Register to reply 
Classical and quantum fields 
Share this thread: 
#1
May1414, 05:36 PM

P: 86

In QFT, all particles can be interpreted as excitations of some fundamental quantum fields in the vacuum. This is the quantum picture. But in classical world, only photons and gravitons have classical counterparts. How to explain this? The common feature of these two is that they are intermediate particles of longrange interactions. But This is far from satisfactory to me. So I was wondering whether there is a deeper and better explanation of this problem.



#2
May1414, 05:59 PM

P: 846

Roughly speaking, quantum fields look like classical waves when there are many particles in the same state. So classical electromagnetic waves are states of many photons and classical gravitational waves are states of many gravitons.
Fermion fields don't have any states that look classical, because you cannot put more than one fermion in the same state. So there is no classical analog of the electron field. The W, Z, and Higgs fields are bosonic but they never look classical because these bosons all decay long before you could hope to construct a state containing lots of them. (This is pretty much the same thing as saying that they don't mediate longrange interactions.) The gluon field undergoes confinement and so there aren't actually any states that look like gluons, let alone states with many coherent gluons. There are only hadrons and glueballs. 


#3
May1414, 09:16 PM

Sci Advisor
HW Helper
PF Gold
P: 1,991




#4
May1514, 02:38 AM

P: 86

Classical and quantum fields



#5
May1514, 03:03 AM

C. Spirit
Sci Advisor
Thanks
P: 5,447




#6
May1514, 10:42 PM

P: 86

If there is no test particle, where do the scalar and longitudinal modes end? 


Register to reply 
Related Discussions  
How classical fields, particles emerge from quantum theory  Quantum Physics  0  
Relations between classical and quantum timeevolution of fields  Quantum Physics  27  
Classical and quantum fields  Quantum Physics  3  
Quantum to classical transition or classical limit ?  Quantum Physics  0  
Classical fields and quantum fields  Quantum Physics  11 