Stringy instanton effects in N= 2 gauge theories (original) (raw)

Stringy instanton effects in models with rigid magnetised D-branes

Nuclear Physics B, 2009

We compute instantonic effects in globally consistent T 6 /Z 2 × Z 2 orientifold models with discrete torsion and magnetised D-branes. We consider fractional branes and instantons wrapping the same rigid cycles. We clarify and analyse in detail the lowenergy effective action on D-branes in these models. We provide explicit examples where instantons induce linear terms in the charged fields, or non-perturbative mass terms are generated. We also find examples where the gauge theory on fractional branes has conformal symmetry at one-loop, broken by instantonic mass terms at a hierarchically small energy scale.

D-brane Instantons on the T^ 6/Z_3 orientifold

Arxiv preprint arXiv:0704.0784, 2007

We give a detailed microscopic derivation of gauge and stringy instanton generated superpotentials for gauge theories living on D3-branes at 3orientifold singularities. Gauge instantons are generated by D(-1)-branes and lead to Affleck, Dine and Seiberg (ADS) like superpotentials in the effective N = 1 gauge theories with three generations of bifundamental and anti/symmetric matter. Stringy instanton effects are generated by Euclidean ED3-branes wrapping four-cycles on T 6 / 3. They give rise to Majorana masses, Yukawa couplings or non-renormalizable superpotentials depending on the gauge theory. Finally we determine the conditions under which ADS like superpotentials are generated in N = 1 gauge theories with adjoints, fundamentals, symmetric and antisymmetric chiral matter.

N = 2 Instanton Calculus in Closed String Background

Progress of Theoretical Physics Supplement, 2007

In 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 Z2 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. * )

N = 2 gauge theories on systems of fractional D3/D7-branes

Nuclear Physics B, 2002

We study a bound state of fractional D3/D7-branes in the ten-dimensional space IR 1,5 × IR 4 /Z 2 using the boundary state formalism. We construct the boundary actions for this system and show that higher order terms in the twisted fields are needed in order to satisfy the zero-force condition. We then find the classical background associated to the bound state and show that the gauge theory living on a probe fractional D3-brane correctly reproduces the perturbative behavior of a four-dimensional N = 2 supersymmetric gauge theory with fundamental matter.

D-brane instantons on the T 6 /Bbb Z 3 orientifold

Journal of High Energy Physics, 2007

We give a detailed microscopic derivation of gauge and stringy instanton generated superpotentials for gauge theories living on D3-branes at 3orientifold singularities. Gauge instantons are generated by D(-1)-branes and lead to Affleck, Dine and Seiberg (ADS) like superpotentials in the effective N = 1 gauge theories with three generations of bifundamental and anti/symmetric matter. Stringy instanton effects are generated by Euclidean ED3-branes wrapping four-cycles on T 6 / 3 . They give rise to Majorana masses, Yukawa couplings or non-renormalizable superpotentials depending on the gauge theory. Finally we determine the conditions under which ADS like superpotentials are generated in N = 1 gauge theories with adjoints, fundamentals, symmetric and antisymmetric chiral matter.

Gauge instantons from open strings

Fortschritte der Physik, 2004

In 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 show that the disks with mixed boundary conditions, which are typical of the D3/D(-1) system, are the sources for the classical instanton solution.

Fortschritte der Physik Stringy instantons and dualities

2016

We discuss non-perturbative corrections to the gauge kinetic functions in a four-dimensional N = 2 gauge theory realized with a system of D7/D3-branes in a compactification of type I ′ theory on T4/Z2 × Z2. The non-perturbative contributions arise when D(-1) branes, corresponding to stringy instantons, are added to the system; such contributions can be explicitly evaluated using localization techniques and precisely match the results predicted by the heterotic/type I ′ duality. This agreement represents a very non-trivial test of the stringy multi-instanton calculus.

