Luciano Girardello - Academia.edu (original) (raw)
Papers by Luciano Girardello
Physics Letters B, 1994
We study strong-weak coupling duality (S-duality) in N=4 supersymmetric non-Abelian Yang-Mills th... more We study strong-weak coupling duality (S-duality) in N=4 supersymmetric non-Abelian Yang-Mills theories. These theories arise naturally as the low-energy limit of four-dimensional toroidal compactifications of the heterotic string.
We investigate features of duality in three dimensional N = 2 Chern-Simons matter theories conjec... more We investigate features of duality in three dimensional N = 2 Chern-Simons matter theories conjectured to describe M2 branes at toric Calabi Yau four-fold singularities. For 3D theories with non-chiral 4D parents we propone a Seiberg-like duality which turns out to be a toric duality. For theories with chiral 4D parents we discuss the conditions under which that Seiberg-like duality leads to toric duality. We comment on such duality in 3D theories without 4D parents.
Nuclear Physics B - Proceedings Supplements, 1995
In this talk we review some results concerning a mechanism for reducing the moduli space of a top... more In this talk we review some results concerning a mechanism for reducing the moduli space of a topological field theory to a proper submanifold of the ordinary moduli space. Such mechanism is explicitly realized in the example of constrained topological gravity, obtained by topologically twisting the N=2 Liouville theory.
Journal of High Energy Physics, 2006
We investigate models of SU(N) SQCD with adjoint matter and non trivial mesonic deformations. We ... more We investigate models of SU(N) SQCD with adjoint matter and non trivial mesonic deformations. We apply standard methods in the dual magnetic theory and we find meta-stable supersymmetry breaking vacua with arbitrary large lifetime. We comment on the difference with known models.
Nuclear Physics B, 1994
In this paper we show that there exists a new class of topological field theories, whose correlat... more In this paper we show that there exists a new class of topological field theories, whose correlators are intersection numbers of cohomology classes in a constrained moduli space. Our specific example is a formulation of 2D topological gravity. The constrained modulispace is the Poincaré dual of the top Chern-class of the bundle E hol −→ M g , whose sections are the holomorphic differentials. Its complex dimension is 2g − 3, rather then 3g − 3. We derive our model by performing the A-topological twist of N=2 supergravity, that we identify with N=2 Liouville theory, whose rheonomic construction is also presented. The peculiar field theoretical mechanism, rooted in BRST cohomology, that is responsible for the constraint on moduli space is discussed, the key point being the fact that the graviphoton becomes a Lagrange multiplier after twist. The relation with conformal field theories is also explored. Our formulation of N=2 Liouville theory leads to a representation of the N=2 superconformal algebra with c = 6, instead of the value c = 9 that is obtained by untwisting the Verlinde and Verlinde formulation of topological gravity. The reduced central charge is the shadow, in conformal field theory, of the constraint on moduli space. Our representation of the N=2 algebra can be split into the direct sum of a minimal model with c = 3/2 and a "maximal" model with c = 9/2. Considerations on the matter coupling of constrained topological gravity are also presented. Their study requires the analysis of both the A-twist and the B-twist of N=2 matter coupled supergravity, that we postpone to future work.
Journal of High Energy Physics, 2011
We study dynamical supersymmetry breaking in vector-like superconformal N = 1 gauge theories. We ... more We study dynamical supersymmetry breaking in vector-like superconformal N = 1 gauge theories. We find appropriate deformations of the superpotential to overcome the problem of the instability of the non supersymmetric vacuum. The request for long lifetime translates into constraints on the physical couplings which in this regime can be controlled through efficient RG analysis.
Physics Letters B, 1994
We derive a model of constrained topological gravity, a theory recently introduced by us through ... more We derive a model of constrained topological gravity, a theory recently introduced by us through the twist of N=2 Liouville theory, starting from the general BRST algebra and imposing the moduli space constraint as a gauge fixing. To do this, it is necessary to introduce a formalism that allows a careful treatment of the global and the local degrees of freedom of the fields. Surprisingly, the moduli space constraint arises from the simplest and most natural gauge-fermion (antighost × Lagrange multiplier), confirming the previous results. The simplified technical set-up provides a deeper understanding for constrained topological gravity and a convenient framework for future investigations, like the matter coupling and the analysis of the effects of the constraint on the holomorphic anomaly.
