Sunday, June 01, 2014

Are the laws of nature beautiful?

Physicists like to talk about the beauty and elegance of theories, books have been written about the beautiful equations, and the internet, being the internet, offers a selection of various lists that are just a Google search away.

Max Tegmark famously believes all math is equally real, but most physicists are pickier. Garrett Lisi may be the most outspoken example who likes to say that the mathematics of reality has to be beautiful. Now Garrett’s idea of beautiful is a large root diagram which may not be everybody’s first choice, but symmetry is a common ingredient to beauty.

Physicists also like to speak about simplicity, but simplicity isn’t useful as an absolute criterion. The laws of nature would be much simpler if there was no matter or if symmetries were never broken or if the universe was two dimensional. But this just isn’t our reality. As Einstein said, things should be made as simple as possible but not any simpler, and that limits the use of simplicity as guiding principle. When simplicity reaches its limits, physicists call upon beauty.

Personally, I value interesting over beautiful. Symmetry and order is to art what harmony and repetition is to music – it’s bland in excess. But more importantly, there is no reason why the sense of beauty that humans have developed during evolution should have any relevance for the fundamental laws of nature. Using beauty as guide is even worse than appealing to naturalness. Naturalness, like beauty, is a requirement based on experience, not on logic, but at least naturalness can be quantified while beauty is subjective, and malleable in addition.

Frank Wilczek has an interesting transcript of a talk about “Quantum Beauty” online in which he writes
“The Standard Model is a very powerful, very compact framework. It would be difficult... to exaggerate.. its beauty.”
He then goes on to explain why this is an exaggeration. The Standard Model really isn’t all that beautiful as with all these generations and families of particles and let’s not even mention Yukawa couplings. Frank thinks a grand unification would be much more beautiful, especially when supersymmetric:
“If [SUSY’s new particles] exist, and are light enough to do the job, they will be produced and detected at [the] new Large Hadron Collider – a fantastic undertaking at the CERN laboratory, near Geneva, just now coming into operation. There will be a trial by fire. Will the particles SUSY requires reveal themselves? If not, we will have the satisfaction of knowing we have done our job, according to Popper, by producing a falsifiable theory and showing that it is false.”
Particle physicists who have wasted their time working out SUSY cross-sections don’t seem to be very “satisfied” with the LHC no-show. In fact they seem to be insulted because nature didn’t obey their beauty demands. In a recent cover story for Scientific American Joseph Lykken and Maria Spiropulu wrote:
“It is not an exaggeration to say that most of the world’s particle physicists believe that supersymmetry must be true.”
That is another exaggeration of course, a cognitive bias known as the “false-consensus effect”. People tend to think that others share their opinion, but let’s not dwell on the sociological issues this raises. Yes, symmetry and unification has historically been very successful and these are good reasons to try to use it as a guide. But is it sufficient reason for a scientist to believe that it must be true? Is this something a scientist should ever believe?

Somewhere along the line theoretical physicists have mistaken their success in describing the natural world for evidence that they must be able to recognize truth by beauty, that introspection suffices to reveal the laws of nature. It’s not like it’s only particle physicists. Lee Smolin likes to speak about the “ring of truth” that the theory of quantum gravity must have. He hasn’t yet heard that ring. String theorists on the other hand have heard that bell of truth ringing for some decades and, ach, aren’t these Calabi-Yaus oh-so beautiful and these theorems so elegant etc. pp. One ring to rule them all.

But relying on beauty as a guide leads nowhere because understanding changes our perception of beauty. Many people seem to be afraid of science because they believe understanding will diminish their perception of beauty, but in the end understanding most often contributes to beauty. However, there seems to be an uncanny valley of understanding: When you start learning, it first gets messy and confused and ugly, and only after some effort do you come to see the beauty. But spend enough time with something, anything really, and in most cases it will become interesting and eventually you almost always find beauty.

If you don’t know what I mean, watch this classic music critic going off on 12 tone music. [Video embedding didn't work, sorry for the ad.]

Chances are, if you listen to that sufficiently often you’ll stop hearing cacophony and also start thinking of it as “delicate” and “emancipating”. The student who goes on about the beauty of broken supersymmetry with all its 105 parameters and scatter plots went down that very same road.

