Riemann Definition and 586 Threads

  1. M

    (Riemann) Integrability under composition of functions

    Homework Statement I've been looking at how integrable functions behave under composition, and I know that if f and g are integrable, f(g(x)) is not necessarily integrable, but it -is- necessarily integrable if f is continuous, regardless of whether g is. So I was wondering, what about if g is...
  2. D

    Evaluating Riemann Sum f(x,y) - 4x^2+y

    The problem says: evaluate 4x^2+y by breaking into four congruent subrectangles and evaluating at the midpoints, 1=<x<=5 0=<y<=2 When i setup the rectangles these are my coordinates: (1,1/2),(1,3/2),(3,1/2),(3,3/2) and delta A = 2 My answer comes out to be 168...
  3. D

    Proving Riemann Integral: Non-Negative f(x)=0 $\rightarrow \int^{b}_{a}f=0$

    Homework Statement Suppose f(x):[a,b]\rightarrow\Re is bounded, non-negative and f(x)=0. Prove that \int^{b}_{a}f=0. Homework Equations The Attempt at a Solution I am trying to use the idea that lower sums are zero, and show that the upper sums go to zero as the norm of the...
  4. D

    Riemann geometry and hydrostatic

    I read in Elie CARTAN book : "la Géométrie des espace de Riemann" that when R = cte, you can compare space-time to hydrostatic description of a liquid. Is it true ?
  5. G

    Riemann Geometry: Where is the Flaw in My Thinking?

    One of the axioms of Riemann's geometry holds that there are no parallel lines and that any two lines meet. Since Riemann's geometry fits for that of a sphere, any two great circles of the sphere should intersect. However, if we were to take 2 longitudinal lines, then it is possible that these...
  6. L

    Integrals (Riemann-Darboux, Riemann, Lebesgue,etc)

    Homework Statement My book presents the Riemann-Darboux integral. It has a small supplemental section on the Riemann integral. Then a later section on the Riemann-Stieljes integral. Then a later chapter on the Lebesgue integral. A supplementary text that I have has a section on...
  7. M

    Calculating the Area of a Strip Using a Riemann Sum

    Homework Statement Write a Riemann sum and then a definite integral representing the area of the region, using the strip shown in the figure below where the upper line is defined by 6x + y = 12 and the other line is defined by y=x^2-4. The figure, which I can't get on here, is just the...
  8. Y

    Riemann sum question, with picture

    Homework Statement http://img4.imageshack.us/img4/898/integerqj5.jpg Homework Equations The Attempt at a Solution It does appear to be a Riemann sum, I figured the 1/n is probably the width of the intervals and the sum in brackets is related to the sums of the heights of the rectangles. But my...
  9. A

    Is the characteristic function of the irrationals Riemann integrable on [a,b]?

    The characteristic function of the RATIONALS is a well-known example of a bounded function that is not Riemann integrable. But is the characteristic function of the IRRATIONALS (that is, the function that is 1 at every irrational number and 0 at every rational number) Riemann integrable on an...
  10. T

    Grander than the Riemann Hypothesis

    ...But it may not exist yet. Has any mathematician thought about producing a formula or function which spits out all the prime numbers? i.e 1->2, 2->3, 3->3, 4->5, 5->7, 6->11 etc. Any attempts been made? What the closest that people have thought?
  11. science_rules

    Area approximation and (riemann?) sums

    Homework Statement I am a first-year physics student learning calculus. my question is about the approximation of the area of a region bounded by y = 0. Homework Equations Use rectangles (four of them) to approximate the area of the region bounded by y = 5/x (already did this one), and y =...
  12. J

    Mathematica Help with Right and Left Riemann Sums

    Homework Statement I am given a left riemann sum program module in Mathematica and need to convert it into the right riemann sum. The program takes values for x and f/x and the partition and graphs on a certain interval provided. leftRiemannGraph[f_, a_, b_, n_] := Module[{expr}, expr[1]...
  13. S