Journal of High Energy Physics, 2006
We investigate the Dijkgraaf-Vafa proposal when supersymmetry is broken. We consider U(N) SYM wit... more We investigate the Dijkgraaf-Vafa proposal when supersymmetry is broken. We consider U(N) SYM with chiral adjoint matter where the coupling constants in the tree-level superpotential are promoted to chiral spurions. The holomorphic part of the low-energy glueball superpotential can still be analyzed. We compute the holomorphic supersymmetry breaking contributions using methods of the geometry underlying the N = 1 effective gauge theory viewed as a Whitham system. We also study the change in the effective glueball superpotential using perturbative supergraph techniques in the presence of spurions.
Journal of High Energy Physics, 2007
We study metastable dynamical breaking of supersymmetry in A n quiver gauge theories. We present ... more We study metastable dynamical breaking of supersymmetry in A n quiver gauge theories. We present a general analysis and criteria for the perturbative existence of metastable vacua in quivers of any length. Different mechanisms of gauge mediation can be realized.
Journal of High Energy Physics, 2008
We study the geometric interpretation of metastable vacua for systems of D3 branes at non isolate... more We study the geometric interpretation of metastable vacua for systems of D3 branes at non isolated toric deformable singularities. Using the L aba examples, we investigate the relations between the field theoretic susy breaking and restoration and the complex deformations of the CY singularities.
Journal of High Energy Physics, 2002
We extend the pp-wave correspondence to a non supersymmetric example. The model is the type 0B st... more We extend the pp-wave correspondence to a non supersymmetric example. The model is the type 0B string theory on the pp-wave R-R background. We explicitly solve the model and give the spectrum of physical states. The field theory counterpart is given by a sector of the large N SU(N) × SU(N) CFT living on a stack of N electric and N magnetic D3-branes. The relevant effective coupling constant is g ef f = g s N/J 2 . The string theory has a tachyon in the spectrum, whose light-cone energy can be exactly computed as a function of g ef f . We argue that the perturbative analysis in g ef f in the dual gauge theory is reliable, with corrections of non perturbative type. We find a precise state/operator map, showing that the first perturbative corrections to the anomalous dimensions of the operators have the behavior expected from the string analysis. bigazzif@ictp.trieste.it aldo.cotrone@mib.infn.it luciano.girardello@mib.infn.it alberto.zaffaroni@mib.infn.it (5.52) where χ i and Z are 2N× 2N matrices, k = 0, 1. I commutes with all Z's and anticommutes with χ i . Most of the leading contribution in O k,qŌk,q come from contracting the l term in the sum with itself. However, in the BPS case q = k = 0, a λ J contribution, coming from the exchange graphs for the two impurities, cancels when summing the l = 0/l = 0, l = J/l = J and l = 0/l = J contractions. For generic q and k, the l = 0/l = J contraction carries an extra (−1) k e 2πiq factor, where the (−1) k is due to the fact that I anticommutes with the impurities. We thus obtain an exact cancellation of the λ J terms only for (−1) k e 2πiq = 1. This correlates the integer or half-integer modding of the phase with the insertion of I.
Journal of High Energy Physics, 1999
We discuss a solution of the equations of motion of five-dimensional gauged type IIB supergravity... more We discuss a solution of the equations of motion of five-dimensional gauged type IIB supergravity that describes confining SU(N) gauge theories at large N and large 't Hooft parameter. We prove confinement by computing the Wilson loop, and we show that our solution is generic, independent of most of the details of the theory.
Journal of High Energy Physics, 2010
We investigate features of duality in three dimensional N = 2 Chern-Simons matter theories conjec... more We investigate features of duality in three dimensional N = 2 Chern-Simons matter theories conjectured to describe M2 branes at toric Calabi Yau four-fold singularities. For 3D theories with non-chiral 4D parents we propone a Seiberg-like duality which turns out to be a toric duality. For theories with chiral 4D parents we discuss the conditions under which that Seiberg-like duality leads to toric duality. We comment on such duality in 3D theories without 4D parents.
Journal of High Energy Physics, 2010
We investigate supersymmetric models for dark matter which is represented by pseudomoduli in weak... more We investigate supersymmetric models for dark matter which is represented by pseudomoduli in weakly coupled hidden sectors. We propose a scheme to add a dark matter sector to quiver gauge theories with metastable supersymmetry breaking. We discuss the embedding of such scheme in string theory and we describe the dark matter sector in terms of D7 flavour branes. We explore the phenomenology in various regions of the parameters. * Postdoctoral researcher of FWO-Vlaanderen.
