# Search results

1. ### Length of an infinite square well?

Actually, this is more of a general question relating to a homework problem I already did. I was given the initial wavefunction of a particle in an infinite square well: \Psi(x,0) = Ax if (0 \leq x \leq \frac{a}{2}), and =A(a-x) if (\frac{a}{2} \leq x \leq a) And of course \Psi(0,0) =...
2. ### Linear Algebra: Invariant Subspaces

My textbook states that for operators on complex vector spaces with dimension greater than one, and real vector spaces with dimension greater than two, that there will be invariant subspaces other than {0} and V. Maybe the book means for a particular operator?
3. ### Linear Algebra: Invariant Subspaces

Homework Statement Prove or give a counterexample: If U is a subspace of V that is invariant under every operator on V, then U = {0} or U = V. Assume that V is finite dimensional. The attempt at a solution I really think that I should be able to produce a counterexample, however...
4. ### Specific Linear Map Example

Homework Statement Give a specific example of an operator T on R^4 such that, 1. dim(nullT) = dim(rangeT) and 2. dim(the intersection of nullT and rangeT) = 1 The attempt at a solution I know that dim(R^4) = dim(nullT) + dim(rangeT) = 4, so dim(nullT) = dim(rangeT) = 2. I also...
5. ### More linear maps

ok, but can I at least write a basis for null(T) and range(T)? I can't see how to prove this without defining something, because I know I can't prove this by only referring to the finite dimensions of null and range.
6. ### More linear maps

Homework Statement Prove that if there exists a linear map on V whose null space and range are both finite dimensional, then V is finite dimensional. The attempt at a solution I *think* the following is true: For all v in V, T(v) is in range(T), otherwise T(v) = 0 which implies v is in...
7. ### Linear Algebra, Linear Maps

:zzz: I should be able to stay awake long enough to write down my solution. Thanks for the help!
8. ### What's the integral of u''(x)/u'(x)?

you need to do u substitution
9. ### Linear Algebra, Linear Maps

Gosh, I must be getting sleepy to overlook the importance of n being unique. So, I can show that each element of V can be written uniquely as a sum of u + n. Should I also prove U = {au : a is in F} is a subspace of V
10. ### Linear Algebra, Linear Maps

n and n' could definitely be different, but I don't think it matters much since they both get mapped to zero. Is the result of a = a' is enough to prove uniqueness for a direct sum?
11. ### Linear Algebra, Linear Maps

if V were finite dimensional then I could say, dim{null(T)} = dim(V) - dim{range(T)}. But nothing given in the problem statement will let me assume V is finite.
12. ### Linear Algebra, Linear Maps

Homework Statement Suppose that T is a linear map from V to F, where F is either R or C. Prove that if u is an element of V and u is not an element of null(T), then V = null(T) (direct sum) {au : a is in F}. 2. Relevant information null(T) is a subspace of V For all u in V, u is not...
13. ### Epidemic models which incorporate disease evolution

I was wondering if anyone knew anything about epidemic models which take into account the ability of a disease to mutate. Basically I’m curious if there are any existing models which could predict how a rapidly changing disease might affect the progression of an epidemic, or how slower...
14. ### LaTeX Including graphics in LaTeX Help!

Ok, I went into my maple worksheet and chose to export my graph as an .eps, but the file says that it is postscript. I'm also very confused by some of the instructions on the links. For example at http://amath.colorado.edu/documentation/LaTeX/reference/figures.html In the 'Only...
15. ### LaTeX Including graphics in LaTeX Help!

I included all those commands, but I still got the same warning and error. What's the difference between .ps and .eps and why would latex require me to use .eps?
16. ### LaTeX Including graphics in LaTeX Help!

Latex gave me one warning and one error. Latex warning: file 'myfile.ps' not found on line41 ! Latex error: unknown graphics extention: .ps I did use \usepackage{graphicx} in my document, I just typed it wrong in this thread. And as far as having a graphics package instaled, I'm...
17. ### LaTeX Including graphics in LaTeX Help!

hi, I'm trying to put a graph generated in maple into a latex document, but I have no experience using either program. So far I've been able to save my maple plot in postscript format, and based on various online tutorials I've included the \usepackage{graphics} comand after...

Thanks!
19. ### Linear Algebra: Subspace Proof

Since u and v are elements of the intersection, u and v will also be elements of any subspace W that is in the intersection. And since u and v are in W and W is a subspace, this guarantees that u+v will also be in W. This same argument would apply to scalar multiplication. Is that the...
20. ### Linear Algebra: Subspace Proof

Prove that the intersection of any collection of subspaces of V is a subspace of V. Ok, I know I need to show that: 1. For all u and v in the intersection, it must imply that u+v is in the intersection, and 2. For all u in the intersection and c in some field, cu must be in the...
21. ### G.c.d.'s and PID's

Homework Statement Prove: If a, b are nonzero elements in a PID, then there are elements s, t in the domain such that sa + tb = g.c.d.(a,b). Homework Equations g.c.d.(a,b) = sa + tb if sa + tb is an element of the domain such that, (i) (sa + tb)|a and (sa + tb)|b and (ii) If f|a and...
22. ### Guided proof to the isomorphism theorems.

