On the Structure of Infrared Singularities of Gauge-Theory Amplitudes

A closed formula is obtained for the infrared singularities of dimensionally regularized, massless gauge-theory scattering amplitudes with an arbitrary number of legs and loops. It follows from an all-order conjecture for the anomalous-dimension matrix of n-jet operators in soft-collinear effective theory. We show that the form of this anomalous dimension is severely constrained by soft-collinear factorization, non-abelian exponentiation, and the behavior of amplitudes in collinear limits. Using a diagrammatic analysis, we demonstrate that these constraints imply that to three-loop order the anomalous dimension involves only two-parton correlations, with the possible exception of a single color structure multiplying a function of conformal cross ratios depending on the momenta of four external partons, which would have to vanish in all two-particle collinear limits. We argue that such a function does not appear at three-loop order, and that the same is true in higher orders. Our formula predicts Casimir scaling of the cusp anomalous dimension to all orders in perturbation theory, and we explicitly check that the constraints exclude the appearance of higher Casimir invariants at four loops. Using known results for the quark and gluon form factors, we derive the three-loop coefficients of the 1/epsilon^n pole terms (with n=1,...,6) for an arbitrary n-parton scattering amplitude in massless QCD. This generalizes Catani's two-loop formula proposed in 1998.Comment: 46 pages, 9 figures; v2: improved treatment of collinear limits, references added; v3: improved discussion of non-abelian exponentiation, references updated; v4: typo in eq. (17) fixed, references updated; v5: additional term in (17

Behavioral Adjustment in Children with Life Threatening Illness A Qualitative Study

This study investigated factors that affect adjustment in children with life-threatening illness from the viewpoint of the parents/caregivers. The data were collected from parents/caregivers whose children have a life threatening diagnosis. Parents/caregivers were interviewed and asked to complete the Parent Request Questionnaire (PRQ) which was given to them after the in-person interview. This newly developed PRQ was utilized into prior research to predict the levels of adjustment in children. It includes age, whether the child has been informed of the diagnosis, whether the child engages in age-appropriate activities, the child\u27s prior experience with death, the child\u27s family\u27s involvement in treatment, and the child\u27s belief in an after-life. Prior literature suggests associations between these factors and the child\u27s ability to adjust to the diagnosis. This study examined these factors revealed by the parents/caregivers and any similarities were noted. There has been limited research conducted on behavioral adjustment in children with life threatening illness. This qualitative study utilized an open-ended interview process to gather information about the factors that promote behavioral adjustment and whether or not the factors already researched in quantitative studies applied. The interviewees were participants in independent support groups benefiting the caregivers/parents of the children with life threatening illness. Participants were also recruited by word-of-mouth after calling such groups and individuals in California. The PRQ was distributed after the interview as an additional measure. The interview revealed factors as noted by the caregivers and indicated the emergent themes of: isolation, fear, inquisitiveness, age-appropriate activities, diagnoses shared, and support systems. The interview and the PRQ were used to analyze child adjustment reported during the interview sessions. The participants in this study were all parents/caregivers. Instrumentation was a structured interview and a demographic questionnaire (PRQ). The texts were transcribed and analyzed using Thematic Analysis. Narratives of their life experience with the child having life-threatening illness were examined. Emergent themes, previously mentioned, were elicited from the interview material in hopes of providing additional support services needed as voiced by the parents/caregivers. “The electronic version of the dissertation is accessible at the Ohiolink ETD center http://www.ohiolink.edu/etd

Behavioral Adjustment in Children with Life Threatening Illness A Qualitative Study

