I got an invitation to visit Austria for 11 days as a guest scientist. What type of visa should I apply for?
I am from Egypt. As I'm a researcher for doctoral degree, I've invited as a guest scientist for an international training program.
You will need an Austria Type C visa to enter Austria, which is within the Schengen Area.
This Austrian government page discusses the visa, but the pages that follow are mostly in German.
However, the Austrian Embassy in the United States has an informative English-language web presence that includes this visa page. While the page is directed at US residents, it illustrates the visa application process. One must apply for a visa at the embassy or consulates in the country of the applicant's residence. This non-governmental page says Austria maintains its embassy to Egypt in Cairo, and consulates in Alexandria and Hurgada. The application can be made 90 days before the date of travel, but no earlier.
Since you did not mention your nationality, it makes it impossible to answer this question. However, I will answer it based on my own country, the United States. For an American to travel to Austria, for a trip that is less than 90 days, the only requirement is a valid passport. More than 90 days in a 180 day period requires a tourist visa. Best of luck and enjoy your travels.