Gravity duals of supersymmetric gauge theories on three-manifolds

We study gravity duals to a broad class of N=2 supersymmetric gauge theories defined on a general class of three-manifold geometries. The gravity backgrounds are based on Euclidean self-dual solutions to four-dimensional gauged supergravity. As well as constructing new examples, we prove in general that for solutions defined on the four-ball the gravitational free energy depends only on the supersymmetric Killing vector, finding a simple closed formula when the solution has U(1) x U(1) symmetry. Our result agrees with the large N limit of the free energy of the dual gauge theory, computed using localization. This constitutes an exact check of the gauge/gravity correspondence for a very broad class of gauge theories with a large N limit, defined on a general class of background three-manifold geometries.Comment: 74 pages, 2 figures; v2: minor change

Viroids of grapevines in Italy

Rebviroide in ItalienEs wird über das Vorkommen niedermolekularer RNAs bei 48 Vitis-vinifera-Stämmen und 15 amerikanischen Vitis-Arten und Kreuzungen aus Italien, Osteuropa, Mittelmeer- und Nahost-Ländern berichtet. In den Sämlingen zweier Sorten wurden keine derartigen RNAs gefunden. Aufgrund ihres elektrophoretischen Verhaltens wurden diese RNAs vorläufig identifiziert als Grapevine yellow speckle-Viroid (GYSVd), Grapeivine-Viroid 2 (GVd2) und Hop stunt-Viroid (HSVd). Das letztere Viroid löste bei künstlich infizierten Pflanzen von Tomate cv. Rutgers und Gurke cv. Suyo Befallssymptome aus. HSVd, GYSVd und GVd2 wurden in 97, 92 bzw. 11 % der untersuchten Proben wiedergefunden. In der Regel lagen Mischinfektionen vor, wobei die Kombination von HSVd mit GYSVd überwog. Diese beiden Viroide kamen regelmäßig in Reben mit den Symptomen von Yellow speckle oder Vein banding vor. Es wurde keine eindeutige Beziehung zwischen dem Vorkommen eines der Viroide und Rebkrankheiten mit unklarer Ätiologie, wie Vein necrosis oder Fleck, gefunden

Virus-like particles and ultrastructural modifications in the phloem of leafroll-affected grapevines

Ultrastructural studies were carried out on thin-sectioned phloem and mesophyll tissues of 42 grapevine accessions with leafroll symptoms, coming from 12 different countries (Italy, Portugal, Spain, France, Yugoslavia, Hungary, Soviet Union, Bulgaria, Greece, Cyprus, Malta and Nigeria). A total of 47 specimens were observed with the electron microscope. About half (48 %) the samples examined contained isometric virus-like particles in one or more phloem elements (sieve tubes, companion and parenchyma cells), whereas only 15 % of the samples contained filamentous virus-like particles in the same type of cells. None of these viruses could be transmitted by sap inoculation. Ultrastructural features of major importance were double-membraned vesiculated bodies possibly representing profoundly modified cell organelles (mitochondria and/or plastids) and bundles of tubular structures 40-45 nm or 60-100 nm in diameter, the !arger of which exhibited a central core seemingly made up of one or more filaments of tubular P-protein. The present results are discussed in the light of the findings reported in the literature on leafroll-infected grapevine tissues.Virusartige Partikeln und Veränderungen der Ultrastruktur im Phloem blattrollkranker RebenBei 42 Rebenstämmen mit Blattrollsymptomen wurde die Ultrastruktur des Blattphloems und Mesophylls untersucht. Die Reben stammten aus 12 verschiedenen Ländern (Italien, Portugal, Spanien, Frankreich, Jugoslawien, Ungarn, Sowjetunion, Bulgarien, Griechenland, Cypern, Malta und Nigeria). Insgesamt wurden 47 Exemplare elektronenmikroskopisch untersucht. Etwa die Hälfte der Proben (48 %) enthielt isometrische virusartige Partikeln in einem oder mehreren Phloemelementen (Siebröhren, Geleit- und Parenchymzellen); bei 15 % der Proben waren in denselben Zelltypen filamentöse virusartige Partikeln enthalten. Eine Saftübertragung der Viren war in keinem Falle möglich. Wichtige ultrastrukturelle Bildungen waren doppelwandige vesiculäre Körper, die möglicherweise stark abgewandelte Zellorganellen (Mitochondrien und/oder Plastiden) darstellen, sowie Bündel tubulärer Strukturen vom Durchmesser 40-45 nm oder 60-100 nm; die größeren Tubuli zeigten einen zentralen Kern, der anscheinend von einem oder mehreren Filamenten tubulären P-Proteins gebildet wurde. Die vorliegenden Ergebnisse werden im Zusammenhang mit den Literaturbefunden über blattrollinfiziertes Rebengewebe diskutiert

