Commute Definition and 68 Threads

  1. M

    Solving Esther's Morning Commute Problem

    Homework Statement Esther drove to work in the morning at an average speed of 40 miles per hour. She returned home in the evening along the same route and averaged 30 miles per hour. If Esther spent a total of one hour commuting to and from work how many miles did Esther drive to work in the...
  2. B

    Simultaneously unitarily diagonalizeable matrices commute

    Homework Statement Matrices A and B are simultaneously unitarily diagonalizeable. Prove that they commute. Homework Equations As A and B are simultaneously unitarily diagonalizeable, there exists a unitary matrix P such that P^{-1}AP = D_{1} and P^{-1}BP = D_{2}, where D_{1} and D_{2}...
  3. BobG

    Death Defying Commute: Harrowing Commute to Work

    You think your commute to work can be harrowing, how about this commute: Death Defying Commute. That dog seems so trusting. You just know that someday... Imagine moving to the other side of the bridge with your bed, your TV, your television, your stereo, the dog house... I've actually...
  4. A

    If two operators commute (eigenvector question)

    Suppose \Omega_1 and \Omega_2 satisfy [\Omega_1,\Omega_2]=0 and \Omega = \Omega_1 + \Omega_2. If \Psi_1 and \Psi_2 are eigenvectors of \Omega_1 and \Omega_2, respectively, don't we know that the (tensor?) product \Psi = \Psi_1 \Psi_2 is an eigenvector of \Omega? Also, if the \Psi_i are...
  5. haael

    Can Momentum and Spin Be Measured Simultaneously?

    I did some maths and I found that angular momentum operator does not commute with normal mometum: [ J_{\alpha \beta}, P_{\gamma}] = \eta_{\alpha \gamma} P_{\beta} - \eta_{\beta \gamma} P_{\alpha} Now, the "third" component of angular momentum: J_{z} := J_{x y} [J_{z}, P_{x}] = -P_{y} [J_{z}...
  6. L

    How to prove that if x^n*y=y*x^n, then x and y commute

    Let x and y be elements of a group. I can see that it works the other way, i.e. if x and y commute, then y*x^n = x^n*y...
  7. V

    Does the Riemman tensor and the covariant derivate commute?

    A random question - Does the Riemman tensor and the covariant derivate commute? a yes/no answer would suffice, but any explanation would be welcome:) From the equations, it looks as though they do for flat metrics - but if we have other manifolds, it seems to me that the Christoffel...
  8. D

    Hermitian operator-prove product of operators is Hermitian if they commute

    Hermitian operator--prove product of operators is Hermitian if they commute Homework Statement If A and B are Hermitian operators, prove that their product AB is Hermitian if and only if A and B commute. Homework Equations 1. A is Hermitian if, for any well-behaved functions f and g...
  9. V

    Commutators and Their Properties in Quantum Mechanics

    If we define: A_{j}=\omega \hat{x}_{j}+i \hat{p}_{j} and A^{+}_{j}=\omega \hat{x}_{j}-i \hat{p}_{j} Would it be true to say: [A_k , (A^{+}_{i}+A_i)(A^{+}_{j}-A_j)]=0 My reasoning is that, because [\hat{x}_{j}, \hat{p}_{i}]=0 the the ordering of the contents of commutation...
  10. 3

    If two permutations commute they are disjoint

    Homework Statement If \alpha,\beta\in S_n and if \alpha \beta = \beta \alpha, prove that \beta permutes those integers which are left fixed by \alpha. Show that \beta must be a power of \alpha when \alpha is a n-cycle. The other way round is easy to see, since if two cycles are disjoint...
  11. D

    Do L² and r² Commute in Quantum Mechanics?

    Hi The subject says it all. I'm wondering if [L^2,r^2] = 0 is true? regards Frímannn
  12. R

    What's considered a long commute time to consider residence?

    2 hours? (1 hour there and back)
  13. O

    What Makes the Middle of the Drawbridge the Highlight of Your Commute?

    http://photos-853.ll.facebook.com/photos-ll-sf2p/v236/27/91/575983853/n575983853_940536_3472.jpg The middle of the drawbridge - where the two platforms meet - is pointy (like f(x)=-|x|). So you get up a bit of speed on your bike as you approach the centre and then enjoy the weird...
  14. C

    Does every observable commute with the hamiltonian?

    I would guess that they would as every observable is a function of the q's and p's and as those commute with the hamiltonian I couldn't imagine an observable that wouldn't commute, however are there any other cases where an observable won't commute with the hamiltonian?
  15. T

    Kids Zip Line to School - Sure Beats the Commute!

    http://www.noob.us/miscellaneous/kids-ride-a-zip-line-to-go-to-school/ That's just awesome. It's like Six Flags every day, but without the accidents.
  16. edward

    What makes Stremnaya Road in Bolivia a popular route for mountain bikers?

    Stremnaya Road Bolivia. http://www.driftlive.com/dl/2006/12/11/stremnaya-road-in-bolivia/
  17. DaveC426913

    How do I only work 3.5 days a week but still have a full-time job?

    I live in one town on the weekend and work in another during the week, commuting only once each way per week. I do not work in my home town. I work four full days a week, yet in any given week I manage to spend as many days at home as I do at work. How do I manage this?
  18. S

    Finding Commuting Permutations in S_6 for alpha=(1 2 4 5)

    8 permutations that commute... Find 8 Permutations that commute with alpha=(1,2,4,5) I do not understand the concept of commuting with permutations.
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