    Convergence of Riemann Sums for Limit of Series

    Homework Statement I need to find the following: \lim_{n\rightarrow\infty}\left(\frac{1^2+2^2+3^2+...+n^2}{n^3} \right) Homework Equations The Attempt at a Solution I know I could do the sum of the series to find the result but I would like to use Riemann sums. I think I have to start by...
  14. W

    Mathematicians' Original Work: Riemann & Taylor Theorems

    Can anyone provide me with a website that has copies of the original works of Riemann, Taylor, famous mathematicians. I am looking for papers on proved theorems.
  15. T

    Complex Zeros in Riemann Zeta Function: Is it Possible?

    in the Riemann Zeta function, is it possible to have two complex zeros off the critical strip that both have the same imaginary part?
  16. K

    Proof on a property of Riemann integrals

    Homework Statement Let f be continuous on [a,b] and suppose that f(x) \geq 0 for all x Є [a,b] Prove that if there exists a point c Є [a,b] such that f(c) > 0 , then \int_{a}^{b} f > 0 Homework Equations The Attempt at a Solution Using my books notation, Suppose P =...
  17. K

    Need some help with Riemann Sums.

    Need some urgent help with Riemann Sums. Homework Statement PART A: In all of this question, let I = \int ^{2}_{-2} f(x)dx where f(x) = -2x + 1 Evaluate I. PART B: Use the defintion of the definite integral to evaluate I. i.e Riemann Sum. Homework Equations The...
  18. N

    Comp Sci Calculating pi using Riemann Sum and Fortran77

    My assignment: Solve for pi using a Riemann Sum with n= 40,000,000. The function is the antiderivate of 4/(1+x^2) dx. The bounds are from 0 to 1. Solving this gives you pi. Anyone know how to do this? Preferably with fortran77?
  19. U

    Solving Riemann Sums for \int_0^{2\pi} x^{2}sin(x)\,dx | Homework Help

    Homework Statement Express the integral as a limit of Riemann sums. Do not evaluate the limit. Homework Equations \int_0^{2\pi} x^{2}sin(x)\,dx The Attempt at a Solution I really don't know where to start...any help getting me started would be highly appreciated!
  20. N

    Examples where it's Riemann integrable but no derivative exists at pts

    What is an example where it's Riemann integrable int(f(t),t,a,x) but no derivative exists at certain pts?
  21. N

    Example of Lebesgue Integral but not Riemann Integrable

    What's Example of Lebesgue Integrable function which is not Riemann Integrable?
  22. N

    Is the given function Riemann integrable?

    Here is the classic Dirichlet function: Let, for x ∈ [0, 1], f (x) =1 /q if x = p /q, p,q in Z or 0 if x is irrational. Show that f (x) is Riemann integrable and give the value of the integral. Is this actually true?
  23. S

    Real Analysis: Finding the Limit of a Riemann Sum

    Homework Statement Find the limit, as n -> infinity, of \sum_{k=1}^nk3/n4 Homework Equations Riemann sum: S(f, \pi, \sigma) = \sum_{k=1}^nf(\xi)(xk - xk-1) The Attempt at a Solution My guess is that I should try to put this sum in terms of a Riemann sum, and then taking n -> infinity will...
  24. E

    Does the Exponential k Term Complicate Proving the Riemann Hypothesis?

    \zeta (s)= \frac{1}{(1-2^{1-s})} \sum_{n=0}^{\infty} \frac {1}{(2^{n+1})} \sum_{k=0}^{n}(-1)^k{n \choose k}(k+1)^{-s} Is the main problem with trying to prove the hypothesis algebraically boil down to the fact that s is an exponent to a "k" term? Would a derivation of the function that had...
  25. E

    What makes the Riemann Hypothesis so difficult to prove?

    I have two questions: Why hasn't the hypothesis been proved yet? Is it because we don't know why re(s) has to be 1/2 and thus can't prove it, or is it because we know why re(s) has to be 1/2 but we just don't know how to prove it. Why exactly does re(s) have to be 1/2? \zeta...
  26. W

    Ricci-Tensor from Riemann in higher dimensional flat space

    This is driving me nuts. (I originally posted this to the coursework section, but in thinking about this, I felt that it might not be the right place (this is for a term paper, not really any ongoing coursework, so there). Hope I'm not imposing ... I feel quite embarrassed on this one, since it...
  27. E

    Can someone help me understand and evaluate the Riemann zeta function?

