Of Particular Significance

How the Higgs Field Does Its Thing

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 09/24/2012

Last week I finished up a set of articles explaining what Fields and “Particles” are.  These articles require a small amount of math and physics, the sort you’d get in an advanced pre-university or a beginning university course.

[Articles with no technical requirements will come soon; in the meantime, try my widely read article on Why the Higgs Particle Matters.]

The Particles and Fields articles are a prerequisite to the next set of articles, which will explain what the (simplest type of) Higgs field is and how it does what it does. The first article, just completed, outlines the basic idea. Future articles to appear over coming days and weeks will fill in many details.

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34 Responses

  1. Dear Dr. strassler :
    If all quantum fields are existing in a state of inter-penetration — in same place in same time — in the arena of space-time , then why ALL possible interactions does not occur simultaneously resulting in a state of total chaos ?
    What is the directing mechanism that controls interactions so that they result in our ordered universe while ALL interactions are simultaneously possible.?

  2. Sorry to repeat but it posted in the wrong place in the thread…..

    To expand a bit further I’ve always envisaged that once you have mass (through the Higgs field) it is easier to accumulate it but if you don’t have mass there is no way to ‘gain weight’, hence particles get heavier as they move faster or interact with other fields but photons don’t. – that Higgs is somehow responsible for e equaling mc squared as opposed to being equivalent (which is why I guess I have always doubted the graviton)

    1. Without the Higgs, the Universe would be a very different place, but many fundamental particles would still be massive (the suite of fundamental particles would be different, masses would be different, the interactions would be different, but it’s not like rest energy would no longer exist). I’m not really sure what you’re saying in this comment other than that. It is a reasonable position to doubt the graviton as envisioned now (massless spin 2 particle with minuscule coupling) so long as it is outside the realm of experimental testing, but not because of anything related to the Higgs or the generation of rest energy.

      1. I think your first line ‘fundamental particles would still be massive is the point I’m questioning – take away the only consistent source of mass (Higgs field) and would the other mechanisms still act as we see today – is there a fundamentalism we are missing??
        My concerns with graviton come from a bigger issue with quantum mechanics – I know it works but I’m with Einstein in my dislike for it… I really hope I see a theory to replace it and combine QM & relativity removing uncertainty in the process in my lifetime!

  3. Thanks again these are really helpful descriptions, particularly the description of the differences between the fields but I’m old and slow! You said before energy of any form warps spacetime to create gravity. A high energy photon therefore warps spacetime? How’s is that warping different from a rest energy warping of spacetime (assuming I’ve understood correctly and rest energy warping = mass)?

    Looking at it another way around in my head, why can you not have a particle which interacts with the Higgs field which can travel at the speed of light if there is no difference between the warping of spacetime from rest energy and that from kinetics?

    I do apologise for the slightly low level questions its just that I always had this image of photons skating around the contours of spacetime with no friction (warping of spacetime through the Higgs field) and therefore never slowing down, but if I understand you correctly they do have friction through their kinetic energy so why doesn’t it slow them down?

    1. Quick answer? Rest energy and contributions from moving energy such as that of photons show up in different entries in the stress-energy tensor in general relativity. They are not, precisely, equivalent.


      The contribution from anything but rest energy is normally so small that we don’t include the contribution.

      To your second question: thinking about mass and energy in terms of how it produces gravity is confusing and I don’t do it. Just remember special relativity as to why a massive (= gets rest energy from some source) particle can’t go c–infinite energy is required to accelerate any starting rest energy to c. If a particle isn’t burdened with a starting bucket of energy, it is *required* to travel at c.

      Friction from space is not a good way to think of a photon’s experience, either. It’s not that massive particles feel friction that slows them down. It’s that they must accelerate their rest energy to c in order to travel c, and this requires infinite energy. A photon or other massless particle has no energy it must accelerate to c, and moreover if it ever travelled slower than c special relativity would break down, fundamentally because there would exist a reference frame in which the photon does not exist (the photon’s *own rest frame*).

