that the claim was not presented as afactual claim but only as part of a parody, that rather changes tngs.-- Run mathematicians, RUN!!! I'm coming for you. It may take a fewmonths, but I'll get [computer verification of my proof] and then yourlives will be ended as you previously knew it. -- JSH === I.e., it is possible to prove directly, using only the definition of> derivative, that (e^x)' = e^x? No, you also need the definition of e^x.No comment ...> Calculus texts often do it ts way: First define ln(x) by integrating> 1/x. Then the derivative of ln(x) is easy. Then define exp(x) as the> inverse function. So you get its derivative.But the order usual in secondary school (at least in Spain) is :1) Definition an properties of the functions. Logarithms as inverses ofexponentiations, a^x using rational aproximations of x. The number e isintroduced as Lim(1 + 1/n)^n.2) Derivatives3) IntegralsIn that environment, the usual way to get the derivative of f(x) = e^x isthrought the logarithmic derivative or the derivative of the inversefunction. The derivative of the logarithmic function is easily obtained fromits properties.I was looking for a alternative to get the derivative of the exponentialfunction directly from the properties of that function or the loarithmicfunctuion, but without make use of the chain's rule. But I have it yet, as Isaid in a previous message.-- Saludos,Ignacio Larrosa Ca.96estroA Coru.96a === NY Times Science 11/11/03 >> I tnk we are so confused that we should keep an open mind to>> tinkering with gravity, said Dr. Michael Turner, a cosmologist at>> the University of Ccago.>> previously>> Q to Ed Witten: How can the cosmological constant be so close to>> zero but not zero? DL> Close to zero? WTF does close mean? Is there a maximum value> DL> we can compare it to to see how close it is? The current estimates are that the energy density contributed by the> cosmological constant (or dark energy) is 0.7, in units of the closure> physics that make predictions about the cosmological constant. The> typical value predicted is 10^50 or so.Excellent! . (I'm going to pretend to understand that.) ;-)--Denis === determing the inside of a set of pointsI've got a list of points (in x,y form) that are the corners of> a polygon, in order. It's not necessarily a convex polygon. Is> there a standard algorithm for determining whether a given point> is inside or outside the polygon? All ts takes place in> the plane... For practical purposes, an algorithm is ok if it> can handle up to 7 points decently.Covered adequately in Sedgewicks Algorithms (in C).-- Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net) Available for consulting/temporary embedded and systems. USE worldnet === thoughts on creating a theory of sets prior to a theory of> : > propositions and quantifiers:> : > : > Let's start with the empty set, 0, and logical identity, =, then we can> : > define T, for true, by> : > : > T =def 0 = 0> : > : > Let's define ordered pair a la Kuratowski, then we can define> : > conjunction by : > Kuratowksy defines as {a,{a,b}}. But how do you make sense of> : > that latter notation at ts stage of the presentation? Note that in> : > ZF, you can only make sense of it because of the Axiom of Pairing; you> : > can only verify that it satisfies the ordered pair axiom because of> : > the Axiom of Extensionality. Those axioms both seem to require the> : > apparatus of first order logic to be formulated.I already said that. Why don't *I* rate a reply? : Well, we cannot define un-ordered pair in context by> :> : u in {x,y) iff u = x or u = y> :> : since we don't have or. So let's take {x,y} as primitive and define> : {x} =def {x,x}> : =def {{x},{x,y}}Nobody is impressed. You'd be much better off just taking> as primitive. Your mission, now, wch will be much harder,> is, given that you've taken {x,y} as primitive, how on earth is> anybody supposed to parse {x,y,z} ?I need to define &. _After_ I've got the logic I can use settheory to define {x, y, ..., z} in the usual way.More to the point, you said before that we don't have Ôor',> but you have a much bigger problem: you don't have *in*, EITHER.in is in the set theory, just as in any other set theory.> What good does it do you to take {x,y} as primitive, and to claim> that you've presumed some set theory, if you STILL have NO wayI presume _all_ of set theory: it's axioms and their first orderconsequences.> of deciding whether z is or isn't *in* === police and so forth only exist insofar as they can demonstrate>their authority. They say they're here to preserve order, but in fact>they'd go absolutely mad if all the criminals of the world went on>strike for only a month. They'd be on their knees waiting for a>crime. That's the only existence they have.>William S. Burroughs (American writer)> Guardian, 1966>huffyYou got it right that time. But that other post where you> signed your name sort of gave it away. Giggle.> For about a second ts morning it looked like you'd> found someone who tends to agree with you. But you> had to make m up.How sad, a grown man depending on imaginary playmates that way.> Your Fuffy, my Pzuffy. Deal with === question)The whole problem is just that you're misquoting the axiom. You say: Everynonempty B contains a y with (B intersect y) = empty. I say: Every nonempty Bcontains a y for wch there is no z with z in y and z in B. My axiom sayssubstantially the same tng, but it allows for the possibility that there existcitrus fruits that are not sets. Alternatively, you could banish such citrusfruits from your theory. Citrus fruits that have no elements, but aren't theempty set, are technically called individuals. Whether you want them to existor not is basically a matter of taste, wch I suppose would have to be fairlysour. HTH| folks,|| Okay, ts is going to be some very stupid question to most of you.|| The axiom of foundation says that:|| ForAll B ~= emptyset, ThereExists y in B such that (y intersect B)=| emptyset.|| Now suppose B = {lime, orange, lemon}. What is such y among ts set| of citruses? Suppose y = lime. How can lime be a set? (my| understanding is that only sets can intersect).