Can I define the creation and annihilation operator commutation relations with an explicit momentum dependence?

The goal is to implement an expression of a discrete scalar plane-wave solution to the Klein-Gordon equation that makes use of the creation and annihilation operators in the Physics package.

We don't bother solving the Klein-Gordon equation explicitly. Instead, we just take a solution from literature. This approach is sufficient to show the difficulty in defining the the creation and annihilation operators in this way.

how_to_define_creation_and_annihilation_operators_with_a_momentum_dependence.mw

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How do I generate a plot within a plot as shown in my example below? The fundemental issue is plot structures like Histogram() etc are not images and so combining them in the way I imagine is non-trivial. I couldn't find a standard way to do this in the help section.

Plot_within_a_plot.mw

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I am trying to animate images generated in a do loop using display and insequence. I get an output but there is no flipping of the image even while I see the frames count flip through the frames. What am I doing wrong? See attached code. Thanks!

Why_cant_I_animate_still_images_like_this.mw

How do I mute the action of an accent applied to a symbol so that the accented symbol is itself an inert object? See the attached example.

How_do_I_make_an_accented_symbol_inert.mw
 

Is there a way to re-index an existing dataframe? See attachment for example.

how_do_i_re-index_a_dataframe.mw