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How the Higgs field gives mass to elementary particles

quantamagazine.org

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Re: How the Higgs field gives mass to elementary particles

#41

Post by halyconWays »

oezi wrote: post #37
throw0101d wrote: post #17

> Quantum field theory, the powerful framework of modern particle physics, says the universe is filled with fields. Examples include the electromagnetic field, the gravitational field and the Higgs field itself. For each field, there’s a corresponding type of particle, best understood as a little ripple in that field. The electromagnetic field’s ripples are light waves, and its gentlest ripples are the particles of l…

I always thought the fields are just the mathematical representation of the respective force carrier particles travelling through space. Such particles (the photon is certainly the most relevant for us) are having such a big size due to their statistical nature that the fill space even though their own size when probed is tiny.

Particles don't actually exist, however. They're excitations in various fields. A proton, for example, is actually a sea of three quarks of different "colors" that continually exchange energy (and only have potential positions) via gluons, and those quarks and gluons themselves aren't particles, but excitations in fields

Re: How the Higgs field gives mass to elementary particles

#42

Post by simpaticoder »

Maxatar wrote: post #38
emrah wrote: post #32

Earlier quoted context omitted.

Aether has a specific definition and it still does not exist. It was not rediscovered. QFT is not aether-like. Aether was a substance filling all space, while QFT fields like higgs are not physical at all (but rather give rise to physical properties)

What was the "specific" definition of the aether? It looks from reviewing the history that there was no consensus on what the aether was or what its properties were. Interestingly enough what I did manage to find is a lecture given by Einstein in 1920 where he argues that the ether is in fact essential towards the understanding of general relativity, and that it could be through the ether that gravity and electromagn…

The aether (or just ether) was assumed to be the substance in which light waves waved, just as air is the substance that sound waves. If this substance existed it was likely that the Earth was moving through it at some velocity, and the Michelson-Morley experiment famously showed that this is not so. There were also observations of Jupiter's moons. These null results led to Lorentz' quantification of what would become Einstein's definition of special relativity in 1905.

Our confidence in SR is so strong now that c is defined and length unit defined as the distance light travels during a set time.

Re: How the Higgs field gives mass to elementary particles

#43

Post by LegitShady »

emblaegh wrote: post #29
LegitShady wrote: post #21

Earlier quoted context omitted.

If the higgs field did not exist, particles would not have enough mass to attract each other, and the universe as we know it would not exist. So while I do not know if there is some particular cause of the higgs field, no reality like ours would exist without it, and realities without it would not look like anything we recognize (although maybe scientists could simulate it).

Beware when mixing quantum field theory (Higgs) with gravity (attraction). We don’t have any idea how these two relate to each other.

the entire theory of the higgs field and its discovery came from understanding that the model without it lacked sufficient gravity to match the world around us.

So I understand what you're saying, I disagree that we don't know how these to relate to each other. The reason Peter Higgs theorized the higgs field is because we have some idea of it.Maybe it gets more complicated than we understand currently, but we understood it enough to guess some properties of the higgs boson and discover it experimentally.

Re: How the Higgs field gives mass to elementary particles

#44

Post by tsimionescu »

If anyone wants to dig deeper, there is an excellent lecture on YouTube by Leonard Susskind. This goes into some details on how fields in general give mass to (composite) particles, and how the Higgs field has certain properties that allow it to give mass to elementary particles. It goes only into a tiny bit of math, absolutely intelligible at the high-school or at least undergraduate level.

https://youtube.com/watch?v=JqNg819PiZY

Re: How the Higgs field gives mass to elementary particles

#45

Post by pdonis »

throw0101d wrote: post #19

> Once upon a time, there came into being a universe. Searingly hot, it swarmed with elementary particles. Among its fields was a Higgs field, initially switched off. But as the universe expanded and cooled, the Higgs field suddenly switched on, developing a nonzero strength. Any particular reason/mechanism why the Higgs field suddenly (gradually?) switched on?

> Any particular reason/mechanism why the Higgs field suddenly (gradually?) switched on?

"Switched on" is not really a good description. According to my understanding of our best current model, the Higgs field was not in its vacuum state in the very early universe--there were lots of Higgs particles around--so it was not "switched off" any more than any of the other Standard Model fields were. But in the very early universe, the electroweak interaction worked differently than it does now. As the universe cooled, there was a phase transition that changed how the electroweak interaction worked, and after that phase transition, the Higgs field acquired what is called a nonzero "vacuum expectation value", meaning that even though there were no longer any Higgs particles around-- the Higgs field was in its vacuum state--that vacuum state now corresponded to a nonzero value of the Higgs field, meaning that the field can interact with other fields, and that interaction is what we observe as mass for those other fields.

