Tagged Questions
3
votes
1answer
61 views
Four-gauge-boson vertex in non-Abelian gauge theories
In Peskin & Schroeder's book page 524, the following diagram is calculated for the gauge boson self-energy in order $g^2$:
In dimensional regularization, its contribution is given by
...
4
votes
1answer
147 views
Yang-Mills instanton
How can instanton solution to Yang-Mills theory with gauge group $SU(3)$ or $SU(N)$ be obtained? For $SU(2)$ it is explained in textbooks but what about more general color gauge groups?
EDIT: How ...
2
votes
0answers
24 views
Holomorphic coupling as a source for gaugino condensation
On the top of page 23 of hep-th/03061119, it is pointed out that treating the holomorphic gauge coupling $\tau$ as a background (spurion) superfield allows one to think of its $F$-term, $F_\tau$ as ...
6
votes
1answer
76 views
Do instantons support quantum bound states?
When one quantizes a scalar in the 1+1 dimensions in the kink background of a double well potential, one finds a spectrum that includes: (1) a zero mode corresponding to the classical particle ...
2
votes
1answer
96 views
Moose Models (Purpose, Examples)
A problem set for my QFT class is titled "Moose Models" and deals with the moose model for a gauge symmetry of $U(1)\times U(1)$. I was wondering if I could get an explanation of what a Moose Model ...
6
votes
1answer
247 views
Why is color conserved in QCD?
According to Noether's theorem, global invariance under $SU(N)$ leads to $N^2-1$ conserved charges. But in QCD gluons are not conserved; color is. There are N colors, not $N^2-1$ colors. Am I ...
10
votes
2answers
348 views
Gauge invariance and diffeomorphism invariance in Chern-Simons theory
I have studied Chern-Simons (CS) theory somewhat and I am puzzled by the question of how diff. and gauge invariance in CS theory are related, e.g. in $SU(2)$ CS theory. In particular, I would like to ...
6
votes
2answers
198 views
Chern-Simons degrees of freedom
I'm currently reading the paper http://arxiv.org/abs/hep-th/9405171 by Banados. I am just getting acquainted with the details of Chern-Simons theory, and I'm hoping that someone can explain/elaborate ...
4
votes
0answers
36 views
axial and vector resonances in composite higgs models
Is there a reason to believe that the axial resonances be heavier than the vector resonances in the composite higgs models?
For instance, in http://arxiv.org/abs/0808.2071, to have zero tree level ...
0
votes
1answer
102 views
Interaction potential analysis from $\phi^4$ model
In this paper, the authors consider a real scalar field theory in $d$-dimensional flat Minkowski space-time, with the action given by
$$S=\int d^d\! x ...
5
votes
2answers
197 views
Why is the Yang-Mills gauge group assumed compact and semi-simple?
What is the motivation for including the compactness and semi-simplicity assumptions on the groups that one gauges to obtain Yang-Mills theories? I'd think that these hypotheses lead to physically ...
1
vote
0answers
48 views
Do Boundary Conditions depend on spin connections for gauge fields?
In the article arXiv:1206.5642, which talks about gauge fields in conical spacetime, I came across the statement in footnote 4 that the boundary conditions on the gauge field depend on the spin ...
2
votes
1answer
118 views
Construction of the supersymmetric Faraday tensor
When I first learned gauge theories in my introductory quantum field theory course, I was taught that the Faraday (field-strength) tensor can be constructed by computing the commutator of the ...
5
votes
2answers
231 views
Geometrical significance of gauge invariance of the QED Lagrangian
The QED Lagrangian is invariant under
$\psi(x) \to e^{i\alpha(x)} \psi (x)$, $A_{\mu} \to A_{\mu}- \frac{1}{e}\partial_{\mu}\alpha(x)$. What is the geometric significance of this result? Also why is ...
0
votes
0answers
27 views
Good Books on Gauge Theory [duplicate]
Possible Duplicate:
Comprehensive book on group theory for physicists?
I'm having a hard time trying to get my head around the fundamentals of gauge theory. I've taken classes in QFT and ...
3
votes
1answer
190 views
Local and Global Symmetries
Could somebody point me in the direction of a mathematically rigorous definition local symmetries and global symmetries for a given (classical) field theory?
Heuristically I know that global ...
3
votes
0answers
162 views
About the gauge invariance of Chern-Simons' theory (in local coordinates)
I am aware of the differential form language proof of the fact that for arbitrary gauge transformations the Chern-Simons' term shifts by a WZW term (on the boundary).
But I am getting confused if ...
