  The extremely close proximity of hot Jupiters to their parent stars has
dramatically affected both their atmospheres and interiors, inflating them to
up to twice the radius of Jupiter. The physical mechanism responsible for this
inflation remains unknown, though many proposals have been put forward. I will
review the known hot Jupiter population, the proposed inflation mechanisms, and
the evidence for and against them collected thus far. In doing so, I will cover
the ways that hot Jupiter interiors may be simulated computationally in detail,
and present some useful formulas for estimating their radii, heating, intrinsic
temperature, and tentative magnetic field strength. I will also cover the
related issues of hot Jupiter intrinsic temperatures and radiative-convective
boundaries, the potential connection with planetary magnetic fields, and the
effects of stellar tides on the planet. Finally, I conclude with the suggestion
that more than one mechanism may be operating in concert with each other and
propose various avenues for future progress in understanding these objects.
