> The real takeaway is that researchers may have found a potential test for string theory.
Not really. All this paper is really saying is that they have found solutions in classical theories of gravity with extra dimensions that, in four dimensions, can look like standard black holes. So even observing effects predicted by these models would not be evidence for string theory. It would at best be evidence for possible extra dimensions of spacetime at the classical level.
Also, the paper only compares its models with the standard Schwarzschild black hole. But first, most black holes are spinning so the comparison should be with Kerr, not Schwarzschild; and second, as the paper notes early on, there are many other proposed models of compact objects that can look similar to standard black holes. Any given set of observations would have to be tested against all proposed models, not just this one.
I think there are all sorts of other potential tests of string theory. The problem is that for all the actual tests that were ever proposed, it failed (supersymmetry, various proposals for sizes of the extra dimensions).
To be fair, what failed is low-energy Supersymmetry and large extra dimensions, because these things were actually accessible by current gen experiments. But there's a huuuge amount of room left unexplored.
Even if it were testable, and the test failed to validate string theory, I don't think that would convince string theorists one way or another. Strings are a de facto religion within physics.
This line of talk is way overplayed. Like people who have an enthusiast amount of knowledge follow a few people who have professional knowledge who are just unreasonably fixated on what other physicists pursue.
Doubt and questioning are a part of science but this "religion" meme about string theory et al is silly. If you're really upset that somebody is pursuing something is a blind alley, go ahead and do some physics that shows results, otherwise I really wish people would tone the unhelpful criticisms down.
I don't think string theorists are being unreasonable by not having changed their minds yet, given that no evidence has come out one way or the other.
I don't think we can extrapolate from "string theorists didn't update when presented with no evidence" to "string theorists won't update when presented with evidence".
>If the researchers can discover an important observational difference between topological solitons and traditional black holes, this might pave the way to finding a way to test string theory itself.
This is a big if. For now they've just shown that once again something in the string theory landscape could look like something in real life.
I know it is the standard nomenclature, but I object to it being called string theory, as it is at best a hypothesis, if not even just philosophical speculation with more math.
It can make no predictions, it is not falsifiable, it meets none of the constraints that allow something to be science.
Speaking of nomenclature, this is not a good characterization of what philosophy is, if your intention is to reduce philosophy to what you seem to have in mind for “philosophical speculation”. Metaphysical theory thoroughly supported by argument (hylomorphic dualism, theory of act and potency) is actually stronger than mere empirical science. Empirically testable predictions do not transcend reasoned argument as observation is interpreted though the body of propositions of prior theory and enters into scientific argument as argument.
> Its presumed lack of falsifiability has been one of its drawbacks[..]
Given that the definition of a theory is an hypothesis that can be tested for falsehood, it isn't a theory by definition. It is a hypothesis.. but presumably "string hypothesis" doesn't sound as nice.
> We show that topological solitons are remarkably similar to black holes in apparent size and scattering properties, while being smooth and horizonless. Incoming photons experience very high redshift, inducing phenomenological horizonlike behaviors from the point of view of photon scattering. Thus, they provide a compelling case for real-world gravitational solitons and topological alternatives to black holes from string theory.
This is certainly interesting but so far they have only looked into Schwarzschild black holes (the simplest kind of black holes). Their case would be much more compelling if they also found soliton solutions that looked like non-static (Kerr) or even non-stationary/dynamic black hole solutions (<-> black hole formation). I know far too little about solitons, unfortunately, to estimate how easy/difficult it would be to find/construct those.
What plane is the authors' "equatorial plane"? Shortly after their eqn (31), "One should a priori do a similar computation out of the equatorial plane to obtain the total size of the solitons. Due to the complexity of the geodesic equations, this is only possible numerically. However, we will see in the next section that the outer photon shell is actually almost spherically symmetric and slightly flattened at its poles". (ETA: "... the Schwarzschild topological solution is not spherically symmetric ...", just before section A. Methodology).
