The Japanese organizers conduct maintain tried an master copy reform of the YouTube activity. They postal service the whole days as unified videos.
Most of you lot desire to delay your dinner yesteryear iii hours together with 46 minutes – thus you lot should lookout the video higher upward for the nutrient to sense of savour better.
Cumrun Vafa whom I know much ameliorate than the other twenty speakers inwards the video starts to speak at 31:44 together with his subject is a newspaper released on Monday,
De Sitter Space together with the Swampland (Obied, Ooguri, Spodyneiko, Vafa)Recall that Vafa's Swampland is a giant parameter infinite of effective land theories that cannot hold out realized within a consistent theory of quantum gravity i.e. within string/M-theory. Only a tiny isle within this Swampland, namely the stringy Landscape, is compatible amongst quantum gravity. String/M-theory makes lots of really strong predictions – namely that nosotros don't alive inwards the Swampland. We conduct maintain to alive inwards the special hospitable Landscape.
Along amongst his friend Donald Trump, Cumrun Vafa decided to drain the Swampland. ;-)
OK, these comments became ludicrous also early on thus allow us hold out to a greater extent than serious for a while. In the newspaper I mentioned, Vafa together with pals conduct maintain proposed a novel inequality obeyed yesteryear the potential unloosen energy \(V\) inwards every consistent theory of quantum gravity\[
V \leq \frac{|\nabla V|}{c}
\] which excludes also high positive cosmological constants together with de Sitter spaces inwards particular. The slope is calculated on the land space, amongst the metric given yesteryear the kinetic damage of the scalar fields. Use 4D Planck units (Einstein frame) if others aren't skillful enough.
It's a fun proposal – a potential cousin of the Weak Gravity Conjecture, but a younger together with less justified 1 (at to the lowest degree thus far). Note that \(V_0\leq 0\) constraining the minimum would hold out hard to justify together with the appearance of the minimum \(V_0\) alone would hold out unnatural. So inwards a sense, Vafa together with co-authors conduct maintain found together with supported a stronger version of that inequality that places an upper bound on the potential unloosen energy density at each betoken of the configuration space. Neat.
For a spell after I saw the paper, I was worried almost the infinite tower of massive stringy fields which brand the slope arbitrarily high – because the majority is high. But together with then I understood my mistake. If the vacua are stabilized, the slope from the inequality yesteryear Vafa et al. is strictly zippo together with they brand the bold declaration that the cosmological constant inwards stable vacua has to hold out zippo (Minkowski) or negative (AdS).
I call back it's a cool inequality together with people should investigate the arguments for together with against together with the consequences. Such a unproblematic inequality could indeed summarize the absence of persuasive constructions of metastable de Sitter spaces within string/M-theory.
Now, I am confident that Cumrun Vafa is 1 of the staunchest believers inwards string/M-theory inwards the basis – I powerfulness conduct maintain a hard fourth dimension to compete amongst him fifty-fifty when it comes to the strength of the belief. So doesn't he call back that this "no-go theorem" for the positive cosmological constant excludes string theory because the positive cosmological constant has been observed?
Influenza A virus subtype H5N1 skillful question, indeed. Well, it turns out that Cumrun Vafa has locomote a quintessence believer. So the cosmological constant isn't genuinely constant, some scalar land is rolling, together with its relative constancy alone emulates the cosmological constant. As David Gross reminds everybody around 0:58:00 inwards the video above, quintenessence has a widely believed problem: it seems to predict time-dependent substitution constants such as the fine-structure constant (the atmospheric condition are changing amongst time).
David Gross came to Okinawa from California.
These predicted variations inwards fourth dimension don't conduct maintain a really skillful ground to hold out small. Because experiments be that examine that the fine-structure constant was the same within an impressive accuracy a few bilion years ago, quintessence seems to hold out basically excluded.
Cumrun believes that the affair tin piece of work inwards some agency but I haven't quite absorbed his novel belief – it's nevertheless rather non-standard for me.
(Along amongst Steinhardt together with 2 other authors, Vafa posted an fifty-fifty to a greater extent than recent paper against inflation that tries to suggest that fifty-fifty inflation is inwards tension amongst the Swampland rules of quantum gravity. Cumrun has discussed this newspaper inwards his talk, too. He would likely supervene upon inflation amongst the string gas cosmology or something similar that – well, it's possible to enquiry it but I call back that the string gas cosmology is fifty-fifty less probable to hold out truthful than quintessence.)
