A conversation between Andy Strominger and Stephen Wolfram at the Wolfram Summer School 2021

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[JAYMOAP]

Wolfram, if you want to see how this strings look like and how you get wave function, density and energy levels, can send you some i did in blender. The good thing is when you work woth certain fibres, you essentially work with background/ spaces, and certain transformations correspond to curvature. So you simultaneously work with quantum mechanics and curved spacetime in a sense. You can scale these system, you get condensed matter physics on lattice with majorana fermions, dirac cones and insulators/superconductors. Genus expansion is an important element as well

[frun]

The conversations are not only interesting but often fun.

[berniethejet]

Very interesting interview, interesting format. To see incredible scientists interviewing one another.

[JAYMOAP]

What is really interesting is that you get inertia effects out this, and chaos, also certain correspondence related to spin frustration or spin squeezing. When you get such correspondence, you can understand the way, such as the outcomes of certain states arise from this spin frustration or squeeze related to quantum processors and how certain discrete properties fall out as consequence of competing spins

[paxdriver]

I don't think a string's spin is literally supposed to reflect spin, since strings are quantized in more than 4 dimensional space it's specifically referencing perpendicular angular momentum to which ever perspective it's being visualized from. Like time and distance aren't literally lines on a 2d graph, the 2d graph is a 2d representation of 4d space-time, it's only valuable as a reference to relative values not the literal physical direction and time extrapolated onto a sheet of paper. Spin is a representation of relative energetic expression in lower dimensional space, it's not literally spinning in space though.

Or I guess then maybe I've been seeing it wrong all this time lol

[JAYMOAP]

Great conversation, you should bring on Juan Maldacena, he would give you latest update, also Douglas stanford, xiao gang wen, would be interesting as well

[Achrononmaster]

@5:07 the reason QFT "works" is because it is only (one might say "merely") a technical tool for computing amplitudes for multiparticle processes. That is also why you can do QTF in different ways: path integral, or creation/annihilation operators, these days Amplituhedron methods too. It is not really a causal theory. GR is causal, so does not "go" into QFT. However, if you ask me, one "solution path" to all this is to recognize GR is not necessarily causal either, e.g., if you admit non-trivial spacetime topology, because then you get wormholes, CTC's and hence causality violation (at least on the Planck scale where such structure will exist). You can then easily see how quantum mechanics is already contained within GR, you just have to extend GR to non-trivial spacetime topologies. You get entanglement and nonlocality directly from wormhole traversals, and particle phenomenology from all the "stringy-like" dynamics with nontrivial spacetimes --- which is already party understood by the folks working on the octonion and Clifford algebra models for the gauge groups (it's spacetime _algebra_ really, not just group theory, treating phenomenology as just group theory (fibre bundles) is too weak).

[dpshtcty]

I'd love to See Stephen Wolfram talk to Ben Goertzel.

[kostoglotov]

I have always thought CDT ( Renate LOll ) could be incorporated into a computational explanation.

[Achrononmaster]

@1:33:00 Strominger is correct. Your Branchial ST slicing (quantum/classical) is a duality, if anything, not holography. Holographies or gauge/gravity dualities, are when your field theory _lives_ on the boundary, so it is _not_ a slicing in the way Wolfram's people imagine. It is not a dual description, because the bulk spacetime does not "go away", if it did there'd be no boundary and thus no CFT. When 't Hooft and others talk holography they almost literally mean "like a hologram." In a real solid state laser hologram the bulk must be present for the surface hologram to exist. That's just an analogy, but it applies well to gauge/gravity duality.
When you have a quantum/classical duality (one classical theory becomes quantum when a parameter is varied, the simplest example being Planck's constant for certain well-behaved Lagrangians) it is does not mean you have holography necessarily. Slicing Branchial spacetime is a lot more like choosing Planck's constant differently than it is like looking at a boundary asymptotics. Although with a graph theoretic approach these analogies are not precise, so in some ways it makes no sense to even compare G/G holography to anything involving branchial space models. Same goes for the causal set/causal triangulation toy models. They have to build a spacetime first (which they cannot do so far with correct phenomenology, successfully), and only _then_ they can explore holography.

[JAYMOAP]

The massless excitations in a sense has mass as inertia effect, so its a confined deformation/degeneracy of the string but not conserved. So the system has a potential without conservation. Its like a second mass term, coupled to the original function. It emerges from the degeneracy. Hence this, you see it as a ghost/ or imaginary mass but its impact your system and how it evolves because its coupled to it.

[username-izel]

Ok I pick Andrew as my spirit animal whatever that is I've heard people say it so I want andrew as mine. Dude is awesome!!!

