How does QFT explain the world around us?

[jlcd]

In molecules, the system (say dna or ribosomes) environment are the cells.. id like to know how much is the momentum basis selected and how this can affect the molecules energies and to what extend and actual examples of that in this internal human body decoherence scenerio. Thank you.

 

[bhobba]

id like to know how much is the momentum basis selected

I would say not at all. Most interactions, and that certainly would be the interactions in a cell, are radial in nature (ie have rotational symmetry) and it is well known that singles out the position basis.

Singling out the momentum basis is pretty much a contrived thing - not occurring naturally.

Thanks
Bill

 

[jlcd]

I would say not at all. Most interactions, and that certainly would be the interactions in a cell, are radial in nature (ie have rotational symmetry) and it is well known that singles out the position basis.

Singling out the momentum basis is pretty much a contrived thing - not occurring naturally.

Thanks
Bill

Could you give an example of inducing a molecular system to choose momentum basis? What would be the effect of it? Can it make the molecular have more kinetic energy?

 

[bhobba]

Could you give an example of inducing a molecular system to choose momentum basis?

I have zero idea how to do that.

The only momentum outcomes I know of are contrived where you have a set-up designed to measure momentum.

Thanks
Bill

 

[jlcd]

I have zero idea how to do that.

The only momentum outcomes I know of are contrived where you have a set-up designed to measure momentum.

Thanks
Bill

Can you give example of a simple quantum system where the momentum is measured.. and does it mean the system has no position or localization? Or does momentum measurement also involve position?

 

[bhobba]

Can you give example of a simple quantum system where the momentum is measured.

Sure. Run an electron beam through a magnet an the circular path gives you the momentum. And no I can't really think of others - you will need to chat to an experimental type.

Thanks
Bill

 

[jlcd]

Sure. Run an electron beam through a magnet an the circular path gives you the momentum. And no I can't really think of others - you will need to chat to an experimental type.

Thanks
Bill

Does this this running electron beam through a magnet an the circular path giving the momentum also give the position? Or is there no localization?

For molecules. Giving it more kinetic energy or even causing electron transitions is still related to position basis or momentum?

 

[jlcd]

added: but momentum is supposed to be the energy of the atom.. so I thought giving it more kinetic energy means it is momentum related...

 

[bhobba]

Does this this running electron beam through a magnet an the circular path giving the momentum also give the position?

Of course not - how does it tell the position of any electron in the beam.

Thanks
Bill

 

[bhobba]

added: but momentum is supposed to be the energy of the atom..

It isn't. That's really basic classical physics.

Thanks
Bill

 

[jlcd]

It isn't. That's really basic classical physics.

Thanks
Bill

http://chemwiki.ucdavis.edu/Physica...nics/10:_Multi-electron_Atoms/Quantum_Numbers

"The Orbital Angular Momentum Quantum Number (l'>l l )
The orbital angular momentum quantum number l determines the shape of an orbital, and therefore the angular distribution. The number of angular nodes is equal to the value of the angular momentum quantum number l'>l"

Mr. Hobba. The orbital angular momentum still use the position basis?? Then what is the momentum basis about?

 

[bhobba]

Mr. Hobba. The orbital angular momentum still use the position basis?? Then what is the momentum basis about?

Operators are basis independent, as are states.

Sometimes the momentum basis is better for solving problems than the position basis - mostly the wave-function which is a state expanded in terms of the position basis is used, but sometimes its better to use the momentum basis - especially in Quantum Field Theory.

Thanks
Bill

 

[jlcd]

Operators are basis independent, as are states.

Sometimes the momentum basis is better for solving problems than the position basis - mostly the wave-function which is a state expanded in terms of the position basis is used, but sometimes its better to use the momentum basis - especially in Quantum Field Theory.

Thanks
Bill

In QFT.. there is no position.. so no position basis is used.. but how come chairs and tables based on QFT (and momentum basis) has position and localizations?

 

[bhobba]

In QFT.. there is no position.. so no position basis is used..

What makes you say that?
http://arnold-neumaier.at/physfaq/topics/positionQFT

Normal QM is the 'dilute' limit of QFT - the following gives the detail:
https://www.amazon.com/dp/9812381767/?tag=pfamazon01-20

No one in their right mind would attempt to use QFT to explain the world around us.

Thanks
Bill