Journal of High Energy Physics, 1998
We find new, local, non-supersymmetric conformal field theories obtained by relevant deformations... more We find new, local, non-supersymmetric conformal field theories obtained by relevant deformations of the N=4 super Yang Mills theory in the large N limit. We contruct interpolating supergravity solutions that naturally represent the flow from the N=4 super Yang Mills UV theory to these non-supersymmetric IR fixed points. We also study the linearization around the N=4 superconformal point of N=1 supersymmetric, marginal deformations. We show that they give rise to N=1 superconformal fixed points, as expected from field-theoretical arguments.
Physics Letters B, 2003
We study a duality, recently conjectured by Klebanov and Polyakov, between higher-spin theories o... more We study a duality, recently conjectured by Klebanov and Polyakov, between higher-spin theories on AdS 4 and O(N ) vector models in 3-d. These theories are free in the UV and interacting in the IR. At the UV fixed point, the O(N ) model has an infinite number of higher-spin conserved currents. In the IR, these currents are no longer conserved for spin s > 2. In this paper, we show that the dual interpretation of this fact is that all fields of spin s > 2 in AdS 4 become massive by a Higgs mechanism, that leaves the spin-2 field massless. We identify the Higgs field and show how it relates to the RG flow connecting the two CFTs, which is induced by a double trace deformation.
Physics Letters B, 2000
The holographic RG flow in AdS/CFT correspondence naturally defines a holographic scheme in which... more The holographic RG flow in AdS/CFT correspondence naturally defines a holographic scheme in which the central charge c and the beta function are related by the formulaċ = −2cβ a β b G ab , where G ab is the metric of the kinetic term of the supergravity scalars. In particular, the metric in the space of couplings is f ab = 2cG ab . We perform some checks of that result and we compare it with the quantum field theory expectations. We discuss alternative definitions of the c-function. In particular, we compare, for a particular supersymmetric flow, the holographic c-function with the central charge computed directly from the two-point function of the stressenergy tensor.
Physics Letters B, 1994
We study strong-weak coupling duality (S-duality) in N=4 supersymmetric non-Abelian Yang-Mills th... more We study strong-weak coupling duality (S-duality) in N=4 supersymmetric non-Abelian Yang-Mills theories. These theories arise naturally as the low-energy limit of four-dimensional toroidal compactifications of the heterotic string.
We investigate features of duality in three dimensional N = 2 Chern-Simons matter theories conjec... more We investigate features of duality in three dimensional N = 2 Chern-Simons matter theories conjectured to describe M2 branes at toric Calabi Yau four-fold singularities. For 3D theories with non-chiral 4D parents we propone a Seiberg-like duality which turns out to be a toric duality. For theories with chiral 4D parents we discuss the conditions under which that Seiberg-like duality leads to toric duality. We comment on such duality in 3D theories without 4D parents.
Nuclear Physics B - Proceedings Supplements, 1995
In this talk we review some results concerning a mechanism for reducing the moduli space of a top... more In this talk we review some results concerning a mechanism for reducing the moduli space of a topological field theory to a proper submanifold of the ordinary moduli space. Such mechanism is explicitly realized in the example of constrained topological gravity, obtained by topologically twisting the N=2 Liouville theory.
Journal of High Energy Physics, 2006
We investigate models of SU(N) SQCD with adjoint matter and non trivial mesonic deformations. We ... more We investigate models of SU(N) SQCD with adjoint matter and non trivial mesonic deformations. We apply standard methods in the dual magnetic theory and we find meta-stable supersymmetry breaking vacua with arbitrary large lifetime. We comment on the difference with known models.