3
votes
0answers
110 views
Gauge-invariance of pole mass using Ward Identity
I am able to explicitly verify to one-loop order that pole masses are independent of the choice of gauge paramter.
But how do I use the Ward-Identity/Taylor-Slavnov identity show that the position of ...
5
votes
1answer
330 views
Faddeev-Popov ghost propagator in canonical quantization
Obtaining the propagator for the Faddeev-Popov (FP) ghosts from the path integral language is straightforward. It is simply
$$\langle T(c(x) \bar c(y))\rangle~=~\int\frac{d^4 p}{(2\pi)^4}\frac{i ...
0
votes
0answers
37 views
Taylor-Slavnov Identity in spontaneously broken gauge theories
Where can I find a list of important Taylor-Slavnov identities in Spontaneously broken gauge theories? I am looking for not just the generating functional form, but rather a list of explicit ones ...
2
votes
0answers
29 views
What is the physical meaning of the higher order structure functions in the BRST quantization of open algebras?
What is the physical meaning of the higher order structure functions in the BRST quantization of open algebras? As opposed to formal algebraic manipulations.
Thanks.
4
votes
2answers
264 views
Gauge fixing and equations of motion
Consider an action that is gauge invariant. Do we obtain the same information from the following:
Find the equations of motion, and then fix the gauge?
Fix the gauge in the action, and then find the ...
2
votes
3answers
129 views
Quantizing first-class constraints for open algebras: can Hermiticity and noncommutativity coexist?
An open algebra for a collection of first-class constraints, $G_a$, $a=1,\cdots, r$, is given by the Poisson bracket $\{ G_a, G_b \} = {f_{ab}}^c[\phi] G_c$ classically, where the structure constants ...
2
votes
0answers
92 views
Pseudo scalar mass and Pure scalar mass
Since the only difference between pseudo scalar and a scalar term is just a change of sign under a parity inversion, is it possible that both of them be present in the same field and interact?
For ...
4
votes
2answers
267 views
Intuition for gauge parallel transport (Wilson loops)
I'm looking for a geometrical interpretation of the statement that "Wilson loop is a gauge parallel transport".
I have seen QFT notes describe U(x,y) as "transporting the gauge transformation", and ...
2
votes
1answer
144 views
For nonabelian Yang-Mills in the Coulomb phase, can soft gluons render the charge orientation of charged particles indefinite?
For nonabelian Yang-Mills in the Coulomb phase, can soft gluons render the charge orientation of charged particles indefinite? Let's say the gauge group is a nonabelian simple Lie group G. Suppose ...
2
votes
0answers
108 views
Derivation of the enhancement of U(1)$_L$ x U(1)$_R$ to SU(2)$_L$ x SU(2)$_R$ at the self-dual radius
Towards the end of the paragraph with the title String theory's added value 2: enhanced non-Abelian symmetries at self-dual radii and abstract C with current algebras of this article, it is explained ...
2
votes
1answer
207 views
Wilson loops and gauge invariant operators (Part 2)
These questions are sort of a continuation of this previous question.
I would like to know of the proof/reference to the fact that in a pure gauge theory Wilson loops are all the possible gauge ...
5
votes
3answers
358 views
Gauge fixing choice for the gauge field $A_0$
In many situations, I have seen that the the author makes a gauge choice $A_0=0$, e.g. Manton in his paper on the force between the 't Hooft Polyakov monopole.
Please can you provide me a ...
2
votes
1answer
256 views
Wilson loops and gauge invariant operators (Part 1)
I guess the Hilbert space of the theory is precisely the space of all gauge invariant operators (mod equations of motion..as pointed out in the answers)
Is it possible that in a gauge theory the ...
5
votes
1answer
305 views
Taking the continuum limit of $U(N)$ gauge theories
I would like to draw your attention to appendix $C$ on page 38 of this paper.
The equation $C.2$ there seems to be evaluating the sum $\sum_R \chi _R (U^m)$ in equation 3.16 of this paper. I ...
2
votes
1answer
125 views
Is there any good gauge-fixing prescription for discrete gauge symmetries?
Nearly all gauge-fixing prescriptions are based upon setting some function involving the gauge fields to be zero. That function is continuous and varies over the real/complex numbers. Trying the same ...
2
votes
1answer
68 views
How do we deal with Gribov ambiguities when calculating in quantum gauge theories?
How do we deal with Gribov ambiguities when actually calculating in quantum gauge theories? Any literature references?