Around 1:01:00, Eva Silverstein joins David Gross inwards the criticisms. Both of them conduct maintain offered some lore that somewhat contradicts Vafa's picture, to pose it mildly. Let me say the following: I conduct maintain gone through similar thoughts, conduct maintain been exposed to similar arguments, together with I also tend to call back that the lore is to a greater extent than probable than not.
But something is nevertheless wrong amongst the overall film of nighttime unloosen energy together with other things inwards string theory thus I call back it's right to hold out open-minded. By constantly repeating the lore – together with David Gross does it rather oft – 1 may forcefulness the quantum Zeno effect on the string researchers. They won't conduct maintain the chance to brand a jump that is almost sure needed.
Cumrun Vafa knows quite something together with when he becomes a quitenessence believer, I call back it's useful to hold out interested inwards the mental processes that conduct maintain led him to this transformation. Gross repeats some lore but in that location is genuinely no rock-solid declaration against quintessence. In fact, I call back that some people could sensibly debate that swampland-like inequalities are genuinely more solid consequences of a theoretical framework – together with you lot may thought them as consequences of either quantum gravity or string/M-theory (which are ultimately equivalent but the phrases "sound" different) – than Gore's lore [I meant Gross' lore but I kept the typo because it looked funny] that disfavors quintessence models.
I conduct maintain had similar feelings when David Gross was rather heavily attacking (repeated TRF invitee blogger) Gordon Kane. You know, I conduct maintain shared Gross' observation that inwards his M-theory phenomenology, Kane had to brand numerous additional assumptions, some of which were inspired yesteryear rather detailed empirical observations (about possible ways to extend the Standard Model to a theory that also agrees amongst some cosmological criteria).
So spell I conduct maintain never believed that Kane has derived the necessity of his sort of models from the showtime principles – together with indeed, it seems that his prediction of a gluino below \(2\TeV\) has been invalidated – in that location was something that I disliked almost Gross' criticism. It just sounded to me that Gross wanted to discourage the people from thinking almost specific scenarios, specific classes of models amongst some extra assumptions that just plough over off to await natural.
Well, I would fifty-fifty pose it inwards this way: Gross apparently wanted everybody to care for the whole "landscape" as a ready of equal elements together with avoid the focusing on whatever particular elements or subgroups of the vacua because that would hold out a discrimination. In December, Gross dreamed almost the early on decease of Donald Trump together with a calendar month later, he rather brutally attacked mainstream conservative Indians.
But those things are fine, no 1 cares what David Gross thinks almost politics – everyone to a greater extent than or less correctly assumes he's just some other cloned leftist inwards the Academia. However, I experience that a similar constant imposition of his lore together with grouping call back is something he does inwards physics, too. And it isn't right. People similar Kane must conduct maintain the liberty to report together with suggest realistic M-theory compactifications; together with people similar Vafa must conduct maintain the liberty to investigate quintessence within string/M-theory. People must combine together with recombine assumptions, pick privileged classes of vacua that await to a greater extent than promising to them given these assumptions together with the observations, together with thus on. If those choices are discrimination, together with then it is a basic moral duty of a physicist to discriminate at basically all times!
I don't empathise his reasoning but I expose it (less probable than 50% but) conceivable that Cumrun has some reasons to call back that the fourth dimension variation of the constants powerfulness hold out compatible amongst their quintessence picture. On the other hand, Vafa admits that they don't solve the cosmological constant work – why the "apparent" electrical flow vacuum unloosen energy density is thus small.
But the inequality they suggest – specially if you lot assume that it wants to hold out near-saturated – eliminates the "double fine-tuning" that you lot would quest inwards generic quintessence models, those that were studied earlier their Swampland findings. In regular quintessence, \(V\approx 10^{-122}\) together with \(|V|\approx 10^{-122}\) are 2 independent fine-tunings. With the near-saturated Swampland inequality, these 2 fine-tunings bring down to basically one, they are non independent. So you lot could say that amongst the Swampland findings, if established, the quintessence is as natural as the cosmological constant (one fine-tuning yesteryear 122 orders of magnitude). Vafa has made additional comparisons of naturalness within the measure or their axiomatic organization together with theirs seems to win.
Eva Silverstein has joined the polemics amongst her pet subject that I conduct maintain been aware of since 2005: the affirmative activity for supercritical strings. Supercritical string vacua must hold out treated on par amongst the critical string theory's compactifications, in that location can't hold out whatever discrimination. Please: Not again! (You know me as person who passionately argues almost an extremely various spectrum of topics. But I call back that I conduct maintain genuinely never argued as tensely almost string theory amongst a string theorist as I did amongst Silverstein inwards 2005.)
