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Luca Mazzucato

Publications and source records attributed to Luca Mazzucato.

32 records · Page 2Linked to original sources
arXiv2010

Taming the b antighost with Ramond-Ramond flux

In the pure spinor formalism for the superstring, the b antighost is necessary for multiloop amplitude computations and is a composite operator constructed to satisfy {Q,b}=T where Q is the BRST operator and T is the holomorphic stress-tensor. In superstring backgrounds with only NS-NS fields turned on, or in flat space, one needs to introduce "non-minimal" variables in order to construct the b antighost. However, in Type II backgrounds where the Ramond-Ramond bispinor field-strength satisfies certain conditions, the b antighost can be constructed without the non-minimal variables. Although the b antighost in these backgrounds is not holomorphic, its antiholomorphic derivative is BRST-trivial. We discuss the properties of this operator both in the AdS_5 x S^5 background and in a generic curved background.

hep-th↗
arXiv2009

On the Non-renormalization of the AdS Radius

We show that the relation between the 't Hooft coupling and the radius of AdS is not renormalized at one-loop in the sigma model perturbation theory. We prove this by computing the quantum effective action for the superstring on AdS_5 x S^5 and showing that it does not receive any finite alpha' corrections. We also show that the central charge of the interacting worldsheet conformal field theory vanishes at one-loop.

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arXiv2009

Dark Matter and Pseudo-flat Directions in Weakly Coupled SUSY Breaking Sectors

We consider candidates for dark matter in models of gauge mediated supersymmetry breaking, in which the supersymmetry breaking sector is weakly coupled and calculable. Such models typically contain classically flat directions, that receive one-loop masses of a few TeV. These pseudo-flat directions provide a new mechanism to account for the cold dark matter relic abundance. We discuss also the possibility of heavy gravitino dark matter in such models.

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arXiv2009

Direct Mediation and a Visible Metastable Supersymmetry Breaking Sector

We analyze an R-symmetry breaking deformation of the ISS model for a direct mediation of supersymmetry breaking from a metastable vacuum. The model is weakly coupled and calculable. The LSP gravitino is light (m_{3/2}<16 eV) and the MSSM spectrum is natural with a light Higgs. The supersymmetry breaking sector, which is usually hidden, is observable (m~1 TeV) and may be a candidate for cold dark matter. We discuss its production and signature at LHC. We propose a UV completion of the model in terms of a duality cascade.

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arXiv2009

Non-relativistic Branes

We construct gravitational non-relativistic brane solutions of type IIA/IIB string theories and M-theory and their near-horizon geometries. The non-relativistic M2 and M5-brane metrics have Schroedinger symmetries with dynamical exponent z=3/2 and z=3, respectively, whereas the known D3-brane solution has z=2. The non-relativistic D-brane, NS5-brane, F-string and KK monopole metrics have asymptotically space and time translations, space rotations, Galilean symmetries and a particle number symmetry. We construct two different gravitational backgrounds of a non-relativistic D1-D5 system, both having asymptotically Schroedinger symmetry with exponent z=2. We study the properties of the solutions and their phase diagram.

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arXiv2007

Supersymmetry Breaking Vacua from M Theory Fivebranes

We consider intersecting brane configurations realizing N=2 supersymmetric gauge theories broken to N=1 by multitrace superpotentials, and softly to N=0. We analyze, in the framework of M5-brane wrapping a curve, the supersymmetric vacua and the analogs of spontaneous supersymmetry breaking and soft supersymmetry breaking in gauge theories. We show that the M5-brane does not exhibit the analog of metastable spontaneous supersymmetry breaking, and does not have non-holomorphic minimal volume curves with holomorphic boundary conditions. However, we find that any point in the N=2 moduli space can be rotated to a non-holomorphic minimal volume curve, whose boundary conditions break supersymmetry. We interpret these as the analogs of soft supersymmetry breaking vacua in the gauge theory.

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arXiv2007

Non-Critical Pure Spinor Superstrings

We construct non-critical pure spinor superstrings in two, four and six dimensions. We find explicitly the map between the RNS variables and the pure spinor ones in the linear dilaton background. The RNS variables map onto a patch of the pure spinor space and the holomorphic top form on the pure spinor space is an essential ingredient of the mapping. A basic feature of the map is the requirement of doubling the superspace, which we analyze in detail. We study the structure of the non-critical pure spinor space, which is different from the ten-dimensional one, and its quantum anomalies. We compute the pure spinor lowest lying BRST cohomology and find an agreement with the RNS spectra. The analysis is generalized to curved backgrounds and we construct as an example the non-critical pure spinor type IIA superstring on AdS_4 with RR 4-form flux.

