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nec209

string theory / M theory or extra dimension

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What is your view on string theory / M theory or extra dimension or many dimensions? From what I read the people that came up with this theory are trying to understand and deal with problems with gravity and quantum mechanics phenomenon. That if there was no quantum mechanics phenomenon or problem with gravity there would be no need for this theory.

The quantum mechanics phenomenon are mostly dealing with the phenomenon of double slit experiment, the Schrödinger's cat and quantum tunneling.

 

 

 

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So far to date, string theory etc. has no experimental basis.  The basic problem is reconciling quantum theory and general relativity when both are needed (black holes).

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Posted (edited)
13 minutes ago, mathematic said:

So far to date, string theory etc. has no experimental basis.  The basic problem is reconciling quantum theory and general relativity when both are needed (black holes).

From what I understand string theory / M theory does not replace general relativity. It still needs dark matter and dark energy.

Unless you think gravity is seeking in from other universe counting for the mass.

The string theory / M theory never gone that far to claim gravity is seeking in from other universe counting for the mass.

 I know many people would like support other universe theory to explain what caused the big bang.

 

Edited by nec209

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Posted (edited)

The first step to understand is that in physics models including string theory is that a dimension is any independent variable or quantity/function that can change in value without changing any other. ( This includes string theory) the extra dimensions correspond to particle degrees of freedom that correspond to their interactions.

 It does not refer to dimension as per another universe etc.

 String theory applies waveform descriptives to the properties we describe as a particle. In this sense it isn't different from QFT. A string is a waveform descriptive.

It follows GR but more so in the SR regime as gravity is so weakly in the quantum regime.

Edited by Mordred

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Personally I think there is a great mathematical beauty in String Theory, and a number of important advances in both mathematics and theoretical physics have emerged from the study of this model. 

However, “it’s beautiful” is not a scientific argument, and no indicator as to its value as a valid model of quantum gravity. One of the main problems I see right now is this - String Theory doesn’t actually produce GR in the classical limit, it produces GR plus a large number of scalar fields. There is no evidence for any of these scalar particles in the real world, nor is there any known way to mathematically remove them from the theory. This is an awkward problem, and I don’t see it being discussed very often in the ST community. Furthermore, we don’t actually know whether or not ST is even capable of reproducing all the particles of the Standard Model (plus their interactions and symmetries) in a self-consistent manner. 

My take on this is - String Theory certainly warrants further research, but it is at best unclear whether or not it can produce a workable model of quantum gravity. There are a lot of fundamental problems associated with this model, which would need addressing.

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Posted (edited)

A major hurdle being the graviton being the fundamental particle. I agree QFT via perturbation does a far better job of matching observational criteria. Though a careful study of both theories naturally involve highly similar mathematics. One thing I have learned from studying numerous treatments. Many of the same methodologies are applied in all theories once you get down to the nitty gritty.

Developments to overcome are a part of physics. Regardless of model. String theory is still considered viable however myself I feel QFT does a more accurate and robust job with regards to particle physics. However that is only based on my studies (though intensive).

Lol though all tools are handy in any personal modelling I do. I find a lot of lessons of value in the higher tensors in String theory. Ie past 4d symmetry treatments.

Edited by Mordred

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String Theory as a mathematical 'framework' is certainly useful and a valid area of study.
String Theory, applied to our Universe ( as a Physical theory ), not so much

Supersymmetry ( in its various forms ) and supersymmetric particles, have stubbornly refused to be found, and ( I believe ) that is a requirement for a workable ( Physical ) theory.
I have also read that proton decay, as required by SU(5) and SO(10) GUTs, is incompatible with String Theory.

So the race is on, Supersymmetry or proton decay; which will be found first ?

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22 hours ago, Mordred said:

I find a lot of lessons of value in the higher tensors in String theory. Ie past 4d symmetry treatments.

I agree, though I have never studied it in any great detail. 

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Posted (edited)
On 3/4/2020 at 8:14 PM, Mordred said:

The first step to understand is that in physics models including string theory is that a dimension is any independent variable or quantity/function that can change in value without changing any other. ( This includes string theory) the extra dimensions correspond to particle degrees of freedom that correspond to their interactions.

 It does not refer to dimension as per another universe etc.

 String theory applies waveform descriptives to the properties we describe as a particle. In this sense it isn't different from QFT. A string is a waveform descriptive.

It follows GR but more so in the SR regime as gravity is so weakly in the quantum regime.

I don't like the idea of the parallel universe to explain the Schrödinger's cat, uncertainty principle and double slit experiment.