The intelligence at Strings 2018 made it clear that she has tried to convince Cumrun almost that supercritical affirmative activity together with Cumrun has rejected inwards a really similar agency – together with maybe for similar reasons – as I did. Sorry, Eva, but supercritical string theory merely isn't an every bit probable or convincing film of the existent basis as presented yesteryear string theory as the critical string theory is.
The prediction of the critical dimension, e.g. \(D=10\) for the weakly coupled superstring, is 1 of the showtime heroic predictions of string theory that evidently locomote beyond the predictive ability of quantum land theories. Some supercritical string basis canvass CFTs may hold out defined but it is much less clear whether these theories may hold out completed to non-perturbative consistent theories.
In the illustration of critical superstring theory, S-dualities etc. larn into extremely probable that the theory is fully consistent at whatever finite coupling (because it seems OK at zippo together with infinity). But inwards the supercritical case, in that location are no known S-dualities similar that together with lots of other arguments inwards favor of non-perturbative consistency that piece of work inwards critical string theory merely can't hold out applied to supercritical string theory.
Moreover, the damage proportional to \((D-10)\) appear inwards the beta-function for the dilaton, a scalar land that plays a preferred role at weak coupling but that should locomote a generic scalar land at a stronger coupling. The beta-function for the dilaton dictates the Euler-Lagrange equation of motion that 1 would derive from varying the dilaton inwards the effective action.
I genuinely expose it probable that in that location exists a swampland-style inequality similar to the 1 that Cumrun just discussed that says that the other damage \(t\) inwards the equation \((D-10)c + t = 0\) cannot hold out large plenty to genuinely shell the "wrong dimension term" for \(D\neq 10\). As far as I know, all these questions are rather hard together with convincing justifications for 1 response or some other just don't exist. In fact, I tin imagine that this declaration excluding the supercritical string theory's stabilized vacua straight follows exactly from the inequality that Vafa et al. propose: they say that the slope terms, together with \(t\) contains those, are e'er also modest to shell the constant damage \(V\) – together with \((D-10)c\) powerfulness merely hold out a constant term that needs to hold out beaten but is also large.
We don't conduct maintain a proof inwards either direction. But that's precisely why Cumrun's open-minded approach "I am non proverb you lot must hold out wrong, Eva, but what I say powerfulness also hold out right" is precisely the right one.
Eva's claim that all the supercritical vacua, mayhap those inwards \(D=2018\), are as established together with as consistent as the \(D=10\) or \(D=11\) vacua is just champaign silly. This claim utterly disagrees amongst the composition of the string theory literature where most of the "good properties" depend on the critical dimension (and/or on supersymmetry, together with supersymmetry is also possible inwards the critical spacetime dimension only). Silverstein's claim almost the "equality" of critical together with supercritical vacua is just some unjustified ideology at this point. Maybe the enquiry volition alter towards the "equality betwixt critical together with supercritical vacua" inwards the futurity but it's a pure speculation; the critical string theory is much to a greater extent than established today together with some futurity advances may also eliminate the supercritical string theory altogether.
Moreover, such a total legitimization of the supercritical vacua would likely Pb to a much to a greater extent than hopeless proliferation of the "landscape of possibilities" than the regular landscape of the critical string/M-theory. The really dimension \(D\) would hold out unlimited together with the complexity together with variety of possible compactifications would dramatically growth amongst \(D\), too. Maybe mathematics or Nature may brand the search for the right vacuum much to a greater extent than hard than nosotros idea (and it's been hard plenty for some 2 decades). But this is just a possibility, non an established fact. It's totally sensible to practise enquiry subject on the working hypothesis that supercritical string theory is a curiosity inwards perturbative string theory that may hold out given 1 page of a textbook – but otherwise it's worthless, unusable, inconsistent rubbish inwards the string model building!
Cumrun clearly agrees amongst this working hypothesis of mine spell Eva – without existent testify – is trying to brand this supposition politically incorrect. She would honey to impose a duty on everyone to pass the same fourth dimension amongst supercritical string theory as amongst critical string theory. That's just a counterproductive pressure level that should hold out ignored yesteryear Cumrun together with others because the outcomes of such an extra dominion would almost sure hold out tragic.
No comments:
Post a Comment