|| I told you, it is a stupid question. === personality assessmentIn another post by huffy, you signed (and clearly spoke as> Correy).>> Presumably it wants to avoid killfiling. I have no idea why it>> tnks that the opinion of ts late novelist, heroin addict>> and wife-murderer is at all relevant though. These huffy posts>> are considerably more tedious than the rantings of D S Kabatoff.Posting the exact same quote 47 times is an odd way to avoid> killfiling.Well I have now killfiled Correy under its new alias. Choosinga new username is a way of forcing one's postings on peoplewho have chosen to killfile one. Kabatoff does ts too.Perhaps I should jus killfile all posts from yahoo.comas ts ISP seems to attact === about upper bound of magnitude of a complex root of polynomialCan anyone help me to solve the question? I have no idea on it...Let f(t) be a polynomial with complex coefficients of degree n and with leadingcoefficient = 1.Let a be a root.Show that | a | <= n b, where b is the maximum of the magnitude of === Recommendations on Complex Analysis books?> THE classic text on complex functions is Ahlfors, _Complex Analysis_ .> BArry Mazur has recently published a popular book on complex> numbers _Imagining Numbers_. I would also recommend _Complex Numbers> and Geometry_ by Hahn. Finally, a great old book: Theory of> Functions_ by Caratheodory.I second the Ahlfors book. We used it as our Complex Analysistextbook when I was a === My use of my initials>Some of you may have realized that I have remarkable power to draw>attention on several newsgroups to the extent that I even have my own>dedicated repliers, like or Ullrich, who like to>obsessively insult me! Anyone have a good term for people who just>follow around a popular poster insulting m? Well I call them critic>trolls.Around here we === Re: Need advice on letters of recommendation permission for an emailed response.X-Zippy-Says: I selected E5... but I didn't hear ``Sam the Sham and the Pharaohs''!> I've had students walk into my office with the letter > written for me and asking me to sign it. Let's call> that not standard (and not acceptable.)Eek! The tng to do of course is to agree to write a letter anyway,insist that it be confidential, and then mention the details of thetransaction in the === open interval (0,2pi) define a function f byf(x) = (1-cos(x)) sum_{n=0}^{infty} 1/(2pi n + x)^2.The problem is to prove, preferably without using any WMD's, thatf(pi + x) + f(pi - x) = 1/2for all x in (0,pi]. (The function f is not === are there? permission for an emailed response. The GNU project will probably not be Posix conformant, Tom said noncommittally> How many continuous functions are there from R to R?It seems it must be same as the number of reals, since a continuous> function is determined by its value at the rationals, and c ^ a_0 => (2 ^ a_0) ^ a_0 = 2 ^ (a_0 * a_0) = 2 ^ a_0 = c.Is that right?Exactly right.I have been tnking for sometime that many of the weirdnesses thatfollow from CH or from AC of course involve creepily non-topologicalproperties of the reals. (For example, thethrowing-darts-at-the-real-line argument, or the existence ofnonlinear functions where f(a+b)=f(a)+f(b) everywhere.Cantor noted that the closed set analog of CH does hold. (Everyclosed subset of a closed set is either countable or cardinality c.)The AC-related weirdnesses that I am familiar with all depend on thespecification of well-orderings of the reals, and of course there isno construction of such a well ordering. Indeed, if we had aconstruction of well-ordering, that would generally amount to also afixing of the cardinality of c.Indeed, the more one works with the subject (though I am strictlyamateur here), the more it seems to me that a central issue is thefollowing:We simply have no intuitions for topologically crazy sets of reals.Our intuitions for the reals connect very very heavily with theirtopological properties, and we don't have a good sense for them apartfrom those properties.I'm still trying to put ts idea into a more careful form, but thegeneral thrust is that most of the weirdnesses attributed to ACreally ought to be attributed to the indeterminancy of CH; that theindeterminancy of CH ought to be attributed to a lack of intuitionabout === How many continuous functions are there?> How many continuous functions are there from R to R?It seems it must be same as the number of reals, since a continuous> function is determined by its value at the rationals, and c ^ a_0 => (2 ^ a_0) ^ a_0 = 2 ^ (a_0 * a_0) = 2 ^ a_0 = c.Is that right?I don't tnk so. I may be wrong, but I believe two functions can beidentical on the rationals but not on the irrationals and both stillbe continuous. However, at best only one can be differentiable. Sothe cardinality of differentiable functions is c, but I tnk that thecardinality of continuous functions is still 2^c.It's been a wle, so someone with knowledge of ts may === sft, core issues>Don't you agree, , that from C1-C4--indeed, from C3,C4 alone--any>*competent* mathematician could have deduced Ex~(x=x)?Two comments, the second for anyone who missed your first few hundred> repetitions of ts question:(i) your question has no relevance here - you seem to be confusing> a statement and its converse.(ii) the original claim was that Ex~(x=x) followed _in_ standard> set theory. Since Ax(x=x) is a theorem of standard set theory, if> ts follows then it also follows that C1-C4 are simply inconsistent> with standard set theory.>C1 AxAy[x=y -> Az(z in x <-> z in y)]>C2 AxAy[Az(z in x <-> z in y) -> Az(x in z <-> y in z)] >C3 EyAx[x in y <-> Et(x in t) & A] (with y not free in>A)Classification>C4 AxAy[Az(z in x <-> z in y) -> {Et(x in t & y in t) <-> x=y}] (Weak>Extensionality)>someone will point out the error.?>Did your Homies correct you? Or did they *defend* your mistake-->and you for having made it? A few people recently have pointed out that to conclude that what> I said was erroneous you need to take it out of context. Wch is> of course true.Don't *all* of the following indicate that you had *no idea* (and*still* have no idea) wh Ex~(x=x) follows from C1-C4? =When you said set theory I assumed you meantZF. That's what set theory with no qualificationmeans these days.If you meant NGB set theory then no, C1-C4 arenot inconsistent with set theory. It does _not_follow that C1-C4 give an example of sometngwch is not equal to itself, or an example ofsometng wch does not exist. [DON'T SNIP--J.C.]It is correct that I have no idea why Ex~(x=x)follows from C1-C4. Ts is because (assumingthat NBG is consistent) NBG has a model inFOL=. In that model everytng is equal toitself.