What is Numerical: Definition and 772 Discussions

Numerical analysis is the study of algorithms that use numerical approximation (as opposed to symbolic manipulations) for the problems of mathematical analysis (as distinguished from discrete mathematics). Numerical analysis naturally finds application in all fields of engineering and the physical sciences, but in the 21st century also the life sciences, social sciences, medicine, business and even the arts have adopted elements of scientific computations. The growth in computing power has revolutionized the use of realistic mathematical models in science and engineering, and subtle numerical analysis is required to implement these detailed models of the world. For example, ordinary differential equations appear in celestial mechanics (predicting the motions of planets, stars and galaxies); numerical linear algebra is important for data analysis; stochastic differential equations and Markov chains are essential in simulating living cells for medicine and biology.
Before the advent of modern computers, numerical methods often depended on hand interpolation formulas applied to data from large printed tables. Since the mid 20th century, computers calculate the required functions instead, but many of the same formulas nevertheless continue to be used as part of the software algorithms.The numerical point of view goes back to the earliest mathematical writings. A tablet from the Yale Babylonian Collection (YBC 7289), gives a sexagesimal numerical approximation of the square root of 2, the length of the diagonal in a unit square.
Numerical analysis continues this long tradition: rather than exact symbolic answers, which can only be applied to real-world measurements by translation into digits, it gives approximate solutions within specified error bounds.

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  1. E

    Can Gaussian Wave Functions Describe Particle Motion in Magnetic Fields?

    Hi there! I have to numerically solve the Schroedinger equation for a particle in a static magnetic field. Until now I've used the split operator technique using the Fourier transform. The problem is that this technique requires that the hamiltonian operator can be decoupled as: H(\vec x, \vec...
  2. sankalpmittal

    A Numerical on motion in one dimension .

    Homework Statement A boy throws a ball with v velocity upwards as well as downwards . What will be the displacement covered by the two balls if air friction and external force or viscosity is neglected ? Homework Equations According to me the equations of motions are relevant here ...
  3. S

    MATLAB Numerical Integration in MATLAB

    Hello, found this forum very instructive! I had this doubt of numerical integration in MATLAB. I have to perform this integration in matlab: r = 0:0.01:22.5; //necessary because they automatically become lower and upper limits of integration! theta=0:pi/100:pi; // limits are not to be...
  4. J

    What is an easy way to calculate numerical integration uncertainty/error

    i'm measuring a waveform (pulse) that i want to integrate the area under. i take a bunch of samples and use one of the basic numeric integration methods (Trapezoidal, Simpson's, Boole's) what is a fairly easy method to estimate the uncertainty/error of the numeric integration compared to...
  5. H

    What is the best numerical method for

    An equation of the form: \frac{\partial A}{\partial t}+\frac{\partial B}{\partial x}=C I am thinking Lax-Wendroff.
  6. S

    How Do Eigenvalues of a Three-Dimensional Harmonic Oscillator Arise?

    Homework Statement Kindly look at the attachment for the statement. Homework Equations L^2 (psi) = E (psi) The Attempt at a Solution For Part B, I wrote Lx, Ly, Lz in operator form. Thus I get L^2. L^2 (psi) = E (psi) psi = E^-alpha.r^2/2 So I get energy eigenvalue 2 h cross...
  7. I

    Numerical real-space, real-time green's functions?

    Is there any numerical work on Green's functions in real-space and real-time? The reason I ask is that it seem the self-energy diagrams correspond to much simpler expressions in space-time than in energy-momentum. However, I suspect the space-time greens functions are sort of pathological...
  8. J

    Numerical 2D Harmonic Oscillator

    I'm solving the 2D harmonic oscillator, numerically. -\frac{1}{2}\left( u_{xx} + u_{yy}\right) + \frac{1}{2}(x^2+y^2)u = Eu The solutions my solver spits out for say, the |01> state, are linear combinations of the form |u\rangle = \alpha_1 |01\rangle + \alpha_2 |10\rangle which is...
  9. T

    Numerical Simultaneous Solution of Non-Linear Coupled Equations

    For the solution to this problem, I have reduced the number of equations down from 17 to 6. Due to algebra reasons, these equations cannot really be solved symbolically (MAPLE tried, and return four full pages packed with symbols, just for one equation). These three equations need to be solved...
  10. N

    Projectile Motion Help: Calculating Direction of a Ball Thrown from a Cliff

    Homework Statement a ball is throwm horizontally from top of a cliff with velocity 10meter per second. height of cliff above the ground is 45 meters. calculate the direction of ball to horizontal surface just before it hits the grouND The Attempt at a Solution i found time=3s...and horizontal...
  11. D

