All Questions
Tagged with quantum-chromodynamics non-perturbative
30
questions
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Why is it justified to focus on gauge transformations constant at spatial infinity in QCD instantons?
In the context of Yang-Mills theories and QCD instantons, much of the literature and conventional treatment hinges on the consideration of gauge transformations that remain constant at spatial ...
- 841
2
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1
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257
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Why does non-perturbative QCD need to be regularized and renormalized?
The $n$-point correlation functions of QCD, which define the theory, are computed by performing functional derivatives on $Z_{QCD}[J]$, the generating functional of QCD,
$$\frac{\delta^nZ_{QCD}[J]}{\...
- 353
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1
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215
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How does AdS/CFT help us understand non-perturbative aspects of QCD?
I've heard AdS/CFT has found applications in many areas of physics where nonperturbative aspects leave us crippled in making any simple calculations.
Among these applications, I also have heard that ...
- 1,268
2
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1
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Non-perturbative approach to high-energy physics
I know that main numerical approach to modeling high-energy physics events are Monte-Carlo event generators. But they are using perturbative description of collision and decay processes of particles.
...
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268
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Why is the chiral condensate a negative quantity?
The chiral condensate serves as an order parameter for the chiral phase transition. Thus, it is a finite quantity in one phase and vanishes in the other phase. It is given as a vacuum expectation ...
- 457
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Is QCD parity conserving also non-perturbatively?
Since QCD is fundamentally non-perturbative at low energies one may ask if QCD is still Parity conserving. In the path-integral formalism using the Faddeev–Popov ghosts as gauge fixing terms the ...
- 183
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1
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What are some good resources to learn about perturbative and non-perturbative approaches to QCD, for example Lattice QCD, at an introductory level?
I am writing at an introductory level about the anomalous magnetic moment of the muon and part of that is the subsequent Lattice QCD that potentially verifies the results from the experiments that ...
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Physical interpretation of hadron distribution amplitudes
A parton fragmentation function can be interpreted as the probability that a final state hadron originated from that particular hadron.
A parton distribution function can be interpreted as the ...
- 391
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$SU(2)$ gauge SUSY with Affleck-Dine-Seiberg term
Consider SUSY gauge theory with $SU(2)$ group and matter fields $Q$ and $\bar{Q}$ in fundamental and anti-fundamental representations correspondently and the following superpotential:
$$W=\frac{{\...
- 93
5
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3
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740
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How is $\Lambda_{\textrm{QCD}}$ relevant in the non-perturbative regime?
The famous $\Lambda_{\textrm{QCD}}$ parameter enters through the one-loop running of the QCD coupling, through a relation similar to the following:
$$\alpha_S(Q^2)=\frac{\alpha_S(Q^2_0)}{1+b\ln(Q^2/Q^...
- 5,371
2
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QCD generating functional and QCD vacuum from nonperturbative to perturbative regime!
The complete generating functional in QCD (starting from the most general renormalizable, Lorentz invariant and gauge invariant Lagrangian) given by $$Z_\theta[J]=\int \mathcal{D}A \exp i\int d^4x~ {\...
- 26.8k
8
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What's the difference between perturbative QCD, non-perturbative QCD, and gauge theory QCD?
I'm trying to get the ideal of QCD, and it turns out that there seems to be several versions, and some of which does not appear to agree with each other at a glance.
What's the difference, and how ...
- 3,256
3
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1
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485
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Why is lattice QCD called non-perturbative?
Like, if you are approximating a smooth structure with a discrete lattice, isn't this like a perturbation from smooth space-time?
If Feynman diagrams are a perturbative method, why are Feynamn ...
user84158
8
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Question about the vacua of the Standard Model
This question is probably based on a misunderstanding. Please correct me if I'm wrong, and if unclear, I'll try to put it in a clearer language.
In Yang-Mills theory such as the theory of strong ...
- 26.8k
0
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1
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Non-Perturbative effects QCD and the Standard Model?
I read in an article that the Standard Model leaves unanswered questions about the non-perturbative effects of the QCD.
