All Questions
Tagged with quantum-chromodynamics lattice-model
27
questions
7
votes
1
answer
217
views
What makes lattice QCD computationally tractable?
I don't know anything about lattice QCD. Therefore, at first glance it seems to me that lattice QCD should be computationally intractable for all practical purposes.
Let's assume that we only care ...
- 6,611
0
votes
1
answer
119
views
How to write a naive Dirac matrix for Lattice QCD?
I'm trying to write down the naive Dirac matrix (with fermion doubling) for a LQCD simulation with one quark, for now. I initialized the $SU(3)$ gauge field and the quark field. The quak field has 4 ...
- 31
4
votes
1
answer
266
views
Real time lattice simulation
A typical simulation of lattice quantum chromodynamics uses imaginary time, so the weight function of the path integral is positive definite $e^{-S_E}$.
In the case of metropolis-hastings, the ...
- 343
0
votes
1
answer
116
views
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 ...
6
votes
1
answer
486
views
Lattice spacing in lattice QCD
It is known that the lattice spacing in lattice QCD is not an external parameter and needs to be calculated, also the lattice beta parameter scales the lattice spacing ($a$) and goes as a function of ...
- 343
3
votes
1
answer
1k
views
Recommend books for learning lattice QCD
I want to learn lattice QCD by myself, but I don't know how to start. Can you recommend some books for lattice QCD?
2
votes
1
answer
75
views
Are gravitons equivalent to extra localised lattice points?
So imagine space is a regular square mesh or lattice. In a theory like QCD, the photon lines are placed along the edges of this graph to form paths.
The space is supposed to represent simple ...
user84158
1
vote
0
answers
58
views
Is is cheating to use alpha strong (instead of V_QCD) to argue that there is asymptotic freedom of QCD?
For asymptotic freedom of QCD, people give the argument that alpha_strong decreases at high energy (thus there is freedom at low distance).
But if we make the reasoning on the QCD potential, for ...
1
vote
2
answers
459
views
Is the QCD potential really monotonic ? How does it prevent two quarks from meson to annihilate?
The QCD potential is made of two terms
-(4/3) * alpha_s / r
that describes the short distance
and
the term
+k*r
that describes the long distance
Of course, alpha is a function of energy, so it is ...
5
votes
1
answer
168
views
Temperature-dependence of quark potential in Abelian lattice gauge theory
I am working with Kapusta's "Finite-Temperature Field Theory" textbook, and am working through the first part of chapter 10. When building the correlator of the two quarks a distance $R$ apart in the ...
- 2,665
2
votes
0
answers
126
views
Questions on how Wilson loops relate to field & charge conservation, and lattice QFT
The path-ordered exponential from which the Wilson loop is traced is, crudely,
$$ \prod (I+ A_\alpha dx^\alpha) = \mathcal{P}\,\mathrm{exp}(i \oint A_\alpha dx^\alpha )$$
which returns a matrix $\...
- 970
3
votes
1
answer
171
views
What is the effect of including additional representations in the action of a lattice gauge theory?
I'm reading Introduction to Quantum Fields on a Lattice by Jan Smit. When introducing the lattice gauge-field action as a sum over plaquettes, Smit says that in general the action should include a sum ...
- 223
0
votes
1
answer
681
views
Computation of String Tension in Lattice QCD
There is a quantity called String Tension in lattice QCD calculation.
How is this quantity (String Tension) defined and computed in Lattice QCD? Are there some useful formulas to define it both in ...
- 4,336
0
votes
0
answers
85
views
Instanton effects on condensates: (pseudo)scalars, (pseudo)vectors, tensor
I have heard that the instanton effect in quark matter causes the di-quark condensate to be Lorentz scalar. As opposed to the Lorentz scalar, there are possibilities that the condensates are Lorentz ...
- 4,336
5
votes
1
answer
543
views
Is quark and gluon orbital angular momentum predicted to have the rest of the proton's spin?
The Phys.org news item How did the proton get its spin? outlines various experiments that probe proton structure and are sensitive to spin, and the current news is that CEBAF's major energy upgrade ...
- 6,273
14
votes
2
answers
2k
views
Why Does Lattice QCD Use Heavier Than Physical Masses For Calculations?
It is common place (e.g. here), for Lattice QCD calculations to be computed using reference masses (such as the pion mass) which are greater that the physical values of those quantities.
Sometimes, ...
- 3,957
5
votes
1
answer
269
views
What observable is visualized in lattice QCD visualizations?
I have seen a couple of visualizations of lattice QCD, for instance the images by Derek Leinweber. Using my own data I would like to make similar visualizations. I am just not sure what I actually see ...
- 8,439
1
vote
1
answer
269
views
Lattice QFT: Non-homogenous lattice spacing
I am interested why we fix the lattice spacing, $a$ to be homogenous in all dimensions. After a Wick rotation, $a=i \epsilon$ where $\epsilon=t_{i+1} - t_{i}$ and with euclidean time given by $\tau = ...
5
votes
1
answer
223
views
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
1
vote
0
answers
55
views
Obtaining the correlator of harmonic oscillator
The two point function for harmonic oscillator can be written as
$$\langle \langle x(t_1)x(t_2) \rangle \rangle =\frac{\int Dx(t) x(t_1)x(t_2) e^{-S(x)}}{\int Dx(t) e^{-S(x)}} \tag{21} \, .$$
In ...
- 185
0
votes
1
answer
125
views
How to calculate thd average of a Wilson loop in LQCD?
I'm am trying to do the excercise in page 35 from Lepage's LQCD notes: http://arxiv.org/abs/hep-lat/0506036.
I want to compute the thermal average of the Wilson loop of size $a\times a$, where $a$ is ...
- 12.5k
3
votes
3
answers
151
views
Are there new physics scenarios that predict low lying hadrons?
There is a significant ongoing experimental effort to search for new hadrons with masses in the GeV range. This is used to find the spectra of QCD bound states, with a particular emphasis on finding ...
- 8,995
1
vote
1
answer
195
views
Is it possible to calculate neutron half-life theoretically?
Is it possible to calculate neutron half-life theoretically? For example, from lattice QCD or something?
- 1,732
4
votes
1
answer
235
views
Has confinement been experimentally observed? [closed]
So, confinement has obviously been shown by lattice gauge theory to be a predicted aspect of QCD. However, to what extent has it been observed in experimental physics?
- 169
1
vote
1
answer
75
views
Construction of Bound states in Lattice QCD
How the proton state is found and renormalized in lattice QCD? Is there any literature shows the method step by step? What about other bound states in QCD if we somehow know their quantum numbers?
- 631
9
votes
0
answers
368
views
Lattice QCD and the 5th dimension
I was digging into the Nielsen-Ninomiya Theorem and doubler fermions, as well as solutions to these problems using Domain Wall Fermions and overlap lattice fermions, both of which make effective use ...
- 99
4
votes
1
answer
1k
views
Lattice QCD and string theory
I've heard the claim that some aspects of string theory are used to improve Monte-Carlo simulations of lattice QCD, for example by people working at the LHC.
I know a bit about Monte-Carlo methods in ...
- 3,735