arXiv subjects

Riccardo Argurio

Publications and source records attributed to Riccardo Argurio.

At least 55 records · Page 3Linked to original sources

arXiv2014

Anatomy of new SUSY breaking holographic RG flows

We find and thoroughly study new supergravity domain wall solutions which are holographic realizations of supersymmetry breaking strongly coupled gauge theories. We set ourselves in an N=2 gauged supergravity with a minimal content in order to reproduce a dual N=1 effective SCFT which has a U(1)_R symmetry, a chiral operator whose components are responsible for triggering the RG flow, and an additional U(1)_F symmetry. We present a full three dimensional parameter space of solutions, which generically break supersymmetry. Some known solutions are recovered for specific sets of values of the parameters, with the new solutions interpolating between them. The generic backgrounds being singular, we provide a stability test of their dual theories by showing that there are no tachyonic resonances in the two point correlators. We compute the latter by holographic renormalization. We also carefully analyze the appearance of massless modes, such as the dilaton and the R axion, when the respective symmetries are spontaneously broken, and their lifting when the breaking is explicit. We further comment on the application of such class of backgrounds as archetypes of strongly coupled hidden sectors for gauge mediation of supersymmetry breaking. In particular, we show that it is possible to model in this way all types of hierarchies between the visible sector gaugino and sfermion masses.

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arXiv2013

Tame D-tadpoles in gauge mediation

We revisit models of gauge mediated supersymmetry breaking where messenger parity is violated. Such a symmetry is usually invoked in order to set to zero potentially dangerous hypercharge D-term tadpoles. A milder hypothesis is that the D-tadpole vanishes only at the first order in the gauge coupling constant. Then the next order leads to a contribution to the sfermion masses which is of the same magnitude as the usual radiative one. This enlarges the parameter space of gauge mediated models. We first give a completely general characterization of this contribution, in terms of particular three-point functions of hidden sector current multiplet operators. We then explore the parameter space by means of two simple weakly coupled models, where the D-tadpole arising at two-loops has actually a mild logarithmic divergence.

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arXiv2012

Field Theory Interpretation of N=2 Stringy Instantons

We consider stringy instanton contributions to the prepotential of low-energy N=2 theories engineered by D-brane set ups at orbifold and orientifold singularities. We show that such contributions can always be reproduced in a purely field theoretic UV completion. We perform the explicit check up to instanton number three, both for Sp(0) and U(1) stringy instantons, the latter being introduced for the purpose. We further argue that the UV completion that we propose, though weakly coupled, can be smoothly mapped to a gravity-dual inspired UV completion consisting of a cascade of baryonic root transitions.

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arXiv2012

Exploring Holographic General Gauge Mediation

We study models of gauge mediation with strongly coupled hidden sectors, employing a hard wall background as an holographic dual description. The structure of the soft spectrum depends crucially on the boundary conditions one imposes on bulk fields at the IR wall. Generically, vector and fermion correlators have poles at zero momentum, leading to gauge mediation by massive vector messengers and/or generating Dirac gaugino masses. Instead, non-generic choices of boundary conditions let one cover all of GGM parameter space. Enriching the background with R-symmetry breaking scalars, the SSM soft term structure becomes more constrained and similar to previously studied top-down models, while retaining the more analytic control the present bottom-up approach offers.

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arXiv2012

Holographic Correlators for General Gauge Mediation

We use holographic techniques to compute two-point functions of operators belonging to a conserved current supermultiplet in theories which break supersymmetry at strong coupling. These are the relevant quantities one has to compute in models of gauge mediation to determine the soft spectrum in supersymmetric extensions of the Standard Model (SSM). Such holographic approach can be used for diverse gravitational backgrounds, but here we focus, for definiteness, on asymptotically AdS backgrounds. After presenting the general framework, we apply our formulas to two explicit examples which differ by the nature of the SSM gauginos, which have Dirac or Majorana masses, corresponding to models that respectively preserve or break R-symmetry.

