7 ms·

Quark Stars

135 points by chmaynard 2y ago

ndsipa_pomu 2y ago
As a layman, I find the idea of neutron and quark stars to be fascinating. What puzzles me though is what distinguishes a compressed mass of neutrons from unconfined quarks/gluons. I thought that the idea of a neutron having a "shell" with quarks inside it was just a visualisation tool, but the compressed neutrons must be providing some force to prevent them from collapsing further into unconfined quarks. That also raises the question of how the unconfined quarks/gluons provide a force to prevent collapse into black holes.
- itishappy 2y ago
  You're looking for the concept of a degeneracy pressure, specifically neutron and quark degeneracy pressures. The short version is that the Pauli exclusion principle forbids fermions from occupying the same state, and this manifests as an actual physical force that resists attempts to bring them close together. https://en.wikipedia.org/wiki/Degenerate_matter https://en.wikipedia.org/wiki/Degenerate_matter
  - ndsipa_pomu 2y ago
    Thanks. It would appear that quark degeneracy pressure is the missing bit that I didn't know about and I don't really understand how that works, but then it does appear to be poorly understood in general.
  - archgoon 2y ago
    > short version is that the Pauli exclusion principle forbids fermions I'd like to point out (for others following along) that the Pauli exclusion principle isn't actually a separate rule (That is, something you'd have to apply after you do 'normal' physics). What is happening with the PEP is that if you start off with a wavefunction that has fermionic symmetry (that is, interchange of two particle swaps the sign of the wavefunction), the evolution via the Schroedinger equation will preserve that (much like it preserves the Integral(|psi|^2)=1 relation). Same for bosons. So if you're writing a Quantum physics simulator, you don't need to put in a "Pauli Exclusion Rule" step.[1] [1] Though depending on your representation you may toss one in for numerical stability.
- pdonis 2y ago
  > what distinguishes a compressed mass of neutrons from unconfined quarks/gluons. If the density and pressure get high enough, there is no longer a stable "neutron" state in which three valence quarks are bound together. You just have a soup of quarks. Calling the quarks "unconfined" is a bit of a misnomer since each of them is restricted to a very small "cell" in space. But they are "unconfined" in the sense of not being bound together by the strong interaction; within their small "cell" they move more or less like free particles. > the compressed neutrons must be providing some force to prevent them from collapsing further into unconfined quarks. "Collapse" isn't really a good word to describe this transition. If you add a small amount of mass to the object, it compresses a little more. If it compresses enough, there is something like a phase transition where the quarks stop being bound into neutrons; but the overall size of the object doesn't "collapse", it just gets a little smaller. > That also raises the question of how the unconfined quarks/gluons provide a force to prevent collapse into black holes. This is just the Pauli exclusion principle, as has already been said in response to you. It's more or less the same whether the quarks are bound into neutrons or not.
  - t8sr 2y ago
    There is an outward force from the neutrons, called neutron degeneracy pressure. It's not really a case of the Pauli Exclusion Principle, as much as they are both different descriptions of what's going on with the wave function.
- wwarner 2y ago
  Not an expert, but it could be that if the radius of a quark star grows slowly enough, then a very massive one would have a schwarzchild radius that is bigger than the star, making it a black hole but without a collapsed singularity.
delichon 2y ago
ChatGPT just told me that ... the Schwarzschild radius for a quark-gluon plasma with a mass of 10^12 kg is approximately 1.485x10^-15 meters, which is extremely small. Extremely small is around the diameter of a proton. Which would mean that any quark star would a black hole. So this estimate must be wrong, right?
- danparsonson 2y ago
  Leaving aside the calculation (I don't know if it's correct), and the sense or not of relying on a fancy word-association machine for such calculations (I wouldn't), your Schwarzchild radius is even smaller than that and you're not a black hole - an object is only a black hole if it is entirely inside its Schwarzchild radius.
  - delichon 2y ago
    If the Schwarzchild radius is reached within a larger mass, wouldn't that radius become inescapable and eventually consume the remainder while growing in proportion? Since I did a sanity check on the result which seems to have failed, why do you think that it's necessary to warn me not to rely on it? The hostility on this site for using LLMs as a tool for exploration is confusing to me. I also learn a lot by asking questions of highly unreliable humans. LLMs don't seem to be much worse than that.
    - ant6n 2y ago
      [flagged]
      - michaelcampbell 2y ago
        Please, no.
    - AnimalMuppet 2y ago
      > If the Schwarzchild radius is reached within a larger mass, wouldn't that radius become inescapable and eventually consume the remainder while growing in proportion? If I understand your question correctly, no. If I have a mass M that corresponds to a Schwarzchild radius r, but the mass occupies a larger radius R, no, it will not create a black hole, since the mass m within r is less than the critical mass M. The portion of M that is within r can still escape that radius.
cryptonector 2y ago
Quark stars might even be a stage on the way to collapse from neutron star to black hole. The collapse is fast, but not instantaneous, so what would those neutrons become once their degeneracy pressure is exceeded?
- sigmoid10 2y ago
  >what would those neutrons become once their degeneracy pressure is exceeded That kind of depends on what the equation of state looks like for quark matter. If you look at black hole formation from a theoretical perspective (e.g. as a collapsing shell of matter), it is very much possible that neutrons transition directly into a black hole before entering a new state. Unfortunately, we have no idea about the equation of state and this stuff is very far beyond anything that could be studied experimentally in a collider. It's admittedly a fascinating topic, but there is very little rigorous science surrounding it.