    I still don't understand a few things. Let's say we had a non-trivial zero counting function, Z_n(n), for the riemann zeta function. Couldn't we fairly easily prove the riemann hypothesis by evaluating \zeta (\sigma+iZ_n), solving for \sigma , then proving it for all n using induction...
  28. B

    Cauchy-Riemann Equations and Complex Derivatives: A Homework Problem

    Homework Statement Show that when f(z)=x^3+i(1-y)^3, it is legitimate to write: f'(z)=u_x+iv_x=3x^2 only when z=i Homework Equations Cauchy riemann equations: u_x=v_y , u_y=-v_x f'(z)=u_x+i*v_y The Attempt at a Solution u=x^3 v=(1-y)^3 u_x=3*x^2 v_y=-3*(1-y)^2...
  29. G

    Why Are Riemann Sums Confusing Without Function Curves?

    Alright, I started doing Riemann sums and I am ripping my hair out in frustration. I just can't wrap my head around how I'm supposed to do it, and my woefully vague textbook isn't helping either. I'm wondering how I'm supposed to solve a Riemann sum question with sigma notation (no limits), and...
  30. E

    Evaluating the Riemann Zeta Function: Step-by-Step Guide for \zeta(c + xi)

    Can someone show me the steps to evaluating \zeta(c + xi), where 0 \leq c<1?
  31. J

    Riemann curvature tensor as second derivative of the metric

    It is a standard fact that at any point p in a Riemannian space one can find coordinates such that \left.g_{\mu\nu}\right|_p = \eta_{\mu\nu} and \left.\partial_\lambda g_{\mu\nu}\right|_p. Consider the Taylor expansion of g_{\mu\nu} about p in these coordinates: g_{\mu\nu} = \eta_{\mu\nu}...
  32. W

    Robertson-Walker metric in higher dimensions (and problematic Riemann tensor)

    Hello folks, this is going to be a bit longish, but please bear with me, I'm going nuts over this. For a term paper I am working through a paper on higher dimensional spacetimes by Andrew, Bolen and Middleton. You can http://arxiv.org/abs/0708.0373" . My problem/confusion is in...
  33. Q

    Unraveling the Mysteries of the Riemann Curvature Tensor

    Homework Statement (My first post on this forum) Background: I am teaching myself General Relativity using Dirac's (very thin) 'General Theory of Relativity' (Princeton, 1996). Chapter 11 introduces the (Riemann) curvature tensor (page 20 in my edition). Problem: Dirac lists several...
  34. J

    Determination of Riemann curvature tensor from tidal forces

    Hi, Given a large number of test particles N, it should be possible to determine the Riemann curvature tensor by tracking their motion as they undergo geodesic deviation. Is there a minimum number N that will achieve this in any situation, or does it vary from problem to problem? How...
  35. B

    Book recs please - complex analysis, riemann surfaces, multi-valued functions

    Hi everyone, hope this is the right place to put this :) I have just finished "Theory of Functions" Vol. 1 & 2 by Konrad Knopp. I'd like to continue with a book that picks up where the second volume it left off. (Especially would be nice is a more "modern" book) The second volume is about...
  36. M

    Cauchy Riemann & Taylor Expansion.

    Hi There. Was working on these and I think I managed to get most of them but still have a few niggling parts. I've managed to do questions 2,3,3Part2 and I've shown my working out so I'd be greatful if you could verify whether they are correct. Please could you also guide me on Q1 & 4...
  37. I

    Riemann Hypothesis: Question on Critical Line

    I have a question concerning the Riemann Hypothesis, a conjecture about the distribution of zeros of the Riemann-zeta function. the trivial zeros (s=-2, s= -4, s=-6) arent much of a concern as the NON-trivial zeros, where any real part of the non-trivial zero is = 1/2. What i am having...
  38. C

