| Records |
| Author |
Aguilar, A.C.; Ferreira, M.N.; Ibañez, D.; Papavassiliou, J. |
| Title |
Schwinger displacement of the quark-gluon vertex |
Type |
Journal Article |
| Year |
2023 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
| Volume |
83 |
Issue |
10 |
Pages |
967 - 22pp |
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| Abstract |
The action of the Schwinger mechanism in pure Yang-Mills theories endows gluons with an effective mass, and, at the same time, induces a measurable displacement to the Ward identity satisfied by the three-gluon vertex. In the present work we turn to Quantum Chromodynamics with two light quark flavors, and explore the appearance of this characteristic displacement at the level of the quark-gluon vertex. When the Schwinger mechanism is activated, this vertex acquires massless poles, whose momentum-dependent residues are determined by a set of coupled integral equations. The main effect of these residues is to displace the Ward identity obeyed by the pole-free part of the vertex, causing modifications to its form factors, and especially the one associated with the tree-level tensor. The comparison between the available lattice data for this form factor and the Ward identity prediction reveals a marked deviation, which is completely compatible with the theoretical expectation for the attendant residue. This analysis corroborates further the self-consistency of this mass-generating scenario in the general context of real-world strong interactions. |
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no |
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yes |
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yes |
| Call Number |
IFIC @ pastor @ |
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6080 |
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| Author |
Aguilar, A.C.; Ferreira, M.N.; Ibañez, D.; Oliveira, B.M.; Papavassiliou, J. |
| Title |
Patterns of gauge symmetry in the background field method |
Type |
Journal Article |
| Year |
2023 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
| Volume |
83 |
Issue |
1 |
Pages |
86 - 20pp |
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| Abstract |
The correlation functions of Yang-Mills theories formulated in the background field method satisfy linear Slavnov-Taylor identities, which are naive generalizations of simple tree level relations, with no deformations originating from the ghost-sector of the theory. In recent years, a stronger version of these identities has been found to hold at the level of the background gluon self-energy, whose transversality is enforced separately for each special block of diagrams contributing to the gluon Schwinger-Dyson equation. In the present work we demonstrate by means of explicit calculations that the same distinct realization of the Slavnov-Taylor identity persists in the case of the background three-gluon vertex. The analysis is carried out at the level of the exact Schwinger-Dyson equation for this vertex, with no truncations or simplifying assumptions. The demonstration entails the contraction of individual vertex diagrams by the relevant momentum, which activates Slavnov-Taylor identities of vertices and multi-particle kernels nested inside these graphs; the final result emerges by virtue of a multitude of extensive cancellations, without the need of performing explicit integrations. In addition, we point out that background Ward identities amount to replacing derivatives of propagators by zero-momentum background-gluon insertions, in exact analogy to standard properties of Abelian gauge theories. Finally, certain potential applications of these results are briefly discussed. |
| Address |
[Aguilar, A. C.; Oliveira, B. M.] Univ Campinas UNICAMP, Inst Phys Gleb Wataghin, BR-13083859 Campinas, SP, Brazil, Email: aguilar@ifi.unicamp.br |
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Springer |
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English |
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1434-6044 |
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| Notes |
WOS:000923274000003 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
5481 |
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| Author |
Aguilar, A.C.; Ibañez, D.; Mathieu, V.; Papavassiliou, J. |
| Title |
Massless bound-state excitations and the Schwinger mechanism in QCD |
Type |
Journal Article |
| Year |
2012 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
| Volume |
85 |
Issue |
1 |
Pages |
014018 - 21pp |
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| Abstract |
The gauge-invariant generation of an effective gluon mass proceeds through the well-known Schwinger mechanism, whose key dynamical ingredient is the nonperturbative formation of longitudinally coupled massless bound-state excitations. These excitations introduce poles in the vertices of the theory, in such a way as to maintain the Slavnov-Taylor identities intact in the presence of massive gluon propagators. In the present work we first focus on the modifications induced to the nonperturbative three-gluon vertex by the inclusion of massless two-gluon bound states into the kernels appearing in its skeleton expansion. Certain general relations between the basic building blocks of these bound states and the gluon mass are then obtained from the Slavnov-Taylor identities and the Schwinger-Dyson equation governing the gluon propagator. The homogeneous Bethe-Salpeter equation determining the wave function of the aforementioned bound state is then derived, under certain simplifying assumptions. It is then shown, through a detailed analytical and numerical study, that this equation admits nontrivial solutions, indicating that the QCD dynamics support indeed the formation of such massless bound states. These solutions are subsequently used, in conjunction with the aforementioned relations, to determine the momentumdependence of the dynamical gluon mass. Finally, further possibilities and open questions are briefly discussed. |