  - cryptonector 2y ago
    > it is very much possible that neutrons transition directly into a black hole before entering a new state At least the neutrons that start out being outside the Schwarzschild radius of the black-hole-to-be cannot transition directly into being in a black hole state because they have to first move from where they are to the event horizon, and that has to take some non-zero amount of time since they can't exceed the speed of light on the way to the event horizon. It's possible that with the degeneracy pressure exceeded they just don't become something else, but instead simply move... through each other? That makes little sense. Since they are made up of quarks what makes sense instead is that they become quark soup on the way to the event horizon. Though there are other possibilities too. Maybe all the neutrons turn to photons going towards the incipient black hole and without becoming quark soup first, they they can travel through each other. > Unfortunately, we have no idea about the equation of state and this stuff is very far beyond anything that could be studied experimentally in a collider. It's admittedly a fascinating topic, but there is very little rigorous science surrounding it. The best we could do is check different theories for consistency, but we can't test them unless those theories make predictions about electromagnetic emissions or gravity wave emissions from a neutron star collapse that we might be able to observe and which could be used to test those predictions.
Modified3019 2y ago
Off topic, but the reference to critical point of water reminded me of this lovely video from ages ago: https://www.youtube.com/watch?v=2xyiqPgZVyw https://www.youtube.com/watch?v=2xyiqPgZVyw The original link is now gone, and archive.org doesn’t have the other two videos, but I’m pretty sure I have them in my archive: https://web.archive.org/web/20080416125148/http://www.science.uva.nl/research/mgrd/video-cp.html https://web.archive.org/web/20080416125148/http://www.scienc...
- deleted 2y ago
  [deleted]
csours 2y ago
I wonder how this would interact with neutrinos? It seems like a quark core would be predominated by the weak interaction, so it might be more opaque to neutrinos.
- rbanffy 2y ago
  I’d imagine it as more opaque just because of the density.
ThouYS 2y ago
nice! just like the strong interaction material from the three body problem!
edem 2y ago
If you are interested in this topic then i __highly__ recommend the PBS Spacetime channel on YouTube: https://youtu.be/1Ou1MckZHTA?si=enfHtWOSa9BwYRZ- https://youtu.be/1Ou1MckZHTA?si=enfHtWOSa9BwYRZ- where they discuss this topic and so much more. it is truly a gold mine on this topic!
- gigatexal 2y ago
  100% can attest I love this channel
- ryandvm 2y ago
  Love Spacetime, but I find there's a point about 2/3 of the way through every video where I realize I am totally lost in the explanation and I'm just letting the science talk spritz over me like a light summer rain. Vaguely hoping that I'm picking up some sort of osmotic education. I think it's like ASMR for wish-they-could-have-been physicists.
  - tessellated 2y ago
    chiming in for a 'me too' post on hn also notable, the q'n'a at the end smells staged since ever
  - edem 2y ago
    > letting the science talk spritz over me like a light summer rain this made my day, thanks! Sometimes I watch an episode 2-3 times before it clicks, maybe you should try it too.
quarkw 2y ago
This is an exceptionally fun read for me since my name is Quark! The terms "quark star" and "quark matter" are completely new to me so I'll have to do some reading!
- deleted 2y ago
  [deleted]
rbanffy 2y ago
> It’s not every day we find quintillions of tonnes of a new state of matter In terms of size, it’d still be quite unimpressive. About the volume of a million matchboxes. Would fit in a truck.
- kamaal 2y ago
  This also means how big a atom actually is compared to the elementary particles that it is made up of. It could be said most of any thing is just empty space.
  - rbanffy 2y ago
    At this point we start wondering what’s the real difference between space and the stuff that occupies it. Or what “occupies” actually means.
    - danwills 2y ago
      I completely agree and although I am guessing that this probably won't be a very popular opinion, I see matter as being genuinely made-out-of-the-same-stuff-as-space but in a highly 'condensed' and dynamic form. If you see matter in this way and imagine that the relationship between the space and the matter is probably-dynamic too, then it doesn't take a big leap to imagine that gravity could be thought-of as the outcome of the constant-consumption-of-space that must usually occur for the matter to continue its normal existence.. as if 'running' the matter uses up the 'execution cycles' of space (however I think space (even a vacuum) is probably quite structured itself and not mere-causation/computation, even at that level!)
CuriouslyC 2y ago
Wouldn't it be funny if black holes were actually made of quarks, with a core of some exotic higher form of quark we can't create in an accelerator.
cozzyd 2y ago
I was on microphone duty as a grad student at a conference that had a crackpot who sat in the front row and asked questions about quark stars no matter the topic of the talk. Unfortunately the chairpeople of the plenaries kept calling on them and I kept having to hand them the mic...
verisimi 2y ago
> Right at the critical point, water looks weird. It look like a blur of droplets floating in gas. But if you look at any droplet you’ll see it’s full of bubbles of gas. And if you look in any of these bubbles you see it’s full of droplets. As you keep zooming in, you keep seeing basically the same thing…. droplets of liquid in gas, bubbles of gas in liquid…. until you get down to the scale of atoms. So we say this stuff has ‘conformal symmetry’. This is akin to a rather derided religious position: "it's turtles all the way down". The problem with all these claims is that one has to accept that we have established this in CERN or wherever. Have we? Can I check? Is it just the turtles story?
- dreamcompiler 2y ago
  Supercritical water is relatively easy to create in a laboratory. So yeah, it's been verified. https://en.m.wikipedia.org/wiki/Supercritical_water_oxidation https://en.m.wikipedia.org/wiki/Supercritical_water_oxidatio...
  - verisimi 2y ago
    Great, how did you do it? PS ... and what did you see?