So if string theory / M theory or extra dimension or many dimensions hold up better we do not need parallel universe  to explain Schrödinger's cat, uncertainty principle and double slit experiment.

Edited by nec209

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Really shocking base on this video I found. There could be more dimensions of space.  Could this explain the problems they are having with gravity today? And also the Schrödinger's cat, uncertainty principle and double slit experiment?

The short video below.

Why does string theory require extra dimensions of space?

 

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17 minutes ago, nec209 said:

Why does string theory require extra dimensions of space?

The reasons are of a mathematical nature. When you formulate the theory, there are two basic requirements that need to be fulfilled - it needs to be internally consistent, and it needs to describe the correct particles (with correct properties etc) which we empirically find the in the real world. It turns out that these requirements are fulfilled only if there are more than 4 spacetime dimensions, otherwise the model doesn’t work.

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On 3/12/2020 at 4:06 AM, Markus Hanke said:

The reasons are of a mathematical nature. When you formulate the theory, there are two basic requirements that need to be fulfilled - it needs to be internally consistent, and it needs to describe the correct particles (with correct properties etc) which we empirically find the in the real world. It turns out that these requirements are fulfilled only if there are more than 4 spacetime dimensions, otherwise the model doesn’t work.

 

Why does string theory / M theory require dark matter and dark energy?

I thought this other gravity they cannot see or detect like dark matter and dark energy where in other dimension or dimensions?

So why does it require dark matter and dark energy?  If it is in other dimension or dimensions and that is why they cannot see or detect it than there is no such thing as dark matter and dark energy? If that is the case than why does it require dark matter and dark energy?

 

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31 minutes ago, nec209 said:

Why does string theory / M theory require dark matter and dark energy?

Any successful theory has to explain dark matter and dark energy, because they are labels for things we observe.

I don't know enough about how string theory deals with dark matter or dark energy. But as far as I know it doesn't say anything about them. If dark matter is a form of matter, then that will presumably be described by string theory when we know what that matter is.

And if dark energy is a form of energy, then I suppose that would have to be included in string theory as well.

I am not aware that it provides any special solutions to the problem.

34 minutes ago, nec209 said:

I thought this other gravity they cannot see or detect like dark matter and dark energy where in other dimension or dimensions?

Neither dark energy or dark matter are "other gravity". And they don't exist on "other dimensions" whatever that means.

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I have studied string and M theory and I do not recall any DE or DM explanation specific to the two theories. Though I would not doubt one can find papers that attempt to do so in those theories. 

 As above a dimension is an independent mathematical object such as a variable/group/tensor etc. DM and DE do not require extra dimensions to model them.

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 Are there going to be better equipment where we can know these things like string theory , extra dimensions and uncertainty principle you never know the particle the speed and position at the same time. You can know the speed but not the position or you know the position but not the speed.  

If we know a particle's speed EXACTLY, then we can't know exactly where it is.  Likewise, if we know exactly where it is, we can't know it's speed.

 Are there going to be better equipment for this?

 

On 4/11/2020 at 10:24 AM, Mordred said:

I have studied string and M theory and I do not recall any DE or DM explanation specific to the two theories. Though I would not doubt one can find papers that attempt to do so in those theories. 

 As above a dimension is an independent mathematical object such as a variable/group/tensor etc. DM and DE do not require extra dimensions to model them.


Some people make reference to things being in other dimension that humans cannot see and there may or may not be tools to see the dimension. And think much of the dark energy or dark matter may be in there.

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59 minutes ago, nec209 said:

 Are there going to be better equipment where we can know these things like string theory , extra dimensions and uncertainty principle you never know the particle the speed and position at the same time. You can know the speed but not the position or you know the position but not the speed.  

If we know a particle's speed EXACTLY, then we can't know exactly where it is.  Likewise, if we know exactly where it is, we can't know it's speed.

 Are there going to be better equipment for this?

 


Some people make reference to things being in other dimension that humans cannot see and there may or may not be tools to see the dimension. And think much of the dark energy or dark matter may be in there.

The uncertainty principle will always remain one can only minimize the measurement interaction to reduce but never eliminate this.

As to the second part, some people are wrong. They are not applying the term dimension in accordance to physics definition.

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6 hours ago, nec209 said:

If we know a particle's speed EXACTLY, then we can't know exactly where it is.  Likewise, if we know exactly where it is, we can't know it's speed.

 Are there going to be better equipment for this?

This is not a limitation due to limitations of the measurement equipment (that would be the observer effect). It is better to think of it as the values not even being defined more accurately than this.

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