Conformal Gauge Theories Research Articles

Central extensions of finite Heisenberg groups in cascading quiver gauge theories

Many conformal quiver gauge theories admit nonconformal generalizations. These generalizations change the rank of some of the gauge groups in a consistent way, inducing a running in the gauge couplings. We find a group of discrete transformations that acts on a large class of these theories. These transformations form a central extension of the Heisenberg group, generalizing the Heisenberg group of the conformal case, when all gauge groups have the same rank. In the AdS/CFT correspondence the nonconformal quiver gauge theory is dual to supergravity backgrounds with both five-form and three-form flux. A direct implication is that operators counting wrapped branes satisfy a central extension of a finite Heisenberg group and therefore do not commute.

Cascading RG Flows from New Sasaki-Einstein Manifolds

In important recent developments, new Sasaki-Einstein spaces $Y^{p,q}$ and conformal gauge theories dual to $AdS_5\times Y^{p,q}$ have been constructed. We consider a stack of N D3-branes and M wrapped D5-branes at the apex of a cone over $Y^{p,q}$. Replacing the D-branes by their fluxes, we construct asymptotic solutions for all p and q in the form of warped products of the cone and $R^{3,1}$. We show that they describe cascading RG flows where N decreases logarithmically with the scale. The warp factor, which we determine explicitly, is a function of the radius of the cone and one of the coordinates on $Y^{p,q}$. We describe the RG cascades in the dual quiver gauge theories, and find an exact agreement between the supergravity and the field theory beta functions. We also discuss certain dibaryon operators and their dual wrapped D3-branes in the conformal case M=0.

Rethinking the properties of the quark-gluon plasma atTc<T<4Tc

We argue that although at asymptotically high temperatures the QGP in bulk behaves as a gas of weakly interacting quasiparticles (modulo long-range magnetism), at temperatures up to few times the critical temperature $T_c$ it displays different properties. If the running of the QCD coupling constant continues in the Coulomb phase till the screening length scale, it reaches the strong coupling treshold $\alpha_s(m_D)\sim 1$. As a result, the Coulomb phase supports weakly bound Coulombic s-wave $\bar c c$, light quark and even $gg$ states. The existence of shallow bound states dramatically increases the quasiparticle rescattering at low energies, reducing the viscosity and thereby explaining why heavy ion collisions at RHIC exhibit robust collective phenomena. In conformal gauge theories at finite temperature the Coulomb binding persists further in the strong coupling regime, as found for ${\cal N}=4$ SUSY YM in the Maldacena regime.

Flavor dynamics with conformal matter and gauge theories on compact hyperbolic manifolds in extra dimensions

We outline a toy model in which a unique mechanism may trigger a dynamical chain resulting in key low-energy regularities. The starting points are a negative cosmological term in the bulk and conformally invariant nongravity sector. These elements ensure compactification of the extra dimensional space on a compact hyperbolic manifold (with the negative and constant scalar curvature). The overall geometry is then M_4 x B_n. The negative curvature on B_n triggers the formation of the four-dimensional defect which provides in turn a dynamical localization of ordinary particles. It also leads, simultaneously, to a spontaneous breaking of gauge symmetry through a Higgs mechanism. Masses of the fermions, gauge bosons and scalars all derive from the curvature of the internal manifold such that the Higgs boson is generally heavier than the gauge bosons. The factorizable geometry M_4 x B_n and flatness of M_4 require fine-tuning.

STRING THEORY AS A UNIVERSAL LANGUAGE

This article, based on the Klein lecture, contains some new results and new speculations on various topics. They include discussion of open strings in the AdS space, unusual features of D-branes, conformal gauge theories in higher dimensions. We also comment on the infrared screening of the cosmological constant and on the ''brane worlds.''

Vacuum states of mass deformations of and conformal gauge theories and their brane interpretations

We find the classical supersymmetric vacuum states of a class of N = 1* field theories obtained by mass deforming superconformal models with simple gauge groups and N = 4 or N =2 supersymmetry. In particular, new classical vacuum states for mass-deformed N = 4 models with Sp(2N) and SO(N) gauge symmetry are found. We also derive the classical vacua for various mass-deformed N=2 models with Sp(2N) and SU(N) gauge groups and antisymmetric (and symmetric) hypermultiplets. We suggest interpretations of the mass-deformed vacua in terms of three-branes expanded into five-brane configurations.

D-instanton probes of non-conformal geometries

D-instanton calculus has proved to be able to probe the AdS near horizon geometry for $N$ D-branes systems which, when decoupled from gravity, yield four dimensional superconformal gauge theories with various matter content. In this work we extend previous analysis to encompass fractional brane models which give rise to non conformal N=2 Super Yang-Mills theories. Via D-instanton calculus we study the geometry of such models for finite $N$ and recover the $\beta$ function of the gauge coupling constants which is expected in non conformal gauge theories. We also give a topological matrix theory formulation for the D-instanton action of these theories. Finally, we revisit the related system where the D3-branes wrap a ${\real}^4/{\zet}_p$ orbifold singularity and the D(-1) branes are associated to instanton solutions of four-dimensional gauge theories in the blown down ALE space.

String theory as a universal language

This article, based on the Klein lecture, contains some new results and new speculations on various topics. They include discussion of open strings in the AdS space, unusual features of D-branes, conformal gauge theories in higher dimensions. We also comment on the infrared screening of the cosmological constant and on the "brane worlds"

Loop dynamics and AdS/CFT correspondence

We consider the strong coupling limit of conformal gauge theories in 4 dimensions. The action of the loop operator on the minimal area in the AdS space is analyzed, and the Schwinger-Dyson equations of gauge theory are checked. The general approach to the loop dynamics developed here goes beyond the special case of conformal theories.

