... og må erstattes med noe annet. Det sier i hvert fall [[Nima Arkani-Hamed]]. ### Notater fra foredraget [The End of Space-Time](https://www.youtube.com/watch?v=GL77oOnrPzY&t=81s), 12 023 Okei, så, hovedargumentet hans er at gitt tankeeksperimentet om hva som skjer hvis du prøver å probere Planck-skalaen—altså at svarte hull oppstår—så må spacetime være et emergent phenomenon, og vi aner ikke hva teorien som skal erstatte den skal se ut som (så i prosessen så anerkjenner han implisitt ikke [[Strengteori]] som et komplett rammeverk, dog han anerkjenner og bygger på oppdagelser av dem som [[AdS-CFT-korrespondansen]]), men at når enn tidligere et paradigmeskifte har funnet sted, så har de i retrospekt vært hintet til av små detaljer og merkelige egenskaper i det gamle paradigmet, som UV-krisen og den elektrovoltaiske effekten (er det det den heter?). Og én veldig konkret merkelig egenskap, som man kan velge å ta som et hint, er hvordan noen flere-hundre-sider-lange [[Kvantekromodynamikk]]-utregninger (altså sum av [[Feynmanndiagrammer]]) ender opp med å kollapse til ett enkelt ledd (etter å ha introdusert litt ny funky notasjon). > Clearly (...) there has to be some new physical and mathematical ideas involved. And the mathematical structures that are emerging are in very, sort of, interesting parts of mathematics that have not typically had any connection with physics, never mind connection with physics at such a basic level—areas like combinatorics, number theory, and various aspects of algebraic geometry. Interessant ... ganske nært mitt nåværende fagmiljø i algebragruppen på [[NTNU]] og som foreleser av [[Diskret matematikk]]. Indeed: > One of the sociologically interesting things about it is that far-flung physicists and mathematicians have been brought together in a fruitful and active collaboration. Han sier også: > My own point of view about what's going on is that the string theorists startet telling us 20 years ago (about), and are continuing to intensively study, the sort of fascinating fact that quantum mechanical systems can in some cases give us space *emergent* from the strong quantum mechanical interaction of particles. But my own suspicion is that further in the future, we need to instead be looking something like this (sic). You see there is here there is an asymmetry: quantum mechanics is sort of on top, as king, and space and gravity and so on emerge from it, whereas at least my own thought is that there is some more abstract set of ideas and that we'll see quantum mechanics and space*time*, not just emergent space but spacetime, emerge together, joined at the hip inexorably. ![[Pasted image 20240210163120.png]] Hovedidé: Kvitte oss med virtuelle partikler? Begynne med tree-diagram for tre gluoner, og limer den sammen til å få det vi trenger, bare at nå krever vi at alle linjene representerer ekte ("on-shell", a.k.a. ikke-virtuelle) partikler: ![[Pasted image 20240210165405.png]] > So, we can write the answer in this incredibly simple way, but the individual pieces do not look like they come from local spacetime physics, nor are they individually compatible with the principles of quantum mechanics. And yet there are (sic) some kind of world of ideas that spits out these basic building blocks, that doesn't care about spacetime in quantum mechanics, but somehow manifests the simplicity of the answer. And also, after you play around with this for a while, you understand that there's a huge array of different ways of expressing the answer in this form, and so you start to wonder, what sort of new world of ideas do these objects come from?