There are limits to what humans can find beautiful, understanding or not. I have for example a phopia of certain patterns which, if you believe Google, is very common. Much of it is probably due to the appearance of some diseases, parasites, poisonous plants and so on, ie, it clearly has an evolutionary origin. So what if space-time foam looks like a skin disease and quantum gravity is ugly as gooseshit? Do we have any reason to believe that our brains should have developed so as to appreciate the beauty of something none of our ancestors could possibly ever have seen?

The laws of nature that you often find listed among the “most beautiful equations” derive much of their beauty not from structure but from meaning. The laws of black hole thermodynamics would be utterly unremarkable without the physical interpretation. In fact, equations in and by themselves are unremarkable generally – it is only the context, the definition of the quantities that are put in relation by the equation that make an equation valuable. X=Y isn’t just one equation. Unless I tell you what X and Y are, this is every equation.

So, are the laws of nature beautiful? You can bet that whatever law of nature wins a Nobel prize will be called “beautiful” by the next generation of physicists who spend their life studying it. Should we use “beauty” as a requirement to construct a scientific theory? That, I’m afraid, would be too simple to be true.

42 comments:

hush said...

By the way you have to trim your nails.
- Bob

(Bob doesn't like the extra sound effect of the nails clacking the keys. HOWEVER, Bob is torn between the beauty of Alice's long nails and simplicity being too good to clack.)

See previous blog.

Bee:
You are playing with fire.

Alessandro said...

This whole story reminds me to the view point of the ancient Greeks:

nature can only be understood by thinking and philosophy

But what they made of this, i.e. the earth is the center of the universe etc., might be beautiful but was simply wrong.

I have the feeling that this also happens somehow in "deep" theoretical physics which departs to much from "measurable" or "visible" phenomena.

Best
Alessandro

L. Edgar Otto said...

Lately I have thought about your earlier discussion on beauty and physics laws because of a deeper experience of a sense of beauty.

How poetic the chance naming of the the mundane top and bottom quarks as truth and beauty, yet if these come together that they are a beautiful mechanism yet colorful metaphors enhances each other and uplifts our sense of the beautiful.

We can love someone initially for their beauty, grow perhaps to cherish the imperfections that make one marked as unique.

My big snapping turtle, quite dangerous for a middle school boy, Myrtle... Shiny black, saw tooth moving lightning, beauty more so in the motion yet of shells in symmetric tiles beauty also, deep eyes like rays from craters on the moon yet full of stars, pimply skin and scars, some encounter. Some survival early on with the crow waiting by the nests. In our eyes, we explorers of the mudflats drawn to snails and puppy dog tails in the sunlight Myrtle was a dragon.

If truth is there in the machine and is there in the beauty then in the darkness of that unknown we cannot see or paint the dots in the sky with constellations and metaphors, see beauty as reflection there of ourselves and yet something beyond ourselves, or that in others, this is the issue on how we try to resolve quantum things, how we enhance,destroy, or entangle with each other.

In the real world opposed to the virtual vacuum each orbiting of stars in a system, each star unto itself, my lonely wandering planet lost in time and space may not connect with the others and yet this is a reaching out to them in a space of unseen beauty, beyond they beauty we outgrow that is decays to ugliness as we dream of new spring infatuations as they the children's lives and my brothers and sisters in solitude we are not alone.

Yet beauty is like drinking from the salty sea that does not abate our thirst, for those enamored of beauty alone- the interconnection of all made of dust and near dreams, we love struck cry out for but reject our fellows.

What strikes me as beautiful then is that time, perhaps the understanding of what gravity is as time itself, the arrow of entropy not a vague notion, the top and bottom of it up and down, cannot be symmetry alone nor asymmetry for both are there at the foundations of all machines and theory. Yet the truth of this in the simple details, a moving scale is part of the beauty that otherwise is the dance and death of our evolving dreams and justified wisdom to address the world. The logic of the day then to make sense and not the rumors of such logic alone of our equations.