    Asymptotes for numerical solution of ordinary differential equation

    Hi! I have a differential equation coming from Boltzmann transport equation which is a bit complicated and should be solved numerically instead of analytically. I managed to get a plot using Runge-Kutta with software Derive. The equation is in the second attachment. In the papers of my...
  12. W

    Numerical mathematics, Newton's method

    Homework Statement "The goal of this task is to check that you understood the derivation of Newton’s method in the lecture. 1. Consider a smooth function G defined from \mathbb{R}^N to \mathbb{R}^N. Suppose it admits a fixed point r \in \mathbb{R}^N. Write down the Taylor development of this...
  13. W

    Numerical multidimensional integration over function of six variables

    So, I'm writing a program in matlab. I have a function of six variables, say f(x1,x2,x3,x4,x5,x6). I want to integrate over x4, x5, and x6 numerically. f is defined over a 10 sided 6-cube of points. I also want to integrate over the whole cube. So I want, F(x_1, x_2, x_3) = \int\int\int...
  14. H

    Approximate Solution for Numerical ODE: Taylor Series Method with Non-Zero Terms

    hi, I'm wondering how to find the approximate solution of dy/dx= e^x y y(0)=1 at x = 0.1 using the Taylor Series method. The expansion should include the first four non-zero terms. Work to six decimal places accuracy. Here is what I did but I am unsure which one is correct : first...
  15. T

    Implementing Numerical Integration

    Say we have some partial differential equation for u(x,t) and we devise a numerical method to solve it. For example if we say unm is the solution at x=hm and t=kn with m=0,...,M and n=0,...,N where h and k are the step-lengths, and then our method is something like...
  16. T

    Mechanics Kinematic General Concept question, not a numerical?

    Mechanics Kinematic General Concept question, not a numerical!? I'm really confused concerning the positive direction and the acceleration taken while concerning the motion of the ball! Well, the main thing that i wanted to ask is that if 2 balls are been projected at the same time in two...
  17. H

    Numerical integration of discrete data

    Hi, I'm searching for days for a numerical integration methode for discrete data given at non-equidistant nodes. The simple Simpson rule can only be used for equidistant nodes so I'm looking for methode which I can solve my problem. Any suggestion is welcome! Thanks in advance!
  18. B

    How can I find the maximum point on a function without using its derivative?

    I have a function with one and only one local/global maxium... (i.e. half the function has positive slope, half the function has negative slope). And I want to find the maximum point on the function. How can I find the function's max? I was thinking of turning the function into its...
  19. C

    Euler's method for numerical approximation

    y' = 3 + t - y, y(0) = 1 A) Find the approximate values of the solution of the given initial value problem at t = 0.1, 0.2, 0.3, 0.4 using the Euler method with h = 0.1. B) Repeat part A with h = 0.05. Compare the results found in A. I did part A correctly, but cannot get the right...
  20. P

    Error in Numerical Solution of ODE by Euler Method - Patrick

    Hi, I recently need to do some numerical simulation by Euler method to solve a PDE. However, I noticed that there are some errors which are obtained with bigger numerical steps, when applying Euler scheme. Since my major is not mathematics, I do not know what this phenomenon is called. I...
  21. H

    Numerical Computation (Euler method)

    Homework Statement Differential equations are important in physics.Consider Solving the differential equation dy/dx = Σ(from i to N) (ai) (x^i) Using Euler ,Midpoint ,4th order Runge -Kutta methods.For each of these methods what is the largest value of N that would lead to an exact solution ...
  22. R

    Numerical Boundary Conditions for Fokker Planck and Kramers equations

    Hi Everyone, Apologies if this is posted in the wrong place. I am trying to produce numerical solutions for the following initial value partial differential equations, namely the overdamped Schmoluchowski equation \frac{\partial p(x,t)}{\partial t}=-\frac{\partial}{\partial...
  23. C

    Numerical Analysis: Evaluating in a numerically stable fashion

    Hi, I need help with the following numerical analysis questions. The textbook I'm using (Intro to Numerical Analysis by Stoer) doesn't have many examples so I'm having a lot of trouble figuring out what exactly I should be doing. "Evaluating the summation as i goes from 1 to n of a sub i in...
  24. A

    The order of error of a numerical method

    Homework Statement Find the order of error of this numerical method: f''(x_i+\frac{h}{2})\simeq \frac{\Delta ^2f_i}{h^2} Homework Equations Taylor's theorem, Newton's interpolation polynomial and its error. The Attempt at a Solution I started from Taylor's expansion at x_i and...
  25. I

