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What are the formal theories/theoretical frameworks that completely characterise the Standard Model in our present state of knowledge?

IH

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- Thread starter Islam Hassan
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What are the formal theories/theoretical frameworks that completely characterise the Standard Model in our present state of knowledge?

IH

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http://en.wikipedia.org/wiki/Classical_field_theory

http://en.wikipedia.org/wiki/Quantum_field_theory

"Quantum field theory" is the general mathematical framework that we've found most useful in particle physics. Quantum field theory provides a generic way of discussing particles and their interactions taking into account both quantum mechanics and relativity. The Standard Model is a specific quantum field theory, where we postulate the existence of a certain set of particles and interactions to explain all the observations we've made. QED, which describes the electromagnetic force, and QCD, which describes the strong force, are both "sub-theories" of the standard model, which includes both the electromagnetic and strong forces.

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mfb

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http://en.wikipedia.org/wiki/Classical_field_theory

http://en.wikipedia.org/wiki/Quantum_field_theory

"Quantum field theory" is the general mathematical framework that we've found most useful in particle physics. Quantum field theory provides a generic way of discussing particles and their interactions taking into account both quantum mechanics and relativity. The Standard Model is a specific quantum field theory, where we postulate the existence of a certain set of particles and interactions to explain all the observations we've made. QED, which describes the electromagnetic force, and QCD, which describes the strong force, are both "sub-theories" of the standard model, which includes both the electromagnetic and strong forces.

Many thanx for the kind feedback. Just to round off my comprehension, can you kindly confirm:

- Quantum field theory in general as well as its QED/QCD incarnations are all necessarily defined as gauge theories;

- There is at present no established (ie, non speculative) quantum gravity field theory and

- Conformal field theory does not concern itself with the SM but is purely a beyond-the-SM theory.

IH

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"Quantum field theory" is the general mathematical framework that we've found most useful in particle physics.

Re that comment, just wondering...does that mean that there are other less prevalent/successful mathematical frameworks which, while less useful, still have something to contribute to our understanding of the SM?

IH

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- Quantum field theory in general as well as its QED/QCD incarnations are all necessarily defined as gauge theories;

No, gauge theories are a specific kind of field theory. Quantum field theories need not be gauge theories. And gauge theories need not be quantum field theories--you can have classical gauge theories (classical electromagnetism is a classical gauge theory).

In the context of quantum field theory, gauge theories are just one way of producing interactions between particles (that is, forces. The electromagnetic, strong, and weak forces are all the results of gauge interactions). But there are other kinds of interactions, like Yukawa interactions (which the Higgs boson experiences): http://en.wikipedia.org/wiki/Yukawa_interaction

There is at present no established (ie, non speculative) quantum gravity field theory

Right. We have general relativity, which is a classical field theory, but we don't know the quantum mechanical version.

Conformal field theory does not concern itself with the SM but is purely a beyond-the-SM theory.

"Conformal field theory," like "quantum field theory," is a broad class of field theories and is not a specific theory. Some quantum field theories are also conformal field theories. You are right that the standard model is not a conformal field theory.

Islam Hassan said:Re that comment, just wondering...does that mean that there are other less prevalent/successful mathematical frameworks which, while less useful, still have something to contribute to our understanding of the SM?

What I meant to imply was: while all current observations (except gravity) are explained by the specific quantum field theory we call the standard model, and most speculative particle physics involves postulating new quantum field theories that extend the standard model, in principle nature need not be described by a quantum field theory at all. It's possible, perhaps likely, that the "true theory" is not a quantum field theory at all. For instance, I'm not sure whether string theory is strictly speaking a quantum field theory; perhaps someone more knowledgeable can say something about that.

Of course, whatever the "true theory" is, it is clearly well approximated by a quantum field theory, namely the standard model.

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K^2

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I don't think so. Pretty much everything past Classical Mechanics is a field theory of some sort or another. Even in classical mechanics classical field theory is pretty useful.Re that comment, just wondering...does that mean that there are other less prevalent/successful mathematical frameworks which, while less useful, still have something to contribute to our understanding of the SM?

If I had to place a bet one way or another, I'd bet on it being a non-quantum field theory.The_Duck said:It's possible, perhaps likely, that the "true theory" is not a quantum field theory at all.

First of all, both GR and standard model make extremely good predictions. It can't be random. However, GR is a non-linear theory. Pretty much any field theory can be approximated by a linear field theory, in which case you can build a quantum field theory. So given that GR works, and based on general Ocam's razor principle, I would guess that success of SM is due to linear approximation working very well due to relatively low energy scales involved. (Low compared to what? Good question.) In which case, a better field theory would be a non-linear one, and non-linear field theory cannot be a quantum field theory.

But this is more of what we should be aware of, and perhaps looking for in high-energy experiments, rather than any kind of statement on quality of Standard Model. So far, everything we've done confirms SM.

P.S. Oh, and even if we discover that underlying field-theory is non-linear, Quantum Mechanics and Standard Model aren't going anywhere. Linear theories are

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Pretty much everything past Classical Mechanics is a field theory of some sort or another. Even in classical mechanics classical field theory is pretty useful.

Very interesting your comment "Pretty much everything past Classical Mechanics is a field theory of some sort or another". So field theory really constitutes

Finally, regarding your use of the term "non-iinear", is this in the simple intuitive sense that x is a linear coefficient and x^2 is not or it is more complicated than that?

IH

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mfb

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I do not remember any non-field theory there.What about string and other beyond-the-SM theories, are they also mostly field theories or not?

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