Re: How the Higgs field gives mass to elementary particles

#46

Post by pdonis »

LegitShady wrote: post #43
emblaegh wrote: post #29

Earlier quoted context omitted.

Beware when mixing quantum field theory (Higgs) with gravity (attraction). We don’t have any idea how these two relate to each other.

the entire theory of the higgs field and its discovery came from understanding that the model without it lacked sufficient gravity to match the world around us. So I understand what you're saying, I disagree that we don't know how these to relate to each other. The reason Peter Higgs theorized the higgs field is because we have some idea of it.Maybe it gets more complicated than we understand currently, but we unders…

> the entire theory of the higgs field and its discovery came from understanding that the model without it lacked sufficient gravity to match the world around us.

No, it didn't. Mass is not required for gravity; only energy is. The energy was there before the electroweak phase transition; it just wasn't in the form of rest mass. It still produced gravity.

Re: How the Higgs field gives mass to elementary particles

#47

Post by simpaticoder »

This article is suspect as it mentions a "stationary electron". Such an electron would have precisely known momentum, and so exist throughout all of spacetime. This is a common starting point for solving the (e.g. Dirac) equations, but it's not physical.

Re: How the Higgs field gives mass to elementary particles

#48

Post by Maxatar »

simpaticoder wrote: post #42
Maxatar wrote: post #38

Earlier quoted context omitted.

What was the "specific" definition of the aether? It looks from reviewing the history that there was no consensus on what the aether was or what its properties were. Interestingly enough what I did manage to find is a lecture given by Einstein in 1920 where he argues that the ether is in fact essential towards the understanding of general relativity, and that it could be through the ether that gravity and electromagn…

The aether (or just ether) was assumed to be the substance in which light waves waved, just as air is the substance that sound waves. If this substance existed it was likely that the Earth was moving through it at some velocity, and the Michelson-Morley experiment famously showed that this is not so. There were also observations of Jupiter's moons. These null results led to Lorentz' quantification of what would becom…

That hardly constitutes a precise definition, but at any rate the lecture I linked to goes over the history and I quote, once again from Einstein himself:

>The next position which it was possible to take up in face of this state of things appeared to be the following. The ether does not exist at all...

>More careful reflection teaches us however, that the special theory of relativity does not compel us to deny ether. We may assume the existence of an ether; only we must give up ascribing a definite state of motion to it

This is about half way through the lecture before Einstein touches on general relativity. Towards the end he is quite adamant that a theory of the ether is necessary to fully appreciate general relativity.

With that said I do not want to fall into an argument from authority, certainly much of what we understand about relativity today along with its implications differs from its original formulation, but I present the lecture because I think a lot of people don't quite have the appreciation or historical understanding of what the ether was or wasn't, they just read about how the Michelson-Morley experiment proved that it can't exist along with sensational views that the experiment represented some kind of embarrassment or catastrophe in physics and the ether became a fall-guy of sorts that we must entirely rid ourselves of.

But if you read through the actual primary sources you get a very different picture of how physics progressed bit by bit.

Re: How the Higgs field gives mass to elementary particles

#49

Post by pdonis »

LegitShady wrote: post #21
throw0101d wrote: post #19

> Once upon a time, there came into being a universe. Searingly hot, it swarmed with elementary particles. Among its fields was a Higgs field, initially switched off. But as the universe expanded and cooled, the Higgs field suddenly switched on, developing a nonzero strength. Any particular reason/mechanism why the Higgs field suddenly (gradually?) switched on?

If the higgs field did not exist, particles would not have enough mass to attract each other, and the universe as we know it would not exist. So while I do not know if there is some particular cause of the higgs field, no reality like ours would exist without it, and realities without it would not look like anything we recognize (although maybe scientists could simulate it).

> If the higgs field did not exist, particles would not have enough mass to attract each other, and the universe as we know it would not exist.

This is not correct. Rest mass is not required for gravity. The source of gravity in GR is the stress-energy tensor, which was nonzero in the early universe even though all of the Standard Model fields were massless. Indeed, a vacuum electromagnetic field today has a nonzero stress-energy tensor even though, at the QFT level, it is a massless field (the photon).

Re: How the Higgs field gives mass to elementary particles

#50

Post by pdonis »

sieste wrote: post #39

> A common approach has been to tell a tall tale. Here’s one version: There’s this substance, like a soup, that fills the universe; that’s the Higgs field. As particles move through it, the soup slows them down, and that’s how particles get mass. Is that really so? I've never heard this analogy, so the whole premise seems a bit of a straw man...

> Is that really so?

As the article notes, no, this is not a correct description.

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