    3D stationary Schrodinger - numerical solution

    Hi! My problem is connected with solving 3-dimentional Schrodinger equation for descrete spectrum. I need to consider arbitrary 3D-potential and find characteristics of boundary levels, produced by this potential (energy levels, quantum numbers...) All I found over the internet were...
  26. S

    Numerical analysis w/euler's method

    The amount of a uniform distributed radioactive contaminant contained in a closed reactor is measured by its concentration (c) (Becquerel/liter or Bq/L). The contaminant decreases at a decay rate proportional to its concentration; that is Decay rate(dc/dt)= -kc Where (dc/dt) is the change in...
  27. P

    MATLAB - for loop for numerical integration

    MATLAB - "for" loop for numerical integration Hi. The following bit of MATLAB function is supposed indefinitely integrate successive points: % Explode triplet format into vectors x_in = data_in(:,1)'; y_in = data_in(:,2)'; e_in = data_in(:,3)'; x_left=x_in(1:end-1)...
  28. diegzumillo

    2d Schrodinger equation - numerical solutions

    Hi there, I was expecting to find a "simulations forums" somewhere here, if there is a better place for this thread please let me know :) OK, here's the problem: I'm trying to make a simulation with PYthon, at first with a square potential, for simpler potential/boundary conditions. But...
  29. Q

    Calculate f''(x) & Error Order | Numerical Analysis

    write program calculate http://<a [/URL] href="http://www.codecogs.com/eqnedit.php?latex=f^{"}\left ( x \right )" target="_blank"><img src="http://latex.codecogs.com/gif.latex?f^{"}\left ( x \right )" title="f^{"}\left ( x \right )" /></a> x=0 http://<a [/URL]...
  30. C

    Numerical Error/Large Condition number

    Hi there, I am working on a problem in Fluid dynamics. I've written a code in MATLAB which finds the shape of the free surface of the liquid based on Newton Relaxation. The code is fairly robust and produces good results which agree with current papers on the same problem. Unfortunately...
  31. T

    Numerical value of complex number

    Homework Statement I need to understand why \left|4+i \right|=4.123 and why this is shown by: \sqrt{4^{2}+1^{2}}=4.123 Homework Equations i^{2}=-1 The Attempt at a Solution If I find the square root of this expression squared, then I come up with \sqrt{16-1+8i} which is...
  32. S

    Numerical analysis(Bisection Method)

    My dear all! Hello! How are you all? Let us assume that we have given an equation of a curve like y=3x2+3x-1 By numerical analysis(bisection method) I want to find its root. Everything is fine in the case if interval is given (a,b). But my problem is that if interval is not given then...
  33. marcus

    AsymSafe QG sees a numerical breakthrough (Benedetti, Groh, Machado, Saueressig)

    http://arxiv.org/abs/1012.3081 The Universal RG Machine Dario Benedetti, Kai Groh, Pedro F. Machado, Frank Saueressig 38 pages (Submitted on 14 Dec 2010) "Functional Renormalization Group Equations constitute a powerful tool to encode the perturbative and non-perturbative properties of a...
  34. M

    Numerical methods for systems of differential equations

    Homework Statement Consider the implicit (not actually sure wether that's the correct english word, my material is in Finnish and I'm Swedish-speaking :smile:) method xj+1=xj+h/2(f(tj,xj)+f(tj+h,xj+1)) a)Write an appropriate Runge-Kutta scheme b) What is the methods rank when we use the...
  35. S

    Approximating Integral w/ Singularity at x=0 Using Trapezoidal Rule

    Homework Statement I want to approximate the following integral: \int^{1}_{0}\frac{1}{x}dx using the trapezoidal quadrature rule. However there is a singularity at x=0. Homework Equations trapezoidal method: \int^{a}_{b}f(x) dx \approx...
  36. D

    Find Numerical Physics Problems in Python

    I'm searching a book, or a place on the net where I'll find tons of examples of numerical problems in physics (mainly quantum mechanics) written in Python. I have tons of books about Python, but none have good examples on problems like tunneling, solving Schrodinger eq for various potentials...
  37. S

    Basic Newton's Rings Numerical Problem

    In Newton's Rings Experiment, what will be the order of the dark ring which will have double the diameter of that of the 20th dark ring? Wavelength(lambda = 5890 Angstrom); Radius of curvature is not given. Thin film is made of air, so refractive index is 1. And the light is incident normally...
  38. P

    MATLAB How Can I Compute a Numerical Jacobian Matrix in MATLAB?

