196,008 research outputs found
Remarks on BPS Wilson loops in non-conformal N = 2 gauge theories and localization
No full textWe consider 1/2 BPS supersymmetric circular Wilson loops in four-dimensional N = 2 SU(N) SYM theories with massless matter content and non-vanishing beta-function. Following Pestun's approach, we can use supersymmetric localization on the sphere S4 to map these observables into a matrix model, provided that the one-loop determinants are consistently regularized. Employing a suitable procedure, we construct the regularized matrix model for these theories and show that, at order g(4 ), the predictions for the 1/2 BPS Wilson loop match standard perturbative renormalization based on the direct evaluation of Feynman diagrams on S-4. Despite conformal symmetry begin broken at the quantum level, we also demonstrate that the matrix model approaches perfectly captures the expression of the renormalized observable in flat space at this perturbative order. Moreover, we revisit in detail the difference theory approach, showing that when the beta-function is non-vanishing, this method does not account for evanescent terms which are made finite by the renormalization procedure and participate to the corrections at order g(6)
N = 2 Instanton Calculus in Closed String Background
No full textIn this contribution we describe how to obtain instanton effects in four dimensional gauge theories by computing string scattering amplitudes in D3/D(-1) brane systems. In particular we study a system of fractional D3/D(-1) branes in a Z_2 orbifold and in a Ramond-Ramond closed string background, and show that it describes the gauge instantons of N=2 super Yang-Mills theory and their interactions with the graviphoton of N=2. Using string theory methods we compute the prepotential of the effective gauge theory exploiting the localization methods of the instanton calculus, showing that this leads to the same information given by the topological string
1/2 BPS Wilson loops in non-conformal N = 2 gauge theories and localization: a three-loop analysis
No full textWe study the 1/2 BPS circular Wilson loop in four-dimensional SU(N) N = 2 SYM theories with massless hypermultiplets and non-vanishing beta-function. Using supersymmetric localization on S4, we map the path-integral associated with this observable onto an interacting matrix model. Despite the breaking of conformal symmetry at the quantum level, we show that, within a specific regime, the matrix model predictions remain consistent with the perturbative results in flat space up to order g6. At this order, our analysis reveals that the reorganization of Feynman diagrams based on the matrix model interaction potential, widely tested in (super)conformal models, also applies to these non-conformal set-ups and is realized by interference mechanisms
Supersymmetric Localization and Nonconformal N=2 Supersymmetric Yang-Mills Theories in the Perturbative Regime
No full text: We examine the relation between supersymmetric localization on S^{4} and standard QFT results for nonconformal theories in flat space. Specifically, we consider 1/2 BPS circular Wilson loops in four-dimensional SU(N) N=2 supersonic Yang-Mills theories with massless hypermultiplets in an arbitrary representation R such that the β function is nonvanishing. On S^{4}, localization maps this observable into an interacting matrix model. Despite broken conformal symmetry at the quantum level, we show that within a specific regime of validity the matrix model predictions are consistent with perturbation theory in flat space up to order g^{6}. At this order, the reorganization of Feynman diagrams based on the matrix model potential, which has been widely tested in conformal models, also applies in nonconformal setups and is realized, in perturbative field theory, through highly nontrivial interference mechanisms
-diagram technique for , superfields
No full textWe describe a diagrammatic procedure to carry out the Grassmann integration in super-Feynman diagrams of 4d theories expressed in terms of superfields. This method is alternative to the well known D-algebra approach. We develop it in detail for theories containing vector, chiral and anti-chiral superfields, with the type of interactions which occur in SYM theories with massless matter, but it would be possible to extend it to other cases. The main advantage is that this method is algorithmic; we implemented it as a Mathematica program that, given the description of a super Feynman diagram in momentum space, returns directly the polynomial in the momenta produced by the Grassmann integration
BPS wilson loops in generic conformal N = 2 SU(N) SYM theories
No full textWe consider the 1/2 BPS circular Wilson loop in a generic N = 2 SU(N) SYM theory with conformal matter content. We study its vacuum expectation value, both at finite N and in the large-N limit, using the interacting matrix model provided by localization results. We single out some families of theories for which the Wilson loop vacuum expectation values approaches the N = 4 result in the large-N limit, in agreement with the fact that they possess a simple holographic dual. At finite N and in the generic case, we explicitly compare the matrix model result with the field-theory perturbative expansion up to order g^8 for the terms proportional to the Riemann value zeta(5), finding perfect agreement. Organizing the Feynman diagrams as suggested by the structure of the matrix model turns out to be very convenient for this computation
Three-point functions in a superconformal gauge theory and their strong-coupling limit
No full textWe study the 3-point functions of single-trace scalar operators in a
four-dimensional SYM theory with gauge group
and matter in the symmetric plus anti-symmetric representation, which has a
vanishing -function. By mapping this computation to the matrix model
arising from localization on a 4-sphere we are able to resum the perturbative
expansion in the large- 't Hooft limit and derive the behavior of the
correlators at strong coupling. Finally, by combining our results on the
3-point functions with those on the 2-point functions that have been recently
found, we obtain the normalized 3-point coefficients of this conformal field
theory at strong coupling and find that they depend in a simple way on the
conformal dimensions of the single-trace operators.Comment: 38 pages, 10 figures, several footnotes, a couple of references and
one appendix added; to be published in JHE
Correlators between Wilson loop and chiral operators in N= 2 conformal gauge theories
No full textWe consider conformal N= 2 super Yang-Mills theories with gauge group SU(N) and Nf = 2N fundamental hypermultiplets in presence of a circular 1/2-BPS Wilson loop. It is natural to conjecture that the matrix model which describes the expectation value of this system also encodes the one-point functions of chiral scalar operators in presence of the Wilson loop. We obtain evidence of this conjecture by successfully comparing, at finite N and at the two-loop order, the one-point functions computed in field theory with the vacuum expectation values of the corresponding normal-ordered operators in the matrix model. For the part of these expressions with transcendentality ζ(3), we also obtain results in the large-N limit that are exact in the ’t Hooft coupling λ.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Surface Defects from Fractional Branes -- I
No full textWe show that the Gukov-Witten monodromy defects of supersymmetric Yang-Mills
theory can be realized in perturbative string theory by considering an orbifold
background of the Kanno-Tachikawa type and placing stacks of fractional
D3-branes whose world-volume partially extends along the orbifold directions.
In particular, we show that turning on a constant background value for some
scalar fields in the closed string twisted sectors induces a non-trivial
profile for the gauge field and one of the complex scalars of the world-volume
theory, and that this profile exactly matches the singular behavior that one
expects for a Gukov-Witten surface defect in the super
Yang-Mills theory. To keep the presentation as simple as possible, in this work
we restrict our analysis to surface defects corresponding to a
orbifold and defer the study of the most general case to a companion paper.Comment: 30 pages; added arXiv number of the companion pape
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
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