Why is String theory not taken seriously?

Study matter and its motion through spacetime...

Moderators: Calilasseia, ADParker

Re: Why is String theory not taken seriously?

#41  Postby Nautilidae » May 11, 2010 10:47 pm

GreyICE wrote:
Alright, what sort of energies will create string-balls?


We should see string balls in the TeV range if string theory is correct.

(Micro black holes can already be created and destroyed through simple relativistic acceleration).


And this is relevant how...?

I am well aware of the fact that micro black holes can be created without string theory. However, if string theory isn't correct, the LHC cannot create micro black holes in proton-proton collisions because the energies needed to create them are beyond the LHC's intended proton-proton collision energies. However, if string theory is correct, the lower limit for black hole masses shrinks considerably. In fact, if string theory is correct, we should observe micro black holes in TeV energy LHC collisions.
User avatar
Nautilidae
RS Donator
 
Posts: 4230
Age: 25
Male

Country: United States
United States (us)
Print view this post

Ads by Google


Re: Why is String theory not taken seriously?

#42  Postby newolder » Jun 19, 2019 4:05 pm

lpetrich wrote:...

New Iron based superconductors might resist magnetic fields over 100 Tesla - the strongest continuous-field magnet has a field of 45 tesla, giving a pressure of 8100 bar, while the strongest pulsed one has 90 tesla, giving 32 kilobar.

...

Just a note to update the technology news... That 45-Tesla continuous magnet weighs in at 35 tons and consumes 30MW of power whilst reports of a continuous 45.5-T "Little Big Coil" magnet weighing in at 390g with a power consumption of 180 MW and incorporating a high temperature superconductor substance, should help brighten someone's days ahead...

...

The downside of this design is that 45-T weighs-in at 35 ton and draws 30 MW, making it impractical for all but a few facilities worldwide.

In comparison, the LBC magnet is a mere 390 g. It requires 18 MW to operate and is about the size of the core of a toilet tissue roll.

...more @ link


Physics World source
Geometric forgetting gives me loops. - Nima A-H
User avatar
newolder
 
Name: Albert Ross
Posts: 6472
Age: 8
Male

Country: Feudal Estate number 9
Print view this post

Re: Why is String theory not taken seriously?

#43  Postby Svartalf » Jun 19, 2019 4:19 pm

uh, was that bit of news really worth performing that scale of thread necromancy?
PC stands for Patronizing Cocksucker Randy Ping

Embrace the Dark Side, it needs a hug
User avatar
Svartalf
 
Posts: 1292
Age: 49
Male

Country: France
Canada (ca)
Print view this post

Re: Why is String theory not taken seriously?

#44  Postby tuco » Jun 19, 2019 4:22 pm

Yeah, unlike starting a new thread and linking this one for context. I guess, it depends on how individual minds are lets organized and value efficiency.
tuco
 
Posts: 15250

Print view this post

Re: Why is String theory not taken seriously?

#45  Postby newolder » Jun 19, 2019 4:30 pm

Svartalf wrote:uh, was that bit of news really worth performing that scale of thread necromancy?

I searched for - superconducting magnet - and this was the most appropriate from the first page returns. If there's another, more suitable topic, I'll copy it there too.
Geometric forgetting gives me loops. - Nima A-H
User avatar
newolder
 
Name: Albert Ross
Posts: 6472
Age: 8
Male

Country: Feudal Estate number 9
Print view this post

Re: Why is String theory not taken seriously?

#46  Postby Calilasseia » Oct 14, 2019 5:43 pm

Re: M-Theory ...

I've covered in the past, two papers by Steinhardt & Turok, which postulate a mechanism for the instantiation of the observable universe via brane collisions. Those papers contain a testable prediction that doesn't need outlandishly huge particle accelerators.

We now have working gravitational wave detectors. Already, these instruments are obtaining data on events such as black hole collisions, that simply wasn't available before. Now, at some point in the future, scientists will discover how to differentiate between primordial gravitational waves (namely, gravitational waves arising from processes that instantiated the current observable universe) and gravitational waves of more recent origin, just as we can differentiate between EM radiation of more recent vintage and the CMB.

Once that learning curve is traversed, one of the results scientists will set out to test, is the Steinhardt-Turok prediction. Which works as follows.

