请列举哈佛大学的一些知名教授，必须以json格式输出，每个教授后面要给出他们在哈佛的研究领域。
user
```json
{
  "professors": [
    {
      "name": "Henry Louis Gates Jr.",
      "field": "African American Studies"
    },
    {
      "name": "Michael Sandel",
      "field": "Political Philosophy"
    },
    {
      "name": "Steven Weinberg",
      "field": "Theoretical Physics"
    },
    {
      "name": "Drew Gilpin Faust",
      "field": "American Civil War History"
    },
    {
      "name": "Mark Joseph Rosen",
      "field": "Jurisprudence"
    }
  ]
}
```
assistant