Lack of understanding of energy, quarks, and the strong force

In summary: Thus via E=mc², the vacuum is filled with these socalled virtual particles. It was Dirac who came up with the idea that the vacuum was filled with virtual positron and electron pairs (the reason that they were pairs has to do with conservation laws like that of electrical charge). You can break up such a pair and make the particles real when you have enough energy coming from some interaction between two charged particles that were placed inside the vaccuum.Indeed, virtual particles and their fields (remember that position is not a well defined quantity in QFT) do not exist for ever. In theory this can be proven by the fact that the socalled number-operator of such particles does NOT commute with the hamiltonian (
  • #1
heartless
220
2
Hello,
Here I go again :tongue2:
I don't understand a few things, let me all questions put in a paragraph so that I don't miss anything

What is an energy? (I can't understand the definition provided by the encyclopedia) And, what's up with the vacuum energy? If no particles are there, how can energy simply exist? Does space alone produces energy? If so, how does it do that? Do forces exist without particles? This thing I don't trully understand. Energy, usually is created by interference of matter with space and electromagnetic force (I only think) So, can you play chess if you lack a chess set? And also, if forces can exist without matter, do our universe have some kind of DNA? (not DNA, word by word, but a concept)
And here's something I just thought about a few seconds ago. My another book :tongue2: says that Before the big bang, time and space weren't created yet. Alright, so first of all, if space wasn't created yet, what gave the energy, a shape of a point particle, (like it's drawn in the book, and some magazines of SciAm)? Dimensions weren't there yet, so actually the energy had no size, no shape and yet it didn't have a place to fit, hence it didn't exist. But on the other hand, if space-time was created already... I don't know what... sorry :cry: Help, Help!

Ok, energy's done, and let's go on with the quarks,

My particle physics book, says that strong force is produced by quark interference, or strong nuclear force exists only between quarks. Notice the word "only". So what about protons and neutrons? What keeps them together if not a strong nuclear force? Alright, and again, if it's somehow different than I think, quarks are joint by nuclear force, and if so, wouldn't the picture of an atom look somehow different, than that shown just everywhere? Because, proton and neutron wouldn't be a point particle if quarks are, and yet wouldn't the quarks also produce a force between the neutron's and proton's quarks creating one super-particle? :biggrin: I don't know but my imagination doesn't draw a nuclei like a ball, but a rectangle :rofl: SOS SOS SOS

I would appreciate any writings,
Thanks
 
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  • #2
anyone? :frown:
 
  • #3
Arrghh, so many questions.

You are asking to explain the entire notion of QFT. You should do a search/study yourself in stead of asking such general questions. That's why nobody is answering.

Here is some info on fields and virtual particles.


The most fundamental QFT-quantity is not "a particle" but "a field". In QFT, particles arise due to fluctuations of fields.

Virtual particles are an intermediate stage of an interaction between elementary particles in QFT. They are a tool to describe these interactions, yet their existence can be proven with experiments : see the Casimir-effect.

The QFT-vaccuum is not empty because the lowest possible energy cannot be zero (you know, because of Heisenberg uncertainty : zero energy implies infinite spread of position). thus via E=mc², the vacuum is filled with these socalled virtual particles. It was Dirac who came up with the idea that the vacuum was filled with virtual positron and electron pairs (the reason that they were pairs has to do with conservation laws like that of electrical charge). You can break up such a pair and make the particles real when you have enough energy coming from some interaction between two charged particles that were placed inside the vaccuum.

Indeed, virtual particles and their fields (remember that position is not a well defined quantity in QFT ) do not exist for ever. In theory this can be proven by the fact that the socalled number-operator of such particles does NOT commute with the hamiltonian (it is not a conserved quantity). Therefore we can call these virtual particles : vacuum-fluctuations.

Problem is that if the vacuum has a gazzillion virtual particles (suppose each such particle is represented by one LOWEST energy quantum of a harmonic oscillator), the energy of this vacuum (the zero-point energy) becomes infinite. This will lead to difficulties with curvature of space time and this effect also predicts a very large cosmological constant. This is however against observations. A possible way out is to renormalize this positive infinity by saying that each such virtual electron and positron has a supersymmetric counterpart with opposite energy. This leads to the situation that the positive infinity is "eliminated" (it is not really gone , though) by a negative infinity coming from the supersymmetry.

marlon
 
  • #4
I have absolutely no notion of quantum field theory. I'd like to learn it, but after I start quantum mechanics. Before I start quantum mechanics I'd like to learn mutli-variable calculus. A long time before me. Should I trust all what QFT says? Why is it considered a theory?

The QFT-vaccuum is not empty because the lowest possible energy cannot be zero (you know, because of Heisenberg uncertainty : zero energy implies infinite spread of position)

Sorry but, What is infinite spread of position?

the vacuum is filled with these socalled virtual particles. It was Dirac who came up with the idea that the vacuum was filled with virtual positron and electron pairs (the reason that they were pairs has to do with conservation laws like that of electrical charge). You can break up such a pair and make the particles real when you have enough energy coming from some interaction between two charged particles that were placed inside the vaccuum.

So virtual particles arise only from the field? Then I conclude that forces may exist without particles, but then 'where is the force?' and where are the mechanics of forces? Everything is based upon something. For example atoms are based on quarks and the like, but what a force is based on?

Indeed, virtual particles and their fields (remember that position is not a well defined quantity in QFT ) do not exist for ever. In theory this can be proven by the fact that the socalled number-operator of such particles does NOT commute with the hamiltonian (it is not a conserved quantity). Therefore we can call these virtual particles : vacuum-fluctuations.

So what happens with those virtual particles after they appear and what causes them to behave that way? Appear and Disappear? When they Disappear what happens with the energy?

This will lead to difficulties with curvature of space time

Has carvature of space time been ever confirmed for sure?

I would also appreciate if you answer the rest of the questions, about Big Bang, atoms and quarks (2nd and 3rd paragraph)
 
  • #5
heartless said:
I have absolutely no notion of quantum field theory.
Ok, in that case i suggest you need to study QM and special relativity. After that, i suggest Zee's book "QFT in a Nutshell" to start with QFT. One does not learn QFT from an open websource.

regards
marlon
 

1. What is energy?

Energy is a fundamental concept in physics that refers to the ability of a system to do work or cause a change. It can exist in various forms, such as kinetic, potential, thermal, electrical, and chemical energy.

2. What are quarks?

Quarks are subatomic particles that are considered to be the building blocks of matter. They are the smallest known particles and make up protons and neutrons, which are the building blocks of atomic nuclei. Quarks also have a property called "color" which is responsible for the strong force that holds atomic nuclei together.

3. What is the strong force?

The strong force is one of the four fundamental forces in nature, along with gravity, electromagnetism, and the weak force. It is responsible for holding the nucleus of an atom together by binding the protons and neutrons together through the exchange of particles called gluons.

4. Why is there a lack of understanding of energy, quarks, and the strong force?

The lack of understanding of these concepts is due to their complexity and the fact that they operate on a very small scale that is not easily observable. Scientists are continually conducting experiments and research to gain a deeper understanding of these fundamental concepts.

5. How are energy, quarks, and the strong force related?

Energy and quarks are closely related as quarks possess energy and can interact with other particles through the exchange of energy. The strong force is also related as it is responsible for the interactions between quarks that make up protons and neutrons, which in turn make up the nucleus of an atom.

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