      Remember E = mc^2/Sqrt{1-v^2/c^2}, so if m is 0, E is also 0, unless v is also equal to c, and so v *must* be equal to c. But if m is nonzero, E = (something nonzero) / 0 if v = c, which can be read as “a massive particle requires infinite kinetic energy in order to travel c, and more than infinite energy in order to travel faster than c.”

      1. Your clarity and patience are both welcome & very helpful – the maths regarding stress tensors is now beyond me without revision but lm glad at least we can class the two ‘masses’ as different – the only question then is one more fundamental (feels like field generated mass should be, and, as the only field always on Higgs is ‘the most’).
        I kinda remember my relativity theory, I guess the point I’m struggling with is because Higgs is always on and therefore gives everything that reacts with it mass it is therefore a gatekeeper which guarantees nothing can travel at c – so it feels like it should have some more fundamental role in relativity something like, ‘the fundamental theory that explains why Higgs is always on is the underlying theory behind relativity’….

  4. Sorry Prof Strassler but I’m still strugginling with the logic… Higgs field gives a particle mass, mass of a particle is proportional to its gravitiational effect BUT Higgs field has no link to gravitational field?

    Equally a massive particle cannot travel at light speed – does this mean Higgs field is at the core of relativity?

    Please help a (20 years) lapsed physics grad!

    1. The Higgs field is a source of energy, most famously some of the rest energy, which we associate with mass, for some particles and all of it for others. QCD is also a source of energy, in fact most of the rest energy of the material around you comes from QCD! The Higgs contribution to the mass of the proton and neutron is tiny compared to the contributions of the enormous strong force energies that are in play, and electrons don’t contribute much to the mass.

      So, not all mass comes from the Higgs in the first place.

      Moreover, energy in any form warps spacetime to produce gravity. A hot potato is in fact very slightly heavier than an identical cold potato. In most real-world situations, rest energy is the dominant form of energy doing the warping, but we can’t conclude from that that there is a special connection between rest energy and gravity, or between the source field(s) of rest energy and gravity. Even if we could, even if gravity came exclusively from rest energy, most rest energy doesn’t even come from the Higgs but from QCD! So, there’s no special connection between the Higgs and gravity whatsoever, any more than there is a special connection between QCD and gravity.

      1. Thanks but I’m still confused, how does this equate to high energy photon? Why does its energy not give it mass? Is there a split between weak & electromagnetic fields and strong and Higgs fields?

      2. Critically, first and foremost, the photon interacts with no “always on” field like the Higgs. Therefore, a photon’s energy is purely kinetic in some sense; it gains no permanent energy from interacting with any fields that would be present even at rest. That is, if you could go to a photon’s rest frame, you would measure it as having no energy since it’s not interacting with anything and not moving.

        So, a photon in a rest frame is nothing at all; you would be able to make something that was there, not there, if you could go into a photon’s rest frame. This means photons must travel at a speed such that you can’t make them disappear entirely simply by catching up to them, and that’s the speed of light.

        The modern standard terminology in physics is that only rest energy is equated with mass, and so the photon has no mass. You might say it has an “effective mass” equal to its energy over c^2, but it’s not what a physicist means when he says “mass.” He means the constant such that, in a particle’s rest frame, it has that constant times c^2 energy associated with it. A photon has no such frame, and no such mass.

        And no, there is nothing special with respect to mass about the strong force except its strength. Some of the mass around you comes from electromagnetism and the weak force, too, but they are so much weaker as to be negligible in comparison. That most mass comes from QCD is just a result of QCD being the most powerful interaction, by far. That’s what’s special about QCD. The Higgs is special because it is always on; it’s influence cannot be escaped or negated. Electromagnetism is special because it has infinite range and is a powerful force. Gravity is special because it has infinite range and is purely additive and so it cannot and does not cancel out on large scales (there’s no such thing as a negative contribution to gravity, but there’s negative charge). The weak force is special because it can violate symmetries and limits that constrain the others, allowing otherwise stable particles to decay. Each interaction plays its role, and the only two that we know for sure have what you might call a special relationship are the electric/weak forces and the Higgs.