    Lagarias’ equivalence to the Riemann hypothesis

    Lagarias’ equivalence to the Riemann hypothesis should be discussed, i.e., if hn := n-th harmonic number := 1/1 + 1/2 + · · · + 1/n, and σn := divisor function of n := sum of positive divisors of n, then if n > 1, hn + ehn ln hn > σn. There is a $1,000,000 prize for the proof of this at...
  39. C

    Proof of the Riemann Hypothesis

    http://arxiv.org/abs/0806.0892"
  40. H

    Prove Riemann Hypothesis: High School Student Guide

    i am a high school student i want to prove the riemann hypothesis but i do not how to start:confused:
  41. D

    Program for graphing Riemann zeta function

    Hello I plan on applying to the university of waterloo next year and due to the fact that many of my marks are not that great (failed gr 10 math) I decided to start a site to showcase my ability in math and programing. For those of you who are interested I wrote a program to graph regions of...
  42. S

    Riemann Integrability of f(x) = x on [0,1]

    f(x) = x , if x is rational = 0 , if x is irrational on the interval [0,1] i just wanted to check if my reasoning is right. take the equipartition of n equal subintervals with choices of t_r's as r/n for each subinterval. calculating the integral as limit of this sum (and...
  43. daniel_i_l

    What is the proof for the Riemann Series Theorem?

    Can anyone tell we how this: http://mathworld.wolfram.com/RiemannSeriesTheorem.html can be proved? The book that I read it in said that it was "beyond the scope of the book". It one of the coolest theorems I've read about. For example, it means that for any number (pi, phi, ...) there's...
  44. T

    Fortran What is the first approximation for Riemann Sum using Fortran 90?

    [SOLVED] Riemann Sum with Fortran 90 My assignment: Use Reimann Sums to estimate pi to 6 decimal places (ie: you can stop when successive iterations yield a change of less than 0.000001. For the Reimann Sums solution, an iteration equals 2X the number of segments as the trial before. Print out...
  45. L

    Lie derivative and Riemann tensor

    Suppose you have a spacetime with an observer at rest at the origin, and the surface at t = 0 going through the origin, and passing through the surface there are geodesics along increasing time. Then as you get a small ways away from the surface, the geodesics start to deviate from each other...
  46. P

    Evaluating a Riemann Sum for $\int^{-2}_{5} t^2 + 6t - 4 dt$

    [SOLVED] Riemann sum Important stuff: \sum i^2 = \frac{n(n+1)(2n+1)}{6} \sum i = \frac{n(n+1)}{2} And the solution: (Where I write "lim" I mean limit as n-->infinity. Where I write the summation sign I mean from i=1 to n.) lim \sum t^2 + 6t - 4 \Delta t \Delta t = \frac{5 -...
  47. M

    Summation - Riemann Intergral -

    [SOLVED] Summation - Riemann Intergral - URGENT Homework Statement Im working on the upper and lower riemann sums of f(x) = exp(-x) where Pn donates the partition of [0,1] into n subintervals of equal length (so that Pn = {0,1/n,2/n,...,1}) Homework Equations The Attempt at...
  48. R

    Proving Riemann Integrability of a Function to Zero

    Homework Statement Prove that the function specified below is Riemann integrable and that its integral is equal to zero. Homework Equations f(x)=1 for x=1/n (n is a natural number) and 0 elsewhere on the interval [0,1]. The Attempt at a Solution I have divided the partition into...
  49. Shaun Culver

    Advice on complex analysis, Riemann surface & complex mappings.

    Could anybody please give advice for the study of complex analysis, Riemann surfaces & complex mappings. These subjects form the content of chapters 7 & 8 of Roger Penrose's "The Road to Reality". Any advice will do: maybe suggestions on books to supplement the learning, or books to further my...
  50. S

    Proving a Function is Riemann Integrable

    Homework Statement Let f, g : [a, b] \rightarrow R be integrable on [a, b]. Then, prove that h(x) = max{f(x), g(x)} for x \in [a, b] is integrable. 1 Homework Equations Definition of integrability: for each epsilon greater than zero there exists a partition P so that...
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