arXiv subjects

Zachary Guralnik

Publications and source records attributed to Zachary Guralnik.

28 records · Page 2Linked to original sources

arXiv2002

Intersecting Branes, Defect Conformal Field Theories and Tensionless Strings

The defect conformal field theory describing intersecting D3-branes at a C^2/Z_k orbifold is used to (de)construct the theory of intersecting M5-branes, as well as M5-branes wrapping the holomorphic curve xy=c. The possibility of a 't Hooft anomaly due to tensionless strings at the intersection is discussed. This note is based on a talk given by Zachary Guralnik at the 35th International Symposium Ahrenshoop on the Theory of Elementary Particles.

hep-th↗

arXiv2002

Four-Dimensional Superconformal Theories with Interacting Boundaries or Defects

We study four-dimensional superconformal field theories coupled to three-dimensional superconformal boundary or defect degrees of freedom. Starting with bulk N=2, d=4 theories, we construct abelian models preserving N=2, d=3 supersymmetry and the conformal symmetries under which the boundary/defect is invariant. We write the action, including the bulk terms, in N=2, d=3 superspace. Moreover we derive Callan-Symanzik equations for these models using their superconformal transformation properties and show that the beta functions vanish to all orders in perturbation theory, such that the models remain superconformal upon quantization. Furthermore we study a model with N=4 SU(N) Yang-Mills theory in the bulk coupled to a N=4, d=3 hypermultiplet on a defect. This model was constructed by DeWolfe, Freedman and Ooguri, and conjectured to be conformal based on its relation to an AdS configuration studied by Karch and Randall. We write this model in N=2, d=3 superspace, which has the distinct advantage that non-renormalization theorems become transparent. Using N=4, d=3 supersymmetry, we argue that the model is conformal.

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arXiv2001

Knots, Braids and BPS States in M-Theory

In previous work we considered M-theory five branes wrapped on elliptic Calabi-Yau threefold near the smooth part of the discriminant curve. In this paper, we extend that work to compute the light states on the worldvolume of five-branes wrapped on fibers near certain singular loci of the discriminant. We regulate the singular behavior near these loci by deforming the discriminant curve and expressing the singularity in terms of knots and their associated braids. There braids allow us to compute the appropriate string junction lattice for the singularity and,hence to determine the spectrum of light BPS states. We find that these techniques are valid near singular points with N=2 supersymmetry.

hep-th↗

arXiv2001

Aspects of Gauge Theory on Commutative and Noncommutative Tori

We study aspects of gauge theory on tori which are a consequences of Morita equivalence. In particular we study the behavior of gauge theory on noncommutative tori for arbitrarily close rational values of Theta. For such values of Theta, there are Morita equivalent descriptions in terms of Yang-Mills theories on commutative tori with very different magnetic fluxes and rank. In order for the correlators of open Wilson lines to depend smoothly on Theta, the correlators of closed Wilson lines in the commutative Yang-Mills theory must satisfy strong constraints. If exactly satisfied, these constraints give relations between small and large N gauge theories. We verify that these constraints are obeyed at leading order in the 1/N expansion of pure 2-d QCD and of strongly coupled N=4 super Yang-Mills theory.

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arXiv2001

String Junctions and Non-Simply Connected Gauge Groups

Relations between the global structure of the gauge group in elliptic F-theory compactifications, fractional null string junctions, and the Mordell-Weil lattice of rational sections are discussed. We extend results in the literature, which pertain primarily to rational elliptic surfaces and obtain pi^1(G) where G is the semi-simple part of the gauge group. We show how to obtain the full global structure of the gauge group, including all U(1) factors. Our methods are not restricted to rational elliptic surfaces. We also consider elliptic K3's and K3-fibered Calabi-Yau three-folds.

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arXiv2000

Five-Brane BPS States in Heterotic M-Theory

We present explicit methods for computing the discriminant curves and the associated Kodaira type fiber degeneracies of elliptically fibered Calabi-Yau threefolds. These methods are applied to a specific three-family, SU(5) grand unified theory of particle physics within the context of Heterotic M-Theory. It is demonstrated that there is always a region of moduli space where a bulk space five-brane is wrapped on a pure fiber in the Calabi-Yau threefold. Restricting the discussion to the smooth parts of the discriminant curve, we explore the properties of the N=2 BPS supermultiplets that arise on the worldvolume of this five-brane due to the degeneration of the elliptic fiber. The associated degenerating M membranes are shown to project to string junctions in the base space. We use string junction techniques to explicitly compute the light BPS hyper- and vector multiplet spectrum for each Kodaira type fiber near the smooth part of the discriminant curve in the SU(5) GUT theory.

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arXiv1999

T-duality of large N QCD

We argue that non-supersymmetric large N QCD compactified on T^2 exhibits properties characteristic of an SL(2,Z) T-duality. The kahler structure on which this SL(2,Z) acts is given by $m/N + iΛ^2 A$, where A is the area of the torus, m is the 't Hooft magnetic flux on the torus, and $Λ^2$ is the QCD string tension.

hep-th↗

arXiv1996

Multiple Vacua and Boundary Conditions of Schwinger-Dyson Equations

We discuss the relationship between the boundary conditions of the Schwinger-Dyson equations and the phase diagram of a bosonic field theory or matrix model. In the thermodynamic limit, many boundary conditions lead to the same solution, while other boundary conditions have no such limit. The list of boundary conditions for which a thermodynamic limit exists depends on the parameters of the theory. The boundary conditions of a physical solution may be quite exotic, corresponding to path integration over various inequivalent complex contours.

hep-th↗

arXiv1992

QCD Mass Inequalities in the Heavy Quark Limit

QCD inequalities are derived for the masses of mesons and baryons containing a single heavy quark using the heavy quark effective field theory. A rigorous lower bound is obtained for the $\barΛ$ parameters of the heavy quark effective theory that parameterize $1/m$ corrections, $\barΛ$ > 237 MeV for mesons, and $\bar Λ> 657$ MeV for baryons. The inequalities on $\barΛ$ imply the inequalities $m_c < 1627$ MeV and $m_b < 5068$ MeV for the mass parameters of the heavy quark effective field theory.

hep-ph↗

arXiv1992

Properties of Baryons Containing a Heavy Quark in the Skyrme Model

The properties of baryons containing one heavy quark are studied in the Skyrme model, where they are treated as bound states of a heavy meson with an $SU(2)$ chiral soliton. In the large $N_c$ limit, the baryon spectrum is an infinite tower of degenerate states with isospin and spin of the light degrees of freedom $I=s_\ell=0,1,2,\dots$, and total spin $s=\abs{s_\ell\pm1/2}$. Exotic states with no quark model analogues in the large $N_c$ limit are found to be unbound. The $Σ_c-Λ_c$ mass difference is computed and found to be in good agreement with experiment. The $Σ_c\,Σ_c\,π$ and $Σ_c\,Λ_c\,π$ coupling constants are calculated to leading order in $N_c$ in terms of $g_A$, the axial coupling constant of the nucleon. We discuss the extension of our results to $SU(3)$ chiral solitons.

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