Factors that influence ponderosa pine duff mound consumption

When applying prescribed fire to long-unburned but fire-dependent ecosystems managers require better decision-support models to determine appropriate conditions for achieving desired effects. Prolonged combustion in duff accumulations at the base of large conifers can lead to fine root mortality, cambial injury, enhanced susceptibility to bark beetle attack, and possibly tree death. Pre-burn sampling to predict duff mound consumption from measurable attributes is vital in order to limit the deleterious effects of prolonged smoldering combustion. The objective of this study was to determine the conditions that influence duff consumption and analyze the variability of these factors in the field. Duff moisture content, mineral content, bulk density, composition and depth were spatially quantified to inform prescribed burning decisions. Variability in factors influencing consumption was analyzed within and between duff mounds to improve pre-burn sampling procedures. Results show that a significant amount of variability in properties that could influence consumption due to differences between and within duff mounds. Duff properties did not vary significantly between uphill and downhill sampling locations. There was a positive relationship between tree size and duff depth. There was no association between lower duff moisture content and duff depth. Sampling recommendations were developed for the most appropriate protocols of efficient and meaningful duff sampling on an operational basis. A laboratory experiment was conducted to investigate how measurable attributes of duff affect smoldering combustion in duff mound fuels. Samples were divided between upper and lower duff for a total of 100 burn tests. Moisture content was adjusted to observe the transition through the ignition and spread limit. Bulk density, mineral content and percent consumption were recorded for each burn. The moisture content threshold for smoldering combustion was 57% and 102% respectively for upper and lower duff. Percent consumption was inversely related to moisture content for both layers of duff, and partially dependent on mineral content for lower duff. Results from this study aim to identify important attributes of duff that control the burning process in order to inform prescribed burning decisions

Path integral formulation of Hodge duality on the brane

In the warped compactification with a single Randall-Sundrum brane, a puzzling claim has been made that scalar fields can be bound to the brane but their Hodge dual higher-rank anti-symmetric tensors cannot. By explicitly requiring the Hodge duality, a prescription to resolve this puzzle was recently proposed by Duff and Liu. In this note, we implement the Hodge duality via path integral formulation in the presence of the background gravity fields of warped compactifications. It is shown that the prescription of Duff and Liu can be naturally understood within this framework.Comment: 7 pages, LaTe

String and Fivebrane Solitons: Singular or Non-singular?

We ask whether the recently discovered superstring and superfivebrane solutions of D=10 supergravity admit the interpretation of non-singular solitons even though, in the absence of Yang-Mills fields, they exhibit curvature singularities at the origin. We answer the question using a test probe/source approach, and find that the nature of the singularity is probe-dependent. If the test probe and source are both superstrings or both superfivebranes, one falls into the other in a finite proper time and the singularity is real, whereas if one is a superstring and the other a superfivebrane it takes an infinite proper time (the force is repulsive!) and the singularity is harmless. Black strings and fivebranes, on the other hand, always display real singularities.Comment: 15 page

Macroscopic superstrings as interpolating solitons

It is known that, in string sigma-model metric, the `extreme' fivebrane solution of D=10 supergravity interpolates between D=10 Minkowski spacetime and a supersymmetric $S^3$ compactification to a linear dilaton vacuum. We show here that, in {\it fivebrane} sigma-model metric, the extreme string solution of D=10 supergravity interpolates between Minkowski spacetime and a hitherto unknown supersymmetric $S^7$ compactification of d=10 supergravity to a three-dimensional anti-de Sitter generalization of the linear dilaton vacuum, which may be invariantly characterized in terms of conformal Killing vectors. The dilaton field diverges near the string core but this divergence may be eliminated by re-interpreting the string solution as the extreme membrane solution of 11-dimensional supergravity. We show that the latter has an analytic extension through a regular degenerate event horizon to an interior region containing a curvature singularity. We obtain analogous results for other extended object solutions of supergravity theories.Comment: 12 page

The Scottish Criminal Jury: A Very Peculiar Institution

Duff describes and discusses the Scottish criminal jury. While the exact origins of the Scottish criminal jury are obscure, it is clear that it developed in tandem with, although in a different fashion from, its English counterpart

The Cosmological Constant is Probably Zero, and a Proof is Possibly Right

Hawking proposed that the cosmological constant is probably zero in quantum cosmology. Duff claimed that Hawking's proof is invalidated. Using the right configuration for the wave function of the universe, we provide a complete proof.Comment: 6 pages, modified versio

