Simplifying instanton corrections to N=4 SYM correlators

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited

An Index for 4 dimensional Super Conformal Theories

We present a trace formula for an index over the spectrum of four dimensional superconformal field theories on $S^3 \times$ time. Our index receives contributions from states invariant under at least one supercharge and captures all information -- that may be obtained purely from group theory -- about protected short representations in 4 dimensional superconformal field theories. In the case of the $\mathcal{N}=4$ theory our index is a function of four continuous variables. We compute it at weak coupling using gauge theory and at strong coupling by summing over the spectrum of free massless particles in $AdS_5\times S^5$ and find perfect agreement at large $N$ and small charges. Our index does not reproduce the entropy of supersymmetric black holes in $AdS_5$, but this is not a contradiction, as it differs qualitatively from the partition function over supersymmetric states of the ${\cal N}=4$ theory. We note that entropy for some small supersymmetric $AdS_5$ black holes may be reproduced via a D-brane counting involving giant gravitons. For big black holes we find a qualitative (but not exact) agreement with the naive counting of BPS states in the free Yang Mills theory. In this paper we also evaluate and study the partition function over the chiral ring in the $\mathcal{N}=4$ Yang Mills theory.Comment: harvmac 40+16 pages, v3: references and table of contents added, typos fixe

Gauge-invariant correlation functions in light-cone superspace

We initiate a study of correlation functions of gauge-invariant operators in N=4 super Yang-Mills theory using the light-cone superspace formalism. Our primary aim is to develop efficient methods to compute perturbative corrections to correlation functions. This analysis also allows us to examine potential subtleties which may arise when calculating off-shell quantities in light-cone gauge. We comment on the intriguing possibility that the manifest N=4 supersymmetry in this approach may allow for a compact description of entire multiplets and their correlation functions.Comment: 35 pages, several figure

Banana Xanthomonas wilt: a review of the disease, management strategies and future research directions

Banana production in Eastern Africa is threatened by the presence of a new devastating bacterial disease caused by Xanthomonas vasicola pv. musacearum (formerly Xanthomonas campestris pv. musacearum). The disease has been identified in Uganda, Eastern Democratic Republic of Congo, Rwanda and Tanzania. Disease symptoms include wilting and yellowing of leaves, excretion of a yellowish bacterial ooze, premature ripening of the bunch, rotting of fruit and internal yellow discolorationof the vascular bundles. Plants are infected either by insects through the inflorescence or by soil-borne bacterial inoculum through the lower parts of the plant. Short- and long-distance transmission of thedisease mainly occurs via contaminated tools and insects, though other organisms such as birds may also be involved. Although no banana cultivar with resistance to the disease has been identified as yet,it appears that certain cultivars have mechanisms to ‘escape’ the disease. Management and control of the disease involve methods that reduce the inoculum’s density and spread of the pathogen. Removalof the male bud (de-budding) has proven to be very effective in preventing the disease incidence since the male bud appears to be the primary infection site. The economic impact of banana Xanthomonaswilt is not fully understood but its impact on food security in the region is very significant. While germplasm screening for the disease is ongoing, efforts to genetically engineer resistance in somebanana cultivars are also making good progress. This paper presents a review of the disease and management strategies that have been successful in curtailing its spread

Comparative investigation of MLOs associated with Caribbean and African coconut lethal decline diseases by DNA hybridization and PCR assays

Mycoplasmalike organisms (MLOs) associated with lethal decline diseases of the coconut palm (Cocos nuciferd) in eastern and western Africa were detected by dot hybridizations using (32P)dATP-labeled cloned DNA probes. Two probes, each consisting of a genomic DNA fragment of the palm lethal yellowing (LY) MLO from Florida, hybridized at moderate stringency to DNAs from four coconut cultivars with lethal disease (LD) in Tanzania and from a solitary West African Tall coconut palm with symptoms of Awka disease in Nigeria. Neither probe hybridized to DNA of the LD-affected hybrid coconut PBI2I or to DNA of symptomless palms. Conserved, mollicute-specific oligonucleotide sequences used for polymerase chain reactions (PCR) primed the amplification of near full-length MLO I6S rRNA genes from all decline-affected palms. No restriction fragment length polymorphisms were observed when rDNA amplified from both LY- and LD-affected coconut palms were singly digested with the restriction endonucieases Alul, BamHI, Oral, EcoRI, Hpal, Hpall, Rsal, and Scal. Polymorphisms were evident after digestion of MLO rDNA with Taql. These data establish the existence of genetic relationships between MLOs associated with coconut lethal decline diseases in the western Caribbean region and in Africa and provide further evidence indicating that the LY and LD MLOs, although very similar, are not genetically identical pathogens

The Soft-Collinear Bootstrap: N=4 Yang-Mills Amplitudes at Six and Seven Loops

Infrared divergences in scattering amplitudes arise when a loop momentum $\ell$ becomes collinear with a massless external momentum $p$. In gauge theories, it is known that the L-loop logarithm of a planar amplitude has much softer infrared singularities than the L-loop amplitude itself. We argue that planar amplitudes in N=4 super-Yang-Mills theory enjoy softer than expected behavior as $\ell \parallel p$ already at the level of the integrand. Moreover, we conjecture that the four-point integrand can be uniquely determined, to any loop-order, by imposing the correct soft-behavior of the logarithm together with dual conformal invariance and dihedral symmetry. We use these simple criteria to determine explicit formulae for the four-point integrand through seven-loops, finding perfect agreement with previously known results through five-loops. As an input to this calculation we enumerate all four-point dual conformally invariant (DCI) integrands through seven-loops, an analysis which is aided by several graph-theoretic theorems we prove about general DCI integrands at arbitrary loop-order. The six- and seven-loop amplitudes receive non-zero contributions from 229 and 1873 individual DCI diagrams respectively.Comment: 27 pages, 48 figures, detailed results including PDF and Mathematica files available at http://goo.gl/qIKe8 v2: minor corrections v3: figure 7 corrected, Lemma 2 remove