We imagine some minimum structure a the limit or end of a skeleton of lines, or bloated chaos, the inner skeleton to prop the mollusk up or the exoskeleton, somewhere in between. We can try to measure say this difference between the neutron and the proton to find the beauty as symmetry but short of breaking the core apart the evidence may not find the unity of truth and beauty, either again. The time then only as beautiful as it holds the truth.

I find it beautiful also, the ongoing journey, the links to the past, and that others come close to future visions lately in the landscape of our science and dreams. Beyond that there may be more to the idea of truths and beauty. We have a world where it seems possible our universe is empty as well as everywhere full and that explains a lot where the wisdom of such questions meet, where we may escape full and empty worlds or renew the quest. But at least we understand why so many think what they do as our world seems wider, save perhaps that with such awakening how can any thinking thing squander their light?

Arun said...

The laws of nature are what they are. After discovering one of them, the retrospective debate on "is it beautiful" I think is best left to people with more time on their hands.

The real question, to me, is, when forming hypotheses for yet-to-be-discovered laws is whether beauty, symmetry, naturalness is a good guide.

hush said...

Geometrizations are the beauty of all physics.

http://www.simonsfoundation.org/quanta/20140527-physicists-prove-surprising-rule-of-threes/

http://www.simonsfoundation.org/quanta/20130917-a-jewel-at-the-heart-of-quantum-physics/

Oddly enough there was the greatest desire to abandon
Geometrization (the beauty)
for the sake of the purely
analytical (what Bee labels 'interesting'.)

Typical gender differences.
What appeals to the mind?
You decide.

Michael Fisher said...

Hi Bee

Are there any physics models [geometrical or equations] that strike you as particularly awkward or "wrong" looking, but which work?

Michael [layman non-mathematician & non-physicist science/maths enthusiast]

Zephir said...

The SUSY manifests itself with many artifacts, but these artifacts are much weaker, subtler and widespread, than the SUSY theorists are probably willing to expect.

The Nature values symmetry AS MUCH as symmetry breaking: this is her actual take of symmetry. SUSY framework is five-dimensional, so it does manifest itself just at the boundary of four-dimensional world, where it gets subsequently broken with another extradimensions.

Sabine Hossenfelder said...

Arun:

I agree with you. I tend to think that beauty has been overused in the recent decades. I say overused in the sense not that I think it is useless or it shouldn't been paid attention to but that its value has been inflated beyond the reasonable, resulting in much time wasted. Best,

B.

Sabine Hossenfelder said...

Hush:

My weapon of choice :p They don't clack on the keys, not at that length. But my piano teacher used to say the same thing. Best,

Alice

Sabine Hossenfelder said...

Michael,

Good question. I have to think about this.

Zephir said...

The current situation with SUSY is similar like with extradimensions or strings and another predictions of theoretical physics of the last forty years: the theorists predicted them rather insightfully. But because they don't understand the physics, only math, they cannot recognize their predictions in well known everyday phenomena. Instead of it, they're seeking for some exotic physics, which they indeed cannot find - so that the theorists forced to abandon their theories, despite they have many observational/experimental evidence for them already. Now they're just harvesting the fruits of their ignorance.

DaveS said...

Hi Sabine: ....in the eye of the beholder. Like quality, it's a fluid thing both with respect to time and the 'nature' or current stances of the both the sender and receiver of such information and evocative feelings that were amplified. So some would find beauty in your "Laws of Nature" video when one animal has made mincemeat of another.

Uncle Al said...

" the beauty of broken supersymmetry with all its 105 parameters"
http://www.youtube.com/watch?v=QVuU2YCwHjw
100 parameters. The second orbit is traced.

Mirror symmetry toward massless boson photons means no vacuum refraction, dispersion, dissipation, dichroism, or gyrotropy to 14+ significant figures. Assume this for massed fermion hadrons: parity violations, symmetry breakings, chiral anomalies, baryogenesis, Chern-Simons repair of Einstein-Hilbert action. Mirror-symmetric theories of matter are unendingly parameterized.

