如何在mathjax方程中呈现多个下标？

Question

我正在尝试以下代码

$$E = a_{12} + m_{12}c^2$$ 

并且由于第二组{}括号而无法呈现。我正在使用hugo博客学术主题。我认为这不是特定于主题的问题。

---

mathjax-config.js

window.MathJax = {
  CommonHTML: { linebreaks: { automatic: true } },
  tex2jax: { inlineMath: [ ['$', '$'], ['\\(','\\)'] ], displayMath: [ ['$$','$$'], ['\\[', '\\]'] ], processEscapes: false },
  TeX: { noUndefined: { attributes: { mathcolor: 'red', mathbackground: '#FFEEEE', mathsize: '90%' } } },
  messageStyle: 'none'
};

footer.html

{{ partial "mathjax_support.html" . }}

      {{/* LaTeX math rendering. */}}
      {{ if or .Params.math site.Params.math }}
      {{ printf "<script src=\"%s\" integrity=\"%s\" crossorigin=\"anonymous\" async></script>" (printf $js.mathJax.url $js.mathJax.version) $js.mathJax.sri | safeHTML }}
      {{ end }}

mathjax_support.html

<script type="text/javascript" async
  src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
  MathJax.Hub.Config({
  tex2jax: {
    inlineMath: [['$','$'], ['\\(','\\)']],
    displayMath: [['$$','$$']],
    processEscapes: true,
    processEnvironments: true,
    skipTags: ['script', 'noscript', 'style', 'textarea', 'pre'],
    TeX: { equationNumbers: { autoNumber: "AMS" },
         extensions: ["AMSmath.js", "AMSsymbols.js"] }
  }
  });
  MathJax.Hub.Queue(function() {
    // Fix <code> tags after MathJax finishes running. This is a
    // hack to overcome a shortcoming of Markdown. Discussion at
    // https://github.com/mojombo/jekyll/issues/199
    var all = MathJax.Hub.getAllJax(), i;
    for(i = 0; i < all.length; i += 1) {
        all[i].SourceElement().parentNode.className += ' has-jax';
    }
  });

  MathJax.Hub.Config({
  // Autonumbering by mathjax
  TeX: { equationNumbers: { autoNumber: "AMS" } }
  });
</script>