### 物理代写|量子力学代写quantum mechanics代考|PHYS2040

statistics-lab™ 为您的留学生涯保驾护航 在代写量子力学quantum mechanics方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写量子力学quantum mechanics代写方面经验极为丰富，各种代写量子力学quantum mechanics相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 物理代写|量子力学代写quantum mechanics代考|Scattering Boundary Condition

We first note that a spherical wave going out from the origin is a solution to the Schrödinger equation, just as in Eq. (4.11),
$$\left(\nabla^{2}+k^{2}\right) \frac{e^{i k r}}{r}=0 \quad \text {; outgoing wave }$$
We now require, on physical grounds, that the solution to the scattering problem for away from the potential should consist of the incident wave plus an outgoing scattered wave
$$\psi=\psi_{\text {inc }}+\psi_{\text {scatt }} \quad ; r \rightarrow \infty$$
This is known as the scattering boundary condition. In detail, this says that
$\psi(\vec{x})=e^{i \vec{k} \cdot \vec{x}}+f(k, \theta) \frac{e^{i k r}}{r} \quad ; r \rightarrow \infty$
; scattering b.c.
The amplitude of the outgoing scattered wave $f(k, \theta)$ is known as the scattering amplitude.

Let us see how this works for our s-wave scattering. In order to satisfy this boundary condition, we must choose a particular form for the amplitude $A$ of the wave function outside of the potential in Eq. (4.16)
\begin{aligned} u_{\text {out }}(r) &=\frac{e^{i \delta_{v}}}{k} \sin \left(k r+\delta_{\mathrm{u}}\right) \quad ; r>d \ \psi(r) &=\frac{u_{\text {out }}(r)}{r} \end{aligned}
Now look at
$$\psi_{\text {scatt }}(r)=\psi(r)-\psi_{\text {inc }}(r) \quad ; r>d$$

## 物理代写|量子力学代写quantum mechanics代考|Cross-Section

The classical concept of a scattering or reaction cross-section is as follows: One prepares a beam of particles, with a certain incident flux $I_{\mathrm{inc}}$, where the incident flux is the number of particles crossing a unit transverse area per unit time. The eross-section is then a little element of transverse area such that if a particle goes through it, a certain event takes place. Hence the rate of such events taking place is
$$I_{\mathrm{inc}} d \sigma_{f i}=\text { number of events } i \rightarrow f \text { per unit time }$$
In quantum mechanics we deal with probability, and its rates and fluxes. The probability flux in three dimensions follows from Eq. (3.10) as
$$\vec{S}(\vec{x})=\frac{\hbar}{2 i m}\left[\psi^{\star} \vec{\nabla} \psi-(\vec{\nabla} \psi)^{*} \psi\right]$$
This has the interpretation as the amount of probability flowing through a unit transverse area per unit time. The elastic scattering cross-section

$d \sigma$ for the scattering of a particle into a solid angle $d \Omega$ (and corresponding area $r^{2} d \Omega$ ) in quantum mechanics is therefore ${ }^{3}$
$$\left(\hat{k} \cdot \vec{S}{\text {inc }}\right) d \sigma=\left(\hat{r} \cdot \vec{S}{\mathrm{scatt}}\right) r^{2} d \Omega$$
With the incident and scattered wave functions in Eq. (4.21), one has
\begin{aligned} \hat{k} \cdot \vec{S}{\text {inc }} &=\frac{\hbar k}{m} \ \hat{r} \cdot \vec{S}{\text {scatt }} &=\frac{\hbar k}{m r^{2}}|f(k, \theta)|^{2} \end{aligned}

## 物理代写|量子力学代写quantum mechanics代考|High Energy

Let us look at the other scattering limit of high energy where very many partial waves contribute to the scattering amplitude. Recall that in electrostatics if we have the electrostatic potential satisfying
$$\nabla^{2} \Phi=-\frac{1}{\varepsilon_{0}} \rho$$

where $\rho$ is the charge density, then the potential is obtained by summing over the Coulomb interaction with each small charge element
$$\Phi(\vec{r})=\frac{1}{4 \pi \varepsilon_{0}} \int \frac{1}{\left|\vec{r}-\vec{r}^{\prime}\right|} \rho\left(\vec{r}^{\prime}\right) d^{3} r^{\prime}$$
Here, we want to solve the equation
$$\left(\nabla^{2}+k^{2}\right) \psi=v \psi \quad ; v=\frac{2 m}{\hbar^{2}} V(r)$$
In direct analogy, we can obtain the scattered wave by summing over the outgoing wave from each little source element ${ }^{4}$
$$\psi_{\mathrm{scatt}}(\vec{r})=-\frac{1}{4 \pi} \int \frac{e^{i k\left|\vec{r}-\vec{r}^{\prime}\right|}}{\left|\vec{r}-\vec{r}^{\prime}\right|} v\left(r^{\prime}\right) \psi\left(\vec{r}^{\prime}\right) d^{3} r^{\prime}$$
With the inclusion of $\psi_{\text {inc }}$, which satisfies the homogeneous differential equation, the whole wave function then looks like
$$\psi(\vec{r})=e^{i \vec{k} \cdot \vec{r}}-\frac{1}{4 \pi} \int \frac{e^{i k\left|\vec{r}-\vec{r}^{\prime}\right|}}{\left|\vec{r}-\vec{r}^{\prime}\right|} v\left(r^{\prime}\right) \psi\left(\vec{r}^{\prime}\right) d^{3} r^{\prime}$$

## 物理代写|量子力学代写quantum mechanics代考|Scattering Boundary Condition

(∇2+ķ2)和一世ķrr=0; 出波

ψ=ψ公司 +ψ散点 ;r→∞

ψ(X→)=和一世ķ→⋅X→+F(ķ,θ)和一世ķrr;r→∞
; 散射 bc

ψ散点 (r)=ψ(r)−ψ公司 (r);r>d

## 物理代写|量子力学代写quantum mechanics代考|Cross-Section

dσ用于将粒子散射成立体角dΩ（及对应区域r2dΩ) 因此在量子力学中是3

(ķ^⋅小号→公司 )dσ=(r^⋅小号→sC一个吨吨)r2dΩ

ķ^⋅小号→公司 =⁇ķ米 r^⋅小号→散点 =⁇ķ米r2|F(ķ,θ)|2

## 物理代写|量子力学代写quantum mechanics代考|High Energy

∇2披=−1e0ρ

(∇2+ķ2)ψ=在ψ;在=2米⁇2在(r)

ψsC一个吨吨(r→)=−14圆周率∫和一世ķ|r→−r→′||r→−r→′|在(r′)ψ(r→′)d3r′

ψ(r→)=和一世ķ→⋅r→−14圆周率∫和一世ķ|r→−r→′||r→−r→′|在(r′)ψ(r→′)d3r′

## 有限元方法代写

tatistics-lab作为专业的留学生服务机构，多年来已为美国、英国、加拿大、澳洲等留学热门地的学生提供专业的学术服务，包括但不限于Essay代写，Assignment代写，Dissertation代写，Report代写，小组作业代写，Proposal代写，Paper代写，Presentation代写，计算机作业代写，论文修改和润色，网课代做，exam代考等等。写作范围涵盖高中，本科，研究生等海外留学全阶段，辐射金融，经济学，会计学，审计学，管理学等全球99%专业科目。写作团队既有专业英语母语作者，也有海外名校硕博留学生，每位写作老师都拥有过硬的语言能力，专业的学科背景和学术写作经验。我们承诺100%原创，100%专业，100%准时，100%满意。

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。