Approximation Definition and 768 Threads

Hi all, Could someone please help me understand a small but significant step in the derivation of the wave equation for a string with stiffness. I am trying to follow the notes here: http://courses.physics.illinois.edu/phys406/Lecture_Notes/Waves/PDF_FIles/Waves_2.pdf The statement...

Hi all, I try to understand the difference which can made by using or not using NWA .. I have a process have cross section (p p > x x) ~ 10^-5 pb , where x is a paricle have mass mx = 2 TeV and dominant decay channel (x > b b~) with Gamma (x > b b~) ~ 6 * 10^2 GeV , while sigma ( p p > x x ...

Prove that a set $A\subset\mathbb{R}^n$ is (Lebesgue) measurable $\iff$ there exist a set $B$ which is an $F_{\sigma}$ and a set $C$ which is a $G_{\delta}$ such that $B\subset A\subset C$ and $C$~$B$ (C without B) is a null set. $F_{\sigma}$ is a countable union of closed sets, and...

Hi, could someone please help me with this one: I'd need to form a sequence of rational functions ##R_{n}(x)## such that ##\lim_{n \to \infty} R_{n}(x)=\theta(x)##, where ##\theta(x)## is the Heaviside step function. The functions ##R_{n}(x)## should preferably be limited in range, i.e. for some...

Homework Statement Suppose that X is the number of successes in a Binomial experiment with n trials and probability of success θ/(1+θ), where 0 ≤ θ < ∞. (a) Find the MLE of θ. (b) Use Fisher’s Theorem to find the approximate distribution of the MLE when n is large. Homework Equations...

I have stumbled upon an approximation to the average of integer square roots. \sum^{n}_{k=1}{\sqrt{k}/n} \approx \sqrt{median(1,2,...,n)} Sorry I am not very good at LaTeX, but I hope this comes across okay. Could anyone explain why this might be happening? In fact, I just discovered that...

Homework Statement https://scontent-b-mia.xx.fbcdn.net/hphotos-prn2/v/1456973_10201043975243279_1765184125_n.jpg?oh=05b39611ad70d28d837ed219e1b0f2aa&oe=52838593 Homework Equations The area can be approximated by using the sum of the areas of the rectangles. Area of rectangle = change...

If I have a polynomial function f(x) and I want to find an approximate polynomial g(x). I can apply the Nth order Taylor Polynomial of f centered at some value a. So suppose I have f(x) = 5 - 6x + 20x^3 + 10x^5 and I want to find an approximate function, g(x), centered at 5. From what I...

Are Local Linear Approximation, Linear Approximation, and Linearization all the same thing? Question is, I learned about something called Local Linear Approximation in Calc 1. Now in Calc 2, the topic of Linearization from Calc 1 was mentioned. But I never did anything that was referred...

https://www.physicsforums.com/attachments/1614 never done this before so this is an intro problem it mentioned that LA is used in Physics a lot hopefully correct no ans in bk(Speechless)

How can I verify that $\lim_{N,M,K \to \infty, \frac{M}{N} \to 0, \frac{KM}{N} \to \lambda} \frac{\binom{M}{x}\binom{N-M}{K-x}}{\binom{N}{K}} = \frac{\lambda^x}{x!}e^{-\lambda}$, **without** using **Stirling's formula** or the **Poisson approximation to the Binomial**? I have been stuck on...

Homework Statement Problem taken from Boas Mathematical Methods book, Section 14 page 35. Prove that if ##S=\sum_{n=1}^{\infty} a_n## is an alternating series with ##|a_{n+1}|<|a_n|##, and ##\lim_{n \to \infty} a_n=0##, then ##|S-(a_1+a_2+...+a_n)|\leq|a_{n+1}|##. The Attempt at a...

Homework Statement Find the linear approximation of (xy)/z at the point (-3,2,1) The Attempt at a Solution So the example my book gives has 2 variables so I'm struggling a bit with this, But I started off by taking the partial derivative with respect to each variable and solving for...

Statistics problem---exponential approximation Homework Statement A box contains 2n balls of n different colors, with 2 of each color. Balls are picked at random from the box with replacement until two balls of the same color have appeared. Let X be the number of draws made. a) Find a...

Homework Statement The question requires me to approximate binomial distribution to get poisson distribution. Show that N!/(N-n)!=N^n. Homework Equations N!/n!(N-n)! p^n q^(N-n)=Binomial distribution The Attempt at a Solution I expanded N!/(N-n)! and got...

Hello everyone, my first post :shy: I'm reading Zee's 'QFT in a Nutshell' and I came to one thing that bothers me - he's short discussion of steepest-descent approximation. I've known this thing for quite a long time now, but I've never seen the approximation of the corrections. Here is what...