[DON'T SNIP--JC]C1 AxAy[x=y -> Az(z in x <-> z in y)]C2 AxAy[Az(z in x <-> z in y) -> Az(x in z <-> y in z)] C3 EyAx[x in y <-> Et(x in t) & A] (with y not free inA)ClassificationC4 AxAy[Az(z in x <-> z in y) -> {Et(x in t & y in t) <-> x=y}] (WeakExtensionality)>You have no idea why Ex~(x=x) follows from C1-C4>because you are brain-dead analysis teacher who>can only work with the routines he has memorized.Could be. Now show us why Ex~(x=x) _does_ followfrom C1-C4.Exbit of proof of Ex~(x=x) from C1-C4 and someone will pointout the error.IT'S ULLRICH BAIL-OUT TIME! SNAP TO IT, MAGIDIN! ON THE DOUBLE,HUGHES!> Giggle: When you set up a new yahoo account with a silly name> like pzuffy the idea is to avoid using your real name in posts> you make under the silly name.(I'm assuming the point to pzuffy was to make it appear that> there's someone other than you out there who agress with the> tngs you say. If the point was sometng other than that> then never mind. Although it's hard to see what other point> there could have been - if the point was to set up a new> account because the reason other than ding your> identity, it's hard to see why you'd choose a name like> Ôpzuffy'.)> You've got your fuffy. === bound of magnitude of a complex root of polynomialdeath & rebirth> Can anyone help me to solve the question? I have no idea on it... Let f(t) be a polynomial with complex coefficients of degree n and withleading> coefficient = 1.> Let a be a root.> Show that | a | <= n b, where b is the maximum of the magnitude of the> coefficients of f(t).Sketch: If we had |a|>nb, the polynomial could not be zero at $a$, by thetriangle === stupid question)>Citrus fruits that have no elements, but aren't the>empty set, are technically called individuals. >Whether you want them to exist>or not is basically a matter of taste, >wch I suppose would have to be fairly>sour. HTHIs === Sets before logicRandom thoughts on creating a theory of sets prior to a theory of> propositions and quantifiers:[Definitions of logical constants snipped.]Now, what theory of sets will yield what logic of propositions and> quantifiers?What are the rules of logical inference, and how are they expresed? === Collatz conjecture> What special numbers other than the easy ones like 1,[case 0] any number whose binary form is1wch becomes 1 after 0 iterations>2^k, [case 1] any number whose binary form is (where {0} means krepetitions of 0)1{0}wch reverts to [case 0] after k iterations>(2^(2k)-1)/3, [case 2] any number whose binary form is{01}wch reverts to [case 1] after 1 iteration>2^k(2^(2n)-1)/3, [case 3] any number whose binary form is{01}{0}wch reverts to [case 2] after k iterations>have been proved to be valid for the Collatz conjecture?You can extend ts list forever. Once you have proven it for 3 (wchreverts to [case 3] after one iteration), you have[case 4] any number whose binary form is11{0}wch reverts to 3[case 5] any number whose binary form is11{01}wch reverts to [case 3] after one iteration[case 6] any number whose binary form is11{01}{0}wch reverts to [case 5] wch reverts to [case 3]So once you have shown that a binary pattern w is true, then youautomatically have proved it true for[case x] any number whose binary form isw{0}[case y] any number whose binary form isw{01}[case z] any number whose === of recommendation Adjunct Assistant Professor at the University of Montana.> I've had students walk into my office with the letter >> written for me and asking me to sign it. Let's call>> that not standard (and not acceptable.)Eek! The tng to do of course is to agree to write a letter anyway,>insist that it be confidential, and then mention the details of the>transaction in the letter.I disagree. There's a chance, at least, that the individual issincerely trying to be helpful. I had, on occasion, had professors Iasked for letters of recommendation tell me to just write it and I'llsign it. Needless to say, I decided to go ask other people forletters when that was the case, and I frown thoroughly on thatpractice. But perhaps the student had encountered a similarlyill-disposed professor, and thought he would save time by bringing aletter ready? Absent other experience, he may well tnk that it->is<- standard.I would certainly tell the student that the practice is not standard,and should not be acceptable. I would also suggest that any professorof s who has suggested ts method to m is NOT a good referencewriter, and he should seek to replace m. And I will usually try torefuse to write letters of recommendation for admission to graduateschool for people that I will not recommend (i.e., people I would notsay good tngs in balance). That does not mean that my letters do notmention any problems, just that if I have a generally bad opinion ofsomeone, then I recommend to the student to find someone else to writeit. (It's happened once or twice; once, I asked a student who had notdone very well in my class why he was asking me. He explained that hewas seeking to be admitted to a specific, applied math program, and hewas hoping that by getting a letter from an algebraist, he would shows breadth. I suggested he just get letters from applied math and uses transcripts to show breadth, and he acquiesced. I usually try tosuggest other courses of actions rather than ßatly refuse, and oncethe student insisted and I said that I would not be able to writeanytng glowing, and would point out that on the balance s work === you may have realized that I have remarkable power to draw> attention on several newsgroups to the extent that I even have my own> dedicated repliers, like or Ullrich, who like to> obsessively insult me! Anyone have a good term for people who just> follow around a popular poster insulting m? Well I call them critic> trolls.I tnk critic of trolls is more accurate, as you of course are thetroll. That real mathematicians are still willing to even look atyour posts is sometng you ought to feel honored, since frankly theirtime is far more valuable than yours.As for calling yourself a popular poster, I'm not sure thatfrequency of posting equates to popularity. Although your infamy inpoor proof-writing has made you well known, it does not mean you areconsidered popular by any conceivable === Recommendations on Complex Analysis books?