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Re: Superstring Theory
[Re: AlbertoT]
#160418
10/19/07 17:46
10/19/07 17:46
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fastlane69
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Quote:
The string theory predict the existance of new particles in a band of energy which is accessible to the new particle accelerator at CERN
Are you talking about the LHC at CERN?
I don't know of any particles that are distinct to String theory that will pop out of that. Consider that...
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This theory can exactly predict all the features of all the known particles.
...the Standard Model of Particle Physics, a almost 50 year old theory, already does that.
What the LHC will do is validate the SM further but I'm unaware that it will be able to test any tenets of String theory. It's main success will be to find direct evidence of a Higgs Boson, a lynchpin of the Standard Model, not String Theory. As well, anothe major thrust of the LHC is the finding of Supersymmetric Particles (very dear to my heart since I did my PhD thesis on them) but even that isn't direct proof of String Theory.
Could you expand on this Alberto? I would very much like to know what is on the horizon in experimental physics, especially as related to String theory! 
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Re: Superstring Theory
[Re: fastlane69]
#160419
10/19/07 18:13
10/19/07 18:13
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AlbertoT
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Quote:
Quote:
I don't know of any particles that are distinct to String theory that will pop out of that. Consider that...
Yes, some new particles should pop out if the theory is right...
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...the Standard Model of Particle Physics, a almost 50 year old theory, already does that.
Not all, the standard theory does not include the "graviton" the string thoery does
Moreover you can use the same arguments also against the standard theory
This theory make use of 18 "arbitrary" parameters which have been duly
" tuned " to make the theory working
A famous scientists, I dont remember whom, claimed that the standard theory was a joke because of that
He said mor or less
" If you exctract 18 parameters out of your sleeve, of course it works, every theory would work "
Last edited by AlbertoT; 10/19/07 18:20.
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Re: Superstring Theory
[Re: AlbertoT]
#160420
10/19/07 20:02
10/19/07 20:02
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fastlane69
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Quote:
Yes, some new particles should pop out if the theory is right...
Yeah, like the Higgs or Supersymmetric partners... but nothing that will prove (or disprove) String theory.
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Not all, the standard theory does not include the "graviton" the string thoery does
The Graviton is a concept based on the idea that every fundamental force has a particle carrier... but Gravity is SO different from all the other forces that we have no idea at which energy ranges it exists or even if it DOES exists. Heck, we might as well be searching for Tachyons as they are as "real" as gravitons! Hence nothing at CERN is looking for a Graviton and there are no experiements that I'm aware of that are trying to look for it (Gravity waves on the other hand...  )
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Moreover you can use the same arguments also against the standard theory
I don't understand which "argument" you are talking "against".
The fine tuning parameter is an unresolved issue and something the String Theory (or any GUT candidate) aims to solve. But that doesn't change the fact that the SM makes predictions that have consistently proven true in the last 50 years, that it's never been proven wrong, and that there are no other theories that have the predictive power the SM has. So whoever this scientist was may have been famous, but as well was famously wrong!
This is why the LHC's search for the Higgs is so critical. If it's not found, it will be a SEVERE blow to the SM... but if it is found, then it will be just another indication that the SM is "right".
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Re: Superstring Theory
[Re: fastlane69]
#160421
10/19/07 21:41
10/19/07 21:41
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AlbertoT
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Quote:
Yeah, like the Higgs or Supersymmetric partners... but nothing that will prove (or disprove) String theory.
All the existing particles are nothing else, according to the theory, that different modes of vibration of basic entities called strings
The higher the frequency of the vibration, the higher the relevant energy and consequently the higher the mass of the particle
If you deliver a huge amount of energy you should be able to excite modes of vibration which do not normally exist in nature in other words you should create very heavy particles , hundreds time heavier than neutrons or protons
Their lifespam is expected to be just a fraction of time but they should leave a track on the screen of the computers
If their mass, electric charge , spin, etc comply with the predictions of the theory than the theory of string is , very likely true, otherwise it is for sure false
The theory of string is accused to abuse of a sort of math formalism
The scientits have tweaked, so to speak, the equations several times to make them compatible with the experience
Up to a certain extent it is however the same thing also for the standard model
In the equations of the standard model there are 18 constants
In classic physics constant have a physical meaning
Take the equation of the gas, for example
pv = kt
K depends on the type of gas
The 18 constant of the standard model , same as the extra dimensions of the string theory ,apparently have no meaning at all
They have "simply " been introduced to make the results of the equations complying with the experience
The equations of the standard model work perfectly but , nobody knows why...:)
Last edited by AlbertoT; 10/19/07 21:47.