Plot a graph, with the wavelength of gravitational waves on the x axis, and the frequency of occurrence of gravitational waves on the y axis, using primordial gravitational wave data (once we know how to obtain it of course). The resulting curve will be the power spectrum curve for primordial gravitational waves. The simplest case is for that curve to be a horizontal line, meaning that primordial gravitational waves were produced in the past in equal amounts right across the wavelength range. Steinhardt & Turok predict a different shape for that power spectrum curve - one in which the short wavelengths are produced more abundantly than the long wavelengths.

Consequently, the moment we are able to collect the data on primordial gravitational waves, we'll have a direct empirical test of Steinhardt & Turok's ideas. If the power spectrum curve differs significantly from their prediction, it's back to the drawing board. If that power spectrum curve matches their prediction, they pick up a Nobel.
Signature temporarily on hold until I can find a reliable image host ...
User avatar
Calilasseia
RS Donator
 
Posts: 22011
Age: 57
Male

Country: England
United Kingdom (uk)
Print view this post

Re: Why is String theory not taken seriously?

#47  Postby Macdoc » Oct 14, 2019 7:38 pm

Nice and concise on a tricky topic. :cheers:
Travel photos > https://500px.com/macdoc/galleries
EO Wilson in On Human Nature wrote:
We are not compelled to believe in biological uniformity in order to affirm human freedom and dignity.
User avatar
Macdoc
 
Posts: 15815
Age: 72
Male

Country: Canada/Australia
Australia (au)
Print view this post

Ads by Google


Re: Why is String theory not taken seriously?

#48  Postby newolder » Oct 15, 2019 8:08 am

Just a cautionary note to add that Paul Steinhardt is of the opinion that inflationary cosmology is equivalent to the end of science because models of inflation can be built to satisfy any set of observations - predicting everything is akin to predicting nothing - to paraphrase*.

For example, Inflation in scale-invariant theories of gravity (published as: Phys. Rev. D 91, 123527 (2015)) shows how these m-theoretic considerations of tensor (gravitational) fluctuation spectra can be reproduced by a model of inflation even if scale invariance is a real feature of early time.

* See, for example, the first minutes of, The unmitigated disaster:

Geometric forgetting gives me loops. - Nima A-H
User avatar
newolder
 
Name: Albert Ross
Posts: 6472
Age: 8
Male

Country: Feudal Estate number 9
Print view this post

Re: Why is String theory not taken seriously?

#49  Postby Calilasseia » Oct 15, 2019 1:15 pm

But of course, the papers in question I referred to, don't cover inflation, they cover instead the moment of instantiation of the observable universe, and what observational data the requisite processes will leave in their wake. Inflation is a different topic - its remit is how we got to the current observable state, given a hypothesised past state, after the instantiation of the observable universe.

Of course, the question remains, whether or not Steinhardt's latest cyclical ideas are consistent with those past papers from 2011.
Signature temporarily on hold until I can find a reliable image host ...
User avatar
Calilasseia
RS Donator
 
Posts: 22011
Age: 57
Male

Country: England
United Kingdom (uk)
Print view this post

Re: Why is String theory not taken seriously?

#50  Postby newolder » Oct 15, 2019 1:56 pm

The 2011-ish claim was that upcoming data on CMBR polarisation and its relation to tensor (gravitational) fluctuation spectra would be a decisive clincher between ekpyrotic (Steinhardt & Turok) and inflationary cosmology models. Since the 2015 paper above, and Steinhardt's earlier warning about how inflationary models may used to predict anything, this is no longer the case.

From Steinhardt's website, his recent work finds the M-theoretic extra dimensions "inessential" to his current ideas on bouncing cosmology.

A. Ijjas, P.J. Steinhardt

Bouncing Cosmology made simple, Class. Quantum Grav. 35 (2018) 135004

An intuitive way to illustrate how cosmological models with a classical (nonsingular) bounce generically resolve fundamental problems in cosmology. (Note that the earliest versions of bouncing cosmology (see Khoury et al. below) were based on colliding branes in extra dimensions; but those elements are inessential in current bouncing cosmology models, which are based on ordinary scalar fields in four space-time dimensions.)


I'm not familiar, yet, with any predictions from this work but from an early read of A new kind of cyclic universe
...
We emphasize that we do not invoke extra dimensions, branes, and other elements inspired by string theory for this new approach to cyclic cosmology.
...
Geometric forgetting gives me loops. - Nima A-H
User avatar
newolder
 
Name: Albert Ross
Posts: 6472
Age: 8
Male

Country: Feudal Estate number 9
Print view this post

Previous

Return to Physics

Who is online

Users viewing this topic: No registered users and 1 guest