Quantum Field theory vs. many-body Quantum Mechanics

[Fractal matter]

I remember I've read a paper, stating qft inherits traits of the particle formalism. In the sense qft formulation is not superior, than the many-body qm.

 

[vanhees71]

QFT formulation is superior in all cases, where you have particle creation and destruction processes and equivalent to (many-body) QM if this is not the case.

 

[Fractal matter]

QFT formulation is superior in all cases, where you have particle creation and destruction processes and equivalent to (many-body) QM if this is not the case.

I agree, this is what it seems. Nevertheless this is what I've read. I'm actually curious if qft can be the result of the missing information. There is a certain analogy with the ordinary information transfer. Quantum fields look like a superposition of causal sets.

 

[Joker93]

I agree, this is what it seems. Nevertheless this is what I've read. I'm actually curious if qft can be the result of the missing information. There is a certain analogy with the ordinary information transfer. Quantum fields look like a superposition of causal sets.

Can you give more details on this or provide a reference?

 

[Fractal matter]

Can you give more details on this or provide a reference?

What exactly are you interested in ? I don't remember the title of the 1st paper. As for the missing information there are quite a few. For example: Quantum States as Ordinary Information - https://www.mdpi.com/2078-2489/5/1/190 I don't know the details, just in general.

 

[Fractal matter]

Some effects may be described by topological effective field theory, in which case it may not have quasiparticle excitations.

Can you give an example please ? I'm interested in all the cases in which the effective theory doesn't have quasiparticles.

 

[Demystifier]

Can you give an example please ? I'm interested in all the cases in which the effective theory doesn't have quasiparticles.

All topological field theories lack propagating degrees of freedom and hence (quasi)particles. An example of topological field theory is Chern-Simons theory. In condensed matter, it plays a role in a description of quantum Hall effect (see e.g. https://arxiv.org/abs/1606.06687). Roughly speaking, in the quantum Hall effect the EM field interacts with matter in such a way that the effective dressed EM field cannot propagate through the material, so the dressed EM field does not have dressed photon excitations.