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arXiv2012

Collider signatures of goldstini in gauge mediation

We investigate the collider signatures of the multiple goldstini scenario in the framework of gauge mediation. This class of models is characterized by a visible sector (e.g. the MSSM or any extension) coupled by gauge interactions to more than one SUSY breaking sector. The spectrum consists of a light gravitino LSP, behaving as a goldstino, and a number of neutral fermions (the pseudo-goldstini) with a mass between that of the LSP and that of the lightest particle of the observable sector (LOSP). We consider the two situations where the LOSP is either a gaugino-like neutralino or a stau and we assume only one pseudo-goldstino of a mass of O(100) GeV. The coupling of the LOSP to the pseudo-goldstino can be enhanced with respect to those of the gravitino giving rise to characteristic signatures. We show that the decay modes of the LOSP into a SM particle and a pseudo-goldstino can be significant. For both LOSP scenarios we analyze (pseudo)-goldstini production at colliders. Compared to standard gauge mediation the final state spectrum is softer and more structured.

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arXiv2011

Pseudo-Goldstini in Field Theory

We consider two SUSY-breaking hidden sectors which decouple when their respective couplings to the visible particles are switched off. In such a scenario one expects to find two light fermions: the Goldstino and the pseudo-Goldstino. While the former remains massless in the rigid limit, the latter becomes massive due to radiative effects which we analyze from several different points of view. This analysis is greatly facilitated by a version of the Goldberger-Treiman relation, which allows us to write a universal non-perturbative formula for the mass. We carry out the analysis in detail in the context of gauge mediation, where we find that the pseudo-Goldstino mass is at least around the GeV scale and can be easily at the electroweak range, even in low scale models. This leads to interesting and unconventional possibilities in collider physics and it also has potential applications in cosmology.

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arXiv2010

Unscreening the Gaugino Mass with Chiral Messengers

Gaugino screening, the absence of next-to-leading order corrections to gaugino masses, is a generic feature of gauge mediation models of supersymmetry breaking. We show that in a specific class of models, known as semi-direct gauge mediation, it is possible to avoid gaugino screening by allowing for a chiral messenger sector. Messengers then acquire a mass at some scale, for instance by higgsing or by some auxiliary strong coupling dynamics. We implement this idea in a simple model which we work out explicitly.

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arXiv2010

Why not a di-NUT? or Gravitational duality and rotating solutions

We study how gravitational duality acts on rotating solutions, using the Kerr-NUT black hole as an example. After properly reconsidering how to take into account both electric (i.e. mass-like) and magnetic (i.e. NUT-like) sources in the equations of general relativity, we propose a set of definitions for the dual Lorentz charges. We then show that the Kerr-NUT solution has non-trivial such charges. Further, we clarify in which respect Kerr's source can be seen as a mass M with a dipole of NUT charges.

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arXiv2010

Patterns of Soft Masses from General Semi-Direct Gauge Mediation

We give a general formulation of semi-direct gauge mediation of supersymmetry breaking where the messengers interact with the hidden sector only through a weakly gauged group. Using this general formulation, we provide an explicit proof that the MSSM gaugino masses are vanishing to leading order in the gauge couplings. On the other hand, the MSSM sfermion masses have, generically, a non-vanishing leading contribution. We discuss how such a mechanism can successfully be combined with other mediation schemes which give tachyonic sfermions, such as sequestered anomaly mediation and some direct gauge mediation models.

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arXiv2009

Natural semi-direct gauge mediation and D-branes at singularities

We consider semi-direct gauge mediation models of supersymmetry breaking where the messengers are composite fields and their supersymmetric mass is naturally generated through quartic superpotential couplings. We show that such composite messenger models can be easily embedded in quiver gauge theories arising from D-branes at Calabi-Yau singularities, and argue that semi-direct gauge mediation is in fact a very natural option for supersymmetry breaking in D-brane models. We provide several explicit examples and discuss their salient phenomenological properties.

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arXiv2009

Supersymmetry and Gravitational Duality

We study how the supersymmetry algebra copes with gravitational duality. As a playground, we consider a charged Taub-NUT solution of D=4, N=2 supergravity. We find explicitly its Killing spinors, and the projection they obey provides evidence that the dual magnetic momenta necessarily have to appear in the supersymmetry algebra. The existence of such a modification is further supported using an approach based on the Nester form. In the process, we find new expressions for the dual magnetic momenta, including the NUT charge. The same expressions are then rederived using gravitational duality.

