Entropia de emaranhamento em Teorias de calibre

Dissertação (mestrado)—Universidade de Brasília, Instituto de Física, Programa de Pós-Graduação em Física, 2017.Neste trabalho, começa-se um estudo sistemático de emaranhamento em teorias de gauge. Adota-se a teoria de Yang-Mills no cilindro como modelo principal. Parte-se da Lagrangiana de Yang-Mills e obtém-se que, resolvendo o vínculo da lei de Gauss, a dinâmica do sistema pode ser reduzida àquela de uma partícula livre movendo-se ao longo da variedade do grupo de gauge. Isso significa que o sistema apresenta somente um grau de liberdade físico. Portanto, não é possível que haja emaranhamento. Acopla-se então a teoria de YangMills à uma partícula livre não-relativística. Uma primeira abordagem é feita considerando o caso abeliano. Obtém-se que o sistema apresenta não só emaranhamento, mas também degenerescência e anomalia axial. Com respeito à anomalia, cálculos analíticos são feitos e sua dependência com relação a outros parâmetros, como energia e degenerescência, é analisada. Com relação ao emaranhamento, cálculos numéricos de entropia de emaranhamento são feitos considerando o estado fundamental. Guiado pelo projeto acima delineado, essa dissertação tem também um objetivo pedagógico, no sentido de introduzir os conceitos de teoria de gauge, teoria de vínculo e teoria de grupos de Lie.In this work a systematic study of entanglement in gauge theories is started. The Yang-Mills theory on a cylinder is adopted as the main model. Starting from the Yang-Mills Lagrangian one obtains that, by solving the Gauss law constraint, the dynamics of the system can be reduced to that of a free particle moving along the gauge group manifold. This means that the system has only one physical degree of freedom. Therefore, the system does not present entanglement. The Yang-Mills theory is then coupled to a non-relativistic free particle. A first approach is made considering the abelian case. One obtains that the system presents not only entanglement, but also degeneracy and axial anomaly. With respect to anomaly, analytical calculations are carried out and its dependence on other parameters, such as energy and degeneracy, is analysed. Concerning entanglement, numerical calculations of entanglement entropy are made considering the ground-state. Guided by the project outlined above, this dissertation also has a pedagogical purpose, in the sense that it introduces concepts of gauge theory, constrained systems and Lie group theory

Classifying BPS bosonic Wilson loops in 3d N=4 Chern-Simons-matter theories

We study the possible BPS Wilson loops in three-dimensional N = 4 Chern-Simons-matter theory which involve only the gauge field and bilinears of the scalars. Previously known examples are the analogues of the Gaiotto-Yin loops preserving four supercharges and “latitude” loops preserving two. We carry out a careful classification and find, in addition, loops preserving three supercharges, further inequivalent classes of loops preserving two supercharges and loops preserving a single supercharge. For each of the classes of loops, we present a representative example and analyse their full orbit under the broken symmetries

Interpolating Wilson loops and enriched RG flows

Abstract We study new 1/24 BPS circular Wilson loops in ABJ(M) theory, which are defined in terms of several parameters that continuously interpolate between previously known 1/6 BPS loops (both bosonic and fermionic) and 1/2 BPS fermionic loops. We compute the expectation value of these operators up to second order in perturbation theory using a one-dimensional effective field theory approach. Within dimensional regularization, we find non-trivial β-functions for the parameters, which are marginally relevant deformations triggering RG flows from a UV fixed point represented by the 1/6 BPS bosonic loop to an IR fixed point represented by a 1/2 BPS fermionic loop. Generically, along all flows at least one supercharge of the theory is preserved, so that we refer to them as enriched RG flows. In particular, fixed points are connected through 1/6 BPS fermionic operators. This holds at framing zero, which is a consequence of the regularization scheme employed. We also establish the validity of the g-theorem, relating the expectation values of the Wilson loops corresponding to the UV and IR fixed points of the flow, and discuss the one-dimensional defect SCFT living on the Wilson loop contour

Wilson loops and defect RG flows in ABJM

We continue our study of renormalization group (RG) flows on Wilson loop defects in ABJM theory, which we have initiated in arXiv:2211.16501. We generalize that analysis by including non-supersymmetric fixed points and RG trajectories. To this end, we first determine the ``ordinary", non-supersymmetric Wilson loops, which turn out to be two and to include an R-symmetry preserving coupling to the scalar fields of the theory, contrary to their four-dimensional counterpart defined solely in terms of the gauge field holonomy. We then deform these operators by turning on bosonic and/or fermionic couplings, which trigger an elaborate, multi-dimensional network of possible RG trajectories connecting a large spectrum of fixed points classified in terms of the amount (possibly zero) of supersymmetry and R-symmetry preserved. The $\beta$-functions are computed to leading order in the ABJM coupling but exactly in the deformation parameters, using an auxiliary one-dimensional theory on the defect and a dimensional regularization scheme. A striking result is the different behavior of the two ordinary Wilson loops, of which one turns out to be a UV unstable point while the other is IR stable. The same is true for the two 1/2 BPS Wilson loops. We interpret our results from a defect CFT (dCFT) point of view, computing the anomalous dimensions of the operators associated to the deformations and establishing appropriate g-theorems. In particular, the fermionic unstable fixed point is associated to a dCFT which is not reflection positive.Comment: 40 pages, 17 figures; minor changes and references adde

Wilson loops and defect RG flows in ABJM

Abstract We continue our study of renormalization group (RG) flows on Wilson loop defects in ABJM theory, which we have initiated in arXiv:2211.16501 . We generalize that analysis by including non-supersymmetric fixed points and RG trajectories. To this end, we first determine the “ordinary”, non-supersymmetric Wilson loops, which turn out to be two and to include an R-symmetry preserving coupling to the scalar fields of the theory, contrary to their four-dimensional counterpart defined solely in terms of the gauge field holonomy. We then deform these operators by turning on bosonic and/or fermionic couplings, which trigger an elaborate, multi-dimensional network of possible RG trajectories connecting a large spectrum of fixed points classified in terms of the amount (possibly zero) of supersymmetry and R-symmetry preserved. The β-functions are computed to leading order in the ABJM coupling but exactly in the deformation parameters, using an auxiliary one-dimensional theory on the defect and a dimensional regularization scheme. A striking result is the different behavior of the two ordinary Wilson loops, of which one turns out to be a UV unstable point while the other is IR stable. The same is true for the two 1/2 BPS Wilson loops. We interpret our results from a defect CFT (dCFT) point of view, computing the anomalous dimensions of the operators associated to the deformations and establishing appropriate g-theorems. In particular, the fermionic unstable fixed point is associated to a dCFT which is not reflection positive

Roadmap on Wilson loops in 3d Chern–Simons-matter theories

This is a compact review of recent results on supersymmetric Wilson loops in ABJ(M) and related theories. It aims to be a quick introduction to the state of the art in the field and a discussion of open problems. It is divided into short chapters devoted to different questions and techniques. Some new results, perspectives and speculations are also presented. We hope this might serve as a baseline for further studies of this topic.Facultad de Ciencias ExactasInstituto de Física La Plat