I just need some help with some basic questions I can't remember from a long time ago, just started up school again... 1) Given a function f(x) = (quadratic on top)/(quadratic on bottom) When at x=1, I am given a tangent line to the function f(x), and also given the equation of the tangent...

Hi guys, I've made a Mathematica n-body simulation of the first few planets in our Solar System and thought it would be a good idea to try and simulate a spacecraft transfer from Earth to Mars. I've thought about using a patched conic approximation, but I was wondering if there is anything...

How can I prove that, for N\gg n \frac{N!}{(N-n)!}\approx N^{n} I've tried doing \frac{N!}{(N-n)!}=\exp\left(\ln\frac{N!}{(N-n)!}\right)=\exp\left(\ln N!-\ln\left(N-n\right)!\right) \underset{stirling}{\approx}\exp\left(N\ln N-N-\left(N-n\right)\ln\left(N-n\right)+N-n\right)...

Homework Statement In order to simplify problems in physics, we often use various approximations. For example, when we investigate diffraction and interference patterns at small angles θ, we frequently approximate sinθ and tanθ by θ (in radians). Here you will calculate over what range these...

Hi, Lets say that I have a 4x4 matrix, and am interested in projecting out the most important information in that matrix into a 2x2 matrix. Is there an optimal projection to a lower dimensional matrix where one keeps most of the matrix intact as best as possible? Thanks.

Hi everyone, I was wondering if you guys could suggest me some good books in cosmology with finely explained WKB method and Perturbations especially in Structure formation area. I have "The early universe" by Klob and Turner and "Cosmology" by Weinberg , but they seem unpalatable at first...

Here is the question: I have posted a link there to this topic so the OP can see my work.

Hello, I am trying to find the effective resistance of the NLR in the attachment (to the first order). It is given that IL = gVL2 + I0. I understand that this is normally achieved via ∂g/∂V at V=V0, but when I do so I get that R should be 1/(2gV0), and not 1/2g as shown in the solution. Could...

Hi there. At first I tought of posting this thread on the homework category, but this is a conceptual doubt rather than anything else. While revisiting Heat Transfer I stumbled upon a simple problem, that yet got me thinking. It is as follows: Before anything else, let me show...

I am in process of designing a homemade capacitance sensor and I'd like to have an approximation of the resulting capacitance of the following geometry. The plates are placed on the outer surface of a food grade plastic cylinder. The distance z between their edges is many times smaller than the...

There is no analytical solution of the integral below. Can we approxiamate the analytical solution? \int_{k}^{K} \frac{exp(-log^2 (x))}{x(x-A)}dx

Hi Guys, I have just started studying about this field. Can you give me some ideas about some best eigen value estimators? Both for SPD and non-SPD matrices. Thanks you. :-)

When I started learning Multivariable calc first we went back and developed a new notion of derivative as a linear approximation. And what we came up with was F(a+h)=F(a)+mh+E(h) * where m is the derivative. Basically the function minus the line tangent to point a. However there is a...

Hello community, I'm new here. I'm using FORTRAN to model the motion of electrons and ions when accelerated under a high voltage potential. I'm using a fluid approximation and MHD-like equations (conservation of mass, energy, momentum) and a finite volumes numerical method to solve the...

I think I've got the basics of forum notation now, thanks to Fredrick from my other thread. Here goes: Show: Z = z_0 + a(x-x_0) + b(y-y_0) where a = f_x = \frac{\partial f}{\partial x} and b = f_y = \frac{\partial f}{\partial y} I'm attempting this using the coordinate method, but how...

What is the most general method of approximating arbitrary systems of ODEs of 4 variables(x,y,z,t) that fit these conditions? The conditions that are assumed true of the ODEs are: 1) that I require differentials to be explicitly defined (but they can be defined in terms of other...

Dirichlet's Approximation Theorem not working for n=8 and α= pi? I am reading a number theory textbook that states Dirichlet's Approximation Theorem as follows: If α is a real number and n is a positive integer, then there exists integers a and b with 1≤ a ≤ n such that |aα-b|< 1/n . There...

Hello, I have read several articles/websites which talk about modelling white dwarfs, In all of these papers they state that it can be assumed the electrons have temperature zero, i.e. T<<T_fermi. I haven't been able to find a solid explanation of why this is approximation is possible...