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arXiv2008

Gauge/gravity duality and the interplay of various fractional branes

We consider different types of fractional branes on a Z_2 orbifold of the conifold and analyze in detail the corresponding gauge/gravity duality. The gauge theory possesses a rich and varied dynamics, both in the UV and in the IR. We find the dual supergravity solution which contains both untwisted and twisted 3-form fluxes, related to what are known as deformation and N=2 fractional branes respectively. We analyze the resulting RG flow from the supergravity perspective, by developing an algorithm to easily extract it. We find hints of a generalization of the familiar cascade of Seiberg dualities due to a non-trivial interplay between the different types of fractional branes. We finally consider the IR behavior in several limits, where the dominant effective dynamics is either confining, in a Coulomb phase or runaway, and discuss the resolution of singularities in the dual geometric background.

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arXiv2008

Boosting Taub-NUT to a BPS NUT-wave

The boosted Taub-NUT metric with zero ADM mass is shown to possess a dual momentum in the direction of the boost giving credit to the existence of another 4-vector K_μin linearized gravity associated to the NUT charge and dual to the usual P_μ. Taking the infinite boost limit we obtain a shock pp-wave with NUT charge. We show that the latter is the gravitational dual of the infinitely boosted Schwarzschild metric, also known as the Aichelburg-Sexl pp-wave. We review the fact that this new shock pp-wave is also an half-BPS solution of N=1 supergravity. It has a BPS bound equal to K_t=|K_z|.

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arXiv2008

Instantons and Toric Quiver Gauge Theories

We show how to construct the general action coupling (multi)instantons to gauge theories arising from branes probing arbitrary toric singularities. We give a general set of rules for how to construct such an action given the knowledge of the superpotential for the gauge theory. The main idea is to obtain the action by higgsing a theory whose instanton dynamics is known, namely an orbifold of N=4 super Yang-Mills. We find that the couplings of the fermionic zero-modes with the holomorphic fields are dictated by the structure of the superpotential describing the toric singularity. We present explicit examples such as the Suspended Pinch Point, the Conifold and the first three del Pezzo's. We perform various checks on these results by further higgsing to smaller orbifolds and present some applications, including both gauge theory and stringy instantons.

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arXiv2007

A Quiver of Many Runaways

We study the quantum corrections to the moduli space of the quiver gauge theory corresponding to regular and fractional D3-branes at the dP_1 singularity. We find that besides the known runaway behavior at the lowest step of the duality cascade, there is a runaway direction along a mesonic branch at every higher step of the cascade. Moreover, the algebra of the chiral operators which obtain the large expectation values is such that we reproduce Altmann's first order deformation of the dP_1 cone.

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arXiv2007

Stringy Instantons at Orbifold Singularities

We study the effects produced by D-brane instantons on the holomorphic quantities of a D-brane gauge theory at an orbifold singularity. These effects are not limited to reproducing the well known contributions of the gauge theory instantons but also generate extra terms in the superpotential or the prepotential. On these brane instantons there are some neutral fermionic zero-modes in addition to the ones expected from broken supertranslations. They are crucial in correctly reproducing effects which are dual to gauge theory instantons, but they may make some other interesting contributions vanish. We analyze how orientifold projections can remove these zero-modes and thus allow for new superpotential terms. These terms contribute to the dynamics of the effective gauge theory, for instance in the stabilization of runaway directions.

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arXiv2007

Metastable vacua and D-branes at the conifold

We consider quiver gauge theories arising on D-branes at simple Calabi-Yau singularities (quotients of the conifold). These theories have metastable supersymmetry breaking vacua. The field theoretic mechanism is basically the one exhibited by the examples of Intriligator, Seiberg and Shih in SUSY QCD. In a dual description, the SUSY breaking is captured by the presence of anti-branes. In comparison to our earlier related work, the main improvements of the present construction are that we can reach the free magnetic range of the SUSY QCD theory where the existence of the metastable vacua is on firm footing, and we can see explicitly how the small masses for the quark flavors (necessary to the existence of the SUSY breaking vacua) are dynamically stabilized. One crucial mass term is generated by a stringy instanton. Finally, our models naturally incorporate R-symmetry breaking in the non-supersymmetric vacuum, in a way similar to the examples of Kitano, Ooguri and Ookouchi.

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