Ok first of all you do relize that for pV to be constant it has to be applied at the same time. The Ideal gas model tends to fail at lower temperatures or higher pressures, when intermolecular forces and molecular size become important. At some point of low temperature and high pressure, real gases would have to undergo a phase transition, such as to a liquid or a solid. The model of an ideal gas, however, does not describe or allow phase transitions.
Secondly I don't completly agree with star cycle charts seeing as how I don't think stars can form again once they blow up. Even if all of the particals of matter did manage meet in one place it would be impossible to prove that anything would happen to it. And even more so highly unlikely that anything would seeing as how you need pressure, gas, and heat to all be applied constantly through out the process.
If I have said anything out of line pleas straighten me up.