601 research outputs found
On Holographic Defect Entropy
We study a number of (3+1)- and (2+1)-dimensional defect and boundary
conformal field theories holographically dual to supergravity theories. In all
cases the defects or boundaries are planar, and the defects are
codimension-one. Using holography, we compute the entanglement entropy of a
(hemi-)spherical region centered on the defect (boundary). We define defect and
boundary entropies from the entanglement entropy by an appropriate background
subtraction. For some (3+1)-dimensional theories we find evidence that the
defect/boundary entropy changes monotonically under certain renormalization
group flows triggered by operators localized at the defect or boundary. This
provides evidence that the g-theorem of (1+1)-dimensional field theories
generalizes to higher dimensions.Comment: 40 pages, 1 appendix, 6 figures (7 pdf files
A Benefit Transfer Toolkit for Fish, Wildlife, Wetlands, and Open Space
Resource /Energy Economics and Policy,
The mechanism of porosity formation during solvent-mediated phase transformations
Solvent-mediated solid-solid phase transformations often result in the
formation of a porous medium, which may be stable on long time scales or
undergo ripening and consolidation. We have studied replace- ment processes in
the KBr-KCl-H2O system using both in situ and ex situ experiments. The
replacement of a KBr crystal by a K(Br,Cl) solid solution in the presence of an
aqueous solution is facilitated by the gen- eration of a surprisingly stable,
highly anisotropic and connected pore structure that pervades the product
phase. This pore structure ensures efficient solute transport from the bulk
solution to the reacting KBr and K(Br,Cl) surfaces. The compositional profile
of the K(Br,Cl) solid solu- tion exhibits striking discontinuities across
disc-like cavities in the product phase. Similar transformation mechanisms are
probably important in con- trolling phase transformation processes and rates in
a variety of natural and man-made systems.Comment: 22 pages, 7 figure
Pseudonovibos spiralis (Artiodactyla: Bovidae): new information on this enigmatic South-east Asian ox
Two bovid frontlets with horns collected in 1929 and now housed in the collections of the University of Kansas Natural History Museum (KU) from Suoi Kiet, Binh Tuy Province, Vietnam, were previously identified as koupreys (Bos sauveli). We believe that they are specimens of the recently discovered bovid, Pseudonovibos spiralis Peter & Feiler, 1994. The KU specimens are represented by the posterior half of the frontal bones, the parietals, the horn cores and horns, and the anteriormost supraoccipitals, and are the most complete, best documented, and oldest specimens known of this poorly known species. We believe that both an adult male and an adult female are represented. Although the specimens are fragmentary, they still provide significant information that allows us to describe some aspects of P. spiralis, and they are especially critical to our understanding of the relationships of this animal to other bovids. We propose the English name spiral-horned ox, which reflects both its distinctively shaped horns and close relationship to other wild oxen. The Khmer name, Khting Vor, is also an appropriate common name. Previously overlooked references from the 1880s and 1950s document that the spiral-horned ox was believed to have magical powers over poisonous snakes
Mock Modular Mathieu Moonshine Modules
We construct super vertex operator algebras which lead to modules for
moonshine relations connecting the four smaller sporadic simple Mathieu groups
with distinguished mock modular forms. Starting with an orbifold of a free
fermion theory, any subgroup of Co_0 that fixes a 3-dimensional subspace of its
unique non-trivial 24-dimensional representation commutes with a certain N=4
superconformal algebra. Similarly, any subgroup of Co_0 that fixes a
2-dimensional subspace of the 24-dimensional representation commutes with a
certain N=2 superconformal algebra. Through the decomposition of the
corresponding twined partition functions into characters of the N=4 (resp. N=2)
superconformal algebra, we arrive at mock modular forms which coincide with the
graded characters of an infinite-dimensional Z-graded module for the
corresponding group. The Mathieu groups are singled out amongst various other
possibilities by the moonshine property: requiring the corresponding weak
Jacobi forms to have certain asymptotic behaviour near cusps. Our constructions
constitute the first examples of explicitly realized modules underlying
moonshine phenomena relating mock modular forms to sporadic simple groups.