>>The subject says it -- however, I'd like to clarify>>one detail: I'm looking for a book on *analysis*, as>>opposed to Calculus (i.e., that covers rigorously>>the concepts and proofs on Complex numbers and>>Complex variables functions).I was amazed by the way you've put it. Ts means that for you it is> obvious that Calculus is *not* rigorous and it is *not* analysis. No, that's not what I meant.When I say Calculus in that context, I'm referring totypical College courses in math: a Calculus course wouldtypically emphasizes on the applications, and understandingtngs well enough to apply them in different contexts(i.e., it is engineering oriented).Another way to put it is that I want sometng that ismore like analysis for mathematicians, instead ofcalculus for engineers> My favorite one: Theory of Complex Functions by Reinhold === are there? permission for an emailed response.X-Zippy-Says: I had pancake makeup for brunch!> How many continuous functions are there from R to R?It seems it must be same as the number of reals, since a continuous> function is determined by its value at the rationals, and c ^ a_0 => (2 ^ a_0) ^ a_0 = 2 ^ (a_0 * a_0) = 2 ^ a_0 = c.Is that right?I don't tnk so. I may be wrong, but I believe two functions can be> identical on the rationals but not on the irrationals and both still> be continuous.Nope, identity on the rationals and continuity uniquely determines thefunction at all points. Consider some irrational x; it is the limitof some increasing sequence of rational x0, x1, x2, ... Bycontinuity, f(x) must be the limit === conjectureHow about 2^k -1? Has anyone proved for that yet?> What special numbers other than the easy ones like1,2^k, (2^(2k)-1)/3, 2^k> (2^(2n)-1)/3, have been proved to be valid === letters of recommendation>> I've had students walk into my office with the letter >> written for me and asking me to sign it. Let's call>> that not standard (and not acceptable.)Eek! The tng to do of course is to agree to write a letter anyway,> insist that it be confidential, and then mention the details of the> transaction in the letter.Well, I should have said student, not students. Andin ts case, I treated it as a special situation. First,it was a (very) foreign student. Second, the letter wasonly for a summer job, not an internsp or grad school.Trd, the situation came up suddenly, where few opportunitiesare available for (very) foreign students and it was a rush job (due that day) and the student thought she was doing me a favor AND was quite polite about it. Fourth, the letterwas accurate and well-written, to a collaborationof some friends. So I had no trouble signing my name toit. I would have written a more glowing letter for her,since she was a stellar student.Then we had a discussion about proper procedure. No harm done. (She _was_ jerking her boyfriend around at the time,so if that character trait manifests itself again in a moreserious situation, then she _will_ get nuked. But it won'tbe because someone wasn't frank with her at least === equation, such as f2(x,y,z)=c2, can describe in a 3d space>>a surface, possibly a plane, but not a line.>> I could *swear* that {(x,y,z) in R^3 : x^2+y^2=0} was a line,>> last time I looked.>> Lee RudolphTs actually happened.>Many years ago a problem similar to ts came up in a CalcIII class I was>teacng.I mentioned that situations like ts are called Degenerate caseA girl raised her hand and saidBut that's what my Father says *I* am!!Bob Pease>There is a certain beauty to ts. If you define a line as theintersections of two planes, and these are defined by P1 = 0 and P2 = 0 then you can define the line as a cylinder, P1^2 + P2^2 = R^2, where R = 0. Now take the cylinder of radius 0 andexpand the radius. sooner or later it itersects the surface f1 = 0.So it is possible, even without using gradients, to solve for theintersection and then minimize R. (Though to say the two gradientsmust point in the same or === Convergence on a space with no topology?> Probably been asked before...Let X be a metric space (or just a topological one). Let>> B* be any subset of P(X), the set of all subsets of X. Choose an>> element A in B*. Then, without attempting to define a topology on B,>> we just say A_n -> A in B* if for every a' in A there exists a >> sequence (a'_n) in X wch converges to a' in the metric >> topology of X with a'_n in A_n for all n.Ts looks complicated. Somehow you want to say the maximal A wchsatisfies ts condition, and wch sets of limit points are containedin B* depends entirely on the definition of B*, so there is noguarantee that maximal is meaningful. I tnk that to simulateCauchy sequences would have to wait until some other tngs gotstraightened out.Ts is related to the Hausdorff metric on subsets of a metric space.>And for your limit you probably want the set of all a' such that>there is a sequence as written. In case your sets are all compact,>ts will coincide with convergence in the Hausdorff metric,>as I recall.