Central SMBHs' spin appears to be largely far from parallel to their host galaxies' angular momentum[1]. Spin gives us an equatorial plane for the SMBH. Is there physical motivation for picking an equatorial plane if we found an SMBH with negligible J (and no jets)? I don't doubt that people would land on some convention (e.g. equatorial plane parallel to host galaxy's north if available, our galaxy's north if not), but do doubt that the convention would reflect physics (i.e., that there is such a plane where J = 0 or even that such a plane is relevant where J <<< 1, even if the plane is thereby picked out) rather than useful coordinates.
I scanned the paper only briefly (I'm not really interested in black holes out of a cosmological or at least astrophysical context and am in no hurry to jump ahead of further EHT results) but found myself curious about the authors' "these solutions can be embedded in string theory" as their ref [17] at first glance seems to be about AdS, an acronym which is found only once in this paper.
What provokes my wondering is in particular, "and so an asymptotic observer will barely notice the difference between the parallax angles" (among other references to an asymptotic observer), drawing a comparison with a distant Schwarzschild observer, again around eqn (31). "Barely notice" is, at least qualitatively, interesting wording. Can an observer at infinity more than barely notice the difference between a cold noncompact spherically symmetric uncharged nonspinning central mass and a Schwarzschild BH?
From a layperson's perspective, "discovered" is doing a LOT of work in the linked article given it appears to be a hypothetical construct (topological soliton) within a hypothetical construct (string theory).
If it were phrased as "discovered a mathematical solution in string theory that would, if confirmed, represent a topological soliton" that would strike me as more accurate. But this is the reason I stated up front that I'm a layperson: I can certainly imagine that within the community there are conventional uses of language that differ from a layperson's use. That's certainly the case in my own. But the way it is phrased appears, to a layperson, to indicate that the thing has been found to exist.
From another layperson's perspective, it sounds like you are arguing it is "perfectly common" whereas the parent is arguing "it is unreasonable, even if it is common"
All my life, they've been hawking string theory; what feels like 40-odd years of breathless articles in New Scientist and on "Horizon". I don't really understand why it's still funded.
> “It’s hard to say really where you should draw the boundary around and say: This is string theory; this is not string theory,” said Douglas Stanford, a physicist at the IAS. “Nobody knows whether to say they’re a string theorist anymore,” said Chris Beem, a mathematical physicist at the University of Oxford. “It’s become very confusing.”
I knew some string people who easily transitioned into other fields (like condensed matter) because the work was similar. I don't personally see it as a huge waste of time, and it's like the least expensive thing to fund.
I find this funny as well. A lot of complaints about all the funding for string theory, but it seems like just funding mathematicians, which is dirt cheap compared to anything else.
Of course they don’t know whether they’re string theorists! Nobody knows whether theorists are made of strings or not! That’s the whole point of lacking experimental verification!
The basic thing here is that 1) we can guess from pretty basic physics that black holes have an entropy. 2) in order for a black hole to have an entropy it must have microscopic degrees of freedom. 3) String theory is one of the few ways we've ever come close to actually calculating from microscopic degrees of freedom the entropy we "know" black holes should have. I think most physicists, even string theorists (perhaps them more than others) understand that there are physical and philosophical problems with string theory, but I think most folks also think its the closest thing we have to a working theory and that it is probably a useful language in which to cast certain calculations in lieu of a more complete or rigorous theory.
I'd also like to point out that the actual total funding for string theory is extremely tiny compared to scientific research funding in general since it is a theoretical discipline with very few practitioners. If you want to attach inefficiencies in scientific funding, the LHC is a much better target. I'm a physicist and have an interest in theory, and even I think that we spend too much money on particle accelerators given what we stand to learn from them and the other pressing problems the human race has. I'd be delighted to see all that money re-allocated to large scale public works building solar panels and infrastructure or just giving it to poor people.
