Relativity vs. Quantum vs. String

[Thikr]

I understand that Relativity is Einstein's theory of the macroverse and it has been used to predict things with scary accuracy, and I understand that Quantum physics is a theory created by many men to define the microverse. I also understand that it can be used to predict the level of unpredictability at an atomic level. I know the absolute rudimentary concepts of string theory as well, though I know also that this is the most theoretical of these three theories, having no proof or experiments done to prove it.

 

So, why do Quantum and General Relativistic theories counteract each other? What are the conflicting principles between the two? Which has more flaws? Who is the "father" of Quantum theory (most prominent thinker behind it... I want to say Heisenberg)? Why is String theory wrong (I hear it from all sides)? And why is it so hard to create good backing principles for string theory?

[J.C.MacSwell]

I understand that Relativity is Einstein's theory of the macroverse and it has been used to predict things with scary accuracy, and I understand that Quantum physics is a theory created by many men to define the microverse. I also understand that it can be used to predict the level of unpredictability at an atomic level. I know the absolute rudimentary concepts of string theory as well, though I know also that this is the most theoretical of these three theories, having no proof or experiments done to prove it.

 

So, why do Quantum and General Relativistic theories counteract each other? What are the conflicting principles between the two? Which has more flaws? Who is the "father" of Quantum theory (most prominent thinker behind it... I want to say Heisenberg)? Why is String theory wrong (I hear it from all sides)? And why is it so hard to create good backing principles for string theory?

 

I would say Niels Bohr was one of the most central figures as it developed.

[ajb]

So, why do Quantum and General Relativistic theories counteract each other? What are the conflicting principles between the two?

 

So, the "unification" of quantum theory and special relativity is called relativistic quantum field theory, or QFT for short.

 

Ever since Dirac in 1928 first developed QFT, much technology and many techniques have been developed. The most successful is perturbation theory.

 

In perturbation theory one write the theory as "free part" + "interacting part" and consider the interacting part as a correction.

 

The is one snag here, as with any approach to QFT one encounters infinities. At first glance it is not clear that splitting the theory (some what arbitrarily) works.

 

So, people like Feynman, Schwinger, Dyson and Tomonaga worked out how to how to deal with these infinities in quantum electrodynamics. This is renormalisation theory.

 

Now on to gravity in the form of general relativity. At first it was hoped that a similar decomposition of the the theory would work. So, for example you can write the theory as "flat bit" + "small curved bit". This works fine in classical theory. The small curved bit are gravitational waves.

 

As usual we get infinities when trying to quantise. However, trying to use renormalisation theory just does not work. The tools that worked so well for electromagnetism just don't work. This is the "conflict" you speak of.

 

However, it is possible and there is theoretical evidence that general relativity (+ some extra terms) may be well defined (i.e. renormalisable) outside of perturbation theory. So all hope is not lost.

 

 

Which has more flaws?

 

Both general relativity and the standard model of particle physics (which is a QFT) are incomplete.

 

General relativity has infinities and misses quantum effects. The standard model does not include gravity.

 

Why is String theory wrong (I hear it from all sides)?

 

There are different answers to this, depending on what you understand already.

 

The basic issue that (like many other theories) there is a whole load of solutions. One of these may describe our universe. It is not clear is such a solution exists. If it does exist why was it "selected"?

 

Until this solution is found string theory can only make very generic predictions (as a possible unification scheme).

 

There is also another application of string theory, in the strong force. Without any details, one can do "stringy" calculations in quantum gravity and relate these to calculations involving the forces between nucleons.

 

And why is it so hard to create good backing principles for string theory?

 

I do not this this is the case. String theory is based on well-understood principles.

 

The amazing things about string theory, that is passing from points to one dimensional objects include

 

1) (Perturbative) Quantum gravity is necessarily included.

2) It does not require renormalisation.

3) Includes fermions.

4) Predicts the number of space-time dimensions.

5)The symmetries are "large enough" to include the interactions of the standard model.

 

All things that make it very interesting form a unification point if view.

[Thikr]

So, the "unification" of quantum theory and special relativity is called relativistic quantum field theory, or QFT for short.

 

Ever since Dirac in 1928 first developed QFT, much technology and many techniques have been developed. The most successful is perturbation theory.

 

In perturbation theory one write the theory as "free part" + "interacting part" and consider the interacting part as a correction.

 

The is one snag here, as with any approach to QFT one encounters infinities. At first glance it is not clear that splitting the theory (some what arbitrarily) works.

 

So, people like Feynman, Schwinger, Dyson and Tomonaga worked out how to how to deal with these infinities in quantum electrodynamics. This is renormalisation theory.

 

Now on to gravity in the form of general relativity. At first it was hoped that a similar decomposition of the the theory would work. So, for example you can write the theory as "flat bit" + "small curved bit". This works fine in classical theory. The small curved bit are gravitational waves.

 

As usual we get infinities when trying to quantise. However, trying to use renormalisation theory just does not work. The tools that worked so well for electromagnetism just don't work. This is the "conflict" you speak of.

 

However, it is possible and there is theoretical evidence that general relativity (+ some extra terms) may be well defined (i.e. renormalisable) outside of perturbation theory. So all hope is not lost.

 

 

 

 

Both general relativity and the standard model of particle physics (which is a QFT) are incomplete.

 

General relativity has infinities and misses quantum effects. The standard model does not include gravity.

 

 

 

There are different answers to this, depending on what you understand already.

 

The basic issue that (like many other theories) there is a whole load of solutions. One of these may describe our universe. It is not clear is such a solution exists. If it does exist why was it "selected"?

 

Until this solution is found string theory can only make very generic predictions (as a possible unification scheme).

 

There is also another application of string theory, in the strong force. Without any details, one can do "stringy" calculations in quantum gravity and relate these to calculations involving the forces between nucleons.

 

 

 

I do not this this is the case. String theory is based on well-understood principles.

 

The amazing things about string theory, that is passing from points to one dimensional objects include

 

1) (Perturbative) Quantum gravity is necessarily included.

2) It does not require renormalisation.

3) Includes fermions.

4) Predicts the number of space-time dimensions.

5)The symmetries are "large enough" to include the interactions of the standard model.

 

All things that make it very interesting form a unification point if view.

 

Wow, thank you