Running Coupling: QF Theory, Asymptotic Freedom & RG Law

In summary, the process of renormalization in QF theory introduces a renormalization scale μ, but physical quantities do not depend on it due to the RG law. However, the physics can still change significantly along the RG trajectory, such as in the case of asymptotic freedom in QCD where the unphysical (μ,g(μ)) behavior is attributed. The μ is not meant to represent the physical energy of a process, but rather choosing it near the relevant energy scale can result in a good description of physics through perturbation theory.
  • #1
anthony2005
25
0
First a little intro.

The process of renormalization introduces in a QF theory a renormalization scale μ. Physical quantities do not depend on it, as a change of μ comes along with the change of the coupling g(μ) according to the RG law.

But why then the physics can change so drastically along the RG trajectory? For instance, why asymptotic freedom in QCD is attributed to the unphysical ( μ,g(μ) ) RG behaviour? The μ is not introduced as the physical energy of a given process.

Thanks
 
Physics news on Phys.org
  • #2
Physics changes with the physical energy scale, not with μ. But if you choose μ near the relevant physical energy scale, and g(μ) happens to be small, then low orders of perturbation theory will give a good description of physics at that physical energy scale. If not, not.
 

1. What is running coupling in QF theory?

Running coupling refers to the coupling constant in quantum field theory (QFT) that changes as a function of the energy scale. This is in contrast to the constant coupling used in classical field theory, where the coupling remains the same at all energy scales.

2. What is asymptotic freedom in QF theory?

Asymptotic freedom is a property of some quantum field theories where the coupling constant becomes weak at high energies. This means that the particles in the theory interact less strongly at high energies, allowing for more precise calculations.

3. How does the renormalization group (RG) law play a role in running coupling?

The RG law is a mathematical framework used in QFT to understand how the coupling constant changes with energy scale. It allows for the calculation of the running coupling and determines its dependence on the energy scale.

4. What is the significance of running coupling in QF theory?

Running coupling is important in QFT because it allows for more accurate predictions of particle interactions at different energy scales. It also helps to address the issue of infinities that arise in QFT calculations, as the running coupling becomes weaker at high energies.

5. Are there any experimental confirmations of running coupling and asymptotic freedom?

Yes, there have been several experimental confirmations of running coupling and asymptotic freedom, particularly in the theory of quantum chromodynamics (QCD). These experiments have shown that the coupling constant in QCD becomes weaker at high energies, supporting the idea of asymptotic freedom.

Similar threads

A Wilsonian RG and Effective Field Theories
    • High Energy, Nuclear, Particle Physics
Replies
2
Views
2K
Why is the center of mass energy linked to the parameter \mu?
    • Quantum Physics
Replies
1
Views
1K
I Is there new LHC data on coupling constant running?
    • Beyond the Standard Models
Replies
1
Views
2K
I Asymptotic safety and loop quantum gravity
    • Beyond the Standard Models
Replies
2
Views
2K
I A Bold New Take on Quantum Theory
    • Quantum Interpretations and Foundations
Replies
25
Views
992
A MOND Theory Primer: Stacy McGaugh's Research Program Explored
    • Beyond the Standard Models
Replies
11
Views
2K
A Could the 3D percolation model explain Regge-Trajectories?
    • High Energy, Nuclear, Particle Physics
Replies
4
Views
2K
B Infrared Detectors & The 2nd Law of Thermodynamics
    • Thermodynamics
5
Replies
152
Views
5K
  • Poll
Corrected third quarter 2007 M.I.P. poll
    • Beyond the Standard Models
Replies
2
Views
2K
A Falsifications and constraints due to GW measurements
    • Astronomy and Astrophysics
Replies
19
Views
4K

Hot Threads

Recent Insights

Back
Top