Instantons in 𝒩 = 2 magnetized D-brane worlds

In a toroidal orbifold of type IIB string theory we study instanton effects in N = 2 super Yang-Mills theories engineered with systems of wrapped magnetized D9 branes and Euclidean D5 branes. We analyze the various open string sectors in this brane system and study the 1-loop amplitudes described by annulus diagrams with mixed boundary conditions, explaining their rôle in the stringy instanton calculus. We show in particular that the non-holomorphic terms in these annulus amplitudes precisely reconstruct the appropriate Kähler metric factors that are needed to write the instanton correlators in terms of purely holomorphic variables. We also explicitly derive the correct holomorphic structure of the instanton induced low energy effective action in the Coulomb branch.

Instantons in Script N= 2 magnetized D-brane worlds

Stringy instanton corrections to N=2 gauge couplings

2010

We discuss a string model where a conformal four-dimensional N=2 gauge theory receives corrections to its gauge kinetic functions from "stringy" instantons. These contributions are explicitly evaluated by exploiting the localization properties of the integral over the stringy instanton moduli space. The model we consider corresponds to a setup with D7/D3-branes in type I' theory compactified on T4/Z2 x T2, and possesses a perturbatively computable heterotic dual. In the heteoric side the corrections to the quadratic gauge couplings are provided by a 1-loop threshold computation and, under the duality map, match precisely the first few stringy instanton effects in the type I' setup. This agreement represents a very non-trivial test of our approach to the exotic instanton calculus.

2 gauge theories on systems of fractional D3/D7-branes

Nuclear Physics B, 2002

Instanton effects in N=1 brane models and the Kahler metric of twisted matter

2007

We consider locally consistent systems of magnetized D9 branes on an orbifolded six-torus which support N=1 gauge theories. In such realizations, the matter multiplets arise from "twisted" strings connecting different stacks of branes. The introduction of Euclidean 5 branes (E5) wrapped on the six-dimensional compact space leads to instanton effects. For instance, if the system is engineered so as to yield SQCD, a single E5 brane may account for the ADS/TVY superpotential. We discuss the subtle interplay that exists between the annuli diagrams with an E5 boundary and the holomorphicity properties of the effective low-energy action of the N=1 theory. The consistency of this picture allows to obtain information on the Kahler metric of the chiral matter multiplets arising from twisted strings.

Stringy instanton corrections to $ \mathcal{N} = 2 $ gauge couplings

Journal of High Energy Physics, 2010

We discuss a string model where a conformal four-dimensional N = 2 gauge theory receives corrections to its gauge kinetic functions from "stringy" instantons. These contributions are explicitly evaluated by exploiting the localization properties of the integral over the stringy instanton moduli space. The model we consider corresponds to a setup with D7/D3-branes in type I theory compactified on T 4 /Z 2 × T 2 , and possesses a perturbatively computable heterotic dual. In the heteoric side the corrections to the quadratic gauge couplings are provided by a 1-loop threshold computation and, under the duality map, match precisely the first few stringy instanton effects in the type I setup. This agreement represents a very non-trivial test of our approach to the exotic instanton calculus.

Classical gauge instantons from open strings

Journal of High Energy Physics, 2003

We study the D3/D(−1) brane system and show how to compute instanton corrections to correlation functions of gauge theories in four dimensions using open string techniques. In particular we show that the disks with mixed boundary conditions that are typical of the D3/D(−1) system are the sources for the classical instanton solution. This can then be recovered from simple calculations of open string scattering amplitudes in the presence of D-instantons. Exploiting this fact we also relate this stringy description to the standard instanton calculus of field theory.

Stringy instantons and dualities

Fortschritte der Physik, 2011

Flux interactions on D-branes and instantons

Journal of High Energy Physics, 2008

We provide a direct world-sheet derivation of the couplings of NS-NS and R-R fluxes to various types of D-branes (including instantonic ones) by evaluating disk amplitudes among two open string vertex operators at a generic brane intersection and one closed string vertex representing the background fluxes. This world-sheet approach is in full agreement with the derivation of the flux couplings in the brane effective actions based on supergravity methods, but it is applicable also to more general brane configurations involving fields with twisted boundary conditions. As an application, we consider an orbifold compactification of Type IIB string theory with fractional D-branes preserving N = 1 supersymmetry and study the flux-induced fermionic mass terms both on space-filling branes and on instantonic ones. Our results show the existence of a relation between the soft supersymmetry breaking and the lifting of some instanton fermionic zero-modes, which may lead to new types of non-perturbative couplings in brane-world models.