Spacetime curvature is racemic (re Ashtekar and Immirzi chirally resolving GR). Spacetime torsion is chiral (re GR superset Einstein-Cartan-Kibble-Sciama gravitation, Fernparallelismus, Weitzenböck spacetime with a metric). Quantum gravitation and SUSY must fail. Trace chiral vacuum torsion background cannot be true, so do no run geometric Eötvös experiments to find out.

http://mathforum.org/mathimages/imgUpload/Markus-Lyapunov_Play.png
http://good-wallpapers.com/pictures/2016/bigpreview_Fractals.jpg
Symmetry is not necessary for beauty - fractals.

Stuart said...

Bee
There is order in the apparent chaos of quantum foam.Latent beauty inwhich quantum gravity resides.

Tyler said...

Hi Sabine, I share many of these thoughts in a chapter of my PhD (of philosophy of science, not physics, though!), but then I argue for something I'd like to know if you would be sympathetic (or at least accept as a consistent possibility, which is the only thing I argue).

I argue that our current physics is not simple nor natural. I analyze the gauge symmetries of QFT, in the same vein as you point out not only the unnaturalness of parameters but also of equations (differentiable functions, etc.).
But my main goal is to reflect upon whether the *fundamental* laws of the *fundamental* level should verify some of these criteria.
One option is to expect in the future the traditional unified picture (of GUT's/ToE...). But I cite some arguments against good prospects of such an option.

Then, I defend that is plausible another option: a qualitatively different new physics in higher-energy scales (crucially, in the fundamental scale) is plausible, instead of something looking like our current physics. That is, instead of looking like a finite set of (unnatural, complex, "whimsical") laws. Specifically, I consider that a fundamental level not ruled by a (mysterious) finite set of fundamental laws, but exhibits a highly-complex dynamics (chaotic, or random).

What's your impression about that?
Does it make sense to consider such a scenario (which has some virtues, I think), given that current theories are EFT, and that there are many orders of magnitude up to the Planck scale?

Thanks!! :)

Neil Bates said...

There is much beauty, however
1. The big mysterious messes like how do wavefunctions hash out into definite outcomes, black hole problems, etc.
2. The asymmetry for example as manifested in fall of conservation of parity, and as actually *needed* for having matter left over and not a reduction of matter+antimatter to gamma rays etc.
3. The ugly things that don't really work out on their own, like the infinities that need renormalization.
4. Weird little wrinkles like "ghost particles" that play roles in theory but aren't really found or workable into other frameworks.

And to the extent there is beauty, what does that mean?

Robert L. Oldershaw said...

The Mandelbrot set is a thing of beauty and awe.

Rastus Odinga Odinga said...

In the real world, professional physicists almost never talk about beauty unless they are writing yet another corny pop-sci book or talk. [By the way, did you notice that Wilczek's slides could have been, and possibly were, prepared 25 years ago? I guess they are time-translation invariant, thus highly symmetrical, yet, strangely, that has not rendered them beautiful...].

Professionals are only impressed by "interestingness" and explanatory power. And, alas, especially nowadays, by whether an idea will help them to write another paper.....

Phillip Helbig said...

"The laws of nature would be much simpler if there was no matter or if symmetries were never broken or if the universe was two dimensional. But this just isn’t our reality. As Einstein said, things should be made as simple as possible but not any simpler, and that limits the use of simplicity as guiding principle."

John Barrow noted that if the universe were much simpler, then we would be too simple to perceive it. In other words, our own existence implies a certain minimal complexity (3 dimensions, for example, are necessary; for carbon-based life, a minimal age and hence size of the universe, and so on).

Uncle Al said...

Grant-funded physics only demands a marketable model: Gravitation (GR) and quantum mechanics are immiscible because they have different characteristic lengths,

http://www.simonsfoundation.org/multimedia/mathematical-impressions-multimedia/mathematical-impressions-spontaneous-stratification/

Binary mixed ball bearings remove differential anisotropy, shape, and density contributors. Then, trinary mixtures re amorphous metals. How does only chiral anisotropy pour and equilibrium mix?

http://mathartfun.com/shopsite_sc/store/html/WP15.jpg
http://en.wikipedia.org/wiki/Category:Chiral_polyhedra
http://www.georgehart.com/propello/propello.html
Beautiful!