This study investigated factors that affect adjustment in children with life-threatening illness from the viewpoint of the parents/caregivers. The data were collected from parents/caregivers whose children have a life threatening diagnosis. Parents/caregivers were interviewed and asked to complete the Parent Request Questionnaire (PRQ) which was given to them after the in-person interview. This newly developed PRQ was utilized into prior research to predict the levels of adjustment in children. It includes age, whether the child has been informed of the diagnosis, whether the child engages in age-appropriate activities, the child\u27s prior experience with death, the child\u27s family\u27s involvement in treatment, and the child\u27s belief in an after-life. Prior literature suggests associations between these factors and the child\u27s ability to adjust to the diagnosis. This study examined these factors revealed by the parents/caregivers and any similarities were noted. There has been limited research conducted on behavioral adjustment in children with life threatening illness. This qualitative study utilized an open-ended interview process to gather information about the factors that promote behavioral adjustment and whether or not the factors already researched in quantitative studies applied. The interviewees were participants in independent support groups benefiting the caregivers/parents of the children with life threatening illness. Participants were also recruited by word-of-mouth after calling such groups and individuals in California. The PRQ was distributed after the interview as an additional measure. The interview revealed factors as noted by the caregivers and indicated the emergent themes of: isolation, fear, inquisitiveness, age-appropriate activities, diagnoses shared, and support systems. The interview and the PRQ were used to analyze child adjustment reported during the interview sessions. The participants in this study were all parents/caregivers. Instrumentation was a structured interview and a demographic questionnaire (PRQ). The texts were transcribed and analyzed using Thematic Analysis. Narratives of their life experience with the child having life-threatening illness were examined. Emergent themes, previously mentioned, were elicited from the interview material in hopes of providing additional support services needed as voiced by the parents/caregivers. “The electronic version of the dissertation is accessible at the Ohiolink ETD center http://www.ohiolink.edu/etd

An Effective Field Theory Look at Deep Inelastic Scattering

This talk discusses the effective field theory view of deep inelastic scattering. In such an approach, the standard factorization formula of a hard coefficient multiplied by a parton distribution function arises from matching of QCD onto an effective field theory. The DGLAP equations can then be viewed as the standard renormalization group equations that determines the cut-off dependence of the non-local operator whose forward matrix element is the parton distribution function. As an example, the non-singlet quark splitting functions is derived directly from the renormalization properties of the non-local operator itself. This approach, although discussed in the literature, does not appear to be well known to the larger high energy community. In this talk we give a pedagogical introduction to this subject.Comment: 11 pages, 1 figure, To appear in Modern Physics Letters

The oxygen-independent metabolism of cyclic monoterpenes in Castellaniella defragrans 65Phen

BACKGROUND: The facultatively anaerobic betaproteobacterium Castellaniella defragrans 65Phen utilizes acyclic, monocyclic and bicyclic monoterpenes as sole carbon source under oxic as well as anoxic conditions. A biotransformation pathway of the acyclic β-myrcene required linalool dehydratase-isomerase as initial enzyme acting on the hydrocarbon. An in-frame deletion mutant did not use myrcene, but was able to grow on monocyclic monoterpenes. The genome sequence and a comparative proteome analysis together with a random transposon mutagenesis were conducted to identify genes involved in the monocyclic monoterpene metabolism. Metabolites accumulating in cultures of transposon and in-frame deletion mutants disclosed the degradation pathway. RESULTS: Castellaniella defragrans 65Phen oxidizes the monocyclic monoterpene limonene at the primary methyl group forming perillyl alcohol. The genome of 3.95 Mb contained a 70 kb genome island coding for over 50 proteins involved in the monoterpene metabolism. This island showed higher homology to genes of another monoterpene-mineralizing betaproteobacterium, Thauera terpenica 58Eu(T), than to genomes of the family Alcaligenaceae, which harbors the genus Castellaniella. A collection of 72 transposon mutants unable to grow on limonene contained 17 inactivated genes, with 46 mutants located in the two genes ctmAB (cyclic terpene metabolism). CtmA and ctmB were annotated as FAD-dependent oxidoreductases and clustered together with ctmE, a 2Fe-2S ferredoxin gene, and ctmF, coding for a NADH:ferredoxin oxidoreductase. Transposon mutants of ctmA, B or E did not grow aerobically or anaerobically on limonene, but on perillyl alcohol. The next steps in the pathway are catalyzed by the geraniol dehydrogenase GeoA and the geranial dehydrogenase GeoB, yielding perillic acid. Two transposon mutants had inactivated genes of the monoterpene ring cleavage (mrc) pathway. 2-Methylcitrate synthase and 2-methylcitrate dehydratase were also essential for the monoterpene metabolism but not for growth on acetate. CONCLUSIONS: The genome of Castellaniella defragrans 65Phen is related to other genomes of Alcaligenaceae, but contains a genomic island with genes of the monoterpene metabolism. Castellaniella defragrans 65Phen degrades limonene via a limonene dehydrogenase and the oxidation of perillyl alcohol. The initial oxidation at the primary methyl group is independent of molecular oxygen