I have basic knowledge about the perturbative and non-perturbative QCD. Could ...
- 215
5
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2
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Are perturbative and non-perturbative QCD both signs of new physics?
I was studying about quarkonia systems and reached this page at CERN Courier. Here, I came across the following text:
While the failure to reproduce an experimental observable that is ...
- 4,954
3
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1
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Is the non-perturbative approach to QFT a path integral approach? If so then how, given we don't have simple path integral formula for Dirac equation?
Here is my understanding of the scenario. Please correct me if i go wrong somewhere.
Initially, the perturbative approach to QED (Feynman diagrams) was very successful. But the same approach to QCD ...
- 2,326
7
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1
answer
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Why is the temporal gauge $A_0=0$ so popular in discussions of non-perturbative effects?
Almost every discussion of non-perturbative effects in Yang-Mills theory mentions in passing that they work in the temporal gauge. Why is this the case?
A good example is the QCD vacuum. Almost ...
- 10.1k
4
votes
2
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389
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Reference request for non-perturbative QCD
I am looking for some good books or lecture notes that discuss non-perturbative aspects of QCD such as: chiral symmetry and chiral symmetry breaking; the QCD phase transition and the QCD phase diagram;...
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Perturbative coupling for QFT
I'm confused about the definition of a perturbative coupling for QFT that it should be less than 4 $\pi$, because the higher order corrections comes of order $\lambda/(4 \pi)$ ..
Now why QCD is not ...
- 453
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1
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Is CP problem the problem?
I've heard an argument that the question of smallness of QCD $\theta$ parameter is called the problem (namely, strong CP problem), since the other dimensionless couplings (like $\alpha_{s}$), are of ...
- 8,901
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Some questions about QCD [closed]
About QCD, I have two questions. I know I should propose one question one time, but they are actually two steps of the same question: Non-perturbative aspects of QCD.
1, Why do we need to solve QCD ...
- 3,691
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Does an instanton couple equally to all flavors?
Do gravitational / electroweak / QCD / ... instantons couple equally to all fermion flavors? For example, do QCD instantons distinguish between the different quark flavors?
Edit, due to comment (...
- 1,783
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1
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223
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Continuum of lattice QCD is free?
I am having a hard time getting to grips with the statement that
$$g_{0}(a) \to 0 \text{ as } a \to 0$$
where $g_{0}$ is the bare coupling in lattice QCD and $a$ the lattice spacing.
How come this ...
- 609
2
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1
answer
240
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Topological susceptibility in QCD and corresponding pole
The topological susceptibility in QCD (here I've used path integral approach, and hence I will neglect all contact terms) is defined as
$$
\kappa (p) \equiv \lim_{y \to 0}\int d^{4}x e^{ip(x-y)}Q(x)Q(...
- 8,901
2
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1
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954
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complicated QCD Color factor formula?
I was doing higher order calculations for purely gluonic system and came across complicated color factors like the product of six structure constants product $f_{a_1a_2a_3}f_{a_4a_2a_7}f_{a_7a_8a_1}f_{...
- 21
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322
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Why is QCD hard to solve if I know the beta functions?
Why is it still hard to solve QCD if we know the beta functions of the coupling? Aren't only the loops causing problems? And am I not able to write every possible interaction exact at tree-level with ...
- 2,147
2
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0
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40
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Decay of some particle involved quarks vs mesons as outgoing states
Let's have decay width of some mother particle into the state which involves hadrons. For simplicity, let's assume that creation of hadrons (on diagram) is possible only through electroweak vertices (...
- 8,901
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QCD in the non-perturbative regime
In the list of unsolved problems in physics.
Confinement: the equations of QCD remain unsolved at energy scales relevant for describing atomic nuclei. How does QCD give rise to the physics of nuclei ...
- 441
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What constitutes a 'reliable' instanton calculation?
In Modern Supersymmetry, John Terning, on pgs 151, and 153 performs a so called 'reliable' instanton calculation when dealing with the ADS superpotential 'since the gauge group is completely broken'. ...
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