    Hello everyone, Does anyone know how I can compute the jacobian matrix numerically in matlab? So, I have the following. A 100x100 image and at each pixel, I have a 2 element gradient vector. What I would like to do is compute the jacobian matrix (wrt to the spatial location), at each pixel...
  39. J

    How can the stability of this numerical method be proven?

    Please anyone help me with stability proof this next numerical method \dfrac{u^{n+1} - u^{n}}{\vartriangle t} = (u^{n+1}u^n)I am trying make : \begin{equation*} \begin{split} u_2^{n+1} - u_1^{n+1} & = \displaystyle\frac{u_2^{n}}{1-\vartriangle tu_2^{n}} -...
  40. P

    Numerical Analysis - Matrix Norm equalities.

    Homework Statement Determine constants c and C that do not depend on vector x. For this to be true: Use this result and the definition of matrix norms to determine constants k and K so that: Homework Equations The Attempt at a Solution I've done half of this...
  41. M

    I want to analise this problem by numerical method

    Homework Statement y=(a*exp^b*x)/(c+d*exp^m*x) The Attempt at a Solution (1/y)=(c+d*exp^m*x)/(a*exp^b*x) y(new)=1/y y(new)=(c/(a*exp^b*x))+(d*exp^m*x)/(a*exp^b*x) i stopped here and i don't know how can i complete?
  42. U

    MATLAB Help with MATLAB Numerical Integration

    First off, I know I can use the trapz or quad functions on matlab, but I want to derive my own numerical integration code. The problem is more complicated than this, but basically I need to be able to numerically integrate in MATLAB to continue with the homework assignment. If y = x^2 is...
  43. U

    Help with MATLAB Numerical Integration

    First off, I know I can use the trapz or quad functions on matlab, but I want to derive my own numerical integration code. The problem is more complicated than this, but basically I need to be able to numerically integrate in MATLAB to continue with the homework assignment. If y = x^2 is the...
  44. B

    How to Derive Eq. 9.4.6 in Numerical Recipes from Given Expressions?

    Homework Statement I want to derive equation Eq. 9.4.6 in Numerical Recipes from the expressions given, as stated in the book! The equation represents the next (i+1 th) deviation \epsilon from the true root. Eq. 9.4.6: \epsilon_{i+1} = -\epsilon_i^2 \frac{f''(x)}{2f'(x)} Homework...
  45. F

    Mathematica Numerical solution in Mathematica

    Hello, I have a problem with numerical solution of the system of ODE's (geodesic eqs.) in Mathematica. The only relevant command I have found is NDSolve. It works perfectly, unless my equations contain functions which are again computed using numerical methods. Simple example illustrating...
  46. M

    Numerical evaluation of modified Bessel equation

    Not sure if this is the right place. Mathematica has a function BesselK[0,x] that returns the value of the modified Bessel function K_0 at x. Is there public documentation of how this algorithm works? If not, is there documentation regarding any algorithm of K_0? I am hoping it doesn't...
  47. D

    Find Parameter Set for N Intersections of 2 Implicit Functions

    Sorry for the wordiness of the thread title. Basically I'm wondering, if you have two implicit functions, F(x,y)=0 and G(x,y)=0 (typically rational functions with numerator and denominator very high degree polynomials), both dependent upon the same K (in my case > 34) dimensional set of...
  48. C

    Numerical modelling of electrostatic potential energy of a system

    Hi there, Lately, I've been trying to gain a deeper understanding of the relationship between the Coulomb force F, electric field E, electric potential V, and electrostatic potential energy U. In regards to electrostatic potential energy, as I understand it, if you had, say (made up a few...
  49. G

    1D Heat equation, numerical solution with ONLY one heat source

    Hi, I have the following problem. I am tried to numerically solve the 1D heat equation for a metal bar of length L. Using the forward time, centered space equation a(t+1) = a(t)+(alpha*deltaA/(deltaX)^2)*(a(x+1,t)-2*a(x,t)+a(x-1,t)) The problem is that I only have ONE heat source at...
  50. V

    I am trying to plot the following numerical solutions:Input:

    I am trying to plot the following numerical solutions: Input: NDSolve[{y''[x] + (2/x) y'[x] + 1 == 0, y[10^(-10)] == 0.9999999, y'[10^(-10)] == 0}, y, {x, 0, 30}] Output: {{y->InterpolatingFunction[{{3.34649*10^-105, 30.}},<>]}} But when I plot it, I just get a completely blank...
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