[Achrononmaster]

@1:26:00 "Why it works?" (holography.) It's because of asymptotics. The CFT is valid on the _boundary_ of the spacetime, but you also need the spacetime to be fictional (so far at least, has to be anti-de Sitter, which ain't our universe). So although gauge/gravity duality is a nice tool for studying toy models, it is not a mature picture of our universe yet, assuming we live in a flat or de Sitter spacetime as must astronomical measurements suggest.

[Anders]

Interesting history of string theories. I hope that the Wolfram Physics Project will be able to unify QM and GR. Really challenging problem it seems.

[mz-dzyn]

the universe is holographic in the dimension of time, through out time, in that, in stephen's concept of "space" in a new kind of physics and QM atomic matter are conserved across time from some early point after the big bang until now. For example one descriptive model of a hologram i came up with 35 years ago to describe a hologram to a layman is that if u drop a pebble into a bit of water and then instantly freeze it (u have the rings and the wave patterns) and then completely instantly unfreeze it, that is like a holographic photograph. similarly the the universe is holographic in the dimension of time, through out time, in that, the structure of atoms is the same over vast time spans, I have to think about this in regards to gravity, based on stephens new concepts of gravity in A new kind of physics.

[nolan]

A chart of composite particle masses didn't make Wikipedia...last I saw.

[Achrononmaster]

@28:00 omg! Strominger doing his best, but he sounds drunk[^]. Spin (of the QM variety) is _not_ angular momentum. Never confuse two manifestations of the same algebras as describing the same physics. Quantum spin is a symmetry property, not a literal dynamical spinning. The fact a particle with a certain symmetry can exist in many states under rotation is why the angular momentum (or orbital spinning) algebra appears. In QM you have to sum over all states, so have to imagine the thing is spinning when it need not be --- I mean it probably is spinning [who would really know?], but that's not what gives it the symmetry, the symmetry is more fundamental and exists even if the graviton/fermion is not literally spinning around.
This is all much clearer if you ditch the old fashioned clunky matrix algebra and use the geometric (Clifford) algebra formalism. Spinors then become very natural: they tell you the spinor (bivector plus scalar or "rotor") part of the wavefunction is an instruction to rotate your laboratory frame onto the rest frame of the particle (or "geon" or string"). That is a fundamental aspect of QM: measurement! It's all about measurement. Why spin symmetry is so important is due to this measurement requirement, and the way QM is set up as a measurement theory (eigenvalue problems). For a spacetime particle, there are few symmetries available without exploring exotic extra dimensions, basically the Poincaré algebra, and that's why spinors play the fundamental role (or for bosons "vector" algebra rather than spinor). Spinors are just the Lorentz rotations but in spacetime Clifford algebra form rather than matrix form. If you know any relativity, that should fully explain what I mean by the spin being an instruction to rotate your lab frame onto the particle's frame.
Actual orbital angular momenta obey the same algebra, but only because the symmetry operation involved is the same: a rotation. Anyone how knows Emmy Noether _should_ know this. Most physicists do not understand this bizarrely, so they call the spinor (or vector boson spin/polarization) a kind of "intrinsic angular momentum, " and that's just really bad understanding being manifested, a sort of misguided mysticism from reading too many textbooks and not exploring things for yourself.

[^] I know he always does, I'm just joking. He's brilliant.

[roelrovira]

Andy and Stephen, to realize the unification of Quantum Mechanics with Gravity paving the way to the Theory of Everything in Physics, the last and final puzzle conundrum of Quantum Gravity has to be solved first. The scientific community and you knew that String Theory is not yet a scientific theory. And General Relativity's Curvature of Spacetime Gravity is hugely incomplete, highly flawed and therefore wrong- the reason why it did not win a Nobel Prize for Einstein. Instead, he won a Nobel Prize for Physics for his work in Quantum Mechanics' Photoelectric Effect.

