Variation method Definition and 14 Threads

Summary:: Can anyone introduce an informative resource with solved examples for learning variation principle? For example I cannot do the variation for the electromagnetic lagrangian when ##A_\mu J^\mu## added to the free lagrangian and also some other terms which are possible: $$ L =...

I have a paper and on that paper I only can read: Let $$f:\mathbb{S^{1}} \to \mathbb{R^2}$$ be a function and $$f_{\epsilon}=f+\epsilon hn$$ and $$\mathbb{S^1}$$ is the unit circle. $$\dot{f_\epsilon}=\dot{f}+\epsilon\dot{h}n+\epsilon h\dot{n}$$ $$\delta\dot{f}=\dot{h}n+h\dot{n}$$ can you...

<Moderator's note: Moved from a technical forum and thus no template.> Problem: One dimensional quartic oscillator, V(x) = cx^4 (c is a constant) Use the trial function e^(-aplha(x^2)/2) to determine the value of the appropriate variational integral W. I've attached a picture of my work. I...

I need to calculate the energy of the ground state of a helium athom with the variational method using the wave function: $$\psi_{Z_e}(r_1,r_2)=u_{1s,Z_e}(r1)u_{1s, Z_e}(r2)=\frac{1}{\pi}\biggr(\frac{Z_e}{a_0}\biggr)^3e^{-\frac{Z_e(r_1+r_2)}{a_0}}$$ with ##Z_e## the effective charge considered...

The Variational Method allows us to obtain an upper bound on energy of the ground state (and sometimes excited states). Is there any way of determining an upper bound on the error of the energy obtained by the variational method without an analytic or numerical solution to the problem? i.e. Is...

I work with an electromagnetic molecule trap, and I'd like to determine which orbits are chaotic. To this end, I intend to study the evolution of a perturbation on a trajectory with time. I'd like to compute something called the fast lyapunov indicator for various trajectories y(t), where I...

In the chapter 9-5 "The Linear Variation Method" p. 363 from the book: Basic Principles and Techniques of Molecular Quantum Mechanics by Ralph Christoffersen, the first thing he does is to minimize the energy, E = c†Hc/c†Sc, by requiring its derivative with respect to the...

Homework Statement Use the variation method to find a approximately value on the ground state energy at the one dimensional harmonic oscillator, H = -ħ^2/(2m) * d^2/dx^2 + 1/2mω^2*x^2 Homework Equations H = -ħ^2/(2m) * d^2/dx^2 + 1/2mω^2*x^2 u(x) = Nexp(-ax^2) <H> = <u|Hu> The Attempt at a...

Homework Statement Okay, I have no idea about the method they want me to solve it with. What in this case is the indicator that a function is appropriate? A particle mass m affects a potential of the form ##V(x)=V_0 \frac{|x|}{a}## where ##V_0## and ##a## are positive constants. a) Draw a...

The variation method for approximating the the ground state eigenvalue, when applied to higher energy states requires that the trial function be orthogonal to the lower energy eigenfunctions.In that respect this book I am referring(by Leonard Schiff) mentions the following function as the...

Homework Statement The Schrodinger equation (in atomic units) of an electron moving in one dimension under the influence of the potential -delta(x) [dirac delta function] is: (-1/2.d2/dx2-delta(x)).psi=E.psi use the variation method with the trial function psi'=Ne-a.x2 to show that...

Homework Statement Show that variation principle (parameters ci) leads to equations \sum\limits_{i = 1}^n {\left\langle i \right|H\left| j \right\rangle c_j = Ec_i {\rm{ where }}} \left\langle j \right|H\left| i \right\rangle = \int {d\textbf{r}^3 \chi _j^* \left( \textbf{r} \right)\left(...

Homework Statement This is the problem 8.10 from Levine's Quantum Chemistry 5th edition: Prove that, for a system with nondegenerate ground state, \int \phi^{*} \hat{H} \phi d\tau>E_{1}, if \phi is any normalized, well-behaved function that is not equal to the true ground-state wave function...

Hi, Here's the problem: Homework Statement Quantum particle moving in 1D. Potential energy function is V(x) = C|x|^{3}. Using the variational method, find an approx. ground-state wave function for the particle. The Attempt at a Solution Using \psi = Ae^{-ax^{2}}, I find that A =...