Nuclear Physics B, 1994
In this paper we show that there exists a new class of topological field theories, whose correlat... more In this paper we show that there exists a new class of topological field theories, whose correlators are intersection numbers of cohomology classes in a constrained moduli space. Our specific example is a formulation of 2D topological gravity. The constrained modulispace is the Poincaré dual of the top Chern-class of the bundle E hol −→ M g , whose sections are the holomorphic differentials. Its complex dimension is 2g − 3, rather then 3g − 3. We derive our model by performing the A-topological twist of N=2 supergravity, that we identify with N=2 Liouville theory, whose rheonomic construction is also presented. The peculiar field theoretical mechanism, rooted in BRST cohomology, that is responsible for the constraint on moduli space is discussed, the key point being the fact that the graviphoton becomes a Lagrange multiplier after twist. The relation with conformal field theories is also explored. Our formulation of N=2 Liouville theory leads to a representation of the N=2 superconformal algebra with c = 6, instead of the value c = 9 that is obtained by untwisting the Verlinde and Verlinde formulation of topological gravity. The reduced central charge is the shadow, in conformal field theory, of the constraint on moduli space. Our representation of the N=2 algebra can be split into the direct sum of a minimal model with c = 3/2 and a "maximal" model with c = 9/2. Considerations on the matter coupling of constrained topological gravity are also presented. Their study requires the analysis of both the A-twist and the B-twist of N=2 matter coupled supergravity, that we postpone to future work.
Journal of High Energy Physics, 2011
We study dynamical supersymmetry breaking in vector-like superconformal N = 1 gauge theories. We ... more We study dynamical supersymmetry breaking in vector-like superconformal N = 1 gauge theories. We find appropriate deformations of the superpotential to overcome the problem of the instability of the non supersymmetric vacuum. The request for long lifetime translates into constraints on the physical couplings which in this regime can be controlled through efficient RG analysis.
Physics Letters B, 1994
We derive a model of constrained topological gravity, a theory recently introduced by us through ... more We derive a model of constrained topological gravity, a theory recently introduced by us through the twist of N=2 Liouville theory, starting from the general BRST algebra and imposing the moduli space constraint as a gauge fixing. To do this, it is necessary to introduce a formalism that allows a careful treatment of the global and the local degrees of freedom of the fields. Surprisingly, the moduli space constraint arises from the simplest and most natural gauge-fermion (antighost × Lagrange multiplier), confirming the previous results. The simplified technical set-up provides a deeper understanding for constrained topological gravity and a convenient framework for future investigations, like the matter coupling and the analysis of the effects of the constraint on the holomorphic anomaly.
Journal of High Energy Physics, 2006
We investigate the Dijkgraaf-Vafa proposal when supersymmetry is broken. We consider U(N) SYM wit... more We investigate the Dijkgraaf-Vafa proposal when supersymmetry is broken. We consider U(N) SYM with chiral adjoint matter where the coupling constants in the tree-level superpotential are promoted to chiral spurions. The holomorphic part of the low-energy glueball superpotential can still be analyzed. We compute the holomorphic supersymmetry breaking contributions using methods of the geometry underlying the N = 1 effective gauge theory viewed as a Whitham system. We also study the change in the effective glueball superpotential using perturbative supergraph techniques in the presence of spurions.
Journal of High Energy Physics, 2007
We study metastable dynamical breaking of supersymmetry in A n quiver gauge theories. We present ... more We study metastable dynamical breaking of supersymmetry in A n quiver gauge theories. We present a general analysis and criteria for the perturbative existence of metastable vacua in quivers of any length. Different mechanisms of gauge mediation can be realized.
Journal of High Energy Physics, 2008
We study the geometric interpretation of metastable vacua for systems of D3 branes at non isolate... more We study the geometric interpretation of metastable vacua for systems of D3 branes at non isolated toric deformable singularities. Using the L aba examples, we investigate the relations between the field theoretic susy breaking and restoration and the complex deformations of the CY singularities.