Quantum Gravity is real. We now have a working Quantum Theory of Gravity that is testable and complete with reproducible empirical experiments with the same results if repeated over and over again and again, confirmed by empirical observations in nature with 7-Sigma level results, guided by empirical laws and physical/mathematical Trinity God Equations that are predictive, precise and does no collapse even in high energies of Big Bang and singularity of Black Hole. FYI: Quantum Gravity or Quantum Gravitation have three types that are equivalent to and manifested by Quantum Computational Gravitation- the biggest and most powerful Computer Software Program and Hardware in the Universe and Quantum Gravitational Entanglement - a Quantum Entanglement in Macroscopic Cosmic Scale namely: 1. Quantum Anti-Gravity = Spin Up Quantum Entanglement State; 2. Quantum Neutral Gravity = Superposition Quantum Entanglement State; and 3. Quantum Gravity = Spin Down Quantum Entanglement State. More detailed information could be found on the published papers 2 years ago in London, Paris, and Zurich, online and at the two scientific Journals ACADEMIA and REAL TRUE NATURE. Alternatively, you can google the name of the author ROEL REAL ROVIRA to arrive at the published paper on Quantum Gravity. Most recently, additional two well respected scientific journals namely NATURE and the AMERICAN PHYSICAL SOCIETY APS Physical Review Journals have officially invited this author to submit manuscripts on his Research on Quantum Gravity for publication for PRX QUANTUM in preparation for a celebration for International Year of Quantum IYQ 2025 to showcase the best papers of the year.

[Achrononmaster]

@1:00:00 The relationship mentoned here is suss. It's incestuous! Gravitons "carry" gravity, but the "background" spacetime is already a theory of gravity. So while not an anomaly, this is a terrible redundancy hiding in plain sight in string theories. You do not need a graviton if you already have gravity. Just my 2 cents, but I think it far more likely there are no stringy gravitons so-to-speak, just gravity waves from conventional GR, which of course have quantum properties arsing from entanglement/nonlocality etc (which can be described in GR with wormhole topologies). If that is so (not sayin' it is, or maybe I am!) then we have to completely rethink the lessons from string theory and maybe discard it mostly, including extra dimensions, and instead rewrite it all as a theory of spacetime with non-trivial topology. That's my bet, or at least my story, I'm sticking to it (till proven otherwise).

[Achrononmaster]

@1:48:00 this last segment is good dialectic, but terribly confused and naïve by Stephen. Statistical mechanics and relativity are _not_ theories of observers. They only say "IF there was an observer THEN...[coarse graining, boosts, etc]" so they are _entirely_ observer independent. Lesson: never confuse _your_ view of the world being different to someone elses with nonexistence of a global description and universal invariants.

If you inject strict observer dependence into relativity or statistical mechanics you destroy the theories, it's a needless redundancy, a type of corrupt postmodernism nonsense. There is no evidence anywhere of privileged observer status, not in QM not in gravity. Observer relativity is ready built-in to such theories. What do you guys not understand about "frame of reference" and the _Six Blind Men and the Elephant_ parable? It's the _same_ g'damn elephant people!

For philosophy nerds: the string landscape is _not_ licence for postmodernism. We either live in one type of vacuum or another, not all of them at once depending on your identity! Possibly we live in a dynamic string vacua (the underlying CY manifolds chance at each point in 4-space dynamically, but that's still not observer dependent. The observer "sees" a different universe to others, but the universe is not any different, it's just dynamic, so observer decisions effect reality, but by probabilistic lawful causal action, not by metaphysics. There is to date no evidence to the contrary, so the burden of proof the universe depends on observers is on those who believe so, not on people like myself.

This is entirely different to the causal effect of the observer. Of course we alter the universe, all the time, but in doing so we are not changing the fundamental laws, we are changing states (in classical parlance, we change the boundary/IV conditions locally).

In the context of Einstein gravity the "conscious" observer gets to change microstates in the past & future _if_ the hypothetical spacetime foam contains closed timelike curves (which at the Planck scale is almost inevitable, though to date also unproven). But this is _not_ observer-dependence of the laws, it is observer dependence of boundary conditions on compact Cauchy regions. There is a big difference!

My plea (in the politics/sociology of science): do not give-in to postmodernism if at all possible, it's intellectually corrupt and a cause of incredible social harm, so don't let it leak into physics. Do better instead! If (in political economy) you throw your hands up and say, "oh, it is all culturally relative, anything goes, " then you are essentially unscientific (which, as per Feyerabend, can sometimes be good [the dirt antagonises the oyster to produce the pearl], but can also be bad [the dirt irritates, infects and kills you]). I'd say similar for physics sociology, resist, "oh it's all relative, " talk, unless it is warranted (artistic appreciation, choice of LaTeX font, formal theorem-proof style or more discursive pedagogy). General relativity and SR are, recall, giant misnomers, they are the opposite of "relativity": they are saying the laws of physics are invariants, and why we perceive motion and force to be relative is a reference frame bias, which once corrected allows us to agree with a relative observer on the invariant laws. Einstein said as much and regretted using the description "relativity". QM is no exception, it is a formal system for getting measurement invariants, *_so that_*_ all observers can agree!_