Hi everyone I have trouble with this task Homework Statement the specific heat cv is given by c_v =\frac {N_A k_b \hbar^2}{{\Omega_D}^3 {k_b}^2 T^2} \int \limits_{0}^{\Omega_D} \! \frac {\Omega^4 exp\frac{\hbar \Omega}{k_b T}}{{(exp\frac{\hbar \Omega}{k_b T}-1})^2} \, d\Omega I...

Homework Statement Take 50 free throws in basketball, and record the number of successful shots. 1) Use this data to estimate your free throw percentage. 2) Construct a 95% confidence interval for this estimated quantity.Homework Equations X ~ Binomial(n,p) The Attempt at a Solution I...

This feels silly asking but I have a question about units using the double harmonic approximation to determine IR spectral intensities. In the double harmonic approximation the intensity is given by the square of the derivative of the dipole with respect to a normal mode coordinate times a...

I'm working through a solved problem in a fluid mechanics textbook. In it, the group velocity of a dispersive wave is calculated as: $$c_g = \frac{1}{2}c\left (1 + 2kh\ \text{cosech} (2kh) \right)$$ Where k is the angular wavenumber, and h is the depth of the water, which is fine. Now for...

Hello all, Which of the following asymptotic equations (as rho goes to infinity) correct: 1-\prod_{m=1}^M(1-\rho^{-x_m})\doteq \sum_{m=1}^M \rho^{-x_m} or 1-\prod_{m=1}^M(1-\rho^{-x_m})\doteq \rho^{-\underset{m}{\min}x_m} Thanks

Hello, I'm trying to solve for the allowed energies with the WKB approximation of the Schrodinger equation, using the Morse potential. So I have (as per equation 35 at http://hitoshi.berkeley.edu/221a/WKB.pdf), \int_a^b \sqrt{2m(E-V(x))}dx=\left(n+\frac{1}{2}\right)\pi\hbar However, how do I...

Homework Statement The IPA potential-energy function ##U(r)## is the potential energy "felt" by an atomic electron in the average field of the other ##Z-1## electrons plus the nucleus. If one knew the average charge distribution ##p(r)## of the ##Z-1## electrons, it would be a fairly simple...

Dear forum members, I am trying to solve the following system of equations. ψ(x,y,z)=∫∫ψ(x',y',z)K(x',y',z)dx'dy' z=f(ψ) What I do is to solve the integral equation with a Monte Carlo method, evaluate "z" and do a loop until convergence. My question to you is whether it is...

\frac{\sqrt{1-a}}{\sqrt{1-b}}\approx \left ( 1-\frac{1}{2}a\right )\left ( 1+\frac{1}{2}b\right ) I know that the binomial approximation is first used, \frac{\sqrt{1-a}}{\sqrt{1-b}}\approx \frac{1-\frac{1}{2}a}{1-\frac{1}{2}b} But how does one approximate...

Homework Statement Given this data: hours / value ----------- 2 | 1.6 4 | 1.5 6 | 1.45 8 | 1.42 10 | 1.38 12 | 1.36 fit a curve of the form Y ≈ ae^{-bx} What value can you predict after 15 hours? The Attempt at a Solution So i can rewrite the equation as Y ≈ log(a)-bx...

Homework Statement Given that the scattering amplitude off of a single atom is f_{1}(\vec{q}), find the scattering amplitude for 1) four atoms each placed in the corner of a square of length a, and 2) two atoms a distance d apart Homework Equations The total scattering amplitude can...

Hi, I have been looking for rigorous mathematical conditions for when the WKB approximation may be applied. Here is my understanding of the topic. We start with the most general form that the wavefunction could take, i.e. exp[if(x)/h] , Where "i" stands for square root of -1, f(x) is...

Here is the question: Here is a link to the question: Approx. series help please? - Yahoo! AnswersI have posted a link there to this topic so the OP can find my response.

Hello, If tau<<T which of the following relations are true: \int_{\tau/(1+a)}^{(T+\tau)/(1+a)}v(t)e^{-j2\pi f_0 at}e^{-j2\pi\frac{k}{T}t[1+a]}\,dt=\int_{0}^{T/(1+a)}v(t)e^{-j2\pi f_0 at}e^{-j2\pi\frac{k}{T}t[1+a]}\,dt or \int_{\tau/(1+a)}^{(T+\tau)/(1+a)}v(t)e^{-j2\pi f_0...

Here is the question: Here is a link to the question: Need help with calculus word problem? - Yahoo! Answers I have posted a link there to this topic so the OP can find my response.

Hi all, i have a problem to solve that i want maybe to solve with MATLAB o excel. I have a numerical samples and with linear approsimation i have a function, but now i want to use less samples for example only 20 and i want to find the best set of samples to approsimate in the best way the...