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[Aguilar, A. C.] Fed Univ ABC, CCNH, BR-09210170 Santo Andre, Brazil |
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Amer Physical Soc |
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English |
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1550-7998 |
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Conference |
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| Notes |
WOS:000299293600005 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
881 |
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| Author |
Aguilar, A.C.; Ibañez, D.; Papavassiliou, J. |
| Title |
Ghost propagator and ghost-gluon vertex from Schwinger-Dyson equations |
Type |
Journal Article |
| Year |
2013 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
| Volume |
87 |
Issue |
11 |
Pages |
114020 - 14pp |
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We study an approximate version of the Schwinger-Dyson equation that controls the nonperturbative behavior of the ghost-gluon vertex in the Landau gauge. In particular, we focus on the form factor that enters in the dynamical equation for the ghost dressing function, in the same gauge, and derive its integral equation, in the “one-loop dressed” approximation. We consider two special kinematic configurations, which simplify the momentum dependence of the unknown quantity; in particular, we study the soft gluon case and the well-known Taylor limit. When coupled with the Schwinger-Dyson equation of the ghost dressing function, the contribution of this form factor provides considerable support to the relevant integral kernel. As a consequence, the solution of this coupled system of integral equations furnishes a ghost dressing function that reproduces the standard lattice results rather accurately, without the need to artificially increase the value of the gauge coupling. |
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[Aguilar, A. C.] Univ Estadual Campinas, Inst Phys Gleb Wataghin, BR-13083859 Sao Paulo, Brazil |
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Amer Physical Soc |
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English |
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1550-7998 |
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Conference |
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| Notes |
WOS:000321001100003 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
1508 |
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| Author |
Aguilar, A.C.; Binosi, D.; Ibañez, D.; Papavassiliou, J. |
| Title |
Effects of divergent ghost loops on the Green's functions of QCD |
Type |
Journal Article |
| Year |
2014 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
| Volume |
89 |
Issue |
8 |
Pages |
085008 - 26pp |
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| Abstract |
In the present work, we discuss certain characteristic features encoded in some of the fundamental QCD Green's functions, for which the origin can be traced back to the nonperturbative masslessness of the ghost field, in the Landau gauge. Specifically, the ghost loops that contribute to these Green's functions display infrared divergences, akin to those encountered in the perturbative treatment, in contradistinction to the gluonic loops, for which perturbative divergences are tamed by the dynamical generation of an effective gluon mass. In d = 4, the aforementioned divergences are logarithmic, thus causing a relatively mild impact, whereas in d = 3 they are linear, giving rise to enhanced effects. In the case of the gluon propagator, these effects do not interfere with its finiteness, but make its first derivative diverge at the origin, and introduce a maximum in the region of infrared momenta. The three-gluon vertex is also affected, and the induced divergent behavior is clearly exposed in certain special kinematic configurations, usually considered in lattice simulations; the sign of the corresponding divergence is unambiguously determined. The main underlying concepts are developed in the context of a simple toy model, which demonstrates clearly the interconnected nature of the various effects. The picture that emerges is subsequently corroborated by a detailed nonperturbative analysis, combining lattice results with the dynamical integral equations governing the relevant ingredients, such as the nonperturbative ghost loop and the momentumdependent gluon mass. |
| Address |
[Aguilar, A. C.] Univ Estadual Campinas, UNICAMP, Inst Phys Gleb Wataghin, BR-13083859 Sao Paulo, Brazil |
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| Publisher |
Amer Physical Soc |
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English |
Summary Language |
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Series Title |
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Series Issue |
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| ISSN |
1550-7998 |
ISBN |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000334335000020 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
1769 |
| Permanent link to this record |