>> Then we have (at least) a notion of convergence on a space >> that is not directly equipped with a topology itself. Thus,>> we may also speak of the continuity of functions from >> B* to B* or from B* to any other (metric) spaces. >>> To further demonstrate ts, let C be any finite subset of X and>> f_C: B* -> N (the natural numbers) the counting function, i.e.f_C(A) gives how many elements of A coincide with C. Is f_C>> continuous? (not mathematition)>>I tnk he is saying that you don't need the Hausdorff metric or anyother metric to define convergence in B*. But then he's saying youneed the definition of convergence from the first topology. Without using a topology, you can define A_n as convergent-type-A ifthe intersection is nonempty, and taking n to infinity [where A_(n+1)adds one set to A_n ], its limit-point-type-A would be the set, emptyor nonempty, of the intersection limit.What he is looking for is convergence-type-B of some kind. I tnk itmight result from selecting only closed sets from the first topology,ie, Let B* be any subset of Q(X), the set of all CLOSED sets in X.Then you do not have to refer afterwards to the first topology orestablish a second. Maybe Compact set should be substituted forclosed - some of you may know ts - > In case your sets are all compact,>ts will coincide with convergence in the Hausdorff metric,>as I recall. Cauchy-like sequences could be deifined afterwards - I don't know howmuch === Cube (the movie) wants to make money, he should become a script writer. s bullst> sounds more plausible than that produced by Hollywood. I can see it now: Aliens invade and because of the core error, the mathematical> establishment is rendered helpless and only JSH, with s Advanced> Polynomial Factorization, can save the Earth.>The entire cast and crew were sealed on set for the duration ofthe shoot.After post production was completed, everyone involved with the projectwas Ôdisappeared'.All materials connected with the production were destroyed.In short, everytng was done to prevent knowledge of ts featurebecoming public before it went on general release.Explain, then, if you would, how *you* managed to post a spoiler for tsforthcoming sci-fi[1] epic in ts froup.[1]: I'm unsure whether to desribe it as Ôscience fiction' or'fictional science'.-- P.A.C. SmithThe vast majority of Iraqis want to live in a peaceful, free world.And we will find these people === and we will bring them to justice.Subject: Re: JSH: My use of remarkable power to draw : >attention on several newsgroups to the extent that I even have my own : >dedicated repliers, like or Ullrich, who like to : >obsessively insult me! Anyone have a good term for people who just : >follow around a popular poster insulting m? Well I call them critic : >trolls. : : Around here we call them mathematicians.Who we? People of good will call THOSE people assholes.That is not inconsistent with their also being mathematicians,but the overlap is a BAD tng. The people who merit mathematicianin the honorific sense in wch you are trying to use it are peoplelike Dik Winter, who, even in the face of potent distractions, are willingto stay focused on mathematics.-- --- It's difficult ... you need to be united to have any strength, but internal issues have to be addressed. --- E. Ray Lewis, on liberalism in === magnitude of a complex root of polynomialsorry but what is $a$? Hammick b.a6l.97> death & rebirth> Can anyone help me to solve the question? I have no idea on it...> Let f(t) be a polynomial with complex coefficients of degree n and with> leading> coefficient = 1.> Let a be a root.> Show that | a | <= n b, where b is the maximum of the magnitude of the> coefficients of f(t).> Sketch: If we had |a|>nb, the polynomial could not be zero at $a$, by the> triangle === f(a+b)=f(a)+f(b) everywhere. Thomas,that sounds interesting. Can you point me to an example or other resources on such === complex numbers>Why (a,b) x (c,d) = (ac - bd, ad + bc) ? (a,b) x (c,d) = (2ac - bd, ad + bc) also will serve to solve x^2 + 1 = 0. Because witth ts definition and the addition, the complex numbersbecome an akgebraic field. Thus one can have division === numbers...Some physicist will be daft enough to produce a theory that ts is the> number of parallel universes!!!!!!Wait === about upper bound of magnitude of a complex root of polynomial> Let f(t) be a polynomial with complex coefficients of degree n and with > leading> coefficient = 1.> Let a be a root.> Show that | a | <= n b, where b is the maximum of the magnitude of the> coefficients of f(t).If |a| < 1, you're done. So assume |a| >= 1. You have f(t) = t^n + r(t). So a^n = -r(a). === scenarios to get the final score of a hockey gameI once got interested in the number of ways to get a particularbowling score (e.g., 1 way to get a 0 and 1 way to get a 300).Wrote a program to do ts (try it, it was kind of challenging).paper on th topic that had already been written (in J Rec Math or Math Mag orsomewhere similar). As I recall, the score that can be attainedthe most number of ways is in the 70's.Cp Klostermeyer> I use to know how to do ts with my eyes closed - but it's been some> time and I forget the formulas. Can someone help me figure out the> number of different combinations for the following.> The Final score of the hockey game was Team A 13 Team B 4> I went to sleep with the score tied 2-2.> What I am trying to figure out is, how many different ways could the> two teams have scored to arrive at the 13-4 final score.There were 13 goals scored after you went to sleep, and 2 of them were> scored by Team B. The number of combinations is the === Re: uniform convergence & differentiation>In many analysis-type texts I've found statements like since the series>converges uniformly, we can apply term-by-term differentiation and uniform>convergence allows us to differentiate term-by-term, but I've never>actually seen a proof or explanation of WHY you need uniform convergence to>legitimize term-by-term differentiation. Can someone explain ts? As others have noted, in general uniform convergence of a seriessum_n u_n(x) is not sufficient to be able to differentiate term by term.Perhaps the analysis was complex analysis? If sum_n u_n(z) isa sequence of analytic functions converging uniformly on compact subsetsof some domain in C, then you can differentiate === Reality> There was an Indian mathematican called Shakuntala who toured> the west beating the computers at multiplying two large numbers - must> have used vedic methods,Must have? Must have?Cite, or retract.I'll give you a clue - if you go to her website you won't see _one_ _single_ mention of vedic methods. IIRC.She's had my respect for about 25 years, wch was when I firstread her The Joy of Numbers, (I tnk that's what it's called - it was 25 years ago, rememeber). However, almost all of her computational feats have been bettered in recent decades. And none of the guys who've beaten her have claimed any usage of vedic methods either. Pl-- Unpatched IE vulnerability: DNSError folder disclosureDescription: Gaining access to local security zonesReference: === Subject: Re: [Set Theory] A set has a disjoint copy of itself ?