Homework Statement Let G_1 and G_2 be groups with normal subgroups H_1 and H_2, respectively. Further, we let \iota_1 : H_1 \rightarrow G_1 and \iota_2 : H_2 \rightarrow G_2 be the injection homomorphisms, and \nu_1 : G_1 \rightarrow G_1/H_1 and \nu_2 : G_2/H_2 be the quotient epimorphisms...
23. ### Solving trigonometric equations

Actually, aslong as the arguments match it equals one. So (sin(3x))^2 + (cos(3x))^2 does equal one.
24. ### Solving trigonometric equations

What are you trying to solve? You could substitute numbers for the x's and compute the value. I don't believe there's a nifty identity for (sin(3x))^2 + (cos(3x))^2 even though it does look somewhat similar to (sin(x))^2 + (cos(x))^2.
25. ### Infinite Dimensional Linear Algebra Proof

Ironically, the book is called 'Linear Algebra Done Right' 2nd ed. by Sheldon Axler. I don't exactly love it, but it is what I'll be using this fall so I better get used to it. :rolleyes:
26. ### Infinite Dimensional Linear Algebra Proof

Thanks for all the help! The book I'm working from does not discuss infinite dimensional vector spaces. It only gives a brief description of $\mathbf{F}$^{\infty} and P(F), the set of all polynomials with coefficents in $\mathbf{F}$. In particular it says, "because no list spans P(F)...
27. ### Infinite Dimensional Linear Algebra Proof

Prove that $\mathbf{F}$^{\infty} is infinite dimensional. $\mathbf{F}$^{\infty} is the vector space consisting of all sequences of elements of $\mathbf{F}$, and $\mathbf{F}$ denotes the real or complex numbers. I was thinking of showing that no list spans $\mathbf{F}$^{\infty}, which would...
28. ### Spring Forces

Well, in question B. they ask for the spring force which is in units of Newtons. The units in your answer are in joules, but you need them to be in Newtons in order for the answer to make sense.
29. ### Help with freefall problem please.

I think you've got the right idea. You want to split it into two problems; one for going up, and the other for coming back down.
30. ### Help with freefall problem please.

We don't do that here. However, if you show the work you've already done on this problem, people will point out your mistakes and help you solve your own problem.
31. ### Science Fair Project, !

First ask yourself why you believe this would actually happen. Why would the teen time be less than the adult time? The answer to this question should also give you some ideas for a keyword search.
32. ### Smack the Penguin

HA! His fabulous cooking is no match for me! I just act like I have no will of my own. Reverse psychology: He thinks he has superpowers, I get fed, and it insures more fabulous meals in the future! :wink: Shhh... don't tell Tom, he might stop cooking for me.
33. ### Science ? marriage

Why would you ever want to date a normal person? :eek:
34. ### Science ? marriage

Well, when a girl scientist and a boy scientist like each other a lot, they try to impress one another with their intelectual prowess. If their witty banter goes well they exchange tokens of their mutual affection (such as a calculator or a Schaum's outline). If they stay together long...
35. ### Smack the Penguin

You just had to drag me into this :grumpy: didn't you. I'm going to stuff you into a cannon and find out how far you fly! "Oh, wait, MIH, once you get him in your sights, if he's cute, don't shoot! " He won't be so cute after I launch him across the Hudson river :devil:
36. ### Homework talking about time

Look in the section of the book which is associated with that homework set. 'Usually' the information you need is contained in the chapter preceding the question. What topics are you currently learning from your textbook?
37. ### Paper on time travel

Don’t be afraid to post something; people on this forum are here to help, not judge. Besides, that’s the beauty if the internet… It’s anonymous. :biggrin:
38. ### Paper on time travel

"but i didnt make a separate thread abouut it coz moderators wouldn't like it" There would be no point in starting another thread on the same topic. "i have focused my paper on technical and logical aspects of it" I didn't catch this the first time through. It sounds like you're well...
39. ### Paper on time travel

How is it that you have written 7 pages when you do not yet have a thesis statement, a basic outline of what sub-topics you want to discuss, or any idea as to how you want to structure your discussion? :confused:
40. ### Do we have to obey physics

There is nothing that tells us 'things must obey these descriptions' absolutely every single time. This is the big difference between science and other explanations (ie religion) for the state of the world around us. Scientific theories must be falsifiable. When we observe something which...
41. ### Rates of convergence

hi, I'm doing some of the same stuff in my analysis class, and in my class notes the teacher wrote that sin(x) = O(x), not x^2. Going back to the definitions of 'little o' and 'big O' might help. f = O(g) means that the ratio of f/g is bounded by some constant, where f = o(g) means...
42. ### Root of all evil

Evil trees? o:) Actually, I'm curious. What is your definition of evil? I don't think I could really comment on the 'cause of all evil' without knowing your definition of evil itself.
43. ### Simple Question about Partial Derivatives

Try looking in your calculus book for 'chain rule for functions of several variables' or some similar topic. It's just a differentiation formula.
44. ### Fast Talker Project

You've got the right idea, just don't forget to compute t(5).
45. ### Physics Audio Tapes

You could try the math and science tutorial section, or the links here at PF. I don't know if there would be any audio tutorials. You might want to check out your community or university library. Also, try asking local bookstores if they carry such products.
46. ### Good beginner books?

Serway is calculus based, so if you were taking an algebra/trigonometry-based physics course, I could see how Serway would be confusing.
47. ### Good beginner books?

The first physics course I ever took used the 'pre-edition' of Knight's book. The text was free but it was AWFUL! The next semester I was required to buy the 1st ed. of the Knight book. The stupid thing was still chock full of typos and unclear language. And worse than typos; in the...
48. ### QM Value of an infinite sum

:blushing: hey, thanks a bunch! Do you happen to know how it was derived, and if so, was my telescoping series idea correct?
49. ### QM Value of an infinite sum

hi, In the course of doing my quantum homework I ran into a bit of a snag. In one of my calculations I need to replace the sum from n = 1 to infinity of 1/n^2 (for odd n only) with its number value. My book instructs me to get the information from a table and actualy gives the value (for...
50. ### Catching up

Try drawing two pictures; the first showing the initial conditions, and the second showing the final conditions when you've caught the bus. Once you've drawn the pictures, make sure you listed all your knowns. List your kinematics formulas so you can see what you have to work with...