Each student will meet periodically with his/her core thesis committee in closed session to discuss progress. These meetings will occur at least once per year, but could be more frequently at the discretion of the committee.
An important role of the core thesis committee is to ensure that the student has a sufficiently broad knowledge of their subfield. The committee may choose to do this via a more formal procedure which might begin with a thirty minute presentation based on a recently-published article from a refereed journal in the student's field, chosen by the student, with the approval of the committee. This presentation would then serve as a starting point for questions on, and related to, the field and on physics in general.
In addition, students will periodically give presentations (at least once per year) in a public forum, which the core thesis committee members are expected to attend and concerning which the core committee should provide written feedback to the student. Possible forums for such presentations include the Weak Interaction Discussion Group, The Monday Evening Seminar, the Single Molecule Discussion Group, collaboration presentations, group meeting presentations, etc. The format of the presentation should be a talk that lasts 40 minutes or more. The allowable format and content for the ``public presentations'' should be viewed broadly, subject only to the participation of the core thesis committee. Especially early on in her/his research career, to satisfy this requirement, it may be that it makes most sense for a student to make a journal club-type presentation in the context of a group meeting, later on progressing to a research-based presentation in one of the regularly scheduled series.
Preparing for such presentations is likely to improve a students' presentation skills and the ongoing monitoring of a student's research progress will diminish the chances of surprises at the thesis defense. Such monitoring will also provide a protection to both the student and advisor: First, if a student has sufficient material for a PhD, why then the committee can push a reluctant advisor to agree to a thesis defense. Alternatively, if a student's research performance is inadequate, the committee can support academic sanctions on the student, i.e. that the student is not in good academic standing. The required form for written feedback to the student is here.