QFT: Every particle is an excitation of it's own field?

[Silvestru]

Acording to QFT,  the electron is an excitation of the electron field the Higgs boson is an excitation of the Higgs field etc. 

Does every elementary particle have it's own field? According to QFT is the universe reduced to 16-17 fields? 

What keeps the individual field of each particle (the excitation) to be stable? Do these field permeates space and time?

Do these fields interact with each other?

What about antiparticles?  do they reside in the same field as their equivalent particle?

And where do the fields that do not have a particle associated to them fit in? like the Faddeev–Popov ghost fields? 

Is it normal that these questions are enough to keep you up at night?  

I know I raised many questions in this topic but I feel they are related to each other.

References: https://en.wikipedia.org/wiki/Spontaneous_symmetry_breaking
                      https://en.wikipedia.org/wiki/Quantum_field_theory

                      https://en.wikipedia.org/wiki/Faddeev–Popov_ghost

 

 

Edited April 12, 2018 by Silvestru

[geordief]

Great ,just what I was wondering about (and working out an OP but not loosing sleep).

Particle and Field = Chicken and Egg?

 

2 sides of the same phenomenon?

 

Seems like the Fields don't interact with each other (but that an eventual  TOE might "put manners" on them) 

[Mordred]

A field is any collection of assigned values or functions assigned on a coordinate basis. You can have any number of fields of any type. For example the connection between two fields interacting with one another can be treated as its own field.

 Every mediator gauge boson mediates the force field of its particular type ie photons for EM, qluons for the strong etc. However one can arbitrarily assign a field to any individual particle species.

Fields can also be assigned to virtual or quasi particles such as those involved in poppup ghosts. 

 antiparticles are typically part of the same field as their partner but one can arbitrarily choose to assign them to their own field (though this is rarely done) the reason its rarely done is that the creation/annihilation operators work well together for the fields they are used upon.

 Fields can also be and scalar or vector quantity even spinors or tensors. 

Edited April 12, 2018 by Mordred

[Silvestru]

59 minutes ago, geordief said:

Seems like the Fields don't interact with each other

Hmm. From a QFT perspective, how can they not interact if the particles of said fields interact with each other? Electromagnetic field interacts with charged particles, Higgs interacts with the massive ones etc.

 

[Sensei]

2 hours ago, Silvestru said:

What keeps the individual field of each particle (the excitation) to be stable?

(let's assume that answer for premise "Every particle is an excitation of it's own field?" is yes)..

Who said so that they're stable?

e.g. Muon- decays to electron (and electron anti-neutrino, and muon-neutrino)

e.g. Muon+ decays to positron (and electron neutrino, and muon-anti-neutrino)

And this happens extremely fast..

Electron/positron can't decay anymore (at least according to current Standard Model knowledge..), but can e.g. annihilate with its anti-particle. And as a result, different set of particles (and eventually anti-particles) will appear instead.

 

IMHO fields are mathematic models currently used to describe what particles and anti-particles are doing..

 

Edited April 12, 2018 by Sensei

[Silvestru]

4 minutes ago, Sensei said:

Who said so that they're stable?

 

4 minutes ago, Sensei said:

Electron/positron can't decay

Hmm well I guess this is what I meant by stable. It cannot decay. Not by itself at least. Thank you for clarifying Sensei.

8 minutes ago, Mordred said:

Every mediator gauge boson mediates the force field of its particular type ie photons for EM, qluons for the strong etc. However one can arbitrarily assign a field to any individual particle species.

Fields can also be assigned to virtual or quasi particles such as those involved in poppup ghosts. 

Thank you Mordred. 

I didn't even want to mention the quantization of gravity as that I guess is a still ongoing debate. 

When discussing QFT I see that there are not many clear cut answers and even gaps or parts that we still don't know the answer to. I guess it's what makes it interesting to me.

[Mordred]

One thing to remember about QFT is that every particle is a field excitation. VP are not individually observable as they lack the amount of energy for individual action. They form the internal lines on the Feyman diagrams while observables such as real particles form the exyernal lines.

 QFT textbooks rarely ever refer to a particle preferring to refer to them as an excitation or state

Edited April 12, 2018 by Mordred

[Silvestru]

22 minutes ago, Mordred said:

One thing to remember about QFT is that every particle is a field excitation. VP are not individually observable as they lack the amount of energy for individual action. They form the internal lines on the Feyman diagrams while observables such as real particles form the exyernal lines.

 QFT textbooks rarely ever refer to a particle preferring to refer to them as an excitation or state

No worries Mordred. I knew this because I get my QFT knowledge from the highest of high sources explained on a very high level:

Title: A Children’s Picture-book Introduction to Quantum Field Theory

https://www.ribbonfarm.com/2015/08/20/qft/

Jokes aside, I think this is a very nice introduction for people who just found out about QFT and want to know more. 

 

[geordief]

1 hour ago, Silvestru said:

Hmm. From a QFT perspective, how can they not interact if the particles of said fields interact with each other? Electromagnetic field interacts with charged particles, Higgs interacts with the massive ones etc.

 

Maybe so. The onus might be on me to find a field that doesn't interact with another field .

 

So maybe I will will go with you.

 

I wonder how fields  superimpose (if that is the word) mathematically.

 

Does an em field  superimpose on a gravitational field?

Edited April 12, 2018 by geordief

[Sensei]

32 minutes ago, geordief said:

Does an em field  superimpose on a gravitational field?

Elementary electric charge e=1.6021766*10^-19 C is measured in oil drop experiment.

Electric field created on metal electrodes keeps oil drop levitating (or even moving backward) against gravitation which tries to accelerate oil drop toward Earth.

https://en.wikipedia.org/wiki/Oil_drop_experiment

 

Edited April 12, 2018 by Sensei

[Silvestru]

17 minutes ago, geordief said:

Maybe so. The onus might be on me to find a field that doesn't interact with another field .

