[lisper]

> The halting problem isn't scientific, though. It's entirely mathematical

No, it isn't. The halting problem arises out of a mathematical model of a physical system. We don't know for certain that it's impossible to build an oracle for the halting problem, just as we don't know for certain that it's impossible to do an end-run around the Second Law. But the evidence in both cases is (IMHO) equally compelling.

[dekhn]

Everything written about halting machines presumes a mathematical system, not a physical system. It makes statements about model systems, some of which have physical counterparts. THe whole point of a turing machine is that it's abstract, not made of tape or transistors or anything else.

The halting problem is not really widely discussed in physics journals. They care much more about the physical limits of actual computing. If you have good examples of physics people talking about the halting problem in a non-theoretical and distant way, I'm happy to see it. But from waht I can tell, physicists are not concerned with uncomputable functions.

[lisper]

> The halting problem is not really widely discussed in physics journals.

So? Golf clubs aren't widely discussed in physics journals either but they are physical systems nonetheless. You can't draw valid conclusions about what is not a physical system based on what is absent from physics journals.