        1. To expand a bit further I’ve also always envisaged that once you have mass (through the Higgs field) it is easier to accumulate it, but if you don’t have mass their is no way to gain weight, hence particles get heavier as they move faster or interact with other fields but photons don’t – that Higgs is somehow responsible for e equalling mc squared as opposed to being equivalent to it (which I guess is why I’ve always doubted the graviton)…

    2. I feel the need to emphasize how cool it is that most rest energy comes from the interactions of quarks and gluons in the protons and neutrons of nuclei. Think about it! When you struggle to move a box of books around, you’re having a hard time almost entirely because the quarks and gluons in those books have enormous kinetic energies due to the enormous strength of the strong force. Every once in a while, just stop and wonder at it. Similarly, just think about how cool it is that the reason an electron has mass and atoms form at all is because of the action of some exotic scalar field that is always in the “on” position. Everything around you, because of some blip on a graph…

  5. excuse me Matt. for asking again , but i want to know the following :
    In principle is it possible that gravity is not force ,is not geometry , but an ontological field that interacts with quanta masses directly or via the higgs field ? OR something beyond all this ??

  6. Science today has just some hints of how QM and GR interact.

    Even though there are many theories that propose ways of interaction between GR and QM, we also need experiments that can put those theories to the test, and get to know for sure what’s the “real McCoy” behind this.

    Black holes are one such case that may give Science some hints regarding how GR and QM interact.

    But again, we need the experiments that can put theories to the test.

    A theory can be a scientific theory if it is expressed in such a way that can be proven wrong, and then, you need the experiments to back up (or refute) the allegations of the theory.

    Regarding what may happen with geometry once we have a better understanding of how GR and QM interact, well, being myself an engineer I can tell you that most engineers use “classical” newtonian mechanics on a daily basis to do our jobs.

    For the usual stuff that moves slow enough in the presence of “normal” gravitational fields like at the surface of the earth, you can do just as fine with newtonian mechanics, and you will get almost the same numerical result with a much simpler model to deal with.

    In computational chemistry, scientists use Density Functional Theory models to predict the shape and the behavoiur of molecular orbitals on a daily basis, and DFT is based on 1930s QM.

    We all use the paradigm that is the best fit for the problem at hand.

    GR is still “holding the fort”, but eventually will pass the baton to some other “more complete” theory.

  7. Thanks for this (and the whole series). I don’t have the math for it, so it doesn’t make much sense to me, but I really do appreciate you doing this.

    It’s been fun trying to sort it out.

      1. Well, what little math I had is 40 years in the past so it’s pretty unlikely that I’m going to be able to do that. One of the bad things about getting old is that the old brain just doesn’t quite work like it used to.

        I did share your post at Google Plus and a 70 year man (very well educated and with some experience in the field) from Rotterdamn ran across it. He really enjoyed it and understood it quite well. So what you’re doing it not for nothing.

  8. I mean if there are a quantum gravitation field and its graviton , do we understand gravity then as interaction of h-field and g-field ? do we have to reject gravity as geometry ?

    1. We don’t have to worry about the h field in talking about gravity any more than we have to worry about the h field in talking about the photon.

      The reason there are gravitons (presumably) is that we live in a world where all waves are quantized.

      The h field gives mass to the known massive particles; but the gravitational field, like the electromagnetic field, satisfies a “Class 0” equation (in the language of these articles) and therefore its quanta (gravitons, like photons) are massless.

      As for whether we have to reject gravity as geometry; at some level, probably, but to what degree we don’t know. Perhaps a better way to say this is that we will have to accept geometry as something much more complicated than we are used to — we will have to recognize quantum geometry as something quite subtle. There are plenty of suggestions for how to approach quantum geometry, but we do not know which of these (if any) is realized in nature.