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arXiv2007

Integrability of Type II Superstrings on Ramond-Ramond Backgrounds in Various Dimensions

We consider type II superstrings on AdS backgrounds with Ramond-Ramond flux in various dimensions. We realize the backgrounds as supercosets and analyze explicitly two classes of models: non-critical superstrings on AdS_{2d} and critical superstrings on AdS_p\times S^p\times CY. We work both in the Green--Schwarz and in the pure spinor formalisms. We construct a one-parameter family of flat currents (a Lax connection) leading to an infinite number of conserved non-local charges, which imply the classical integrability of both sigma-models. In the pure spinor formulation, we use the BRST symmetry to prove the quantum integrability of the sigma-model. We discuss how classical κ-symmetry implies one-loop conformal invariance. We consider the addition of space-filling D-branes to the pure spinor formalism.

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arXiv2005

Remarks on the analytic structure of supersymmetric effective actions

We study the effective superpotential of N=1 supersymmetric gauge theories with a mass gap, whose analytic properties are encoded in an algebraic curve. We propose that the degree of the curve equals the number of semiclassical branches of the gauge theory. This is true for supersymmetric QCD with one adjoint and polynomial superpotential, where the two sheets of its hyperelliptic curve correspond to the gauge theory pseudoconfining and higgs branches. We verify this proposal in the new case of supersymmetric QCD with two adjoints and superpotential V(X)+XY^2, which is the confining phase deformation of the D_{n+2} SCFT. This theory has three kinds of classical vacua and its curve is cubic. Each of the three sheets of the curve corresponds to one of the three semiclassical branches of the gauge theory. We show that one can continuously interpolate between these branches by varying the couplings along the moduli space.

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arXiv2004

Chiral Rings, Anomalies and Electric-Magnetic Duality

We study electric-magnetic duality in the chiral ring of a supersymmetric U(N_c) gauge theory with adjoint and fundamental matter, in presence of a general confining phase superpotential for the adjoint and the mesons. We find the magnetic solution corresponding to both the pseudoconfining and higgs electric vacua. By means of the Dijkgraaf-Vafa method, we match the effective glueball superpotentials and show that in some cases duality works exactly offshell. We give also a picture of the analytic structure of the resolvents in the magnetic theory, as we smoothly interpolate between different higgs vacua on the electric side.

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arXiv2004

The Liouville Geometry of N=2 Instantons and the Moduli of Punctured Spheres

We study the instanton contributions of N=2 supersymmetric gauge theory and propose that the instanton moduli space is mapped to the moduli space of punctured spheres. Due to the recursive structure of the boundary in the Deligne-Knudsen-Mumford stable compactification, this leads to a new recursion relation for the instanton coefficients, which is bilinear. Instanton contributions are expressed as integrals on M_{0,n} in the framework of the Liouville F-models. This also suggests considering instanton contributions as a kind of Hurwitz numbers and also provides a prediction on the asymptotic form of the Gromov-Witten invariants. We also interpret this map in terms of the geometric engineering approach to the gauge theory, namely the topological A-model, as well as in the noncritical string theory framework. We speculate on the extension to nontrivial gravitational background and its relation to the uniformization program. Finally we point out an intriguing analogy with the self-dual YM equations for the gravitational version of SU(2) where surprisingly the same Hauptmodule of the SW solution appears.

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arXiv2003

Branched Matrix Models and the Scales of Supersymmetric Gauge Theories

In the framework of the matrix model/gauge theory correspondence, we consider supersymmetric U(N) gauge theory with $U(1)^N$ symmetry breaking pattern. Due to the presence of the Veneziano--Yankielowicz effective superpotential, in order to satisfy the $F$--term condition $\sum_iS_i=0$, we are forced to introduce additional terms in the free energy of the corresponding matrix model with respect to the usual formulation. This leads to a matrix model formulation with a cubic potential which is free of parameters and displays a branched structure. In this way we naturally solve the usual problem of the identification between dimensionful and dimensionless quantities. Furthermore, we need not introduce the $\N=1$ scale by hand in the matrix model. These facts are related to remarkable coincidences which arise at the critical point and lead to a branched bare coupling constant. The latter plays the role of the $\N=1$ and $\N=2$ scale tuning parameter. We then show that a suitable rescaling leads to the correct identification of the $\N=2$ variables. Finally, by means of the the mentioned coincidences, we provide a direct expression for the $\N=2$ prepotential, including the gravitational corrections, in terms of the free energy. This suggests that the matrix model provides a triangulation of the istanton moduli space.

hep-th↗
arXiv2002

The Superembedding Origin of the Berkovits Pure Spinor Covariant Quantization of Superstrings

We show that the pure spinor formalism proposed by Berkovits to covariantly quantize superstrings is a gauge fixed, twisted version of the complexified n=2 superembedding formulation of the superstring. This provides the Berkovits approach with a geometrical superdiffeomorphism invariant ground. As a consequence, the absence of the worldsheet (super)diffeomorphism ghosts in the pure spinor quantization prescription and the nature of the Berkovits BRST charge and antighost are clarified. Since superembedding is classically equivalent to the Green-Schwarz formulation, we thus also relate the latter to the pure spinor construction.

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