Unraveling the Conflict between Quantum Mechanics and General Relativity

[dr. candy]

could you explain why quantum mechanics and general relativity don't mix.
please help!


Dr. Candy

 

[alphali]

the conflict arises because the heart of quantum mechanics is uncertainty principal which say that there is no empty space and that what looks like empty space when examined at shorter distances will reveal creation and annihilation of particles and world of frowziness.but the geometry of general relativity is based on the fact that the space were there is no mass the space is flat.and so general relativity says the space is flat while cm says that there is no flat space because there are always particles emerging and vanishing. and string theory is successful in solving this problem.

 

[atyy]

Quantum mechanics and general relativity do mix. http://arxiv.org/abs/gr-qc/0311082

Quantum general relativity fails at high energy, as does quantum electrodynamics. This indicates the need for extra degrees of freedom (unless Asymptotic Safety works out http://arxiv.org/abs/0709.3851). AdS/CFT or gauge/gravity duality is conjectured to provide an example of quantum gravity with extra degrees of freedom that doesn't fail at high energies (it gets gravity, but seems not to describe the matter or cosmology of our universe). http://arxiv.org/abs/gr-qc/0602037

 

[Kevin_Axion]

the conflict arises because the heart of quantum mechanics is uncertainty principal which say that there is no empty space and that what looks like empty space when examined at shorter distances will reveal creation and annihilation of particles and world of frowziness.but the geometry of general relativity is based on the fact that the space were there is no mass the space is flat.and so general relativity says the space is flat while cm says that there is no flat space because there are always particles emerging and vanishing. and string theory is successful in solving this problem.

This is kind of correct. Essentially, when you integrate over all of the loops in graviton self-interactions you get divergent integrals (infinity). This is known as ultraviolet divergence, since the energies at which divergence occurs is in the range of UV radiation. In a semi-classical setting or QFT in curved space-time once you approach highly massive objects such as black holes the theory doesn't work since there are so many self-interactions (because the rank 2 stress-energy tensor interacts with mass energy and momentum and the graviton has energy and momentum) the integrals become far too divergent to be renormalized (which is a process in QFT uses to calculate infinite integrals and get finite results).

 

[Kevin_Axion]

Quantum mechanics and general relativity do mix. http://arxiv.org/abs/gr-qc/0311082

Quantum general relativity fails at high energy, as does quantum electrodynamics. This indicates the need for extra degrees of freedom (unless Asymptotic Safety works out http://arxiv.org/abs/0709.3851). AdS/CFT or gauge/gravity duality is conjectured to provide an example of quantum gravity with extra degrees of freedom that doesn't fail at high energies (it gets gravity, but seems not to describe the matter or cosmology of our universe). http://arxiv.org/abs/gr-qc/0602037

As a semi-classical theory yes, but not as a fully quantum theory that works at high energies. The only theories that have had success are string theory and LQG but LQG hasn't even included matter particles completely or even recovered GR.

 

[Sum1sGruj]

A very simple answer:

There has yet to be a complete observed symmetry between them, if one does in fact exist. They work on their own scales, but when integrating them, they fail for the most part.

Such is why elegant ideas such as string theory come out the woodwork. Some believe that physics is simply missing an extremely fundamental aspect or system of reality as a whole.