3
votes
1answer
178 views
Using the covariant derivative to find force between 't Hooft-Polyakov magnetic monopoles
I am reading this research paper authored by NS Manton on the Force between 't Hooft-Polyakov monopoles. I have a doubt in equation 3.6 and 3.7. We assume the gauge field for a slowly accelerating ...
3
votes
1answer
317 views
Noether current for the Yang-mills-higgs lagrangian
I am trying to calculate the Noether's current, more specifically, the energy density of the Yang-mills-Higgs Lagrangian. Please refer to the equations in the Harvey lectures on Magnetic Monopoles, ...
3
votes
2answers
404 views
What is the ontological status of Faddeev Popov ghosts?
We all know Faddeev-Popov ghosts are needed in manifestly Lorentz covariant nonabelian quantum gauge theories. We also all know they decouple from the rest of matter asymptotically, although they ...
5
votes
2answers
321 views
Winding number in the topology of magnetic monopoles
I am reading on magnetic monopoles from a variety of sources, eg. the Jeff Harvey lectures.. It talks about something called the winding $N$, which is used to calculate the magnetic flux. I searched ...
5
votes
0answers
75 views
How do you simulate a quantum gauge theory in a gauge with negative norms on a quantum computer?
How do you simulate a quantum gauge theory in a gauge with negative norms on a quantum computer? There are some gauges with negative norms. It's true that if restricted to gauge invariant states, the ...
2
votes
0answers
240 views
The meaning of Goldstone boson equivalence theorem
The Goldstone boson equivalence theorem tells us that the amplitude for emission/absorption of a longitudinally polarized gauge boson is equal to the amplitude for emission/absorption of the ...
4
votes
1answer
156 views
Gauge symmetry description for $\phi^4$?
That is a follow-up to this question: Gauge symmetry is not a symmetry?
Ok, gauge symmetry is not a symmetry, but ...
... a redundancy in our description, by introducing fake degrees of freedom ...
7
votes
0answers
189 views
How to determine if an emergent gauge theory is deconfined or not?
2+1D lattice gauge theory can emerge in a spin system through fractionalization. Usually if the gauge structure is broken down to $\mathbb{Z}_N$, it is believed that the fractionalized spinons are ...
1
vote
1answer
485 views
Yukawa Coupling of a Scalar $SU(2)$ Triplet to a Left-Handed Fermionic $SU(2)$ Doublet
Suppose we have a field theory with a single complex scalar field $\phi$ and a single Dirac Fermion $\psi$, both massless. Let us write $\psi _L=\frac{1}{2}(1-\gamma ^5)\psi$. Then, the Yukawa ...
0
votes
0answers
43 views
How to have quark condensation, gaugino condensation, ghost condensation, and gluon condensation?
For each of those condensation process to happen, what special conditions should
Are there any other condensations from elementary fields?
What are the significances/effects of each condensation?
...
3
votes
2answers
327 views
The Faddeev-Popov Lagrangian
This is a non-abelian continuation of this QED question.
The Lagrangian for a non-abelian gauge theory with gauge group $G$, and with fermion fields and ghost fields included is given by
$$
...
6
votes
4answers
587 views
What's the distinctions between Yang-Mills theory and QCD?
So Yang-Mills theory is a non-abelian gauge theory, and we used a lot in QCD calculation.
But what are the distinctions between Yang-Mills theory and QCD?
And distinctions between supersymmetric ...
3
votes
1answer
247 views
QED BRST Symmetry
This is a homework problem that I am confused about because I thought I knew how to solve the problem, but I'm not getting the result I should. I'll simply write the problem verbatim:
"Consider QED ...
2
votes
2answers
74 views
Gauge invariant scalar potentials
If $\Phi$ is a multi-component scalar field which is transforming in some representation of a gauge group say $G$ then how general a proof can one give to argue that the potential can only be a ...
4
votes
1answer
184 views
Gauge invariance and the form of the Rarita-Schwinger action
in Weinberg Vol. I section 5.9 (in particular p. 251 and surrounding discussion), it is explained that the smallest-dimension field operator for a massless particle of spin-1 takes the form of a field ...
3
votes
1answer
177 views
SU(2) yang-mills EOM
I'm just playing around tonight trying to better myself, but I'm having trouble with some indices on my yang-mills lagrangian. I have a gauge group $SU(2)$ and a field strength tensor
$$ ...
5
votes
1answer
212 views
Can a photon see ghosts?
Does it make sense to introduce Faddeev–Popov ghost fields for abelian gauge field theories?
Wikipedia says the coupling term in the Lagrangian "doesn't have any effect", but I don't really know ...