If we follow Pareto principle, then it doesn't make sense to optimize spendings that are close to zero if compared with something like military spendings.
One of the most fundamental scientific facts is that quantum theory (the most precisely tested theory in human history) and general relativity are incomplete. There must be a bridge. And we have no idea what that bridge is. It's been this way for over a century; the lifespan of string theory is not so long in comparison. Until we find a way to falsify it, we have to keep trying, don't we?
Opportunity costs. The real debate has been whether it makes sense for string theory (whatever the prevailing definition is) to dominate funding for theoretical research of the "bridge". There are alternatives besides strings for the bridge, and there should be even more, in theory...
Yep, or at least until we find something else that is explaining things better and testing better and looks like a better path forward. As much as I dislike ST because of the ambiguity/vagueness that means it's so hard to nail down as a single concrete theory, the alternatives so far still also have a lot of those same issues (e.g. too many parameters, effectively impossible to test, etc.) so there's no reason to drop ST just yet as useless or an invalid theory.
> Until we find a way to falsify it, we have to keep trying, don't we?
By that same token, we should keep looking for the fountain of eternal youth in El Dorado until it can be conclusively proven it doesn't exist.
A theory which is not falsifiable is not a scientific theory, at least in principle, and it is hard to tell why it should be entertained for quite so long.
Why do you assume there is a bridge? Or even if there is one, why do you assume that descriptions of that bridge in a mathematical language is at all possible?
We do know that mathematical frameworks cannot be at the same time totally complete and internally consistent. Would it be a stretch to assume descriptions of our physical reality could have the same restriction? General relativity and Quantum mechanics are relatively complete in describing our physical reality, however they are not consistent with each other. Perhaps if we ever find a description that is consistent, it won’t be complete. Perhaps grand unified theories are simply a mathematical impossibility.
Also, Sabine Hossenfelder was trained as a particle physicist and she doesn't like it either. She explains why it's like that and how it's bad and what they should be doing instead (like actively trying to reconcile the contradictory theories of gravity and quantum mechanics). She has changed career to professional youtuber https://en.wikipedia.org/wiki/Sabine_Hossenfelder
It's cheap. A physicist I work with says it was a cheap way to have clout in the 80's in a physics department. Fundamentally, paying for a couple of people to do math on paper all day is a lot cheaper than doing what they do at cern.
String theory is seductive as it is almost a natural progression to go from point-like particles to strings with different patterns of vibration. Also, it seems to have a natural handling of gravity and so promises the holy grail of unification. It's almost like a mathematical formula that's too beautiful to not be true (though there's plenty of examples of beautiful maths that fails).
What I find curious is the “observed” properties of the whirlwinds within each and every proton & neutron are so phenomenally complex, I would not be surprised at all if the mathematical abstractions of strings represent another quantum ecosystem we may never be able to observe
Article states that solitions are not black holes but only seem like black holes from a distance. Also they are hypothesized from string theory but haven’t ever been seen, probably because they’d appear the same as black holes except up close?
Title should be updated to something like: “A theorized defect in space time that appears to be a black hole”
It's a really thin article. It fails to say how "topological solitons" are different from wave-mechanical solitons, nor does it explain why they look like black holes, or why they lack an event horizon.
I'm routinely disappointed with phys.org. It's pop-sci with the "-sci" component reduced to a remnant.
For some reason it really irks me that they are using the word defect. It's like they forgot that the rules/model we set follow what happens in reality. If there is a defect, it's not in spacetime, it's in our understanding.
If your spacetime contains black holes you may be entitled to compensation from the manufacturer. Please retain this notice and your receipt. Known in the state of California to cause spaghettification. Offer not valid in worldlines crossing the event horizon.
Why? At a distance, gravity doesn't really care about density, only mass.
An infinitely dense object would shred anything it touches by its infinitely high tidal force, but there's only a limited amount of material it can touch within a given time and the Universe is not infinitely old.