Journal of High Energy Physics, 2002
We extend the pp-wave correspondence to a non supersymmetric example. The model is the type 0B st... more We extend the pp-wave correspondence to a non supersymmetric example. The model is the type 0B string theory on the pp-wave R-R background. We explicitly solve the model and give the spectrum of physical states. The field theory counterpart is given by a sector of the large N SU(N) × SU(N) CFT living on a stack of N electric and N magnetic D3-branes. The relevant effective coupling constant is g ef f = g s N/J 2 . The string theory has a tachyon in the spectrum, whose light-cone energy can be exactly computed as a function of g ef f . We argue that the perturbative analysis in g ef f in the dual gauge theory is reliable, with corrections of non perturbative type. We find a precise state/operator map, showing that the first perturbative corrections to the anomalous dimensions of the operators have the behavior expected from the string analysis. bigazzif@ictp.trieste.it aldo.cotrone@mib.infn.it luciano.girardello@mib.infn.it alberto.zaffaroni@mib.infn.it (5.52) where χ i and Z are 2N× 2N matrices, k = 0, 1. I commutes with all Z's and anticommutes with χ i . Most of the leading contribution in O k,qŌk,q come from contracting the l term in the sum with itself. However, in the BPS case q = k = 0, a λ J contribution, coming from the exchange graphs for the two impurities, cancels when summing the l = 0/l = 0, l = J/l = J and l = 0/l = J contractions. For generic q and k, the l = 0/l = J contraction carries an extra (−1) k e 2πiq factor, where the (−1) k is due to the fact that I anticommutes with the impurities. We thus obtain an exact cancellation of the λ J terms only for (−1) k e 2πiq = 1. This correlates the integer or half-integer modding of the phase with the insertion of I.
Journal of High Energy Physics, 1999
We discuss a solution of the equations of motion of five-dimensional gauged type IIB supergravity... more We discuss a solution of the equations of motion of five-dimensional gauged type IIB supergravity that describes confining SU(N) gauge theories at large N and large 't Hooft parameter. We prove confinement by computing the Wilson loop, and we show that our solution is generic, independent of most of the details of the theory.
Journal of High Energy Physics, 2010
We investigate features of duality in three dimensional N = 2 Chern-Simons matter theories conjec... more We investigate features of duality in three dimensional N = 2 Chern-Simons matter theories conjectured to describe M2 branes at toric Calabi Yau four-fold singularities. For 3D theories with non-chiral 4D parents we propone a Seiberg-like duality which turns out to be a toric duality. For theories with chiral 4D parents we discuss the conditions under which that Seiberg-like duality leads to toric duality. We comment on such duality in 3D theories without 4D parents.
Journal of High Energy Physics, 2010
We investigate supersymmetric models for dark matter which is represented by pseudomoduli in weak... more We investigate supersymmetric models for dark matter which is represented by pseudomoduli in weakly coupled hidden sectors. We propose a scheme to add a dark matter sector to quiver gauge theories with metastable supersymmetry breaking. We discuss the embedding of such scheme in string theory and we describe the dark matter sector in terms of D7 flavour branes. We explore the phenomenology in various regions of the parameters. * Postdoctoral researcher of FWO-Vlaanderen.
Journal of High Energy Physics, 1998
We find new, local, non-supersymmetric conformal field theories obtained by relevant deformations... more We find new, local, non-supersymmetric conformal field theories obtained by relevant deformations of the N=4 super Yang Mills theory in the large N limit. We contruct interpolating supergravity solutions that naturally represent the flow from the N=4 super Yang Mills UV theory to these non-supersymmetric IR fixed points. We also study the linearization around the N=4 superconformal point of N=1 supersymmetric, marginal deformations. We show that they give rise to N=1 superconformal fixed points, as expected from field-theoretical arguments.
Physics Letters B, 2003
We study a duality, recently conjectured by Klebanov and Polyakov, between higher-spin theories o... more We study a duality, recently conjectured by Klebanov and Polyakov, between higher-spin theories on AdS 4 and O(N ) vector models in 3-d. These theories are free in the UV and interacting in the IR. At the UV fixed point, the O(N ) model has an infinite number of higher-spin conserved currents. In the IR, these currents are no longer conserved for spin s > 2. In this paper, we show that the dual interpretation of this fact is that all fields of spin s > 2 in AdS 4 become massive by a Higgs mechanism, that leaves the spin-2 field massless. We identify the Higgs field and show how it relates to the RG flow connecting the two CFTs, which is induced by a double trace deformation.
Physics Letters B, 2000
The holographic RG flow in AdS/CFT correspondence naturally defines a holographic scheme in which... more The holographic RG flow in AdS/CFT correspondence naturally defines a holographic scheme in which the central charge c and the beta function are related by the formulaċ = −2cβ a β b G ab , where G ab is the metric of the kinetic term of the supergravity scalars. In particular, the metric in the space of couplings is f ab = 2cG ab . We perform some checks of that result and we compare it with the quantum field theory expectations. We discuss alternative definitions of the c-function. In particular, we compare, for a particular supersymmetric flow, the holographic c-function with the central charge computed directly from the two-point function of the stressenergy tensor.