Field theory is one of the cornerstones of classical physics. The most notable
examples of classical fields are the force fields that one encounters in the description
of gravitational and electromagnetic phenomena. These fields are
caused by the presence of masses and electric charges, respectively. In this
chapter we present a framework for classical field theory, which is known as
the Lagrangian formulation. In this formulation the dynamics of a system is
described by a single function, the Lagrangian. Via a variational principle the
Lagrangian yields the equations of motion which govern the time evolution of
that system, so it is a useful mnemonic for summarizing a theory in a concise
form. The use of a variational principle to express the equations of classical
physics is very old. Fermat’s principle in optics (1657) and Maupertuis’
principle in mechanics (1744) are famous examples. 

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[latexpage]

The ket 

The ket is short-hand for a column vector

\[

[+preamble]
\newcommand{\braket}[2]{\left\langle{#1} \, \middle|\, {#2}\right\rangle}
\newcommand{\ket}[1]{\left|\,{#1} \right\rangle}
\newcommand{\bra}[1]{\left\langle{#1} \, \right |}
[/preamble]

\ket{a} = \begin{bmatrix}
a_1 \\
a_2 \\
\vdots \\
a_N
\end{bmatrix} \\

\]

The ket $\ket{a} $ and the vector a represent the same vector in the V space; i.e., $a \in V$ and $\ket{a} \, \,\in V$ Continue reading

# ———————————————————————
# Create a py360 environment (Python 3.6)
# List the environments currently installed
# ———————————————————————
C:\Users\Evan>conda create -n py360 python=3.6

C:\Users\Evan>conda info –envs
# conda environments:
#
py278 C:\Anaconda3\envs\py278
py335 C:\Anaconda3\envs\py335
py350 C:\Anaconda3\envs\py350
py360 C:\Anaconda3\envs\py360
root * C:\Anaconda3

# ———————————————————————
# Install Jupyter notebook into py360 environment
# ———————————————————————
C:\Users\Evan>conda install -n py360 jupyter

# ———————————————————————
# Install matplotlib (ver 2.0.2) into py360 environment – SUCCEEDED
# ———————————————————————
C:\Users\Evan>conda install -n py360 matplotlib

Copied matplotlibsrc from C:\Anaconda3\envs\py360\Lib\site-packages\matplotlib\mpl-data\matplotlibrc
to c:\\Python Docs\\Py3_Notebooks\\matplotlibrc

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