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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

#61

> 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?

My understanding: The Higgs field, uniquely, has a nonzero vacuum expectation value -- so, when it's in its ground state, it's "switched on", it has an effect. In the early universe, it was in a higher energy state; for most fields, that would cause them to have an effect, but for the Higgs field that instead allowed it to take on a zero vacuum expectation value and to be "switched off". The Higgs takes on nonzero values at low energies instead of at high energies like other fields, so it "switched on" as the universe cooled.

Re: How the Higgs field gives mass to elementary particles

#62
post #38
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…

> What was the "specific" definition of the aether?

TL:DR the aether has a reference frame. This is exactly what it's inventors wanted and exactly what modern things don't have.

Here is the long version:

When you put together a couple of the constants of classical electromagnetic theory (specifically the quantities called the permitivity and permeability of free space) you get out a quantity which has the units of a speed. You get this thing which is measured in metres per second.

Now if you're a Victorian era scientist, and you have fully internalised Gallilean relativity and Newtonian mechanics then this is absolutely, completely, insane. There is no way in their worldview for a speed to exist in isolation, without a reference frame for it to be measured with respect to.

If I measure a guy on a bike going at 10 miles per hour, and a guy in a car going at 30 miles per hour past him then the guy on the bike sees the car going at 20 miles per hour relative to him. If I sit opposite you on a train I measure your speed to be 0, even though we're both moving at 100+ km/hour. Speeds are (for Victorian scientists) completely relative.

So they have the theory of electromagnetism, which seems to be giving amazingly accurate predictions, except that it also gives you this apparently absolute speed, which makes no sense. Someone realises pretty fast that it's about the speed that light goes. So what do they do? They propose the existence of this "aether" stuff which is everywhere at all times and critically which has a reference frame. The aether provides a reference frame for the speed of light and the crazy meaningless absolute speed they didn't know what to do with now makes sense, it's relative like any other speed, but the magic quantity they got is the speed in the aether's reference frame.

Of course a few decades later Michelson and Morley show that this idea doesn't work, in an incredibly beautiful experiment, and the aether theory starts to look shaky. A few years after that Einstein (with input from people like Lorentz) cooks up special relativity which is almost like Gallilean relativity in that almost all speeds are relative, except specifically the speed of light is not. The speed of light is absolute, just as it has to be because of the way it pops out of electromagnetism.

Re: How the Higgs field gives mass to elementary particles

#63
post #26

PBS Spacetime has a fantastic video on the Higgs Field that explains it about one level deeper that typical pop science, and answers some of the questions I'm seeing in this thread, include "why did the field switch on suddenly?" and "Why is the Higgs Field different from other fields" link: https://www.youtube.com/watch?v=G0Q4UAiKacw

I can also add this set of articles from Matt Strassler which explains it all with surprisingly simple math. It really is quite understandable and I wish more pop-sci discussions of the subject threw in a few equations now and then to explain such stuff.

https://profmattstrassler.com/articles-and-posts/particle-ph...

Re: How the Higgs field gives mass to elementary particles

#64

As a lay person, I found that a clear and understandable explanation, which in my experience suggests it is a wild wild over simplification - but enjoyable nonetheless A question for the more expert amongst you. Is the Higgs field unique in its interaction with other fields, or are there other similar fields which similarly change the way that other fields (and associated particles) behave?

I’m not a qft-ist, but from the top my head the Higgs field wouldn’t explain the (likely positive) mass of neutrinos. So there could potentially be another mass creation mechanism. But someone else more informed could clarify.

There are essentially two "easy" ways to add neutrino mass to the standard model without breaking things too much.

One is to use the Higgs to give neutrinos mass. For technical reasons this only works if there are both right and left handed neutrinos. We have only ever detected left handed neutrinos, so you'd have to also add right handed neutrinos, and just say that they don't really interact with anything else.

The second way you can do it is add a very heavy Majorana particle to your theory for each of the 3 neutrinos we know about. These Majorana particles are their own anti-particle (just like the photon is) and as a result are able to have a non-zero mass without the Higg's mechanism. The three types of neutrinos we already know about would then get their masses as a result of some slightly complicated maths involving the masses of the three new Majorana neutrinos.

Re: How the Higgs field gives mass to elementary particles

#65

Earlier quoted context omitted.

I believe it's both. All fields can stiffen their fellows like this, but only the Higgs is stably non-zero.

What's another example of cross-field interaction? Where (say) the EM field changes the restoring force of the gravitational field?

Total layman here, but doesn't an EM field carry energy, and thus have similar effects as mass - thus warping spacetime?

Re: How the Higgs field gives mass to elementary particles

#66

Earlier quoted context omitted.

I believe it's both. All fields can stiffen their fellows like this, but only the Higgs is stably non-zero.

What's another example of cross-field interaction? Where (say) the EM field changes the restoring force of the gravitational field?

My mental model is that of the EM field coupling with the internal EM fields of a material to give rise to the phenomenon of index of refraction where light appears to move slower than the speed of light in a vacuum in said material.

As I understand, a more advanced version of this occurs in superconductors which serves as a much better model of the phenomenon. At least I'm told it would if I could claim to understand it!

https://physics.stackexchange.com/questions/33240/how-come-a...

https://physics.stackexchange.com/questions/47791/what-do-ma...

Re: How the Higgs field gives mass to elementary particles

#67
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...

A "tall tale" is one that is likely false.

Re: How the Higgs field gives mass to elementary particles

#68
post #48

Earlier quoted context omitted.

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.…

That hardly constitutes a precise definition

It is precise enough for our purpose: ether is a hypothetical medium for light waves to propagate. Moreover it would need to have no interaction with ordinary matter, or else it would cause planets' orbits to decay.

only we must give up ascribing a definite state of motion to it - Einstein

This is a "No True Scotsman" fallacy wherein one redefines the assertion to deal with specific objections. I hesitate to criticize Einstein, of course, but in this case it's not clear that "ether" minus motion means anything. One can be generous and say he had an intuition about fields, however fields aren't ether, either.

Re: How the Higgs field gives mass to elementary particles

#69
post #50
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.

sorry for the confusion, I meant is it really the case that this is a commonly used description of the higgs field.

Re: How the Higgs field gives mass to elementary particles

#70
post #5

I studied wave mechanics in college, but the origin of mass didn't click for me until several years later (and in fact I don't believe it was every brought up in the context of wave mechanics, which seems like a problem in retrospect). The conceptualization that worked for me is this: The normal wave equation is (ignoring constant factors like mass and propagation velocity): d^2/dt^2 f(x,t) = d^2/dx^2 f(x,t) = This s…

chatgpt convo to understand "temporal frequency" better: https://chatgpt.com/share/f8601523-2d3f-4497-a9b4-071d6a8778...
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