D-branes and Short Distances in String Theory

We study the behavior of D-branes at distances far shorter than the string length scale~$l_s$. We argue that short-distance phenomena are described by the IR behavior of the D-brane world-volume quantum theory. This description is valid until the brane motion becomes relativistic. At weak string coupling \gs this corresponds to momenta and energies far above string scale. We use 0-brane quantum mechanics to study 0-brane collisions and find structure at length scales corresponding to the eleven-dimensional Planck length (\lp11 \sim \gs^{1/3} l_s) and to the radius of the eleventh dimension in M-theory (\R11 \sim \gs l_s). We use 0-branes to probe non-trivial geometries and topologies at sub-stringy scales. We study the 0-brane 4-brane system, calculating the 0-brane moduli space metric, and find the bound state at threshold, which has characteristic size \lp11. We examine the blowup of an orbifold and are able to resolve the resulting $S^2$ down to size \lp11. A 0-brane with momentum approaching $1/\R11$ is able to explore a larger configuration space in which the blowup is embedded. Analogous phenomena occur for small instantons. We finally turn to 1-branes and calculate the size of a bound state to be \sim \gs^{1/2} l_s, the 1-brane tension scale.Comment: 50 pages, harvmac, 3 epsf figures. References added, minor changes in tex

Thermodynamics of the (1,1/2) Ferrimagnet in Finite Magnetic Fields

We investigate the specific heat and magnetisation of a ferrimagnet with gS=1 and S=1/2 spins in a finite magnetic field using the transfer matrix DMRG down to T=0.025J. Ferromagnetic gapless and antiferromagnetic gapped excitations for H=0 lead to rich thermodynamics for H > 0. While the specific heat is characterized by a generic double peak structure, magnetisation reveals two critical fields, Hc1=1.76(1) and Hc2=3.00(1) with square-root behaviour in the T=0 magnetisation. Simple analytical arguments allow to understand these experimentally accessible findings.Comment: 5 pages, 7 eps figures, uses RevTeX, submitted to PR

Punctuated Shutdown of Atlantic Meridional Overturning Circulation during Greenland Stadial 1.

The Greenland Stadial 1 (GS-1; ~12.9 to 11.65 kyr cal BP) was a period of North Atlantic cooling, thought to have been initiated by North America fresh water runoff that caused a sustained reduction of North Atlantic Meridional Overturning Circulation (AMOC), resulting in an antiphase temperature response between the hemispheres (the 'bipolar seesaw'). Here we exploit sub-fossil New Zealand kauri trees to report the first securely dated, decadally-resolved atmospheric radiocarbon ((14)C) record spanning GS-1. By precisely aligning Southern and Northern Hemisphere tree-ring (14)C records with marine (14)C sequences we document two relatively short periods of AMOC collapse during the stadial, at ~12,920-12,640 cal BP and 12,050-11,900 cal BP. In addition, our data show that the interhemispheric atmospheric (14)C offset was close to zero prior to GS-1, before reaching 'near-modern' values at ~12,660 cal BP, consistent with synchronous recovery of overturning in both hemispheres and increased Southern Ocean ventilation. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but probably due to an equatorward migration of the Polar Front, reducing the advection of southwesterly air masses to high latitudes. Our findings suggest opposing hemispheric temperature trends were driven by atmospheric teleconnections, rather than AMOC changes

Characterisation of the upper atmospheres of HAT-P-32 b, WASP-69 b, GJ 1214 b, and WASP-76 b through their He I triplet absorption

Characterisation of atmospheres undergoing photo-evaporation is key to understanding the formation, evolution, and diversity of planets. However, only a few upper atmospheres that experience this kind of hydrodynamic escape have been characterised. Our aim is to characterise the upper atmospheres of the hot Jupiters HAT-P-32 b and WASP-69 b, the warm sub-Neptune GJ 1214 b, and the ultra-hot Jupiter WASP-76 b through high-resolution observations of their HeI triplet absorption. In addition, we also reanalyse the warm Neptune GJ 3470 b and the hot Jupiter HD 189733 b. We used a spherically symmetric 1D hydrodynamic model coupled with a non-local thermodynamic equilibrium model. Comparing synthetic absorption spectra with observations, we constrained the main parameters of the upper atmosphere of these planets and classify them according to their hydrodynamic regime. Our results show that HAT-P-32 b photo-evaporates at (130$\pm$70)$\times$10$^{11}$ gs$^{-1}$ with a hot (12 400$\pm$2900 K) upper atmosphere; WASP-69 b loses its atmosphere at (0.9$\pm$0.5)$\times$10$^{11}$ gs$^{-1}$ and 5250$\pm$750 K; and GJ 1214 b, with a relatively cold outflow of 3750$\pm$750 K, photo-evaporates at (1.3$\pm$1.1)$\times$10$^{11}$ gs$^{-1}$. For WASP-76 b, its weak absorption prevents us from constraining its temperature and mass-loss rate significantly; we obtained ranges of 6000-17 000\,K and 23.5$\pm$21.5$\times$10$^{11}$ gs$^{-1}$. Our reanalysis of GJ 3470 b yields colder temperatures, 3400$\pm$350 K, but practically the same mass-loss rate as in our previous results. Our reanalysis of HD 189733 b yields a slightly higher mass-loss rate, (1.4$\pm$0.5)$\times$10$^{11}$ gs$^{-1}$, and temperature, 12 700$\pm$900 K compared to previous estimates. Our results support that photo-evaporated outflows tend to be very light