The Lore of Low Methane Livestock:Co-Producing Technology and Animals for Reduced Climate Change Impact

Methane emissions from sheep and cattle production have gained increasing profile in the context of climate change. Policy and scientific research communities have suggested a number of technological approaches to mitigate these emissions. This paper uses the concept of co-production as an analytical framework to understand farmers’ evaluation of a 'good animal’. It examines how technology and sheep and beef cattle are co-produced in the context of concerns about the climate change impact of methane. Drawing on 42 semi-structured interviews, this paper demonstrates that methane emissions are viewed as a natural and integral part of sheep and beef cattle by farmers, rather than as a pollutant. Sheep and beef cattle farmers in the UK are found to be an extremely heterogeneous group that need to be understood in their specific social, environmental and consumer contexts. Some are more amenable to appropriating methane reducing measures than others, but largely because animals are already co-constructed from the natural and the technical for reasons of increased production efficiency

On the spectrum of AdS/CFT beyond supergravity

We test the spectrum of string theory on AdS_5 x S^5 derived in hep-th/0305052 against that of single-trace gauge invariant operators in free N=4 super Yang-Mills theory. Masses of string excitations at critical tension are derived by extrapolating plane-wave frequencies at g_{YM}=0 down to finite J. On the SYM side, we present a systematic description of the spectrum of single-trace operators and its reduction to PSU(2,2|4) superconformal primaries via a refined Eratostenes' supersieve. We perform the comparison of the resulting SYM/string spectra of charges and multiplicities order by order in the conformal dimension \Delta up to \Delta=10 and find perfect agreement. Interestingly, the SYM/string massive spectrum exhibits a hidden symmetry structure larger than expected, with bosonic subgroup SO(10,2) and thirty-two supercharges.Comment: 28 pages, LaTeX2

The almost ubiquitous association of 6.7 GHz methanol masers with dust

We report the results of 870-$\mu$m continuum observations, using the Large APEX Bolometer Camera (LABOCA), towards 77 class-II, 6.7-GHz methanol masers identified by the Methanol Multibeam (MMB) survey to map the thermal emission from cool dust towards these objects. These data complement a study of 630 methanol masers associated with compact dense clumps identified from the ATLASGAL survey. Compact dust emission is detected towards 70 sources, which implies a dust-association rate of 99% for the full MMB catalogue. Evaluation of the derived dust and maser properties leads us to conclude that the combined sample represents a single population tracing the same phenomenon. We find median clump masses of a few 10$^3$ M$\odot$ and that all but a handful of sources satisfy the mass-size criterion required for massive star formation. This study provides the strongest evidence of the almost ubiquitous association of methanol masers with massive, star-forming clumps. The fraction of methanol-maser associated clumps is a factor of ~2 lower in the outer Galaxy than the inner Galaxy, possibly a result of the lower metallicity environment of the former. We find no difference in the clump-mass and maser-luminosity distributions of the inner and outer Galaxy. The maser-pumping and clump-formation mechanisms are therefore likely to be relatively invariant to Galactic location. Finally, we use the ratio of maser luminosity and clump mass to investigate the hypothesis that the maser luminosity is a good indicator of the evolutionary stage of the embedded source, however, we find no evidence to support this.Comment: Accepted by MNRAS. 17 pages, 17 figures and 5 tables. The full version of Figs. 3 and 5 are only available in electronic form of the journal while the full versions of Tables 1, 2 and 4 will only be available through CDS. A complete version of the paper is available on reques

The ultra-violet question in maximally supersymmetric field theories

We discuss various approaches to the problem of determining which supersymmetric invariants are permitted as counterterms in maximally supersymmetric super Yang--Mills and supergravity theories in various dimensions. We review the superspace non-renormalisation theorems based on conventional, light-cone, harmonic and certain non-Lorentz covariant superspaces, and we write down explicitly the relevant invariants. While the first two types of superspace admit the possibility of one-half BPS counterterms, of the form $F^4$ and $R^4$ respectively, the last two do not. This suggests that UV divergences begin with one-quarter BPS counterterms, i.e. $d^2 F^4$ and $d^4 R^4$, and this is supported by an entirely different approach based on algebraic renormalisation. The algebraic formalism is discussed for non-renormalisable theories and it is shown how the allowable supersymmetric counterterms can be determined via cohomological methods. These results are in agreement with all the explicit computations that have been carried out to date. In particular, they suggest that maximal supergravity is likely to diverge at four loops in D=5 and at five loops in D=4, unless other infinity suppression mechanisms not involving supersymmetry or gauge invariance are at work.Comment: 56 pages, 1 figure, uses youngtab.sty. Contribution to the proceedings of the W.E. Heraeus Workhop "Quantum Gravity: Challenges and Perspectives", Bad Honnef, 14-16 April 2008. References and clarifying comments adde