So maybe I will will go with you.

No no, I am just speaking from what little I read and less that I understood hehe so a double check is always good. But I guess it's hard to define this as Mordred mentioned above.

[swansont]

3 hours ago, geordief said:

Great ,just what I was wondering about (and working out an OP but not loosing sleep).

Particle and Field = Chicken and Egg?

 

2 sides of the same phenomenon?

 

Seems like the Fields don't interact with each other (but that an eventual  TOE might "put manners" on them) 

A lot if it boils down to "use what model works best"

 

[geordief]

What might be the simplest scenario  that a Field model would be applicable to?

In EM , for example ,what might be the smallest charge that might produce a Field when it interacts with another?

 

 

[StringJunky]

15 minutes ago, geordief said:

What might be the simplest scenario  that a Field model would be applicable to?

In EM , for example ,what might be the smallest charge that might produce a Field when it interacts with another?

 

 

 

Quote

In physics, a quantum (plural: quanta) is the minimum amount of any physical entity involved in an interaction. The fundamental notion that a physical property may be "quantized" is referred to as "the hypothesis of quantization".[1] This means that the magnitude of the physical property can take on only discrete values consisting of integer multiples of one quantum.

For example, a photon is a single quantum of light (or of any other form of electromagnetic radiation), and can be referred to as a "light quantum". Similarly, the energy of an electron bound within an atom is also quantized, and thus can only exist in certain discrete values. Atoms and matter in general are stable because electrons can only exist at discrete energy levels in an atom. Quantization is one of the foundations of the much broader physics of quantum mechanics. Quantization of the energy and its influence on how energy and matter interact (quantum electrodynamics) is part of the fundamental framework for understanding and describing nature.     https://en.wikipedia.org/wiki/Quantum

 

[MigL]

Adding to Mordred's excellent description ( welcome back )...

It is because of the way we define a particle, that quantization of a field, by necessity, gives rise to said particles.
A field which cannot be quantized ( gravity ??? ) may not give rise to an 'excitation', and may have no mediator boson.
( although everyone thinks it is just a stubborn field, that eventually will be quantized )

[geordief]

All Fields  have parameters,do they? Is it just one value(value =value of a parameter**?) at each point or can it be multiple?

It is the parameter (s) that define the Field?

If so ,what are the parameters of a quantum Field?

 

**hope I am not confused with terminology

 

 

Edited April 12, 2018 by geordief

[MigL]

Only scalar fields are single valued at any point.
Vector fields have a magnitude AND direction at any given point ( two valued )
Tensor fields can have as many values as needed at any given point.

[MigL]

For an easy to understand treatment of scalar vector and tensor fields

1973.pdf

Edited April 13, 2018 by MigL

[Mordred]

nice article short and brief but has the essential details. Seems the questions have been answered lol and glad to be back as well

[Butch]

I was going to post this as a new topic, however it seems to fit here... I assume there are still a few around who question the concept of the big bang, I would like to hear from both sides... IYHO what is the soutcreof the original exitation of fields? I could ask where did energy come from, however I hope to hear some more creative ideas than "It's just there!". For example, my thought is that the energy is coming from black holes in other universes, the universe is expanding (that includes fields and matter)and is steady state. The cmb is evidence of this. This could be possible if our universe had no beginning or started with a big bang. Comment on my idea if you wish (I can take a pretty good lashing), however I really am looking to hear your ideas.

[swansont]

15 hours ago, Butch said:

I was going to post this as a new topic, however it seems to fit here... I assume there are still a few around who question the concept of the big bang, I would like to hear from both sides... IYHO what is the soutcreof the original exitation of fields? I could ask where did energy come from, however I hope to hear some more creative ideas than "It's just there!". For example, my thought is that the energy is coming from black holes in other universes, the universe is expanding (that includes fields and matter)and is steady state. The cmb is evidence of this. This could be possible if our universe had no beginning or started with a big bang. Comment on my idea if you wish (I can take a pretty good lashing), however I really am looking to hear your ideas.

Can you show that the energy had to "come from" somewhere? i.e. that the net energy of the universe is nonzero?

[geordief]

45 minutes ago, swansont said:

Can you show that the energy had to "come from" somewhere? i.e. that the net energy of the universe is nonzero?

Is assymetry a synonym for net energy?

Or a closely related concept?

[Silvestru]

16 hours ago, Butch said:

For example, my thought is that the energy is coming from black holes in other universes

Based on your speculation:

 

1. If Energy in Our Universe is coming from Other Universes the question continues, where do the other Universes that are giving us Energy have theirs from? (please don't say other other Universes)

2. How are the BH from other Universes interacting with ours? How does the energy appear? Like from a "white whole", the other end of a black whole like a garden hose? And when did this energy start coming? Before during or after the BB?

3. What if I confidently tell you that the total energy in the Universe is negative because of gravity that only attracts? Would you believe me?

 

[swansont]

15 minutes ago, geordief said:

Is assymetry a synonym for net energy?

Or a closely related concept?

Symmetry can be associated with energy. In thermodynamics, the Gibbs energy and Helmholtz energy both include a TS term. T is temperature, S is entropy. So if a symmetry in a system can be represented by entropy, there would be a contribution to the energy.

[Silvestru]

1 hour ago, swansont said:

Can you show that the energy had to "come from" somewhere? i.e. that the net energy of the universe is nonzero?

Hmm why are we so sure that the net energy of the universe is zero? I am not debating this, I am just curious, what observational data do we have for this?

I know we mentioned before but how are we talking about the energy of an isolated system which is unchanging with time and is not stationary and we have to measure it as an observer sitting "outside" of it. Oh and also it's expanding.