Recent content by ak416

  1. A

    Why Does the Fundamental Solution of Laplace's Equation Cause Infinity in n=3?

    ya you're right. I didn't account for the change of coordinates. thanks.
  2. A

    Why Does the Fundamental Solution of Laplace's Equation Cause Infinity in n=3?

    Homework Statement From the book Evans-PDE, p.24, equation (12), It is written that C ||D^2f||_{L_{\infty}(R^n)} \int_{B(0,\epsilon)}|\Phi(y)|dy \\ \leq \begin{cases} C \epsilon^2 |\log{}\epsilon| & (n=2) \\ C \epsilon^2 & (n \geq 3) \end{cases} How is this?Homework Equations \Phi(y) =...
  3. A

    Example of dense non surjective operator

    Hi, can anyone give me an example of a bounded operator on a Hilbert space that has dense range but is not surjective? (Preferably on a separable Hilbert space) Im pretty sure such an operator exists since the open mapping theorem requires surjectivity and not just dense range, but its just...
  4. A

    Math or Physics for Graduate School in Theoretical Physics?

    So, just to extend my question, does anyone know of any Mathematical Physics programs out there that come with laboratory exposure or is this too much to ask for?
  5. A

    Math or Physics for Graduate School in Theoretical Physics?

    I am currently going into my 4th year of my undergraduate degree and I am looking at various possibilities for graduate school. I still haven't decided what my concentration will be but over the past 3 years I have acquired a pretty diverse background in economics, physics, math, and computer...
  6. A

    Can the Product of Non-Measurable Sets Be Measurable?

    In R2 instead of intervals for the outer and inner measure, rectangles are used (higher dimensional rectangles are used for Rn, and for an arbitrary product of subsets of R we would use the basis elements of the product topology, i guess this is most natural) ok about your counterexample, B...
  7. A

    Can the Product of Non-Measurable Sets Be Measurable?

    well from what i read in a more advanced textbook, is that a measure space is a set equipped with a measure function (with certain properties) that is defined on a sigma algebra (which defines the collection of measurable sets in the space). So ya, obviously, if you define the product measure in...
  8. A

    Boost Your Undergraduate Math Skills with Self-Study Textbook Recommendations

    Spivak - Calculus. Starts from foundations and gets to some real advanced stuff. Exercises are difficult, but you know how it goes, whatever hurts you only makes you stronger...Just make sure youre strong in basic logic. Look for books in predicate logic, it will definitely help.
  9. A

    Difference of two irrational numbers

    that was simple :)
  10. A

    Difference of two irrational numbers

    Im wondering if its possible given x,y irrational, that x-y is rational (other than the case x=y). The reason I am asking this is that I am reading a book on measure theory and they try to construct a non measurable set and they start with an equivalence relation on [0,1} x~y if x-y is rational...
  11. A

    Can the Product of Non-Measurable Sets Be Measurable?

    ok I am not so familiar with the formal definition of a measure space and the product measure. I was think more of something like this: given a finite number of non measurable sets in R (S1,...,Sn), their cartesian product is measurable ( By non measurable in R I mean the outer measure, m*S =...
  12. A

    Can the Product of Non-Measurable Sets Be Measurable?

    finite cartesian product: http://en.wikipedia.org/wiki/Cartesian_product And if yes, what about countable products or arbitrary infinite products?
  13. A

    Can the Product of Non-Measurable Sets Be Measurable?

    This is non measurable right?
  14. A

    Which Canadian University is Best for Mathematics and Physics Majors?

    Either Toronto or Waterloo. They are top in Math. I don't know much about Waterloo, but I do go to Toronto and I think it is perfect preparation if you want to go into grad school for Math/Physics. In your 4th year or even your 3rd year you can select from graduate level courses in such as...
  15. A

    Does a Set with Empty Interior Have Measure Zero?

    no actually it says in my book that the standard middle thirds cantor set has measure zero, but not any cantor set. So I guess its incorrect.
Back
Top