Infinity and singularity are mathematical constructs. They look great on paper, but we don't know if they have actual physical analogs. It could be that relativity and the physics around black holes, the big bang, etc. are wrong.
> But we do have candidates, including string theory.
Oh no, you mean the theory that physicists say we see no evidence of at all? Great, if that is the basis, ... lets see what follows.
> In string theory all the particles of the universe are actually microscopic vibrating loops of string. In order to support the wide variety of particles and forces that we observe in the universe, these strings can't just vibrate in our three spatial dimensions. Instead, there have to be extra spatial dimensions that are curled up on themselves into manifolds so small that they escape everyday notice and experimentation.
Right, it would most definitely escape the experiments I have in my garage ... Who talks about "everyday experimentation" when talking about string theory? I mean, in "everyday experimentation" we don't even see atoms and most of us in their "everyday experimentation" do not even see molecules. Really makes you wonder what "everyday experimentation" they are going on about.
> That exotic structure in spacetime gave a team of researchers the tools they needed to identify a new class of object, something that they call a topological soliton. In their analysis they found that these topological solitons are stable defects in space-time itself. They require no matter or other forces to exist—they are as natural to the fabric of space-time as cracks in ice. The research is published in the journal Physical Review D.
But cracks in ice do consist of something: Usually air that fills the gaps. And even if we put ice in perfect vacuum somehow, there is still space between the parts of the ice. It is not like there is nothing. Seems like a bad analogy. At least they would have to go into what "fills" the gaps like with ice. Some space-time-vacuum?
On top of that, the article tries to explain things by using even more in my vocabulary undefined terms like "soliton".
> Because they are objects of extreme space-time [...]
Ah, they are "of extreme space-time"! Now I know ... nothing.
I don't feel like I understood anything valuable, but more like reading a sci-fi novel. Although, sometimes sci-fi novels do make more sense in their own invented universe than this article. Was this article perhaps generated by some language model?
Readit News
Its presumed lack of falsifiability has been one of its drawbacks and has been the source of some of the controversy around it.
Finding a potential test that could be conducted with telescopes instead of high energy particle accelerators would be a big moment in modern physics.
Not really. All this paper is really saying is that they have found solutions in classical theories of gravity with extra dimensions that, in four dimensions, can look like standard black holes. So even observing effects predicted by these models would not be evidence for string theory. It would at best be evidence for possible extra dimensions of spacetime at the classical level.
Also, the paper only compares its models with the standard Schwarzschild black hole. But first, most black holes are spinning so the comparison should be with Kerr, not Schwarzschild; and second, as the paper notes early on, there are many other proposed models of compact objects that can look similar to standard black holes. Any given set of observations would have to be tested against all proposed models, not just this one.
Can't we just pick as a reference the black hole, and say that the everything else is spinning, just as well?
Have any been detected that are not spinning?
Doubt and questioning are a part of science but this "religion" meme about string theory et al is silly. If you're really upset that somebody is pursuing something is a blind alley, go ahead and do some physics that shows results, otherwise I really wish people would tone the unhelpful criticisms down.
I don't think string theorists are being unreasonable by not having changed their minds yet, given that no evidence has come out one way or the other.
I don't think we can extrapolate from "string theorists didn't update when presented with no evidence" to "string theorists won't update when presented with evidence".
- Max Planck
This is a big if. For now they've just shown that once again something in the string theory landscape could look like something in real life.
It can make no predictions, it is not falsifiable, it meets none of the constraints that allow something to be science.
Speaking of nomenclature, this is not a good characterization of what philosophy is, if your intention is to reduce philosophy to what you seem to have in mind for “philosophical speculation”. Metaphysical theory thoroughly supported by argument (hylomorphic dualism, theory of act and potency) is actually stronger than mere empirical science. Empirically testable predictions do not transcend reasoned argument as observation is interpreted though the body of propositions of prior theory and enters into scientific argument as argument.