135 points by chmaynard 2y ago

As a layman, I find the idea of neutron and quark stars to be fascinating. What puzzles me though is what distinguishes a compressed mass of neutrons from unconfined quarks/gluons. I thought that the idea of a neutron having a "shell" with quarks inside it was just a visualisation tool, but the compressed neutrons must be providing some force to prevent them from collapsing further into unconfined quarks. That also raises the question of how the unconfined quarks/gluons provide a force to prevent collapse into black holes.

itishappy 2y ago
You're looking for the concept of a degeneracy pressure, specifically neutron and quark degeneracy pressures. The short version is that the Pauli exclusion principle forbids fermions from occupying the same state, and this manifests as an actual physical force that resists attempts to bring them close together. https://en.wikipedia.org/wiki/Degenerate_matter https://en.wikipedia.org/wiki/Degenerate_matter
- ndsipa_pomu 2y ago
  Thanks. It would appear that quark degeneracy pressure is the missing bit that I didn't know about and I don't really understand how that works, but then it does appear to be poorly understood in general.
- archgoon 2y ago
  > short version is that the Pauli exclusion principle forbids fermions I'd like to point out (for others following along) that the Pauli exclusion principle isn't actually a separate rule (That is, something you'd have to apply after you do 'normal' physics). What is happening with the PEP is that if you start off with a wavefunction that has fermionic symmetry (that is, interchange of two particle swaps the sign of the wavefunction), the evolution via the Schroedinger equation will preserve that (much like it preserves the Integral(|psi|^2)=1 relation). Same for bosons. So if you're writing a Quantum physics simulator, you don't need to put in a "Pauli Exclusion Rule" step.[1] [1] Though depending on your representation you may toss one in for numerical stability.
pdonis 2y ago
> what distinguishes a compressed mass of neutrons from unconfined quarks/gluons. If the density and pressure get high enough, there is no longer a stable "neutron" state in which three valence quarks are bound together. You just have a soup of quarks. Calling the quarks "unconfined" is a bit of a misnomer since each of them is restricted to a very small "cell" in space. But they are "unconfined" in the sense of not being bound together by the strong interaction; within their small "cell" they move more or less like free particles. > the compressed neutrons must be providing some force to prevent them from collapsing further into unconfined quarks. "Collapse" isn't really a good word to describe this transition. If you add a small amount of mass to the object, it compresses a little more. If it compresses enough, there is something like a phase transition where the quarks stop being bound into neutrons; but the overall size of the object doesn't "collapse", it just gets a little smaller. > That also raises the question of how the unconfined quarks/gluons provide a force to prevent collapse into black holes. This is just the Pauli exclusion principle, as has already been said in response to you. It's more or less the same whether the quarks are bound into neutrons or not.
- t8sr 2y ago
  There is an outward force from the neutrons, called neutron degeneracy pressure. It's not really a case of the Pauli Exclusion Principle, as much as they are both different descriptions of what's going on with the wave function.
wwarner 2y ago
Not an expert, but it could be that if the radius of a quark star grows slowly enough, then a very massive one would have a schwarzchild radius that is bigger than the star, making it a black hole but without a collapsed singularity.

