Beamer arXiv citations aged with Matplotlib colormaps

BarXiv is a very simple `LaTeX2e` package for the `beamer` class. It enables audience-friendly citations of papers which may or may not be on the [arXiv](https://arxiv.org). These are highlighted according to the age of the reference, according to the ubiquitous colormaps of Matplotlib. BarXiv **does not need** Python.

Install and use

Download barxiv.tar.gz from the github repo and unzip to your .tex and .bib working directory:
```
		  tar -C <working_directory_name>/ -xvf barxiv.tar.gz
		  
```

Load the package into your preamble:

		  \usepackage[bib file = <bib_file_name>.bib, cmap = rainbow, saturation = 40]{barxiv}

Try putting \barxiv{<bibtex_label>} in place of \cite{<bibtex_label>} and twiddling the options
- bib file or bibfile: self-explanatory
- cmap: your favorite Matplotlib colormap such as viridis (default), cubehelix or spring; a full list can be found here
- saturation: a percentage value, since many colormaps are rather dark

Demonstration

Here is a simple `beamer` frame to illustrate `barxiv` in use for some `cmap` choices.\

For hsv:

For spring:

For summer:

For winter:

For binary:

For inferno:

For Wistia:

This frame was generated with `presentation.tex` as follows (note I don't include `presentation.bib`). The preamble explicitly contains all current `barxiv` options:

		
		\documentclass{beamer}
		\usepackage[utf8]{inputenc}
		\usepackage[bib file = presentation.bib, cmap = rainbow, saturation = 40]{barxiv}

The body is much as you would expect:

		
		\begin{document}
		\tiny
		\begin{frame}
		  \frametitle{A \texttt{beamer} frame to demonstrate \texttt{barxiv}}
		  \begin{itemize}
		    \item You can recycle the \texttt{.bib} from your latest paper in your \texttt{beamer} talk, and use \texttt{\symbol{92}barxiv} just as you would use \texttt{\symbol{92}cite}.
		    \item Today, all the \textbf{best} papers are on the \textbf{arXiv}, such as \barxiv{2019JMP....60e2504B,2017CQGra..34t5006B,2017CQGra..34p7001B}.
		    \item In a talk, the audience might just have time to note an arXiv telephone number.
		    \item The \textbf{arXiv} contains more than one eprint \textbf{class}, e.g. \barxiv{2019arXiv190800993Y,2016IJMPS..4060010N}.
		    \item Long ago, books such as \barxiv{1984ucp..book.....W}, or very important papers such as \barxiv{Ashtekar_1991}, had no \textbf{arXiv} on which to appear\footnote{Because the \texttt{barxiv} command is \textbf{robust}, \barxiv{2019JMP....60e2504B,1984ucp..book.....W} should appear well in \textbf{footnotes} and \textbf{captions}.}.
		    \item The \textbf{colours} reflect the \textbf{age} of the reference: a decent literature review such as \barxiv{PhysRev.101.1597,1961JMP.....2..212K,1975NCimB..28..127K,1985AmJPh..53..510H,lasenby-doran-heineke-2005,2019arXiv190800993Y,2013CQGra..30t5010C,2015arXiv151201202H,2011CQGra..28u5017B,1972PhLA...39..219K,2011JPhCS.330a2005H,2011PhRvD..83b4001B,1984CQGra...1..651G,2009PhRvD..79b7301L,1979PhLA...75...27T,2008PhRvD..78b3522S,2005NewAR..49...59P,1980PhRvD..21.3269S,1980PhLA...80..232M,RevModPhys.36.463} is thus very \textbf{colourful}.
		    \item Bibliographies are not so common in \texttt{beamer} talks, but the \texttt{bibtex} backend supports them if you so choose: this is compatible with \texttt{barxiv}, though slightly against its spirit!
		    \item {\large Citations \barxiv{1998RSPTA.356..487L} should scale with font \textbf{size} or font \textsc{style \barxiv{Ashtekar_1991}} }
		  \end{itemize}
		\end{frame}

		\end{document}