PROMOTING FINITE TO INFINITE SYMMETRIES: THE (3 + 1)-DIMENSIONAL ANALOGUE OF THE VIRASORO ALGEBRA AND HIGHER-SPIN FIELDS

Infinite enlargements of finite pseudo-unitary symmetries are explicitly provided in this letter. The particular case of u (2, 2) ≃ so (4, 2) ⊕ u (1) constitutes a (Virasoro-like) infinite-dimensional generalization of the (3 + 1) -dimensional conformal symmetry, in addition to matter fields with all conformal spins. These algebras provide a new arena for integrable field models in higher dimensions; for example, anti-de Sitter and conformal gauge theories of higher-so(4, 2)-spin fields. A proposal for a noncommutative geometrical interpretation of space is also outlined.

Conformality and gauge coupling unification

It has been recently proposed to embed the standard model in a conformal gauge theory to resolve the hierarchy problem, and to avoid assuming either grand unification or low-energy supersymmetry. By model building based on string-field duality we show how to maintain the successful prediction of an electroweak mixing angle with $sin^2\theta \simeq 0.231$ in conformal gauge theories with three chiral families.

AdS-CFT string duality and conformal gauge theories

Compactification of Type IIB superstring on an $AdS_5 \times S^5/\Gamma$ background leads to SU(N) gauge field theories with prescribed matter representations. In the 't Hooft limit of large N such theories are conformally finite. For finite N and broken supersymmetry ($\cal N$ = 0) I derive the constraints to be two-loop conformal and examine the consequences for a wide choice of $\Gamma$ and its embedding $\Gamma \subset {\cal C}^3 (\supset S^5)$.

AdS-CFT string duality and conformal gauge theories

AdS-CFT string duality and conformal gauge theories

Conformal gauge theories from AdS/CFT superstring duality?

Conformal gauge theories from AdS/CFT superstring duality?

Gravitational Dressing of Aharonov-Bohm Amplitudes

We investigate Aharonov-Bohm scattering in a theory in which charged bosonic matter field are coupled to topologically massive electrodynamics and topologically massive gravity. We demonstrate that, at one-loop order, the transmuted spins in this theory are related to the ones of ordinary Chern-Simons gauge theory in the same way that the Knizhnik-Polyakov-Zamolodchikov formula relates the Liouville-dressed conformal weights of primary operators to the bare weights of primary operators to the bare weights in two-dimensional conformal field theories. We remark on the implications of this connection two-dimensional conformal field theories and three-dimensional gauge and gravity theories for a topological membrane reformulation of strings. We also discuss some features of the gravitational analog of the Aharonov-Bohm effect.

Conformal gauge theory of (2+1)-dimensional gravity

A conformal gauge theory of (2+1)-dimensional gravity is developed within a fiber-bundle structure. Here gravitational field variables are triads and Lorentz gauge potentials, both introduced under a nonlinear realization, which leads to a spontaneous break of symmetry. The most general gravitational Lagrangian density is given in a quadratic form of the conformal invariant gauge fields. We also obtain the Poincaré gauge theory in vacuum. In a weak-field limit the gravitational field equations for a static and spinless point-like source, are naturally reduced to the Newtonian case.

Auxiliary field in conformal gauge theory.

When the full conformal algebra is gauged there arises a gauge field for inverse translations in addition to the usual translational gauge field. By considering every scale-invariant action constructible from the curvatures of the conformal group and the metric, we show that when the gauge field of the usual translations is identified as the vierbein, the gauge field of inverse translations may always be eliminated by its own field equation. After this elimination, every torsion-free, scale-invariant action reduces to a linear combination of the square of the conformal curvature tensor ${C}_{\ensuremath{\alpha}\ensuremath{\beta}\ensuremath{\mu}\ensuremath{\nu}}$ and the square of the Weyl field strength ${C}_{\ensuremath{\alpha}\ensuremath{\beta}}$.

Indefinite harmonic forms and gauge theory

Indecomposable representations have been extensively used in the construction of conformal and de Sitter gauge theories. It is thus noteworthy that certain unitary highest weight representations have been given a geometric realization as the unitary quotient of an indecomposable representation using indefinite harmonic forms [RSW]. We apply this construction toSU (2,2) and the de Sitter group. The relation is established between these representations and the massless, positive energy representations ofSU (2,2) obtained in the physics literature. We investigate the extent to which this construction allows twistors to be viewed as a gauge theory ofSU (2,2). For the de Sitter group, on which the gauge theory of singletons is based, we find that this construction is not directly applicable.

Conformal nonabelian gauge theory

A conformal nonabelian gauge theory with a five-component gauge potential is considered. In this theory the conformal-invariant two-point function has a nonzero transverse part and a Lagrangian with a conformal-invariant gauge-fixing term is found. The corresponding local effective Lagrangian, where the dimensionless Faddeev-Popov ‘ghost’ field is included, obeys a global supersymmetry of the Becchi-Rouet-Stora type. In the gauge-invariant sector it is shown that this theory is equivalent to the ordinary Yang-Mills theory.

Ghost-free, nonlinear, spin-two, conformal gauge theory

Conformal gravity is examined with the aim of constructing a renormalizable quantum field theory of gravitation. Acting on suggestions of ghost-free, linear conformal gravity, we examine conformal gauge theory. The correct choice of constraints is determined by comparison with the ghost-eliminating constraints of the linear theory. (These are quite different from those introduced previously in conformal gauge theories.) Einstein's field equation appears as the integrability condition for the constraint. Minimal coupling to massless matter preserves local, conformal symmetry.