Plato Hagel said...

Quasicrystals: Prof. Dan Shechtman

When looking toward foundations, you are looking for the pattern? Yes?



Plato Hagel said...

I like Garrett's model......while pleasing as a theoretical model it demonstrates a good grasp of the foundations as I see it, although definitions of different types of symmetry come into play.

Plato Hagel said...

See also: Symmetry

Uncle Al said...

If facets are noisome, ellipsoids with three different semi-axes (e.g., 1:2:3, triaxial) are chiral.

http://www.technologyuk.net/mathematics/geometry/ellipsoids.shtml

L. Edgar Otto said...

For a beautiful ToE for a larger picture it is at best half the theory, the numbers check in the 2007 diagram. But compactification models lack a certain higher beauty we have to impose on it. Still, we have to start somewhere. His funding was justified.
As with such esoteric topology the benefits come much later. Now a higher longing and discovering of beauty describes what, other than a vague being in love with love. How our hearts forget and how ugly that we can remove replace or implant memory - some so called chemistry of nerves - but this cannot be the case for the physics of mind. Nor can we hold as truth before the fact that our further explorations discover it in the main is ultimately teeming ugliness or we make and choose it so. A little bit of theory is a dangerous thing.

Eric said...

What to some may be beautiful does not even register to others and is just meaningless. People differ in their ability to recognize beauty and that is just a fact. Why should it be any different among physicists or mathematicians?

Also a fact, people with poor aesthetic taste in any subject never know they have poor aesthetic taste. That is the heart of the problem.

An example, many of the greatest quantum physicists of the 1920's and 30's, including Schroedinger and Dirac, thought that renormalization was a trick that while it worked to compute correct results was not the whole picture. It was hiding something. They never got the answer of what it might be hiding but they recognized it as being ugly.

Of course they were and are correct. The proof is that the heart of renormalization, addition of plus and minus infinity equaling zero, is not the correct picture of the universe. Everyone, including many famous physicists still today won't accept that despite the fact that it is known that early inflation, (not eternal inflation) and very low acceleration now implies a unitary finite universe in which potential and kinetic energy together equal 1.

In other words, all those early physicists, including Einstein, were right in seeing renormalization as ugly despite the fact that the underlying reason for its necessity is still not understood. And all the scientists that did not see the ugliness there went on to invent supersymmetry and string theory. That is a dead-end because is based on a zero ( plus and minus infinity) background dependence.

Eric said...

Oh, and one more thing: People like Lubos always makes excuses about the small cosmological constant that exists today. He'll see things like "Well, nobody understands it" or "It might be the result of a measurement problem?"

No, it's not. What we still don't understand is renormalization and why it works. If he and others had been able to see the ugliness in renormalization he would never have been so enamored of string theory and supersymmetry.

qsa said...

Like everything else in life things are never black or white. Any TOE theory will have many attributes, say like a person who can have a beautiful body but a face like it was run over by a truck(A schwarzenegger comes to mind!). A theory represented with math could be like that.It maybe conceptually simple but the equation/s ugly. Or like GR the basic equation looks beautiful but expanding it will look like a horror movie and so on. Sometimes the basic equations look so simple but to have a more comprehensive theory it starts to loose that original beauty, you know, like marrying that beautiful and insane (later to be found) person.

L. Edgar Otto said...

Eric, great comments.
Uncle Al, The issue of chirality and variation as an ellipsoid needs a rather simple principle.

Now, the two dimensional world, really the scaling of parameters that amount to the Pythagorean theorem is simplicity but is enough to show Barrow's comment not quite enough to say we could not exist on that level so to understand things.