      1. Photons leaving earth lose energy under the influence of earth’s gravitation. The photon’s amplitude decreases.
        Quanta are supposed to be waves with minimal amplitude.
        Does the energy that leaves Black Holes’event horizons consist of quanta?

        1. Yes, the energy leaving black holes is in quanta (indeed quantum field theory methods were used by Hawking in the computation.)

          The minimum amplitude for a wave depends on its frequency, so just looking to see what the amplitude is doing doesn’t tell you anything.

          The energy and frequency of the photons can and do decrease as a photon leaves earth (or a black hole) and that is perfectly consistent with energy conservation. It is the same reason that a rocket, having turned off its engine, slows down as it leaves the earth (or a black hole) — it is being pulled on by gravitational effects.

          But (until you deal with some really challenging subtleties about what different observers might agree or disagree about) a single photon remains a single photon. The laws that govern the interaction of photons with gravitational fields are such as to assure this.

      2. This is kind of off-topic for this post…sorry.

        What’s the reason for presuming that gravity is quantized? Is it indeed just that all the other fields we know about are quantized, or is there some theoretical reason that having some fields quantized, and others not, leads to a fundamental contradiction?

        (I understand why gravity has to obey the superposition principle — things that experience superposition have energy, and thus gravitate — but I don’t understand how that leads to quantization per se.)

  9. Joe, Hi,

    What you are describing are different consequences of uncertainty relationships, were the uncertainty relationships could be seen as different aspects of a very general principle in quantum physics.

    One of the (many) interesting things about this very general principle is that is pops up in quantum mechanics in many ways and in many forms.

    These many ways and forms (equations) offer different insights into what this principle means and implies.

    One of such forms in the noncommuting operators form, while another form is the wave packet deduction of the uncertainty relationships.

    Let’s stick with these last forms of relationships for a while, as they are both very simple and plenty of insights at the same time.

    Δx.Δp >= h/2Π

    ΔE.Δt >= h/2Π

    Both expressions are scalar expressions, in the sense that the result is a scalar value. A scalar is a physical magnitude that only requires a single value to completely express its measure.

    In the first expression, we have the an operation that involves two vectors (position and linear momentum) while the result is a scalar. A vector is a physical magnitude that requires three values to completely express its measure: modulus (size), sense and direction.

    In the second expression, we have an operaton that involves two scalars (energy and time).

    Regarding the first expression, it tells us a lot of things. We know that we can determine the position of a particle with as much precision as we want.

    It also tells us that we can determine the linear momentum of a particle with as much precision as we want.

    But it also tells us that we cannot determine at the same time the position and the linear momentum of a particle with as much precision as we want.

    The key factor in this concept is “at the same time” and “as much precision as we want”.

    The more precision we want to use to determine one of the magnitudes, the less precision we can get while determining the other magnitude at the same time.

    But this is not the only consequence we may expect from this relationship. To illustrate other interesting consequences, I have an anecdote of my own from my college days.

    A remarkable experiment that does not seem to be related to this principle is the the experiment that explains the rationale behind the Kelvin temperature scale, or the absolute temperature scale.

    One rather intriguing aspect of these experiments is that, no matter how hard they try, experimental scientists can’t get to absolute zero, even though they have been getting closer and closer over time.

    The reason for this rather strange behaviour is the uncertainty principle. As we freeze matter (atoms), atoms and its particles loose energy up to such a point were they get really close to stopping any kind of movement (or so we hope), but that cannot happen if the uncertainty relationship has to hold true: if atoms and its particles were to stop moving completely, both its position and its linear momentum could be determined at the same time with as much precision as we want or care (if atoms were to stop completely all motion, we would have that Δx = 0 and Δp = 0 at the same time, so we would get that Δx.Δp = 0, which is not possible if Δx.Δp has to be larger than or equal to h/2Π).