>>I am looking for a proof that any set has a disjoint copy of itself,>>i.e. that given a set A, there exists a set B with the same>>cardinality as A, and such that A/B=0. I am hoping ts is true with>>ZF or ZFC.>B = {0} x ATs need not be disjoint from A. In fact, if we take a_0 = {0}, a_{n+1} = <0, a_n}, andlet A be the set of all a_n, then only a_0 is not anelement === Myth and Reality>Tell us about the grade-school method.O(N^2) pairs for two N-digit numbers.>What it is, and how it is the same as the method given.O(N^2) pairs for two N-digit numbers. Everytng else is irrelevant.Better than that, it's Theta(N^2).Or do I mean Ôworse than that'?Pl-- Unpatched IE vulnerability: dragDrop invocationDescription: Arbitrary local file reading through native Windows dragDrop invocation.Reference: http://msgs.securepoint.com/cgi-bin/get/bugtraq0302/12. htmlExploit: === Multiplication definition of two complex numbers> Why (a,b) x (c,d) = (ac - bd, ad + bc) ? (a,b) x (c,d) = (2ac - bd, ad + bc) also will serve to solve x^2 + 1 = 0.Another reason...numbers (a,0) are supposed to act like the real === en el> I.e., it is possible to prove directly, using only the definition of> derivative, that (e^x)' = e^x?> Of course it depends on how you define e^x> (and that I suppose depends on whether you tnk of it as e^x, that is> a number e raised to the power x or as an exponential function>> exp(x).)>> The definition of the function f(x) = a^x, a real, a > 0, that I always>> use, since secondary school to now, is the function whose value at x is>> the number a raised to the power x. And the definition of the number>> a^x is>> a^x = Lim(a^(x(n)), n, inf)>> where Lim(x(n), n, inf) = x, and the x(n) are rationals.>That requires proving that ts limit is independent of the sequence>x(n) (under the condition that it converges to x).>So then you have to decide what e is.There are various direct ways to prove that a^x is differentiable; start with a^(x+y) = a^x * a^y, andget bounds on difference quotients, wch have to converge just using that a^z -> 1 as z -> 0. Oneway of showing ts is that, if a > 1, and 0 < z < 1,a^z < z * (a-1).But just assuming a^x is differentiable, one getsits derivative is a^x*L(a), and L(ab) = L(a)+L(b).It is not too hard to get that L is a logarithm tosome base, and we may as === (sorry, maths not psych)Expires: 28 days>> If fields acted instantaneously, we would be>> able to use them for instantaneous communication.>>Please explain how you can use the fact that a force is>a static electric field, for instantaneous communication.>>Paul, puzzled> I'm sure some bright QMian would find a way.>>Backing out again, Henry?>>You cannot defend your assertion,>>but you will repeat it, won't you?>>And you will back out once more when>>asked to defend your repeated assertion, won't you?>>That's Henry Wilson's eternal circle of ßeeing>>restatements of ßed assertions.>>Paul, not surpriseda static electric field in an accelerator, the force doesn't act>the same instant as it enters the field, ts could be>used in instant communication.>> Paul, it should be obvious that if the effect of a field is instantaneous>> throughout the universe, then switcng it on an off in an intelligent manner>> can be used for instantaneous communication.Funny, eh? :-)Paul, enjoying the acrobatic show>Of course you are funny.If electric and magnetic fields acted instantaneously, light would travel atinfinite speed.Henri Wilson. See the Stupidity of === How many continuous functions are there?>>the existence of>>nonlinear functions where f(a+b)=f(a)+f(b) everywhere.> Thomas,that sounds interesting. Can you point me to an example or other > resources on such functions?> ,> There's not really that much to tell about them. You can't explicitly write them down, you need to use the axiom of choice.Here's a rough sketch of the existence of such a function:Use zorn's lemma to prove every vector space has a basis.Consider the vector space R over the field Q. Take a basis for it, B. w.l.o.g. let 1 be an element of ts basis. Let x be any other element.Define a map on the basis sending 1 to x, x to 1 and fixing every other element of the basis. Extend ts to a Q-linear map, f.Now, f is Q-linear so additive, but if f was R-linear then we would have for all t, f(t) = t f(1) = t x.But f(x) = 1. So x^2 = 1, x = +/- 1, wch isn't the case.That's about all you can do to stretch the discussion of such functions out past 5 minutes. :) A more interesting generalisation of ts is that linear operators on infinite dimensional vector spaces need not be === complex numbers> Why (a,b) x (c,d) = (ac - bd, ad + bc) ? (a,b) x (c,d) = (2ac - bd, ad + bc) also will serve to solve x^2 + 1 =0.There is much more to complex numbers than simply solving x^2 + 1 = 0.There are an infinite number of Ômultiplications' that solve it, includingyours.But, that is not an interesting find, with respect to complex numbers.(0,1)^2 + 1 = 0 iff (0,1)^2 = -1.(a,b)x(c,d) = (n(ac)-bd, ad+bc), works for any n.(0,1)x(0,1) = (n(0.0)-(1.1), (0.1)+(1.0)) = (-1, 0) = -1Addition and multiplication that satisfies the field postulates is required.Your multiplication function does not === work.WittSubject: Re: Ex(~x=x), counterpart theory, and self-different, it possesses some : > properties not possessed by it and, hence, must be a self-inconsistent : > object: : > : : you will find a description of a universe that is a proper part of itself. : : He calls it counterintuitive. I view it with about the same sense that you : suggest above.What language is ts description in?Is the tng's being a proper part of itself consistent, or inconsistent,with its being equal to itself, or identical with itself, or non-distinctfrom itself? : I believe it to be a failure to understand the relationsps between mereology : (part), set theory (element), and definite description (equals).How can you say that there is ANY failure involed here AT ALL, if thedescription of the universe is both syntactically grammatical AND