In three space, all parameters being considered and integer equality somewhere (or fractional) the mere mirror negation will not cover all the parameters in three space. I am saying something quite simple here... we cannot subdivide three space without something left over (namely 56) whereas in two space we can so divide (Fermat's last theorem) but eventually it all balances out in the concepts.
Lisi's diagram should be seen like a layer of such diagrams with these mirror ghostly entities or holes. Conceptually, this generational problem is not about a simple elegant proof of Fermat's theorem as we do not have one.
So can our models detect such an asymmetry of resolved positive or negative objects as chiral- which does point to its role in general new physics but not if just two space. It certainly seems beautiful on a higher level which in the end is simpler than a vague idea of renormalization, a arithmetic of sorts, a quantum one. But such numerology does not have to be an ugly picture and let us face it some processes are dependent on these defects of ugliness on the way to further truths. This is perhaps why we cannot just separate left and right politically decisively economically. Why perhaps so much is mysterious in the work of Ramanujan and where numbers are understood beyond the complexity of proofs and practical applications...of course the mirror of hyperbolic is elliptic but linear and exponential is just a notation that in itself is not enough to cover the scope of the problem.
When Fermat framed his laws in the margin mentioning cubes he was not talking algebra but spatial dimensions, and Einstein said the simplest law would probably be algebraic... is it as least simple as intuitionist arithmetic.

Rastus Odinga Odinga said...

Thinking it over, while I stand by my statement that serious physicists almost never talk about beauty, I realise that they quite often talk about *ugly* theories. But even in that case, what they really mean is "contrived" or "implausible". Take a look at the Lagrangian for the Galileon theories which, for some inexplicable reason, have attracted a lot of attention lately --- well, not really a lot, but a lot more than they deserve. It is very ugly indeed, but the point is that no sane person could believe that nature could possibly be described by something so obviously cooked up by people desperate for a paper.

So it might be better to ask: do physicists need to be trained to avoid obviously artificial constructs?

L. Edgar Otto said...

Footnote:
I just read the comments from Aug. 2007 Garret Lisi's inspirational interview. Also downloaded the full projection of the symmetry symbol.

It is quiet a story from my view of the synchronicity involved. The changing themes raise current issues hauntingly but with finer thoughts. There is a sort of tragic beauty almost seen here - I mean all you dramatis personae in the play may one day see this on many levels.

Sure, Planck stuck in peer review but with the glorious time to explore at his own pace- His advisers did not regard entropy as a proper study of physics- then, quantum theory that changed everything.

I went to radio shack today to add to my few tools for fine electronic work, I noticed Sheldon and Leonard 8Gig flash drive icons were sold out on the shelf so I asked the nice lady about it. She said they had moved them to fill up another area across the store then moved a few back.

Well, Lubos was in the Lisi inspiration blog and I rather sympathize with him, that is I understand the desire to challenge anyone who would upset his world view- to kick string theory in the ass. My own work (it feels more like serious work today as the problem Lisi said he needed to solve is one I feel well solved lately, but it took me long enough) and it came long before anyone mentioned string theory or the like. My view is not simply the ideas of Coxeter - that is beautiful but in a sense far from applications to physics- Lubos in some of his posts is just a rehash of Coxeters ideas and not beyond.
So, well there is the tetraquark now to consider and a higher reading of the gene code by fours, when I encountered ideas like compactification from early last century and then Calabi-Yau formulism I, long before Lisi had the desire to kick string theories ass. Been there, done that, did not stoop to calling names but it took awhile to find my private quasic world again. I should have listened more to my intuitions. I did first use crackpot a the announcement of biceps that it supported inflation theory. Sorry.

Creationism is not a threat or boogy man some make it out to be but a philosophy question... as Bee said "time is an illusion..." or "if information is not destroyed there is no death" and "certainly not one in the remote distance." Add that to the dramatic change of her facebook whatever it is about in something close and dark starkly absolute.
We near gods want to extend life it seems, but not all of us.
Tragic beauty can teach us a lot but what a shabby design for our universe.
I am sure in the general indifference we weep... time to develop things, protected, pretended is does not run out and so on... this transcends our modest simplicity and complexity and surely that means something more.
Awaken, my children of Earth, and may you have a fine gathering of dreams and they be new.

L. Edgar Otto said...

Cosmic Heartbeats L. Edgar Otto 06.03.14

(Part 8 - New Dawns in the Philosophy of Cosmology)

The star birth lingers after the closing of the light
the prairie as far as we can see, a field of violets
What spark may restart the cosmic heartbeat
what wall of silence gives up, marks the minute
Healing hands falling feels the rising spirit
so weigh its subtle vapors, evaporating
Beyond the walls of time, virtual singularities?
but only the anointed prophet sees beyond stars
By which our mortal coils collapse, melt away.

