Phases of supersymmetric gauge theories from M-theory on G_2 manifolds

We consider M-theory on compact spaces of G_2 holonomy constructed as orbifolds of the form (CY x S^1)/Z_2 with fixed point set \Sigma on the CY. This describes N=1 SU(2) gauge theories with b_1(\Sigma) chiral multiplets in the adjoint. For b_1=0, it generalizes to compact manifolds the study of the phase transition from the non-Abelian to the confining phase through geometrical S^3 flops. For b_1=1, the non-Abelian and Coulomb phases are realized, where the latter arises by desingularization of the fixed point set, while an S^2 x S^1 flop occurs. In addition, an extremal transition between G_2 spaces can take place at conifold points of the CY moduli space where unoriented membranes wrapped on CP^1 and RP^2 become massless.Comment: 21 pages, LaTeX, v2: mistake in spectra corrected, reference added, v3: one more reference added, version published in JHE

An N=1 Triality by Spectrum Matching

On promoting the type IIA side of the N=1 Heterotic/type IIA dual pairs of [1] to M-theory on a `barely G_2 Manifold' of [2], by spectrum-matching we show a possible triality between Heterotic on a self-mirror Calabi-Yau, M-theory on the above `barely G_2-Manifold' constructed from the Calabi-Yau on the type IIA side and $F$-theory on an elliptically fibered Calabi-Yau 4-fold fibered over a trivially rationally ruled CP^1 x E base, E being the Enriques surface. We raise an apparent puzzle on the F-theory side, namely, the Hodge data of the 4-fold derived can not be obtained by a naive freely acting orbifold of CY_3(3,243) x T^2 as one might have guessed on the basis of arguments related to dualities involving string, M and (definition of) F theories. There are some interesting properties of the antiholomorphic involution used in \cite{VW} for constructing the type IIA orientifold and by us in constructing the 'barely G_2 manifold', that we also study.Comment: 14 pages, LaTex; v3: journal versio

Livatn og Høyeåna. Vannkvalitetsutvikling 1982-1993

Konsentrasjonen av totalfosfor i Livatn var i 1992-93 omlag på nivå med resultatene fra 1982. Pga. noe høyere humusinnhold i 1992-93, kan en forvente en høyere naturlig bakgrunnsverdi for fosfor. Dette kan indikere en viss reduksjon av de menneskeskapte tilførslene siden 1982. Konsentrasjonen av totalnitrogen var noe laver i 1992-93, sammenlignet med 1982 og 1985. Nitrogentilførelene vil variere naturlig fra år til år avhengig av klimaforhold, men noe av nedgangen kan skyldes avløpstiltak i området. Algemengdene var i 1992 lavere enn i 1982, men høyere enn i 1985. Store svinginger gjør det vanskelig å avgjøre om det er oppnådd en generell reduksjon av algekonsentrasjonen i løpet av de siste ti årene. Innholdet av termostabile koliforme bakterier var i 1992-93 lavere enn tilsvarende målinger 1985. Vassdraget er forsuret, men det er store pH-variasjoner gjennom året. Hele vassdraget inneholder forholdsvis mye aluminium pga. forsuringen. pH-verdien i vassdraget var noe høyere enn i 1982 og 1985. Høyeåna utgjør omlag 5% av vannføringen i Mandaslselva nedstrøms samløpet mellom de to elvene. Det må derfor være ekstreme avvik i vannføring og surhet for at Høyeåna kan påvirke vannkvaliteten i Mandalselva i nevneverdig grad. Høyeåna har gjennomgående høyere pH-verdier enn Mandalselva

Naturalistic Study Examining the Data/Frame Model of Sensemaking by Assessing Experts in Complex, Time-Pressured Aviation Domains

Research on expert chess players, radiologists and landmine detection personnel suggests a use of cognitive frameworks, alternatively referred to as schemas, templates, scripts, frames and models, to effectively perceive, interpret, understand, recall, and anticipate information. These experts may use cognitive frameworks to capture past experience in ways that support rapid pattern recognition, adaptive responses and proactivity. The proposed research approach assumes that experienced pilots will similarly rely on cognitive frameworks to handle information and make sense of complex, fast-moving situations experienced in their information-dense environments. Predictions from Klein et al.\u27s (2006) Data/Frame Model of Sensemaking were used to evaluate event-based interview data collected from uninhabited aerial system (UAS) pilots and high performance military aircraft pilots (F-16 and UH-60 Black Hawk) in order to assess the methods with which these experts handle large amounts of critical information in their operations. This effort may benefit the sensemaking model, a model based largely on domains in which situations unfold over time and decision-making can be adapted, such as in information operations, nursing and fire fighting, by comparing its predictions with data collected from UAS pilots. The UAS operations domain, in particular, has characteristics that differ from those of domains on which the model is based because UAS pilot sensemaking must support decisions and continuous adjustments of an aircraft operating in a dynamic, potentially complex, and rapidly shifting environment from which the pilot is physically removed. The military aviation domain may be similar to studied domains that some decisions need to be made rapidly, and situations can change rapidly; nevertheless, as a new domain to the model, offers the potential to reveal new insights. Based on this research, recommendations are offered for aviation training and other information-rich domains, and evidence is provided that addresses the question, How much information can a person handle