logicallyconsistent? : It is not a matter of seeing whose is right and who is wrong.As a general rule, a consistent set of first-order axioms CANNOT POSSIBLYbe wrong. It can at worst be inadequate to its intended task. : It is not a : matter of ts alternative foundation is better than that alternative : foundation. It is a matter of seeing how the identity puzzles are resolving : themselves.You still haven't stated the identity puzzles.If you are appealing to sophomoric natural language stuff thenthe resolutions are pretty trivial. : Of course, everyone is so busy comparing deductive calculi and formal systems, : they seem to have forgotten that these tngs arose from plosopcal : considerations that were being debated prior to the introduction of such : calculi.And good riddance.You, conversely, seem to have forgotten that people couldn't even HAVEcoherent discourse about most of the questions until AFTER acevingformal language. The neologism was HELPFUL. : : Perhaps Mr. Greene is right. Perhaps not.Never say that out of context. Right ABOUT WHAT?WHAT DID I SAY???????????????????????????????????I repeat, the ONE tng I am CERTAINLY right about is thatyou HAVE to QUOTE the people you are disagreeing with!IN context!-- --- It's difficult ... you need to be united to have any strength, but internal issues have to be addressed. --- E. Ray Lewis, on liberalism === there? permission for an emailed response.X-Tom-Swiftie: VI is much better than EMACS, Tom said with joythe existence of> nonlinear functions where f(a+b)=f(a)+f(b) everywhere.> that sounds interesting. Can you point me to an example or other > resources on such functions?It's a consequence of the existence of a basis for every vector space,wch is a consequence of the axiom of choice, with the property thatevery element of the space is a linear combination of some finitesubset of the basis.You can characterize the reals as a vector space over the rationals(where the scalars are Q). The basis is then some (infinite) set of reals, such that every real rcan be expressed as q1*b1 + q2*b2 + q3+b3 + ... + qn*bn, where q1...qnare nonzero and rational, and b1...bn are in the basis and piecewiseunique. (N and the particular q's and b's of course depend on r.)Ok, now let b be some element of the basis. Then every real is:(1) q*b + q1*b1 + q2*b2 + ... + qn*bn, where b, b1, b2, ..., bn arepiecewise unique, q1...qn are nonzero and rational; q is rational butmaybe zero. Since ts is a basis for R, ts decomposition isunique.Define f(x) = the projection of x on the coordinate b. (That is, qin (1) above.)Clearly f(a+b) = f(a) + f(b). (It's a vector space, and b is a basiselement.) But since f(x) is always rational, we === Re: Need advice on letters of recommendation permission for an emailed response.X-Zippy-Says: Yow! Am I in Milwaukee?> Well, I should have said student, not students. And> in ts case, I treated it as a special situation. First,> it was a (very) foreign student. Second, the letter was> only for a summer job, not an internsp or grad school.> Trd, the situation came up suddenly, where few opportunities> are available for (very) foreign students and it was a > rush job (due that day) and the student thought she was doing > me a favor AND was quite polite about it. Fourth, the letter> was accurate and well-written, to a collaboration> of some friends. So I had no trouble signing my name to> it. I would have written a more glowing letter for her,> since she was a stellar student.Ah yes, that is a === Book>I am looking for supplemental text to aid in my learning of ODE and>PDE next semester. Currently my undergraduate text is Elememntary>Differential Equations with Boundry Value Problems by Derrick and>Grossman. Ideally, I would appreciate an text wch emphsizes>theoretical foundation over applied examples. Any suggestions are>greatly appreciated.Wow, that's a refresng change: most students these days are lookingfor lots of examples and no theory.You might look at M. Braun, Differential Equations and Their Applications, Applied Mathematical Sciences 15, Springer-Verlag 1975.Or a somewhat more challenging one: G. Birkhoff and G.-C. Rota, Ordinary === about upper bound of magnitude of a complex root of polynomial> sorry but what is $a$?Like many a guilty party === on Complex Analysis books?The subject says it -- however, I'd like to clarify> one detail: I'm looking for a book on *analysis*, as> opposed to Calculus (i.e., that covers rigorously> the concepts and proofs on Complex numbers and> Complex variables functions).I was amazed by the way you've put it. Ts means that for you it is> obvious that Calculus is *not* rigorous and it is *not* analysis. Have> you ever read, for instance, Michael Spivak's Calculus or Introduction> to Calculus and Analysis by Richard Courant and Fritz ?[...]I tnk he was referring to a fairly common convention; if fact, IIRC,in the preface to the second or the trd edition to s book Spivaksaid he should have called it Analysis or sometng like that but itwere to late to change the === personality assessment> ...>Where huffy == Correy (and so is self-identical)?>In another post by huffy, you signed (and clearly spoke as> Correy). >Why the (additional) pseudonym?> Most of the posts from huffy are not signed . Seems clear to> me that he's tired of having so many people disagree with m> so he's invented a imaginary playmate - he slipped signing one> of huffy's posts .Perhaps an idea for JSH? Setting up tens of imaginary playmates, all> agreeing with m?Well, well, well! If it ain't (Suk My) Dik! What's up, === books?>>THE classic text on complex functions is Ahlfors, _Complex Analysis_ .>> BArry Mazur has recently published a popular book on complex>>numbers _Imagining Numbers_. I would also recommend _Complex Numbers>>and Geometry_ by Hahn. Finally, a great old book: Theory of>>Functions_ by Caratheodory.>> I second the Ahlfors book. We used it as our Complex Analysis>textbook when I was a grad student at the University of Micgan.>I admit to never having looked at Ahlfors, but I have heard that it is a rather intense book - terse, with very difficult exercises. My impression is that it would be at too gh a level for a mathematical hobbyist (as the OP identified mself).