The Mn site in Mn-doped Ga-As nanowires: an EXAFS study

We present an EXAFS study of the Mn atomic environment in Mn-doped GaAs nanowires. Mn doping has been obtained either via the diffusion of the Mn used as seed for the nanowire growth or by providing Mn during the growth of Au-induced wires. As a general finding, we observe that Mn forms chemical bonds with As but is not incorporated in a substitutional site. In Mn-induced GaAs wires, Mn is mostly found bonded to As in a rather disordered environment and with a stretched bond length, reminiscent of that exhibited by MnAs phases. In Au-seeded nanowires, along with stretched Mn-As coordination we have found the presence of Mn in a Mn-Au intermetallic compound.Comment: This is an author-created, un-copyedited version of an article accepted for publication in Semiconductor Science and Technology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher-authenticated version is available online at doi:10.1088/0268-1242/27/8/08500

Operator Counting and Eigenvalue Distributions for 3D Supersymmetric Gauge Theories

We give further support for our conjecture relating eigenvalue distributions of the Kapustin-Willett-Yaakov matrix model in the large N limit to numbers of operators in the chiral ring of the corresponding supersymmetric three-dimensional gauge theory. We show that the relation holds for non-critical R-charges and for examples with {\mathcal N}=2 instead of {\mathcal N}=3 supersymmetry where the bifundamental matter fields are nonchiral. We prove that, for non-critical R-charges, the conjecture is equivalent to a relation between the free energy of the gauge theory on a three sphere and the volume of a Sasaki manifold that is part of the moduli space of the gauge theory. We also investigate the consequences of our conjecture for chiral theories where the matrix model is not well understood.Comment: 27 pages + appendices, 5 figure

Holographic renormalization and supersymmetry

Holographic renormalization is a systematic procedure for regulating divergences in observables in asymptotically locally AdS spacetimes. For dual boundary field theories which are supersymmetric it is natural to ask whether this defines a supersymmetric renormalization scheme. Recent results in localization have brought this question into sharp focus: rigid supersymmetry on a curved boundary requires specific geometric structures, and general arguments imply that BPS observables, such as the partition function, are invariant under certain deformations of these structures. One can then ask if the dual holographic observables are similarly invariant. We study this question in minimal N = 2 gauged supergravity in four and five dimensions. In four dimensions we show that holographic renormalization precisely reproduces the expected field theory results. In five dimensions we find that no choice of standard holographic counterterms is compatible with supersymmetry, which leads us to introduce novel finite boundary terms. For a class of solutions satisfying certain topological assumptions we provide some independent tests of these new boundary terms, in particular showing that they reproduce the expected VEVs of conserved charges.Comment: 70 pages; corrected typo

Identification of the agent of grapevine fleck disease

An antiserum against an Italian isolate of grapevine phloem-limited isometric virus (GPLIV) was used in an ELISA survey carried out for assessing the natural distribution of the virus and its association with fleck disease. A total of 591 vines of Vitis rupestris were checked for the presence of GPLIV. Of 150 plants with fleck symptoms, 138 (92 %) were ELISA-positive and 12 (8 %) negative. Of 441 symptomless V. rupestris, 435 (98,6 %) were ELISA-negative and 6 (1,4 %) positive for GPLIV. The virus was detected in about 30 % of 694 vines of different origin grown in Apulia (Southern Italy). The highest infection (53 %) was in a commercial vineyard of cv. Italia and the lowest (8 %) in a plot of certified and visually selected rootstocks. Fleck-infected, but not fleck-free V. rupestris contained virus particles and vesiculated inclusion bodies in phloem tissues. LN 33 plantlets derived from in vitro culture of meristem tips from ELISA-positive fleck-infected mother plants were found to be free from GPLIV, as ascertained by ELISA and thin-sectioning. These vines failed to induce fleck symptoms when grafted on V. rupestris. It is concluded that GPLIV is the agent of fleck and, therefore, it should be renamed grapevine fleck virus (GFKV)

Comments on F-maximization and R-symmetry in 3D SCFTs

We report preliminary results on the recently proposed F-maximization principle in 3D SCFTs. We compute numerically in the large-N limit the free energy on the three-sphere of an N=2 Chern-Simons-Matter theory with a single adjoint chiral superfield which is known to exhibit a pattern of accidental symmetries associated to chiral superfields that hit the unitarity bound and become free. We observe that the F-maximization principle produces a U(1) R-symmetry consistent with previously obtained bounds but inconsistent with a postulated Seiberg-like duality. Potential modifications of the principle associated to the decoupling fields do not appear to be sufficient to account for the observed violations.Comment: 17 pages, 3 figures; v2 a reference has been added, a missing factor of 2 has been corrected in eq (3.3) and the numerical results have been accordingly updated. The new results do not show any obvious signs of violation of previously obtained bounds. A potential disagreement with a postulated Seiberg-like duality is note