On the equivalence of N=1 brane worlds and geometric singularities with flux

We consider Kaluza Klein reductions of M-theory on the Z_N orbifold of the spin bundle over S^3 along two different U(1) isometries. The first one gives rise to the familiar ``large N duality'' of the N=1 SU(N) gauge theory in which the UV is realized as the world-volume theory of N D6-branes wrapped on S^3, whereas the IR involves N units of RR flux through an S^2. The second reduction gives an equivalent version of this duality in which the UV is realized geometrically in terms of an S^2 of A_{N-1} singularities, with one unit of RR flux through the S^2. The IR is reached via a geometric transition and involves a single D6 brane on a lens space S^3/Z_N or, alternatively, a singular background (S^2\times R^4)/Z_N, with one unit of RR flux through S^2 and, localized at the singularities, an action of their stabilizer group in the U(1) RR gauge bundle, so that no massless twisted states occur. We also consider linear sigma-model descriptions of these backgrounds.Comment: 25 pages, LaTeX; v2: one reference added, published versio

A model realisation of the Jaffe-Wilczek correlation for pentaquarks

We discuss a realisation of the pentaquark structure proposed by Jaffe and Wilczek within a simple quark model with colour-spin contact interactions and coloured harmonic confinement, which accurately describes the $\Delta-N$ splitting. In this model spatially compact diquarks are formed in the pentaquark but no such compact object exists in the nucleon. The colour-spin attraction brings the Jaffe-Wilczek-like state down to a low mass, compatible with the experimental observation and below that of the naive ground state with all $S$-waves. We find, however, that although these trends are maintained, the extreme effects observed do not survive the required ``smearing'' of the delta function contact interaction. We also demonstrate the weakness of the ``schematic'' approximation when applied to a system containing a $P$-wave. An estimate of the anti-charmed pentaquark mass is made which is in line with the Jaffe-Wilczek prediction and significantly less than the value reported by the H1 collaboration.Comment: 10 pages, uses psfra

M-theory moduli spaces and torsion-free structures

Motivated by the description of $\mathcal{N}=1$ M-theory compactifications to four-dimensions given by Exceptional Generalized Geometry, we propose a way to geometrize the M-theory fluxes by appropriately relating the compactification space to a higher-dimensional manifold equipped with a torsion-free structure. As a non-trivial example of this proposal, we construct a bijection from the set of $Spin(7)$-structures on an eight-dimensional $S^{1}$-bundle to the set of $G_{2}$-structures on the base space, fully characterizing the $G_{2}$-torsion clases when the total space is equipped with a torsion-free $Spin(7)$-structure. Finally, we elaborate on how the higher-dimensional manifold and its moduli space of torsion-free structures can be used to obtain information about the moduli space of M-theory compactifications.Comment: 24 pages. Typos fixed. Minor clarifications adde

Asymmetric Hillslope Erosion Following Wildfire in Fourmile Canyon, Colorado

Infrequent, high-magnitude events cause a disproportionate amount of sediment transport on steep hillslopes, but few quantitative data are available that capture these processes. Here we study the influence of wildfire and hillslope aspect on soil erosion in Fourmile Canyon, Colorado. This region experienced the Fourmile Fire of 2010, strong summer convective storms in 2011 and 2012, and extreme flooding in September 2013. We sampled soils shortly after these events and use fallout radionuclides to trace erosion on polar- and equatorial-facing burned slopes and on a polar-facing unburned slope. Because these radionuclides are concentrated in the upper decimeter of soil, soil inventories are sensitive to erosion by surface runoff. The polar-facing burned slope had significantly lower cesium-137 (137Cs) and lead-210 (210Pb) inventories (p \u3c 0.05) than either the polar-facing unburned slope or equatorial-facing burned slope. Local slope magnitude does not appear to control the erosional response to wildfire, as relatively gently sloping (~20%) polar-facing positions were severely eroded in the most intensively burned area. Field evidence and soil profile analyses indicate up to 4 cm of local soil erosion on the polar-facing burned slope, but radionuclide mass balance indicates that much of this was trapped nearby. Using a 137Cs-based erosion model, we find that the burned polar-facing slope had a net mean sediment loss of 2 mm (~1 kg m−2) over a one to three year period, which is one to two orders of magnitude higher than longer-term erosion rates reported for this region. In this part of the Colorado Front Range, strong hillslope asymmetry controls soil moisture and vegetation; polar-facing slopes support significantly denser pine and fir stands, which fuels more intense wildfires. We conclude that polar-facing slopes experience the most severe surface erosion following wildfires in this region, indicating that landscape-scale aridity can control the geomorphic response of hillslopes to wildfires. Copyright © 2018 John Wiley & Sons, Ltd

Heterotic compactifications and nearly-Kahler manifolds

We propose that under certain conditions heterotic string compactifications on half-flat and nearly-Kahler manifolds are equivalent. Based on this correspondence we argue that the moduli space of the nearly-Kahler manifolds under discussion consists only of the Kahler deformations moduli space and there is no correspondent for the complex structure deformations.Comment: 5 pages, references added, typos correcte

G_2 Domain Walls in M-theory

M-theory is considered in its low-energy limit on a G_2 manifold with non-vanishing flux. Using the Killing spinor equations for linear flux, an explicit set of first-order bosonic equations for supersymmetric solutions is found. These solutions describe a warped product of a domain wall in four-dimensional space-time and a deformed G_2 manifold. It is shown how these domain walls arise from the perspective of the associated four-dimensional N=1 effective supergravity theories. We also discuss the inclusion of membrane and M5-brane sources.Comment: 30 pages, Late