-- Stephen J. Herschkorn === continuityim using the following definition of uniform modulus of continuity off:X->Y, where d_x and d_y are the metrics in X and Y respectively:omega_f (delta) = sup { d_y(f(x), f(a)) : a,x in X and d_x(a,x)<=delta}problem: if limit of omega_f(delta)/delta = 0 as delta goes to zero,then f is constant. i have already proved that f is constant iffomega_f(delta)=0 for all delta>=0. i also proved thatomega_f(t/n) >= 1/n omega_f(t) for all n in N and t in Rwch seemed useful at first, but now i can't get anywhere.can === of Gravity?Jack,Your recollection is absolutely correct. A Levi-Civita connection maybe represented as the sum of Affine connection (noncovariant entity) anda covariant tensor of nonmetricity (wch, by the way, in my view,describes gravitational field preserving energy-momentum, as describedin my papers, wch I e-mailed you after our chat in SF).Best metricity in Hagen Kleinert's senseguv^;v = 0i.e. Diff(4) divergence vanishes.I rewrite Einstein's zero torsion 1915 geometrodynamic classical local field equatonGuv = -(8piG/c^4)TuvasGuv = -alpha'Tuvalpha' = (string tension)^-1 = Witten parameterInfinite string tension means no gravity because space-time geometry is too stiff to bend.The local stress-energy density tensor of pure geometry is then triviallyTuv(Geometry) = (alpha')^-1GuvEinstein's field equation is then simply the balanceTuv(Geometry) + Tuv(Ordinary Mass-Energy) = 0Adding random micro-quantum zero point energy density from all quantum fields of spin 1/2 lepto-quarks and spin 1 gauge force bosons gives additional termtuv(zpf) = (alpha')-1/zpfguv/zpf > 0 is exotic vacuum dark energy with w = -1 negative pressure./zpf < 0 is exotic vacuum dark matter with w = -1 positive pressureDark matter detectors will never click except by false positives in my theory.Einstein's equation is thenTuv(Geometry) + Tuv(Ordinary Mass-Energy) + tuv(zpf) = 0In the 1915 theory with /zpf = 0Tuv(Geometry)^;v = 0from the Bianc identities.However these identities FAIL IMHO when /zpf =/= 0 and is variableand if there are torsion fields.In my theory (with Witten's h = c =1 convention)/zpf = (alpha')^-1[(alpha')^3/2[|MACRO-QUANTUM VACUUM COHERENCE|^2 - 1]guv = Minkowski metric + Kleinert World Crystal Lattice Strain TensorMake the Levi-Civita connection from guv in the usual way.World Crystal Lattice Distortion Field = du(x) = alpha'(Goldstone Phase of MACRO-QUANTUM VACUUM COHERENCE),uStrain Tensor = du(x),v + dv(x),uDiff(4) Landau-Ginzburg eq for VACUUM COHERENCE in a two-way feedback loop between IT World Crystal Lattice Distortion Field andBIT VACUUM COHERENCE in sense of Bohm's interpretation of IT(dden variable) + BIT(Pilot Wave of Active Information)Torsion fields meandu(x),v - dv(x),u =/= === >I've had students walk into my office with the letter >written for me and asking me to sign it. Let's call>that not standard (and not acceptable.)>Eek! The tng to do of course is to agree to write a letter anyway,>>insist that it be confidential, and then mention the details of the>>transaction in the letter.>> I disagree. There's a chance, at least, that the individual is>sincerely trying to be helpful. I had, on occasion, had professors I>asked for letters of recommendation tell me to just write it and I'll>sign it. Needless to say, I decided to go ask other people for>letters when that was the case, and I frown thoroughly on that>practice. But perhaps the student had encountered a similarly>ill-disposed professor, and thought he would save time by bringing a>letter ready? Absent other experience, he may well tnk that it>->is<- standard.I would certainly tell the student that the practice is not standard,>and should not be acceptable. I would also suggest that any professor>of s who has suggested ts method to m is NOT a good reference>writer, and he should seek to replace m.>Perhaps (well, more than perhaps) I am just lazy, but I disagree. It sometimes happens that a student has very few choices amongst referees. Ts happened to me (as the referee) once. It was te middle of fall semester, a first-year grad student needed a reference for some scholarsp fast, and I had only had m that semester. I looked at the form and what it asked and I knew that I could not knowledgeably answer the questions. I suggested he write a recommendation mself and give it to me. Then I could modify it to what I thought was appropriate. I would certainly not just sign it carte blanche.However, in ts case, I also suggested as a better procedure that the student contact professors at s undergraduate department; ts is what he did.-- Stephen J. === for NTS on proving a limit[...]>> I don't tnk there is any other way to obtain the> derivative of ln(x), is there? I mean, there is no> closed form expansion for ln(x+dx). And using the> Taylor series expansion of ln(x) (or ln(1+x)) is most> definitely cheating, since that series is justified> by what the derivatives of ln(x) are. (please do let> me know if there is another way that I've always been> missing! The way I remember learning it, is that the> derivative of ln is 1/x as a direct consequence of ln> being the inverse of e^x, and the derivative of e^x> being e^x). >> Another approach is to *define* ln x as int(y=1..x, 1/y) > What could be the justification for that? (other than> knowing that the derivative of the inverse of e^x is 1/x)What I mean is that how would you convince me that the> inverse of such function is e^x? (without using any> properties of e^x, and in particular, without using> the derivative of e^x or the fact that (e^x - 1)/x> has limit 1 when x -> 0 ),Carlos> -- > I like the functional equation approach.For log: we want log(x)+log(y) = log(x*y).log'(x) = lim (log(x+d)-log(x))/d (as d -> 0) = lim(log(1+d/x))/d = lim {(log(1+d/x)/(d/x)}/x = log'(1)/xThe natural log is the one with log'(1) = 1.Similarly, for exp, we want exp(x)*exp(y) = exp(x+y), so thatexp'(x) = lim (exp(x+d)-exp(x))/d as d -> 0 = lim (exp(x)*exp(d) - exp(x))/d = exp(x)*lim(exp(d)-1)/d = exp(x)*exp'(0) Cohen(I previously sent ts out, but I have not === factorization, from basic to advanced>In ts post I'll go from a rather basic factorization to a far more