The smallest dreams that consume us from within
timeless in time's travel reach most far
Beneath the light yet constant in their pulsing
without effort, surf the mythic walls, dusty clouds
Images direct on cotton shrouds, arrhythmia's self correcting
bonds squared.

* * * S

Do not mock each other, children of the Earth,
tempt the holy men who point the way yet not enter therein
The greater fear not we lead astray but leave new stars behind
new constellations imprinted take with them a part of you
Our universe made of ghosts more than minds, four chambered.

* * * * H

DocG said...

I don't know if the laws of nature are beautiful. But some of things scientists have said strike me as pure poetry. At the top of my list is this little number by Neils Bohr:

“There is no quantum world.

There is only an abstract physical description.

It is wrong to think that the task of physics is to find out how nature is.

Physics concerns what we can say about nature...”

Sabine Hossenfelder said...

Tyler,

I am certainly sympathetic to the idea that the fundamental laws may be simple but give rise to complex behavior masking their simplicity. I mean, just look at the Yukawa couplings - I find it hard to imagine they all be explained by the same unified theory without appealing to an anthropic explanation unless you accept some process that can give rise to effects on largely separated scales, which complex systems can do. I am guessing that many people must have toyed with the idea, but I am not aware of any working model. The problem is that, despite decades of talk, complexity is still not very well understood. Best,

B.

Sabine Hossenfelder said...

Rastus,

"In the real world, professional physicists almost never talk about beauty..."

They may not talk about beauty all that often, but they certainly talk about ugliness and use it to discard certain theories/models. That amounts to pretty much the same. Best,

B.

Sabine Hossenfelder said...

Michael,

After some thought I think a good example is the TeVeS/dark matter combo. If you twiddle and tweak it enough you can make it to fit the data (or so is my understanding of the current status), but it's ugly as shit. And being ugly is the main reason physicists don't pay much attention to it. One can't even say it's not simple. Broken SUSY isn't simple either, to just pick one example, if you have a BSM extension with loads of CPT/Lorentz-violating terms, that isn't simple either, but I think most physicists would still prefer it. Best,

B.

Sabine Hossenfelder said...

Phillip,

Yeah, sure, that's why I am saying simplicity is limited in explanatory power. I don't think one has to call specifically upon anthropic reasoning here, it suffices to say that one has to use some kind of observational input (eg stabilty of atoms). Also, as we have discussed in previous posts, there are many observational inputs that physicists don't even list as inputs, such as eg separability or locality. Best,

B.

Sabine Hossenfelder said...

Rastus,
Sorry, I only read your second comment now.

Giotis said...

Beautiful in theoretical physics is what has explanatory power.

As for Frank Wilczek, what he says is completely rubbish. SUSY is not a theory; it is a symmetry that people believe should be realized by Nature (at some energy scale) for deep theoretical reasons. As such it cannot be falsified by LHC.

What can be falsified by LHC are certain BSM *models* that take technical naturalness as a guiding strategy to hypothesize about SUSY’s breaking mechanism and scale.

MarkusM said...

Yep, nature istruly beautiful,
unfortunately not everybody can see it.
Best

DocG said...

I think my theory is beautiful, though it is almost certainly, so I've been told, wrong. Does a wrong theory count?

http://www.fqxi.org/data/forum-attachments/Is_the_Universe_Expanding_Into_a_Black_Hole.pdf

Roy Carvalho said...

Regarding Planck Stars by Rovelli:
Not very good. However, at least an attempt to banish the singularity. I want people to consider that there should be neutrino stars. Neutrinos are fermions and have spin 1/2 and should not be compressable. (If they are massless, they can not be overaccelerated, which is what causes accreting white dwarfs and neutron stars to fail.) So black holes should be composed of degenerate neutrinos. Neutrinos are so simple, this is a way of saying black holes are pure, compressed spacetime - but not a singularity.