Given that the definition of a theory is an hypothesis that can be tested for falsehood, it isn't a theory by definition. It is a hypothesis.. but presumably "string hypothesis" doesn't sound as nice.
> We show that topological solitons are remarkably similar to black holes in apparent size and scattering properties, while being smooth and horizonless. Incoming photons experience very high redshift, inducing phenomenological horizonlike behaviors from the point of view of photon scattering. Thus, they provide a compelling case for real-world gravitational solitons and topological alternatives to black holes from string theory.
This is certainly interesting but so far they have only looked into Schwarzschild black holes (the simplest kind of black holes). Their case would be much more compelling if they also found soliton solutions that looked like non-static (Kerr) or even non-stationary/dynamic black hole solutions (<-> black hole formation). I know far too little about solitons, unfortunately, to estimate how easy/difficult it would be to find/construct those.
What plane is the authors' "equatorial plane"? Shortly after their eqn (31), "One should a priori do a similar computation out of the equatorial plane to obtain the total size of the solitons. Due to the complexity of the geodesic equations, this is only possible numerically. However, we will see in the next section that the outer photon shell is actually almost spherically symmetric and slightly flattened at its poles". (ETA: "... the Schwarzschild topological solution is not spherically symmetric ...", just before section A. Methodology).
Central SMBHs' spin appears to be largely far from parallel to their host galaxies' angular momentum[1]. Spin gives us an equatorial plane for the SMBH. Is there physical motivation for picking an equatorial plane if we found an SMBH with negligible J (and no jets)? I don't doubt that people would land on some convention (e.g. equatorial plane parallel to host galaxy's north if available, our galaxy's north if not), but do doubt that the convention would reflect physics (i.e., that there is such a plane where J = 0 or even that such a plane is relevant where J <<< 1, even if the plane is thereby picked out) rather than useful coordinates.
I scanned the paper only briefly (I'm not really interested in black holes out of a cosmological or at least astrophysical context and am in no hurry to jump ahead of further EHT results) but found myself curious about the authors' "these solutions can be embedded in string theory" as their ref [17] at first glance seems to be about AdS, an acronym which is found only once in this paper.
What provokes my wondering is in particular, "and so an asymptotic observer will barely notice the difference between the parallax angles" (among other references to an asymptotic observer), drawing a comparison with a distant Schwarzschild observer, again around eqn (31). "Barely notice" is, at least qualitatively, interesting wording. Can an observer at infinity more than barely notice the difference between a cold noncompact spherically symmetric uncharged nonspinning central mass and a Schwarzschild BH?
[1] This is especially true for Sgr A*, see EHT paper https://iopscience.iop.org/article/10.3847/2041-8213/ac6674 which is wildly "tilt"ed (to use authors' expression).
> “It’s hard to say really where you should draw the boundary around and say: This is string theory; this is not string theory,” said Douglas Stanford, a physicist at the IAS. “Nobody knows whether to say they’re a string theorist anymore,” said Chris Beem, a mathematical physicist at the University of Oxford. “It’s become very confusing.”
I knew some string people who easily transitioned into other fields (like condensed matter) because the work was similar. I don't personally see it as a huge waste of time, and it's like the least expensive thing to fund.
</humour>
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I'd also like to point out that the actual total funding for string theory is extremely tiny compared to scientific research funding in general since it is a theoretical discipline with very few practitioners. If you want to attach inefficiencies in scientific funding, the LHC is a much better target. I'm a physicist and have an interest in theory, and even I think that we spend too much money on particle accelerators given what we stand to learn from them and the other pressing problems the human race has. I'd be delighted to see all that money re-allocated to large scale public works building solar panels and infrastructure or just giving it to poor people.
https://en.wikipedia.org/wiki/Pareto_principle
Even if string theory is just pure math with no base in reality, it still can be useful (any math domain for that matter).
Almost all the surplus we have could be traced back to our discoveries in physics leading to machines.