Instanton effects in ? = 1 brane models and the Kähler metric of twisted matter

We consider locally consistent systems of magnetized D9 branes on an orbifolded six-torus which support N = 1 gauge theories. In such realizations, the matter multiplets arise from "twisted" strings connecting different stacks of branes. The introduction of Euclidean 5 branes (E5) wrapped on the six-dimensional compact space leads to instanton effects. For instance, if the system is engineered so as to yield SQCD, a single E5 brane may account for the ADS/TVY superpotential. We discuss the subtle interplay that exists between the annuli diagrams with an E5 boundary and the holomorphicity properties of the effective low-energy action of the N = 1 theory. The consistency of this picture allows to obtain information on the Kähler metric of the chiral matter multiplets arising from twisted strings.

(D)-instanton effects in magnetized brane worlds

Fortschritte der Physik, 2008

We consider systems of magnetized D9 branes on orbifolds supporting N = 1 gauge theories. In such realizations, the matter multiplets arise from "twisted" strings connecting different stacks of branes. The introduction of Euclidean 5-branes wrapped on the six-dimensional compact space leads to instanton effects. We examine the interplay between the annuli diagrams with an E5 boundary and the holomorphicity properties of the effective low-energy supergravity action which describes the system, including its instanton corrections. This talk is mostly based on [1].

Fractional D-branes and their gauge duals

Journal of High Energy Physics, 2001

We study the classical geometry associated to fractional D3-branes of type IIB string theory on IR 4 /Z 2 which provide the gravitational dual for N = 2 super Yang-Mills theory in four dimensions. As one can expect from the lack of conformal invariance on the gauge theory side, the gravitational background displays a repulson-like singularity. It turns out however, that such singularity can be excised by an enhançon mechanism. The complete knowledge of the classical supergravity solution allows us to identify the coupling constant of the dual gauge theory in terms of the string parameters and to find a logarithmic running that is governed precisely by the β function of the N = 2 super Yang-Mills theory.

D-branes in non-critical superstrings and duality in Script N = 1 gauge theories with flavor

Journal of High Energy Physics, 2006

We study D-branes in the superstring background IR 3,1 × SL(2, IR) k=1 /U (1) which are extended in the cigar direction. Some of these branes are new. The branes realize flavor in the four dimensional N = 1 gauge theories on the D-branes localized at the tip of the cigar. We study the analytic properties of the boundary conformal field theories on these branes with respect to their defining parameter and find non-trivial monodromies in this parameter. Through this approach, we gain a better understanding of the brane set-ups in ten dimensions involving wrapped NS5-branes. As one application, using the boundary conformal field theory description of the electric and magnetic D-branes, we can understand electric-magnetic (Seiberg) duality in N = 1 SQCD microscopically in a string theoretic context. P 2 , and vanishes at P 2 = 0. For other values of (J, M ), the corresponding boundary states set down in were studied in detail in . One aspect which was not very clear about these branes was whether they have a well-defined unitary self-overlap. 3 . We find here that one can indeed understand these branes systematically following the ideas of and there do exist branes with a unitary spectrum for values of J in the range 0 ≤ J ≤ 1 2 . These branes have a semiclassical interpretation of turning on a worldvolume two form flux in the region near the tip of the cigar. At J = 0, this value of the flux reaches a critical value and localizes at the tip, corresponding to forming a localized brane. In the quantum theory, this is seen in a relation between the boundary states which expresses the localized identity boundary state as a difference between the J = M = 0 and the 1 The branes which are Dirichlet in some of the flat directions are also interesting, they give rise to non-perturbative effects like domain walls and instantons [8] in the gauge theories. 2 These are similar to the ZZ [14] and FZZT [15,16] branes in Liouville theory; in fact the relation between them is more than an analogy [17]. 3 It was noticed [18] that for real values of J ∈ ( 1 4 , 1 2 ], the self-overlaps are well-defined.