You may require a visa to travel to Australia, even for a short period.
Depending on your nationality, you may be eligible for an eVisitor Visa (Subclass 651), the Electronic Travel Authority (Subclass 601), or a Visitor Visa (subclass 600). In general, you should check the Department of Home Affairs website for more information.
If you require a letter from the conference organisers to support your visa application, please contact Adam (a.steinberg@unimelb.edu.au).