delichon 2y ago

ChatGPT just told me that ... the Schwarzschild radius for a quark-gluon plasma with a mass of 10^12 kg is approximately 1.485x10^-15 meters, which is extremely small. Extremely small is around the diameter of a proton. Which would mean that any quark star would a black hole. So this estimate must be wrong, right?

danparsonson 2y ago
Leaving aside the calculation (I don't know if it's correct), and the sense or not of relying on a fancy word-association machine for such calculations (I wouldn't), your Schwarzchild radius is even smaller than that and you're not a black hole - an object is only a black hole if it is entirely inside its Schwarzchild radius.
- delichon 2y ago
  If the Schwarzchild radius is reached within a larger mass, wouldn't that radius become inescapable and eventually consume the remainder while growing in proportion? Since I did a sanity check on the result which seems to have failed, why do you think that it's necessary to warn me not to rely on it? The hostility on this site for using LLMs as a tool for exploration is confusing to me. I also learn a lot by asking questions of highly unreliable humans. LLMs don't seem to be much worse than that.
  - ant6n 2y ago
    [flagged]
    - michaelcampbell 2y ago
      Please, no.
  - AnimalMuppet 2y ago
    > If the Schwarzchild radius is reached within a larger mass, wouldn't that radius become inescapable and eventually consume the remainder while growing in proportion? If I understand your question correctly, no. If I have a mass M that corresponds to a Schwarzchild radius r, but the mass occupies a larger radius R, no, it will not create a black hole, since the mass m within r is less than the critical mass M. The portion of M that is within r can still escape that radius.

cryptonector 2y ago

Quark stars might even be a stage on the way to collapse from neutron star to black hole. The collapse is fast, but not instantaneous, so what would those neutrons become once their degeneracy pressure is exceeded?

sigmoid10 2y ago
>what would those neutrons become once their degeneracy pressure is exceeded That kind of depends on what the equation of state looks like for quark matter. If you look at black hole formation from a theoretical perspective (e.g. as a collapsing shell of matter), it is very much possible that neutrons transition directly into a black hole before entering a new state. Unfortunately, we have no idea about the equation of state and this stuff is very far beyond anything that could be studied experimentally in a collider. It's admittedly a fascinating topic, but there is very little rigorous science surrounding it.
- cryptonector 2y ago
  > it is very much possible that neutrons transition directly into a black hole before entering a new state At least the neutrons that start out being outside the Schwarzschild radius of the black-hole-to-be cannot transition directly into being in a black hole state because they have to first move from where they are to the event horizon, and that has to take some non-zero amount of time since they can't exceed the speed of light on the way to the event horizon. It's possible that with the degeneracy pressure exceeded they just don't become something else, but instead simply move... through each other? That makes little sense. Since they are made up of quarks what makes sense instead is that they become quark soup on the way to the event horizon. Though there are other possibilities too. Maybe all the neutrons turn to photons going towards the incipient black hole and without becoming quark soup first, they they can travel through each other. > Unfortunately, we have no idea about the equation of state and this stuff is very far beyond anything that could be studied experimentally in a collider. It's admittedly a fascinating topic, but there is very little rigorous science surrounding it. The best we could do is check different theories for consistency, but we can't test them unless those theories make predictions about electromagnetic emissions or gravity wave emissions from a neutron star collapse that we might be able to observe and which could be used to test those predictions.