    So, now we know that matter can’t stop from moving and, in fact, we now know and understand that another consequence of this is that no single point in space-time can have zero energy (because of the same line of thinking!: any particle that happens to be in that particular single spec of space-time would also have no energy, that is, no motion, and so, we are back to the same inconsistency!)

    Which means that there cannot be such a thing as “empty” space-time, or any given spec of space-time that has zero energy.

    So. If any given spec of space-time is not allowed to have zero energy, what does the universe do at any given spec of space-time that gets too close to zero energy: well, the universe “borrows” some energy from the surrounds of such spec and uses that “borrowed” energy to create a pair of particles (a particle and its anti-particle) for just a very small fraction of time, plays with the particles a bit and then “returns” the energy back to its surrounds very quickly.

    That funny game is called quantum field fluctuations. But how is this game played? On a first approximation to this game, the rules are very simple.

    Let’s use the other uncertainty relationship:

    ΔE.Δt >= h/2Π

    This equation sets the stage for the “rules of engagement” of this game.

    The laws of physics (the universe) can create any pair of particles (particle-antiparticle) of any given mass (energy, following Einstein’s equation ΔE = Δmc²), as long as the interval of time it takes to play with it and return the energy back to its surrounds is consistent with the expression ΔE.Δt >= h/2Π.

    So, now we know how quantum field fluctuations work, what is the “zero-point energy constraint”, what mandate forces pairs of “unused” particles to “get back together” into energy, and what is the rationale behind it.

    Kind regards, Gastón

  10. Matt,

    I see you’ve been busy. A while ago I asked this question and I would like your help in clearing up my confusion. In your opinion are “continual spontaneous quantum field disturbances,” “quantum fluctuations,” “zero-point energy,” and “virtual particle/antiparticle annihilation,” different words for the same phenomenon or are they different phenomena? If they are different phenomena what are the differences? Thanks again for making many things more understandable.


    >________________________________ > From: Of Particular Significance >To: j1sabella@yahoo.com >Sent: Monday, September 24, 2012 8:44 AM >Subject: [New post] How the Higgs Field Does Its Thing > > > WordPress.com >Matt Strassler posted: “Last week I finished up a set of articles explaining what Fields and “Particles” are.  These articles require a small amount of math and physics, the sort you’d get in an advanced pre-university or a beginning university course. [Articles with no t” >

  11. This is scarey since I just happen to know stuff that you guys haven’t figured out yet … You might call this a first attempt at coming out. Many might call me some nut job that should be dismissed … Let me ask this of you: Have you found the missing mass and energy yet? And no it is not matter being consumed by anti-matter or some feable blind faith as that and yet so much more easily explained. Yes there is math and theoretical junk which measures the existance right up until the point of disappearance, but doesnt explain the mechanics after that point. Ususally the simplest explanation is the most accurate. An analogy is in order. “If you are in a room with a bunch of people and you want to disappear, yes you could get eaten by someone in the room, or you could simply leave the room” But how? … I happen to understand the answer to this and it answers so so many other questions. Who am I? … An engineer that took some extra post graduate study in both Quantum and Crystal Solid State Physics back in the 80s and had my eyes open ever since … just watching. if you have questions … just ask and I will try to answer.

    1. Readers! Behold! A self-declared genius has arrived at my website to save us from our misguided notions! (Too bad we have so many of these geniuses that we don’t know which one to listen to.)

      1. I’m especially fond of the “math and theoretical junk” bit. It’s not like there’s an easily accessible website on theoretical physics that describes quite a lot of the current tests being done to turn that into practical physics. Such a site might even provide explanations of some of the math involved!
        Oh, wait, this is such a website.

        It’s a lot like computer security or cryptography (my field). Anyone can design a system that he/she can’t break, but that is easily broken by others. The same applies to theoretical physics: Anyone can come up with a hypothesis that he/she can’t find flaws in, but which has blatantly obvious flaws to others.

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