Import dependencies in ember-cli (e.g., import math.js)

I am puzzled about importing dependencies in ember-cli, especially about the standard AMD case, as mentioned in the official Ember Cli document. The document doesn't provide much of examples, and seems to me it assumes the readers have good knowledge about AMD, which is not the case for me. My immediate use case is import math.js. Unfortunately, the official document of math.js doesn't provide example about importing with Ember Cli. Then, I found this post with relatively clearer examples, in particular, the following one seems quite relevant.

app.import({
  development: 'vendor/lodash/dist/lodash.js',
  production:  'vendor/lodash/dist/lodash.min.js'
}, {
  'lodash': [
    'default'
  ]
}); 

Then, I did similar thing with math.js like below:

app.import({
  development: 'bower_components/mathjs/dist/math.js',
  production:  'bower_components/mathjs/dist/math.min.js'
}, {
  'mathjs': [
    'default'
  ]
});

However, it doesn't work. When I tried to use it with

import mathjs from 'mathjs'

I got an error. Eventually, I used the following solution:

// Brocfile.js
app.import('bower_components/mathjs/dist/math.min.js');

// some controller.js
var math = window.math

Although above solution works, I don't like it as it may be subject to name conflict. Besides, based on math.js's document, it seems to me it should support standard AMD type of import.

So, my questions are the following.
1. In the lodash example above, what does the 'default' mean? Is that a general reference to whatever exported in the corresponding module? How can I tell whether I can use it in general (for example, math.js)?
2. Is it true that if a module supports require.js, then it is a standard AMD module? If so, given code like below:

require.config({
  paths: {
    mathjs: 'path/to/mathjs',
  }
});
require(['mathjs'], function (math) {
  // use math.js
  math.sqrt(-4); // 2i
});

how can I map it to Ember Cli code?