Modules for other groups, including the sporadic groups of McLaughlin and
Higman--Sims, are also discussed.Comment: 94 pages, including 56 pages of tables; v2: updated references and
minor revisions to abstract, introduction and sections 8 and
Numerical Simulations Reproduce Field Observations Showing Transient Weakening During Shear Zone Formation by Diffusional Hydrogen Influx and H2O Inflow
Exposures on Holsnøy island (Bergen Arcs, Norway) indicate fluid infiltration through fractures into a dry, metastable granulite, which triggered a kinetically delayed eclogitization, a transient weakening during fluid-rock interaction, and formation of shear zones that widened during shearing. It remains unclear whether the effects of grain boundary-assisted aqueous fluid inflow on the duration of granulite hydration were influenced by a diffusional hydrogen influx accompanying the fluid inflow. To better estimate the fluid infiltration efficiencies and the parameter interdependencies, a 1D numerical model of a viscous shear zone is utilized and validated using measured mineral phase abundance distributions and H2O-contents in nominally anhydrous minerals of the original granulite assemblage to constrain the hydration by aqueous fluid inflow and diffusional hydrogen influx, respectively. Both hydrations are described with a diffusion equation and affect the effective viscosity. Shear zone kinematics are constrained by the observed shear strain and thickness. The model fits the phase abundance and H2O-content profiles if the effective hydrogen diffusivity is approximately one order of magnitude higher than the diffusivity for aqueous fluid inflow. The observed shear zone thickness is reproduced if the viscosity ratio between dry granulite and deforming, reequilibrating eclogite is ∼104 and that between dry granulite and hydrated granulite is ∼102. The results suggest shear velocities <10−2 cm/a, hydrogen diffusivities of ∼10−13±1 m2/s, and a shearing duration of <10 years. This study successfully links and validates field data to a shear zone model and highlights the importance of hydrogen diffusion for shear zone widening and eclogitization
Subduction and continental collision in the Lufilian Arc-Zambesi Belt orogen: A petrological, geochemical, and geochronological study of eclogites and whiteschists (Zambia)
Mountain building processes are often the consequence of colliding continental plates which were usually separated by an ocean basin with basaltic crust. I investigated the relation between the Congo and the Kalahari cratons during the formation of the supercontinent Gondwana and the possibility of an ocean basin formerly existing between the two cratons. Eclogites are rocks with a basaltic composition which have undergone the high-pressure / low-temperature metamorphism typical of subduction zones where dense oceanic plates sink under less dense continental plates. Other potentially subduction related rocks beside eclogites are whiteschists (talc-kyanite schists). Whiteschists and eclogites occur in an orogenic belt situated between the Congo and the Kalahari cratons in Zambia. I studied the pressure-temperature evolution and the chemical composition of the eclogites and whiteschists. The results of the study show that the eclogites of Zambia represent former oceanic crust and that the ocean basin was relatively large. The age of the eclogite facies metamorphism is ca. 600 Ma. However, the whiteschists experienced peak metamorphic conditions only reaching the high-pressure amphibolite facies. Their formation is related to a crustal thickening event that affected the whole Lufilian Arc-Zambesi Belt orogen almost simultaneously at ca. 530 Ma. Thus, the conclusion is that the ocean basin was subducted ca. 600 Ma ago leading to the formation of eclogites and the whiteschists were formed ca. 70 my later during final collision of the Congo and the Kalahari craton during the Gondwana assembly
Mathieu Moonshine and N=2 String Compactifications
There is a `Mathieu moonshine' relating the elliptic genus of K3 to the
sporadic group M_{24}. Here, we give evidence that this moonshine extends to
part of the web of dualities connecting heterotic strings compactified on K3
\times T^2 to type IIA strings compactified on Calabi-Yau threefolds. We
demonstrate that dimensions of M_{24} representations govern the new
supersymmetric index of the heterotic compactifications, and appear in the
Gromov--Witten invariants of the dual Calabi-Yau threefolds, which are elliptic
fibrations over the Hirzebruch surfaces F_n.Comment: 28 pages; v2: minor changes, published versio
Revision of New World \u3ci\u3eCosmorrhyncha\u3c/i\u3e Meyrick, 1913 (Lepidoptera: Tortricidae: Olethreutinae), with descriptions of five new species
Although well studied in the Afrotropical Region, the genus Cosmorrhyncha Meyrick, 1913 (Lepidoptera: Tortricidae: Olethreutinae), has received little attention in the New World, where it apparently is restricted to the Neotropics from Guatemala south to Paraguay. Seven species are recognized, five of which are described as new: C. tonsana (Walker, 1863) (Type locality: Brazil); C. ocelliferana (Walker, 1863) (TL: Brazil); C. landryi Brown and Razowski, sp. n. (TL: French Guiana); C. parintina Brown and Razowski, sp. n. (TL: Brazil); C. macrospina Brown and Razowski, sp. n. (TL: Brazil); C. albistrigulana Brown and Razowski, sp. n. (TL: Costa Rica); and C. osana Brown and Razowski, sp. n. (TL: Costa Rica). Our circumscription of C. ocelliferana is rather broad and most likely encompasses a species complex rather than a single entity. Larvae of C. tonsana have been reared from Picramnia latifolia Tul. (Picramniaceae), Dialium guianense (Aubl.) Sandwith (Fabaceae), and Machaerium seemannii Benth. ex Seem. (Fabaceae) in Costa Rica; and those of C. albistrigulana from Dialium guianense (Fabaceae)
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