Qft

[ydoaPs]

is QFT part of standard QM? can someone give me a nonmathematical overview of QFT?

 

here's my current understanding(it is probably completly wrong):

 

there are various quantum fields. when there is an excitement in only the EM field, we get photons. if there is an excitement in only the higgs field, we get chargeless massive "particles." if there is a coupled excitement in the EM and higgs fields, we get massive charged "particles." the higgs field is coupled with the gravitational field such that an excitement in the higgs field caused an excitement in the gravitational field(gravitons).

 

am i anywhere close on any of that?

[ydoaPs]

bump

 

 

 

is there a QFT in which it doesn't assume a flat spacetime, but has spacetime be a property of the fields?

[Severian]

QFT is not contained in QM. In QM only the operators (the things you measure) such as energy, position etc are quantised. In QFT the fields themselves are quantised.

 

Your understanding was pretty reasonable, apart from the bit about gravity. We don't have a consistant QFT for gravity yet, but even if we did, the graviton would couple to energy, not mass. The Higgs mechanism is generating mass.

[□h=-16πT]

Quantum field theory is a relativistic theory of quantum mechanics whose most important tool is Lagrangian and Hamiltonian field theory, though one can drop the Hamiltonian formalism and take the Lagrangian as the more fundamental quantity (as is done in the path integral method). In QFT, matter, described by a field, arises as the quantised excitation of the ground state, the ground state being the vacuum for a free particle, and matter can be coupled to an interaction, which itself can then be quantised.

 

bump

is there a QFT in which it doesn't assume a flat spacetime' date=' but has spacetime be a property of the fields?[/quote']

 

Yeah, QFT in curved space-time. It's how Hawking calculated the emission spectrum for black holes.

 

QFT in curved space-times is background dependant, however, it assumes the space-time to be static: the metric (the fundamental quantity in GR, describing the geometry) does not change with time.

 

The formulation of any quantum field theory in a curved space-time is precisely the same as in flat Minkowski space-time, cannonical or other methods of quantisation are relatively analogous, the problems arise in the interpretation of the excited fields. I thinks it's called the Urah effect, though I've probably spelt it wrong.

[□h=-16πT]

Quantum Field Theory in Curved Space-time

 

Not a bad link, has a bit on the Hawking effect in there.