How Do T and V Relate in Adiabatic Processes for Different Substances?

[RadiumBlue]

Homework Statement

[/B]
a) Black body radiation:

The energy and pressure of black body radiation depend on T and V as E = σV T^4 , p=\frac{1}{3}σT^4 σ = a constant

(1) Suppose that the temperature and volume of a box of radiation change adiabatically, which means that there is no heat flow. First, find the relation between dE and dT in this process. Next using equation (1) show that T ∝ V^-\frac{1}{3}

b)Pressureless glop

Suppose that the energy and pressure of a different substance are given by E = γV T^\frac{2}{3} ,p = 0 γ = constant

The temperature and volume of a box of this substance are changed adiabatically. What is the relation between T and V during this process?

Homework Equations

See problem description

The Attempt at a Solution

I'm not quite sure where to begin with this one. I've solved every other problem in the problem set without a problem, but this one I'm a little confused where to start.

\Delta E = Q - W

The processes are adiabatic, so Q = 0. Also, W = pdV

Therefore
\Delta E = -pdV

Is it asking me to find dE/dT? For part a this would be:
\frac{dE}{dT} = 4σVT^3

After I get these pieces, I'm not sure how to assemble them into the answers the problems are asking for.

 

[haruspex]

$\frac{dE}{dT} = 4σVT^3$

That would only be true if V is constant with respect to changes in T. Is it?