Turning points: the personal and professional circumstances that lead academics to become middle managers

In the current higher education climate, there is a growing perception that the pressures associated with being an academic middle manager outweigh the perceived rewards of the position. This article investigates the personal and professional circumstances that lead academics to become middle managers by drawing on data from life history interviews undertaken with 17 male and female department heads from a range of disciplines, in a post-1992 UK university. The data suggests that experiencing conflict between personal and professional identities, manifested through different socialization experiences over time, can lead to a ‘turning point’ and a decision that affects a person’s career trajectory. Although the results of this study cannot be generalized, the findings may help other individuals and institutions move towards a firmer understanding of the academic who becomes head of department—in relation to theory, practice and research

On the renormalization of multiparton webs

We consider the recently developed diagrammatic approach to soft-gluon exponentiation in multiparton scattering amplitudes, where the exponent is written as a sum of webs - closed sets of diagrams whose colour and kinematic parts are entangled via mixing matrices. A complementary approach to exponentiation is based on the multiplicative renormalizability of intersecting Wilson lines, and their subsequent finite anomalous dimension. Relating this framework to that of webs, we derive renormalization constraints expressing all multiple poles of any given web in terms of lower-order webs. We examine these constraints explicitly up to four loops, and find that they are realised through the action of the web mixing matrices in conjunction with the fact that multiple pole terms in each diagram reduce to sums of products of lower-loop integrals. Relevant singularities of multi-eikonal amplitudes up to three loops are calculated in dimensional regularization using an exponential infrared regulator. Finally, we formulate a new conjecture for web mixing matrices, involving a weighted sum over column entries. Our results form an important step in understanding non-Abelian exponentiation in multiparton amplitudes, and pave the way for higher-loop computations of the soft anomalous dimension.Comment: 60 pages, 15 figure

Direct photon production with effective field theory

The production of hard photons in hadronic collisions is studied using Soft-Collinear Effective Theory (SCET). This is the first application of SCET to a physical, observable cross section involving energetic partons in more than two directions. A factorization formula is derived which involves a non-trivial interplay of the angular dependence in the hard and soft functions, both quark and gluon jet functions, and multiple partonic channels. The relevant hard, jet and soft functions are computed to one loop and their anomalous dimensions are determined to three loops. The final resummed inclusive direct photon distribution is valid to next-to-next-to-leading logarithmic order (NNLL), one order beyond previous work. The result is improved by including non-logarithmic terms and photon isolation cuts through matching, and compared to Tevatron data and to fixed order results at the Tevatron and the LHC. The resummed cross section has a significantly smaller theoretical uncertainty than the next-to-leading fixed-order result, particularly at high transverse momentum.Comment: 42 pages, 9 figures; v2: references added, minor changes; v3: typos; v4: typos, corrections in (16), (47), (72

Factorization Properties of Soft Graviton Amplitudes

We apply recently developed path integral resummation methods to perturbative quantum gravity. In particular, we provide supporting evidence that eikonal graviton amplitudes factorize into hard and soft parts, and confirm a recent hypothesis that soft gravitons are modelled by vacuum expectation values of products of certain Wilson line operators, which differ for massless and massive particles. We also investigate terms which break this factorization, and find that they are subleading with respect to the eikonal amplitude. The results may help in understanding the connections between gravity and gauge theories in more detail, as well as in studying gravitational radiation beyond the eikonal approximation.Comment: 35 pages, 5 figure