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Re: Superstring Theory
[Re: AlbertoT]
#160422
10/19/07 22:14
10/19/07 22:14
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Posts: 3,010
analysis paralysis
NITRO777
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Quote:
In classic physics constant have a physical meaning
Take the equation of the gas, for example
pv = kt
K depends on the type of gas
As I said earlier, I have no knowledge of string theory, but I know that pv=kt is more of a chemistry law than a physics law, but that is a trivial point.
However the only gases this law would describe would be 'ideal gases'. I don't think k depends on a type of gas per se, rather it is used in conjunction with a proportionality constant in the ideal gas law used for the wrangling of the equation So I think you might be using a bad equation to state your point, because this equation itself evolves into the IDEAL GAS LAW PV=nRT. These gases only behave this way at certain conditions, .. ideal conditions which really don't exist. Scientists (like fastlane69) would build new constants and numbers in equations to model real life and varying conditions. 
of course, k is going to be a different value depending upon the gas used, but that value isn't going to be constant at all, and it will only come close to constancy under certain ideal conditions, the closer you get to zero pressure.
So I guess my point is that the 18 physical constants may or may not have a real 'physical meaning', I have never studied physics at school so I dont know. However, constants do not always have a physical meaning, as they can be produced for the balance of proportionality, and they can be based on ideals. Such as the ideal gas law, which is simply a recombination of Boyle's Law.
Last edited by TriNitroToluene; 10/19/07 22:34.
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Re: Superstring Theory
[Re: NITRO777]
#160423
10/19/07 22:54
10/19/07 22:54
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AlbertoT
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It is evident that you did not grasp the concept
For a real gas you must tweak the equation adding the van der Waals constants which depend on the type of gas
However also The Boltzman constant has a physical meaning since it defines the status of the system
The extra dimensions on the contrary , same as the parameters of the standard model have no physical meaning
Or better, their meaning , if any, is not known because we are dealing with entitities which are beyond the limit of our experience
Human beings reason by analogies
Humanity took some thousand years to realize that a gas is made of small particles however it is not hard to grasp this concepts because we have experience of similar entities
Consequently we can associate an " mental image " to each parameter of the the equations of classic physics
In atomic physics is not alwayes possible to reason by analogies consequently modern physics is bound to be, up to a certain extent, pure math
Last edited by AlbertoT; 10/19/07 22:59.
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Re: Superstring Theory
[Re: AlbertoT]
#160424
10/19/07 23:26
10/19/07 23:26
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Joined: Mar 2003
Posts: 3,010
analysis paralysis
NITRO777
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Quote:
In atomic physics is not alwayes possible to reason by analogies consequently modern physics is bound to be, up to a certain extent, pure math
Right, but I would say that our concepts of particles need to be limited to what we can observe, we don't conceptualize things by analogies because of human limitation, but rather because thats the way they exist in real form. In order to get out of the realm of speculation you need to be able to test something.
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It is evident that you did not grasp the concept
For a real gas you must tweak the equation adding the van der Waals constants which depend on the type of gas
No, I didn't read all of the thread now I have looked back and see that you have already taken to account the nature of 'real things'. It appears to me that you were trying to propose that because an equation has a constant that it needs to model real things, which in the example you used, would be wrong.
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modern physics is bound to be, up to a certain extent, pure math
I think a lot of physicists would disagree with you because they seem to value math more for its practical application, rather than for it's theoretical usage. One problem with your reasoning about string theory is in your earlier statement:
Quote:
This theory can exactly predict all the features of all the known particles.
It is hard to beleive that it is just by chance
You are essentially adhering to string theory because you feel that the only alternative is that its 'hard to believe that it is just by chance'.