Hodge Duality on the Brane

It has been claimed that whereas scalars can be bound to a Randall-Sundrum brane, higher p-form potentials cannot, in contradiction with the Hodge duality between 0-form and 3-form potentials in the five-dimensional bulk. Here we show that a 3-form in the bulk correctly yields a 2-form on the brane, in complete agreement with both bulk and brane duality. We also emphasize that the phenomenon of photon screening in the Randall-Sundrum geometry is ruled out by the bulk Einstein equation.Comment: 6 pages, Latex. We emphasize that the phenomenon of photon screening in the Randall-Sundrum geometry is ruled out by the bulk Einstein equatio

On the determination of the dilaton-antisymmetric tensor couplings in supergravity theories

A new approach is provided to determine the dilaton--antisymmetric tensor coupling in a supergravity theory by considering the static supersymmetric field configuration around a super extended object, which is consistently formulated in a curved superspace. By this, the corresponding SUSY transformation rules can also be determined for vanishing fermionic fields as well as bosonic fields other than those in the determined coupling. Therefore, we can, in turn, use this determined part of the supergravity theory to study all the related vacuum-like solutions. We have determined the dilaton--antisymmetric tensor couplings, in which each of the antisymmetric tensors is a singlet of the automorphism group of the corresponding superalgebra, for every supergravity multiplet. This actually happens only for $N \leq 2$ supergravity theories, which agrees completely with the spin-content analysis and the classified $N \leq 2$ super $p$-branes, therefore giving more support to the existence of the fundamental Type II $p$-branes. A prediction is made of the $D = 9, N = 2$ supergravity which has not yet been written down so far.Comment: 23 pages, harvmac, CERN-TH.6691/9

Four Dimensional String/String/String Triality

In six spacetime dimensions, the heterotic string is dual to a Type $IIA$ string. On further toroidal compactification to four spacetime dimensions, the heterotic string acquires an SL(2,\BbbZ)_S strong/weak coupling duality and an SL(2,\BbbZ)_T \times SL(2,\BbbZ)_U target space duality acting on the dilaton/axion, complex Kahler form and the complex structure fields $S,T,U$ respectively. Strong/weak duality in $D=6$ interchanges the roles of $S$ and $T$ in $D=4$ yielding a Type $IIA$ string with fields $T,S,U$. This suggests the existence of a third string (whose six-dimensional interpretation is more obscure) that interchanges the roles of $S$ and $U$. It corresponds in fact to a Type $IIB$ string with fields $U,T,S$ leading to a four-dimensional string/string/string triality. Since SL(2,\BbbZ)_S is perturbative for the Type $IIB$ string, this $D=4$ triality implies $S$-duality for the heterotic string and thus fills a gap left by $D=6$ duality. For all three strings the total symmetry is SL(2,\BbbZ)_S \times O(6,22;\BbbZ)_{TU}. The O(6,22;\BbbZ) is {\it perturbative} for the heterotic string but contains the conjectured {\it non-perturbative} SL(2,\BbbZ)_X, where $X$ is the complex scalar of the $D=10$ Type $IIB$ string. Thus four-dimensional triality also provides a (post-compactification) justification for this conjecture. We interpret the $N=4$ Bogomol'nyi spectrum from all three points of view. In particular we generalize the Sen-Schwarz formula for short multiplets to include intermediate multiplets also and discuss the corresponding black hole spectrum both for the $N=4$ theory and for a truncated $S$--$T$--$U$ symmetric $N=2$ theory. Just as the first two strings are described by the four-dimensional {\it elementary} and {\it dual solitonic} solutions, so theComment: 36 pages, Latex, 2 figures, some references changed, minor changes in formulas and tables; to appear in Nucl. Phys.

Evidence for Heterotic/Heterotic Duality

We re-examine the question of heterotic - heterotic string duality in six dimensions and argue that the $E_8\times E_8$ heterotic string, compactified on $K3$ with equal instanton numbers in the two $E_8$'s, has a self-duality that inverts the coupling, dualizes the antisymmetric tensor, acts non-trivially on the hypermultiplets, and exchanges gauge fields that can be seen in perturbation theory with gauge fields of a non-perturbative origin. The special role of the symmetric embedding of the anomaly in the two $E_8$'s can be seen from field theory considerations or from an eleven-dimensional point of view. The duality can be deduced by looking in two different ways at eleven-dimensional $M$-theory compactified on $K3\times {\bf S}^1/\Z_2$.Comment: 36 pages, LaTe