People lived much much poorer lives without modern physics discoveries.
The expects return on physics is so great we should find ways to afford more long shot experiments not less.
One of the most fundamental scientific facts is that quantum theory (the most precisely tested theory in human history) and general relativity are incomplete. There must be a bridge. And we have no idea what that bridge is. It's been this way for over a century; the lifespan of string theory is not so long in comparison. Until we find a way to falsify it, we have to keep trying, don't we?
By that same token, we should keep looking for the fountain of eternal youth in El Dorado until it can be conclusively proven it doesn't exist.
A theory which is not falsifiable is not a scientific theory, at least in principle, and it is hard to tell why it should be entertained for quite so long.
We do know that mathematical frameworks cannot be at the same time totally complete and internally consistent. Would it be a stretch to assume descriptions of our physical reality could have the same restriction? General relativity and Quantum mechanics are relatively complete in describing our physical reality, however they are not consistent with each other. Perhaps if we ever find a description that is consistent, it won’t be complete. Perhaps grand unified theories are simply a mathematical impossibility.
I see what you did there.
Also, Sabine Hossenfelder was trained as a particle physicist and she doesn't like it either. She explains why it's like that and how it's bad and what they should be doing instead (like actively trying to reconcile the contradictory theories of gravity and quantum mechanics). She has changed career to professional youtuber https://en.wikipedia.org/wiki/Sabine_Hossenfelder
Isn't that exactly what string theory is trying to do?
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A lot of people have spent a lot of their time developing this theory
Title should be updated to something like: “A theorized defect in space time that appears to be a black hole”
I'm routinely disappointed with phys.org. It's pop-sci with the "-sci" component reduced to a remnant.
https://link.aps.org/doi/10.1103/PhysRevD.107.084042
https://en.wikipedia.org/wiki/Crystallographic_defect
An infinitely dense object would shred anything it touches by its infinitely high tidal force, but there's only a limited amount of material it can touch within a given time and the Universe is not infinitely old.
Also, density is mass divided by volume. You have two variables to play with.
But all of this detracts from the notion that infinity and singularity may have no physical analog. They're mathematical constructs.
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> But we do have candidates, including string theory.
Oh no, you mean the theory that physicists say we see no evidence of at all? Great, if that is the basis, ... lets see what follows.
> In string theory all the particles of the universe are actually microscopic vibrating loops of string. In order to support the wide variety of particles and forces that we observe in the universe, these strings can't just vibrate in our three spatial dimensions. Instead, there have to be extra spatial dimensions that are curled up on themselves into manifolds so small that they escape everyday notice and experimentation.
Right, it would most definitely escape the experiments I have in my garage ... Who talks about "everyday experimentation" when talking about string theory? I mean, in "everyday experimentation" we don't even see atoms and most of us in their "everyday experimentation" do not even see molecules. Really makes you wonder what "everyday experimentation" they are going on about.
> That exotic structure in spacetime gave a team of researchers the tools they needed to identify a new class of object, something that they call a topological soliton. In their analysis they found that these topological solitons are stable defects in space-time itself. They require no matter or other forces to exist—they are as natural to the fabric of space-time as cracks in ice. The research is published in the journal Physical Review D.
But cracks in ice do consist of something: Usually air that fills the gaps. And even if we put ice in perfect vacuum somehow, there is still space between the parts of the ice. It is not like there is nothing. Seems like a bad analogy. At least they would have to go into what "fills" the gaps like with ice. Some space-time-vacuum?
On top of that, the article tries to explain things by using even more in my vocabulary undefined terms like "soliton".
> Because they are objects of extreme space-time [...]
Ah, they are "of extreme space-time"! Now I know ... nothing.
I don't feel like I understood anything valuable, but more like reading a sci-fi novel. Although, sometimes sci-fi novels do make more sense in their own invented universe than this article. Was this article perhaps generated by some language model?
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