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Re: Superstring Theory
[Re: AlbertoT]
#160425
10/19/07 23:47
10/19/07 23:47
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fastlane69
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Quote:
The 18 constant of the standard model , same as the extra dimensions of the string theory ,apparently have no meaning at all
It was 18 before the discovery of the neutrino mass. Now it's 25:
-----------------------
the mass of the up quark
the mass of the down quark
the mass of the charmed quark
the mass of the strange quark
the mass of the top quark
the mass of the bottom quark
4 numbers for the Kobayashi-Maskawa matrix
the mass of the electron
the mass of the electron neutrino
the mass of the muon
the mass of the mu neutrino
the mass of the tau
the mass of the tau neutrino
4 numbers for the Maki-Nakagawa-Sakata matrix
the mass of the Higgs boson
the expectation value of the Higgs field
the U(1) coupling constant
the SU(2) coupling constant
the strong coupling constant
--------------------------------
And they are nothing like the extra dimensions of String theory since these values are set by experiments and not arbritraraly determined.
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The scientits have tweaked, so to speak, the equations several times to make them compatible with the experience
Quote:
apparently have no meaning at all
Quote:
They have "simply " been introduced to make the results of the equations complying with the experience
Quote:
consequently modern physics is bound to be, up to a certain extent, pure math
Wrong on all counts. There is no tweaking these values and it's not pure math. They have been experimentally determined through the last 50 years of collider experiments. The equations have been modified to better fit the experimental results (for example using a U(1)xSU(2) grounp instead of an SU(3) group) but it makes sense that experiments guide the theoretical foundation when they are in disagreement. Contrary to popular belief, Physics is guided by experiments and not math. Math is merely one way for us to express what we find, to have a common language, but the "reality" of physics lies in the phenomenology, in what we observe happening in the world and not what we believe an equation tells us. It's only when the math and the experiment coincide that we start treating the math as real (as with the SM)... String theory is not there yet by a long shot.
This is why the SM is on such strong foundation because it has been tested and retested to a sick degree of accuracy and is very robust in it's current incarnation. It is absolutley wrong to think that scientists have just made up these masses so they work; each of the values above corresponds to a physical value which is again why the Higgs Mass and SUSY particles are so critical to the theory as they are the last remaining "unknowns" of the theory.
So again we come to my point: nothing that is being done at CERN will prove or disprove String theory because the energy levels at which String theory becomes testable is currently out of reach. CERN is currently focusing on making the SM stronger by finding Higgs and SUSYs and is not concerned with Strings or Gravitons (for now).
(PS: your gas law analogy fails for "k" is a direct measure of the amount of energy per temperature change and thus is not devoid of physical meaning nor is it up to scientists to "tweak". It is, like the other constants, experimentally determined)
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Re: Superstring Theory
[Re: AlbertoT]
#160427
10/20/07 08:38
10/20/07 08:38
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Joined: Oct 2006
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AlbertoT
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The SM originally included 17 particles but also a lot of parameters which must be set by experiment
While the reduction from hundreds atoms to 17 basic particles had been recognized , by every body, as tremendous step forth ,these parameters were and they are still considered the weak point of the theory
"Give me 18 parameters and I build an elephant for you" A great physician said
Let's make a (silly) example
Suppose that mr Newton claimed :
The attractive force is :
F = k*M1*M2 / D
(I replaced D^2 with D)
K can assume, 18 values given by the experience,see the attached table
Thanks to this formula and the relevant parameters you can calculate all the orbits of the planet with an high degree of accuracy
An obvious remark would have been :
Ok mr Newton , your method is definitly a step forth vs the traditional astronomy but we feel that there is something wrong because you make use of too many parameters
Moreover what's is the physical meaning of these 18 parameters ?
Useless to say that SM is not so trivial but I am sure you grasp the concept
To get rid of the 18 parametrs you must write the right equation ,than you would get one and one only value for K
However tha wrong equation is not completely wrong and , up to a certain extent, it might be of use.
This is the kind of arguments against Standard Model
The theory of the string tries to get rid of the multitude of parameters , whose physical meaning is definitly not clear, of the SM
Is it just a dream ?
Well , I dont know it, of course
Let"s see
However I do not understand why you dont accept that the new generation particle accelerators can cast a light also on this theory,
It is a very well known fact.
Last edited by AlbertoT; 10/20/07 13:49.
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