| 1. |
- Argurio, Riccardo, 1972, et al.
(författare)
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Natural semidirect gauge mediation and D-branes at singularities
- 2009
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Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 2470-0010 .- 2470-0029. ; 80:4, s. 045001-
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Tidskriftsartikel (refereegranskat)abstract
- We consider semidirect 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 semidirect 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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| 2. |
- Argurio, Riccardo, 1972, et al.
(författare)
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Stringy instantons at orbifold singularities
- 2007
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Ingår i: Journal of High Energy Physics. ; 0607
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 3. |
- Argurio, Riccardo, et al.
(författare)
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The Octagon at large M
- 2022
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479.
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Tidskriftsartikel (refereegranskat)abstract
- Recently, the first instance of a model of D-branes at Calabi-Yau singularities where supersymmetry is broken dynamically into stable vacua has been proposed. This construction was based on a system of N regular and M = 1 fractional branes placed at the tip of the so-called (orientifolded) Octagon singularity. In this paper we show that this model admits a large M generalization, having the same low energy effective dynamics. This opens up the possibility that the effect on geometry is smooth, and amenable to describing the gauge theory all along the RG flow, including the deep IR, in terms of a weakly coupled gravity dual background. The relevance of this result in the wider context of the string landscape and the Swampland program is also discussed.
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| 4. |
- Bertolini, Matteo, et al.
(författare)
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BPS three-brane solution on smooth ALE manifolds with flux
- 2002
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Ingår i: Fortsch. Phys.. ; 50, s. 802-
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Tidskriftsartikel (refereegranskat)abstract
- In the present talk I review the construction of a new supersymmetric 3-brane solution of type IIB supergravity on an ALE transverse space in presence of a non trivial flux of the complex 2-form across the ALE cycles. After introducing the ansatz for the solution I will show how the supergravity field equations reduce to a differential equation of Heun type in the non-conformal warp factor H of the metric. Although our analysis is worked out purely at a macroscopic level comments will be made on the general features of the (non-conformal) gauge theory dual to this solution
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| 5. |
- Bertolini, Matteo, et al.
(författare)
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Fractional branes and N = 1 gauge theories
- 2002
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Ingår i: Nuclera Physics. ; B:630, s. 222-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss fractional D3-branes on the orbifold C^3/Z_2*Z_2. We study the open and the closed string spectrum on this orbifold. The corresponding N=1 theory on the brane has, generically, a U(N_1)*U(N_2)*U(N_3)*U(N_4) gauge group with matter in the bifundamental. In particular, when only one type of brane is present, one obtains pure N=1 Yang-Mills. We study the coupling of the branes to the bulk fields and present the corresponding supergravity solution, valid at large distances. By using a probe analysis, we are able to obtain the Wilsonian beta-function for those gauge theories that possess some chiral multiplet. Although, due to the lack of moduli, the probe technique is not directly applicable to the case of pure N=1 Yang-Mills, we point out that the same formula gives the correct result also for this case.
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| 6. |
- Bertolini, Matteo, et al.
(författare)
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Supersymmetric 3-branes on smooth ALE manifolds with flux
- 2001
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Ingår i: Nuclear Physics. ; B:617, s. 3-
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Tidskriftsartikel (refereegranskat)abstract
- We construct a new family of classical BPS solutions of type IIB supergravity describing 3-branes transverse to a 6-dimensional space with topology R^2*ALE. They are characterized by a non-trivial flux of the supergravity 2-forms through the homology 2-cycles of a generic smooth ALE manifold. Our solutions have two Killing spinors and thus preserve N=2 supersymmetry. They are expressed in terms of a quasi harmonic function H (the ``warp factor''), whose properties we study in the case of the simplest ALE, namely the Eguchi-Hanson manifold. The equation for H is identified as an instance of the confluent Heun equation. We write explicit power series solutions and solve the recurrence relation for the coefficients, discussing also the relevant asymptotic expansions. While, as in all such N=2 solutions, supergravity breaks down near the brane, the smoothing out of the vacuum geometry has the effect that the warp factor is regular in a region near the cycle. We interpret the behavior of the warp factor as describing a three-brane charge ``smeared'' over the cycle and consider the asymptotic form of the geometry in that region, showing that conformal invariance is broken even when the complex type IIB 3-form field strength is assumed to vanish. We conclude with a discussion of the basic features of the gauge theory dual.
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| 7. |
- Jung, Christian, et al.
(författare)
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A comparison of very old patients admitted to intensive care unit after acute versus elective surgery or intervention
- 2019
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Ingår i: Journal of critical care. - : W B SAUNDERS CO-ELSEVIER INC. - 0883-9441 .- 1557-8615. ; 52, s. 141-148
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Tidskriftsartikel (refereegranskat)abstract
- Background: We aimed to evaluate differences in outcome between patients admitted to intensive care unit (ICU) after elective versus acute surgery in a multinational cohort of very old patients (80 years; VIP). Predictors of mortality, with special emphasis on frailty, were assessed.Methods: In total, 5063 VIPs were induded in this analysis, 922 were admitted after elective surgery or intervention, 4141 acutely, with 402 after acute surgery. Differences were calculated using Mann-Whitney-U test and Wilcoxon test. Univariate and multivariable logistic regression were used to assess associations with mortality.Results: Compared patients admitted after acute surgery, patients admitted after elective surgery suffered less often from frailty as defined as CFS (28% vs 46%; p < 0.001), evidenced lower SOFA scores (4 +/- 5 vs 7 +/- 7; p < 0.001). Presence of frailty (CFS >4) was associated with significantly increased mortality both in elective surgery patients (7% vs 12%; p = 0.01), in acute surgery (7% vs 12%; p = 0.02).Conclusions: VIPs admitted to ICU after elective surgery evidenced favorable outcome over patients after acute surgery even after correction for relevant confounders. Frailty might be used to guide clinicians in risk stratification in both patients admitted after elective and acute surgery.
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| 8. |
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| 9. |
- Petersson, Christoffer, 1979, et al.
(författare)
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Patterns of Soft Masses from General Semi-Direct Gauge Mediation
- 2010
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Ingår i: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; 2010:3
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 10. |
- Petersson, Christoffer, 1979, et al.
(författare)
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Unscreening the Gaugino Mass with Chiral Messengers
- 2010
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Ingår i: Journal of High Energy Physics. - 1029-8479 .- 1126-6708.
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Tidskriftsartikel (refereegranskat)abstract
- 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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