Exploring Gauge Theories with Adjoint Matter on the Lattice
Round 1
Reviewer 1 Report
I do not have any suggestions to the authors, they have presented their work in a clear form.
Author Response
We thank the referee for comments and consideration of the article.
Reviewer 2 Report
The authors have produced a valuable review of their work on lattice gauge theories with adjoint fermions. They review as well the work of others, covering a long time span and culminating in the latest results. The review can be handed to new students as an entry into the field.
The paper is well written in good English. Nonetheless I allow myself four comments about style:
1. The last sentence of the abstract is incoherent. It needs to be rewritten.
2. The paragraph beginning on line 113 ("Precise signals...") is unnecessarily obscure. The authors should consider the reader who is wondering why PQChPT has suddenly made an appearance. Likewise the discreteness of the chiral symmetry is a puzzle until Sec. 2.2. In general, the complete lack of equations in Sec. 2 makes it more difficult than it needs to be for the untutored reader.
3. The sentence ending Sec. 2 (lines 320-321) makes no sense.
4. The first sentence of Sec. 5 is awkward. That paragraph should be rewritten.
Author Response
We thank the referee for his comments and careful consideration of the article. We have adjusted the article accordingly. The changes are listed below.
1. The last sentence of the abstract is incoherent. It needs to be rewritten.
The sentence has been rewritten:
They also play an important role in uncovering fundamental properties of strongly interacting theories due to distinct features like a substantially different phase diagram.
2. The paragraph beginning on line 113 ("Precise signals...") is unnecessarily obscure. The authors should consider the reader who is wondering why PQChPT has suddenly made an appearance. Likewise the discreteness of the chiral symmetry is a puzzle until Sec. 2.2. In general, the complete lack of equations in Sec. 2 makes it more difficult than it needs to be for the untutored reader.
conserved axial current relations. In SYM, chiral symmetry is broken to a discrete subgroup
only (see sect. 2.2), and the theory doesn't contain pseudo-Goldstone bosons. It is, however,
possible to define an unphysical pion in partially quenched chiral perturbation theory [12].
Its correlation function is given by the fermion-connected part of the correlation function of
the pseudoscalar gluino-ball, and can be measured numerically. From its decay with distance
the so-called adjoint pion mass is obtained, whose vanishing represents a signal of chiral
symmetry. The adjoint pion mass is an easily measurable quantity that can be employed for
tuning to the chiral limit. This approach is not ideal since it relies on an unphysical particle.
As an alternative, the supersymmetric Ward identities can be used to determine the chiral limit.
We have checked that the tuning by means of the adjoint pion mass is consistent with an
approach using the supersymmetric Ward identities [13]. Yet another signature for chiral
symmetry and its breaking is the histogram of the chiral condensate, which will be discussed
in more detail below. For practical purposes, the difference between these tuning signals does
not play a major role. We have confirmed that they all lead (within the uncertainties) to a
consistent picture, which means that possible differences disappear in the continuum limit.
3. The sentence ending Sec. 2 (lines 320-321) makes no sense.
We have changed the whole paragraph:
"Compactified theories with adjoint fermions can also be seen as an extension of the Hosotani mechanism ...."
into:
Compactified theories with adjoint fermions are also considered in the context of the Hosotani mechanism, and extensions towards the non-perturbative domain have been the motivation for numerical investigations of these theories in [53]. In these studies a larger number of fermions than in SYM and a staggered fermion discretization has been chosen, which makes it hard to compare with our results. A confined regime at small compactification radius has been observed. In contrast to the SYM, this confined regime at small radius is never connected to the large radius confined regime in the investigated parameter range. There seems to be always a deconfined intermediate phase between the two confined phases instead of a continuity.
4. The first sentence of Sec. 5 is awkward. That paragraph should be rewritten.
We have changed the whole paragraph:
"Extensions of the Standard Model with an additional strongly interacting sector can be considered in a more general context ...."
into:
Extensions of the Standard Model with an additional strongly interacting sector coupled tothe electroweak/Higgs sector have been considered in order to find more natural
explanations of the Higgs mass. This has been one the motivations for supersymmetric
and composite Higgs theories. Such extensions of the Standard Model can, however,
be considered in a more general context. For example, another application is to find a
strongly interacting theory ...
Reviewer 3 Report
The article reviews lattice simulations of gauge theories with matter fields in the adjoint representation of the gauge group. These are strongly interacting theories which have a gluon sector just like the familiar theory of strong interactions, QCD. The discussed theories include supersymmetric theories as well as other strongly interacting models which can be of relevance to the electroweak symmetry breaking.
The article is well written and I can recommend it for publication.
Author Response
We thank the referee for comments and consideration of the article, in particular regarding the relevance of this work.
