Remembering Joe Polchinski the modest physicist who conceived a multiverse
Creativity and modesty are two of the qualities that made Joe Polchinski an extraordinary theoretical physicist. The early pioneer of string theory died this month at age 63.
Polchinski was an early pioneer of string theory, the mathematical apparatus picturing the basic particles of matter and force as supertiny wriggling strands of energy known as superstrings. His contributions to the field were immense. As a young professor at the University of Texas at Austin in the 1980s, he developed a branch of superstring theory involving objects called supermembranes.
Superstrings are one-dimensional objects (like lines, hence “strings”) vibrating like rubber bands in multidimensional space. (String math presupposed more dimensions than the usual three.) Polchinski explored the possibility that those multiple dimensions could contain two-dimensional membranes, kind of like the film forming the surface of a soap bubble. He and his students derived the math describing such supermembranes living in 11 dimensions (10 of space, one of time).
Maybe, string/brane/M theory would explain the amount of that mysterious “dark” energy in space and all would be well. But no. Working with physicist Raphael Bousso, Polchinski found that string theory did not specify how much energy the vacuum of space contained. Instead the theory predicted a virtually countless number of vacuum states, with nearly any amount of repulsive energy you could imagine. In other words, string theory described a multiverse.
Polchinski’s modesty manifested itself in his reaction to this situation. He hated the idea of a multiverse, because it implied that some questions had no answers that physicists could calculate. No equation could specify the amount of dark energy; it would just be luck — determined by which universe had the right amount of dark energy to make it hospitable to life (an idea known as the anthropic principle).
Interesting Article:
https://www.sciencenews.org/blog/context/remembering-joe-polchinski-modest-physicist-who-conceived-multiverse
#physics #JoePolchinski #stringtheory
Creativity and modesty are two of the qualities that made Joe Polchinski an extraordinary theoretical physicist. The early pioneer of string theory died this month at age 63.
Polchinski was an early pioneer of string theory, the mathematical apparatus picturing the basic particles of matter and force as supertiny wriggling strands of energy known as superstrings. His contributions to the field were immense. As a young professor at the University of Texas at Austin in the 1980s, he developed a branch of superstring theory involving objects called supermembranes.
Superstrings are one-dimensional objects (like lines, hence “strings”) vibrating like rubber bands in multidimensional space. (String math presupposed more dimensions than the usual three.) Polchinski explored the possibility that those multiple dimensions could contain two-dimensional membranes, kind of like the film forming the surface of a soap bubble. He and his students derived the math describing such supermembranes living in 11 dimensions (10 of space, one of time).
Maybe, string/brane/M theory would explain the amount of that mysterious “dark” energy in space and all would be well. But no. Working with physicist Raphael Bousso, Polchinski found that string theory did not specify how much energy the vacuum of space contained. Instead the theory predicted a virtually countless number of vacuum states, with nearly any amount of repulsive energy you could imagine. In other words, string theory described a multiverse.
Polchinski’s modesty manifested itself in his reaction to this situation. He hated the idea of a multiverse, because it implied that some questions had no answers that physicists could calculate. No equation could specify the amount of dark energy; it would just be luck — determined by which universe had the right amount of dark energy to make it hospitable to life (an idea known as the anthropic principle).
Interesting Article:
https://www.sciencenews.org/blog/context/remembering-joe-polchinski-modest-physicist-who-conceived-multiverse
#physics #JoePolchinski #stringtheory
Does one day for unknown people exist? Because many unknown people have got great ideas.27w
Not sure what "unknown people" means in this context. If you're referring to amazing people forgot by history then perhaps they deserve more than one day to be remembered. If you're referring to regular people with a spark...well perhaps they need more courage and determination.27w
"Je pense comme je pense, donc je suis qui je suis. Nous pensons comme nous pensons, donc nous suivons qui nous suivons."
Rumination (les idées doivent être ruminées lorsque l'occasion se présente): ...The anthropic principle is to the mutiverse what the ecological niche is to the biosphere. It's physics borrowing the idea of natural selection from biology, to solve some problem of its own while reversing the usual client-server relationship of these two sciences.
Both concepts express that the presence of a living or intelligent being imply it embedded in a "local" environment that's on the whole biased in favor of the given's being existence and habits. Both concepts provide justification for the prediction of an appearance of divine providence. They are complementary... they are related intuitions... it's tempting to say they are the same thing at different scales... provided is recognized that the smaller scale of the ecological niche allows it to come in many parallel instances forming a huge swarm with secular dynamics and extensive history that an "outside-in" approach disentangles, while the AP is the largest-scale "inside-out" instance that both freezes all secular dynamics and nullifies all observable diversity from widest horizon to widest horizon.27w- I disagree with the use of the anthropic principle in connection with a multiverse or string theory. From my point of view that's illogical and a non-scientific statement.
The anthropic principle simply says that we, observers, exist. And that we exist in this Universe, and therefore the Universe exists in a way that it allows observers to come into existence.
The evidence for our existence means the Universe allows our existence, but it doesn't mean the Universe must have unfolded exactly this way. It doesn't mean our existence is mandatory. And it doesn't mean the Universe must have given rise to us exactly as we are.
However, I do like Descartes ;)27w - +Corina Marinescu Yeah, the anthropic principle borrows from Darwin++ an intuition but projects it beyond cosmological horizons in an obviously deficient non-obvious way...
The "pillar" deficiency imo is what they call "the measure problem". Although the "measure problem" allows interpretation as name for the absence, (in the reality-counterpart of this cosmological castle of the mind) -- for the absence of what implements ecological niches in the actual terrestrial biosphere, that's not quite the terms in which it's stated
-- the latter terms are more abstract, and spell the lack of criteria to attribute a probability distribution over a space of possibles -- the multiverse -- that "polchinski theory" concludes to precede the big bang.
Now my hunch has long been that since the origin of origins string theories are secret brethrens of population genetics. Just take the equation string=minimal abstraction of life history seriously.
The seed of this hunch. I once engaged "string theory" with shamanic procedure in the late eighties, over a couple days. This consisted in fetching all books and articles on string theories in the physics school library, and forcing myself to glance at all their pages.
After two days of this exercise that surprised me by the extend of its immediate fruitlessness, I turned to the second part of what I had initially planned to do: formulate a summarizing, poetic aphorism.
Except I was doing it not according to plan: with little to nothing more in my knowledge base than before engaging the first, now completed, part of the plan.
So what I wrote was: Pour échapper à la supercorde, réfléchir un photon fractal sur le miroir de Planck
I learned only a couple years later of Edward Witten's discovery of string dualities. IIRC, my poetic line was roughly simultaneous, and with "miroir de Planck" captures with singular efficacy an ingredient of (at least some) superstring dualities.
So, loyalty to my own devices and faith in my performance I had to keep in mind the interests of the other parts of the aphorism, in particular the "Pour échapper à la supercorde".
This is what lead my nose into finding cool to imagine that string theories secretly superceded population genetics by a miraculous shortcut of mathematics and nature, similar but more radical than those that the most brilliant physicists already uncovered. And whose nutshell formulation, once again, could be "life histories are secretly strings".
Incidentally, might say I am on the lookout for a first competent adept;)27w - I'll get back to you after the spinning class.27w
- Not sure what the joke is... but this in turn allows useful bundling of a related consideration : how do (or fail to) correlate our attributions of irony and our attributions of intelligent agency?
I believe in the possibility of a threshold level of natural irony of situation above which our expectation of an agency-free universe makes us blind to what would otherwise be or model perfect solutions to our stated puzzles.26w - Why shouldn't my profile pic spin too?... done.26w
