# Search results

1. ### Looking to round out my [math] classes.

Well, I can list some topics, but other people will have more to say (the following is in roughly order of importance with the most important at the top; but lots of people will probably disagree and I might agree with their disagreements once I see them): complex analysis more analysis an...
2. ### Real Analysis or Complex Analysis

Not knowing anything about you personally, I would assume this would be very difficult. I would imagine most grad complex analysis classed already assume you know a lot of stuff (like what is an analytic function, Cauchy's theorems, maximum modulus stuff, etc) and these topics are quickly...
3. ### Why Banach spaces?

We all know the the epsilon delta definition of a limit of a sequence. But, if I give you a sequence, to use this definition to determine if the sequence converges, you have to know (or have a good guess) about what the limit is converging to. If this is a sequene of numbers, it might not be so...
4. ### Does anyone know an infinite series summation that is to 1/5 or 1/7?

If you want a series that converges to c, take a series that converges to b, and add this term: (c-b) to the front.
5. ### Difference between the A conjugate and A dagger

Are you sure the matrix is real? Usually if the matrix is real, people say "Orthogonal" instead of "Unitary" and instead of using a star, they use either a T or a dagger (T is to denote transpose.) Does the paper explicitly say that the matrix is real?
6. ### Is it really true that, for any n > 0 , there is a prime between 2 ^ n

I don't understand why you would want to publish your problem so that other people can solve it? You came up with the problem; don't let someone else solve your problem for you. Publishing a conjecture in some kind of journal might be nice, but working hard to solve it and then publishing the...
7. ### Lazy Group Proofs and Efficiently Using Categories

Well, you could define a group that way, but at some point, you'll have to show that this definition of group and the "normal" definition are the same. And then there's all the stuff that Office_Shredder said. I'm not very experienced with category theory, but it seems that one of the best...
8. ### Interchaning Limits and Inner Products

Well, I was just pointing out that uniform convergence is still important when it comes to lebesgue integral, even though you are certainly correct that uniform convergence doesn't play nearly the same role in lebesgue integration as in riemann.
9. ### Interchaning Limits and Inner Products

I don't think this is quite true. For example, Egorov's Theorem is a theorem about uniform convergence. Most of the time, though, this is used on a compact set, and as long as the functions are also riemann integrable, we can just use riemann integrals, but this isn't always the case and can be...
10. ### Interchaning Limits and Inner Products

I'm not sure this is correct. For example, functions can converge in L2-norm with out converging uniformly. Indeed, functions can converge in L2-norm with out even converging ae. True, but so what? This is not relevant in this case. This is true, but you don't need hypotheses this strong...
11. ### Prove or disprove the following statement using sets frontier points

As a side question, what the heck is a "frontier" of a set? This looks equivalent to the definition of boundary. Is this just another word for boundary? If so, why? That is, why have a new word?
12. ### Lemma Lucas theorem

It means that p divides the numerator of the fraction but not the denominator. So, p divides the fraction.
13. ### Lemma Lucas theorem

I am assuming p is prime. Do you agree that p divides p! and that p does not divide k! and that p does not divide (p-k)! ? If so, then p must divide p choose k since there are no factors of p in the denominator that would "cancel" the p in the numerator. As a side note, I would suggest not...
14. ### Trigonometric Orthogonality Query

Yes, m and n must both be integers. Otherwise, as you pointed out, the two functions are not orthogonal. So, not only must m and n but integer differences of each other, they must both be integers.
15. ### Pumping lemma condition 3

If I understand correctly, the pumping lemma gives you a number, p, such that a bunch of stuff happens. Can you reference the exact pumping lemma you are talking about?
16. ### Integral of sinx/x

Ahhh, yes, I see. It is obvious. Just as we can evaluate \lim_{x\to 0}x/x with out the function existing at 0. Thanks!
17. ### Integral of sinx/x

It is well known that \sin x / x is not Lebesgue integrable on [0, +\infty) though it is (improper) Riemann Integrable. It is also fairly easily shown (integrating by parts) that \Bigg\lvert \int\limits_{a}^{b} \frac{\sin x}{x} dx\Bigg\rvert \leq 4 Since [a,b] is compact, the Riemann and...
18. ### Challenge: Submit Extremely Difficult Math Problems!

You seem to be confusing "trivial" with "the solution is short to write down." I don't think that this problem is all that trivial, and your solution is certainly not. I haven't really given it much thought, but I think most people would use the intermediate value theorem or something...

If P is the variable that you are integrating. For example, \int \sin(x^2) d(x^2) can be computed the way it seems you want to compute it. That is, \int \sin(x^2) d(x^2) = - \cos(x^2) . However, \int \sin(x^2) dx \neq - \cos(x^2). The question you are asking has a lot to do with the integration...
20. ### Moving limits in and out of functions

If you are using the \epsilon - \delta definition of continuity, then the idea is that eventually x_n will be within to x and so f(x_n) will be withi in \epsilon of f(x). But this is exactly what it means for f(x_n) to converge to f(x).
21. ### Way to re-express this equation by writing x and y separate?

If you are trying to get estimates on something (like upper bounds) you can use Cauchy Schawrtz: \sum_{i=0}^{n} x^{i}*y^{i} \leq (\sum_{i=0}^{n} x_i^2)^{1/2}(\sum_{i=0}^{n} y_i^2)^{1/2}
22. ### How to see the forest through the trees? (How not to miss the obvious?

5 minutes?!?! That's all? Come back when that changes to an hour or a day or something.
23. ### Upper-level Linear Algebra or upper-level ODEs?

I don't understand how he can take Diff Eq without linear algebra. Has he already taken some "lesser" linear algebra? Perhaps stuck into the calc sequence?
24. ### Undergraduate Math Outside the Classroom

Well, your proofs probably suck, but don't be worried about that at all. You are thinking about proving stuff, which puts you heads and shoulders above nearly everyone else. Learning to write proofs is hard, and you will not be a great proof writer when you first begin writing them. Good...
25. ### Hey guys! What course should I take? (Pure maths)

Do they offer a topology class? Or perhaps another analysis class (or do you already have to take these?) If it is between these two, I would pick the Geometry class.
26. ### Understanding math - what does it mean?

Why in the world would you think this?? As a matter of fact, the exam you describe seems a lot like ordinary exams I took. Perhaps the one you describe is slightly more involved than an ordinary midterm exam, but it seems about right for a final exam.
27. ### Show L^p(E) is separable for any measurable E.

Though it isn't true if p = infinity, is it?
28. ### Schools Odds of getting into a top 30 math graduate school?

I'm currently at GaTech and your application is much stronger than mine was. Though, I think I was helped by the fact that I did undergrad at GaTech. I know, I know, people say it is bad to do grad school where you do undergrad, but I am married, my wife is in school, and it is just too...
29. ### Preparation Material for Analysis I

That link looks more like an Advanced Calculus class and it is probably more along the lines of what is in Spivak rather than what is in a "true" analysis course. If the Table of Contents is a good indication, the link has a few topic not covered in Spivak (the multivariable stuff.) I would...
30. ### Prove the typewriter sequence does not converge pointwise.

I suggest drawing the graph for each of the functions and you should be able to see what is happening and why fn(x) does not converge for any x.