Modified3019 2y ago

Off topic, but the reference to critical point of water reminded me of this lovely video from ages ago: https://www.youtube.com/watch?v=2xyiqPgZVyw https://www.youtube.com/watch?v=2xyiqPgZVyw The original link is now gone, and archive.org doesn’t have the other two videos, but I’m pretty sure I have them in my archive: https://web.archive.org/web/20080416125148/http://www.science.uva.nl/research/mgrd/video-cp.html https://web.archive.org/web/20080416125148/http://www.scienc...

deleted 2y ago
[deleted]

csours 2y ago

I wonder how this would interact with neutrinos? It seems like a quark core would be predominated by the weak interaction, so it might be more opaque to neutrinos.

rbanffy 2y ago
I’d imagine it as more opaque just because of the density.

ThouYS 2y ago

nice! just like the strong interaction material from the three body problem!

edem 2y ago

If you are interested in this topic then i __highly__ recommend the PBS Spacetime channel on YouTube: https://youtu.be/1Ou1MckZHTA?si=enfHtWOSa9BwYRZ- https://youtu.be/1Ou1MckZHTA?si=enfHtWOSa9BwYRZ- where they discuss this topic and so much more. it is truly a gold mine on this topic!

gigatexal 2y ago
100% can attest I love this channel
ryandvm 2y ago
Love Spacetime, but I find there's a point about 2/3 of the way through every video where I realize I am totally lost in the explanation and I'm just letting the science talk spritz over me like a light summer rain. Vaguely hoping that I'm picking up some sort of osmotic education. I think it's like ASMR for wish-they-could-have-been physicists.
- tessellated 2y ago
  chiming in for a 'me too' post on hn also notable, the q'n'a at the end smells staged since ever
- edem 2y ago
  > letting the science talk spritz over me like a light summer rain this made my day, thanks! Sometimes I watch an episode 2-3 times before it clicks, maybe you should try it too.

quarkw 2y ago

This is an exceptionally fun read for me since my name is Quark! The terms "quark star" and "quark matter" are completely new to me so I'll have to do some reading!

deleted 2y ago
[deleted]

rbanffy 2y ago

> It’s not every day we find quintillions of tonnes of a new state of matter In terms of size, it’d still be quite unimpressive. About the volume of a million matchboxes. Would fit in a truck.

kamaal 2y ago
This also means how big a atom actually is compared to the elementary particles that it is made up of. It could be said most of any thing is just empty space.
- rbanffy 2y ago
  At this point we start wondering what’s the real difference between space and the stuff that occupies it. Or what “occupies” actually means.
  - danwills 2y ago
    I completely agree and although I am guessing that this probably won't be a very popular opinion, I see matter as being genuinely made-out-of-the-same-stuff-as-space but in a highly 'condensed' and dynamic form. If you see matter in this way and imagine that the relationship between the space and the matter is probably-dynamic too, then it doesn't take a big leap to imagine that gravity could be thought-of as the outcome of the constant-consumption-of-space that must usually occur for the matter to continue its normal existence.. as if 'running' the matter uses up the 'execution cycles' of space (however I think space (even a vacuum) is probably quite structured itself and not mere-causation/computation, even at that level!)

CuriouslyC 2y ago

Wouldn't it be funny if black holes were actually made of quarks, with a core of some exotic higher form of quark we can't create in an accelerator.

cozzyd 2y ago

I was on microphone duty as a grad student at a conference that had a crackpot who sat in the front row and asked questions about quark stars no matter the topic of the talk. Unfortunately the chairpeople of the plenaries kept calling on them and I kept having to hand them the mic...

verisimi 2y ago

> Right at the critical point, water looks weird. It look like a blur of droplets floating in gas. But if you look at any droplet you’ll see it’s full of bubbles of gas. And if you look in any of these bubbles you see it’s full of droplets. As you keep zooming in, you keep seeing basically the same thing…. droplets of liquid in gas, bubbles of gas in liquid…. until you get down to the scale of atoms. So we say this stuff has ‘conformal symmetry’. This is akin to a rather derided religious position: "it's turtles all the way down". The problem with all these claims is that one has to accept that we have established this in CERN or wherever. Have we? Can I check? Is it just the turtles story?

dreamcompiler 2y ago
Supercritical water is relatively easy to create in a laboratory. So yeah, it's been verified. https://en.m.wikipedia.org/wiki/Supercritical_water_oxidation https://en.m.wikipedia.org/wiki/Supercritical_water_oxidatio...
- verisimi 2y ago
  Great, how did you do it? PS ... and what did you see?