A stability index for detonation waves in Majda's model for reacting flow

Using Evans function techniques, we develop a stability index for weak and strong detonation waves analogous to that developed for shock waves in [GZ,BSZ], yielding useful necessary conditions for stability. Here, we carry out the analysis in the context of the Majda model, a simplified model for reacting flow; the method is extended to the full Navier-Stokes equations of reacting flow in [Ly,LyZ]. The resulting stability condition is satisfied for all nondegenerate, i.e., spatially exponentially decaying, weak and strong detonations of the Majda model in agreement with numerical experiments of [CMR] and analytical results of [Sz,LY] for a related model of Majda and Rosales. We discuss also the role in the ZND limit of degenerate, subalgebraically decaying weak detonation and (for a modified, ``bump-type'' ignition function) deflagration profiles, as discussed in [GS.1-2] for the full equations.Comment: 36 pages, 3 figure

Effect of starch physiology, gelatinization, and retrogradation on the attributes of rice starch-ι-carrageenan film

Edible films and coatings have been applied as the potential substitutes for conventional plastics in food packaging. However, their physical and mechanical properties still have limitations and thus require further improvement. In this study, we compared the physico–chemical properties of starches extracted from eight rice varieties and attempted to predict their promising effects on the physical (thickness and solubility), mechanical (tensile strength and elongation break), barrier (water vapor permeability), and optical properties (color and transparency) of rice starch-ι-carrageenan films. The results showed that starch amylose content and amylose–amylopectin associations during retrogradation play a significant role in determining various properties of the films. The film containing starch from “Reiziq” variety showed minimum thickness (0.08 mm), water vapor permeability (WVP) (2.7 gs−1 m−1 Pa−1), solubility (43.12%) opacity (0.44%), and better mechanical properties, demonstrating the importance of selection of the source of the starch. The results also indicated that rice starch had compatibility with ι-carrageenan, and the blend of these two polysaccharides can be potentially used for coating fruit and vegetables

The environmental setting for the Lateglacial recolonization of the Scheldt basin (North-west Europe) by the Federmesser Gruppen

In this paper the spatial distribution of Federmesser-Gruppen (FMG) sites in the Scheldt Basin is discussed. A clear pattern of focused occupation and exploitation of the dry banks of former dune slacks and freshwater lakes is observed, while the river floodplains were seemingly avoided. The latter may be due to the highly dynamic environment of the rivers, which were characterised by very high discharges and continuous erosion. During the late Allerød (GI-1a) and the transition towards the Younger Dryas (GS-1) the meandering rivers finally stabilised, gradually turning into slow running and shallow streams. This probably was the result of a general decrease of the ground water table, which also affected the inland lakes and ponds, reducing them to dry or swampy depressions. It is assumed that this marked hydrological event, which may be linked to cooling during the Intra Allerød Cold Period (GI-1b) and the subsequent Younger Dryas (GS-1), had a considerable impact on the settlement system of the FMG hunter-gatherers, who may have been forced to leave the Scheldt Basin

Überprüfung der praktischen Anwendbarkeit des Leitfadens (SFK/TAA-GS-1)

ÜBERPRÜFUNG DER PRAKTISCHEN ANWENDBARKEIT DES LEITFADENS (SFK/TAA-GS-1) Überprüfung der praktischen Anwendbarkeit des Leitfadens (SFK/TAA-GS-1) / Jochum, Christian (Rights reserved) ( -

A Lateglacial archaeological site in the far north-west of Europe at Rubha Port an t-Seilich, Isle of Islay, western Scotland: Ahrensburgian-style artefacts, absolute dating and geoarchaeology

© 2015 The Authors.The exact pattern, process and timing of the human re-colonization of northern Europe after the end of the last Ice Age remain controversial. Recent research has provided increasingly early dates for at least pioneer explorations of latitudes above 54°N in many regions, yet the far north-west of the European landmass, Scotland, has remained an unexplained exception to this pattern. Although the recently described Hamburgian artefacts from Howburn and an assemblage belonging to the arch-backed point complex from Kilmelfort Cave have established at least a sporadic human presence during earlier stages of the Lateglacial Interstadial, we currently lack evidence for Younger Dryas/Greenland Stadial 1 (GS-1) activity other than rare stray finds that have been claimed to be of Ahrensburgian affiliation but are difficult to interpret in isolation. We here report the discovery of chipped stone artefacts with technological and typological characteristics similar to those of the continental Ahrensburgian at a locality in western Scotland. A preliminary analysis of associated tephra, pollen and phytoliths, along with microstratigraphic analysis, suggest the artefacts represent one or more episodes of human activity that fall within the second half of GS-1 and the Preboreal period

Symmetry classification of variable coefficient cubic-quintic nonlinear schrodinger equations

A Lie-algebraic classification of the variable coefficient cubic-quintic nonlinear Schrodinger equations involving 5 arbitrary functions of space and time is performed under the action of equivalence transformations. It is shown that the symmetry group can be at most four-dimensional in the case of genuine cubic-quintic nonlinearity. It may be five-dimensional (isomorphic to the Galilei similitude algebra gs(1)) when the equation is of cubic type, and six-dimensional (isomorphic to the Schrodinger algebra sch(1)) when it is of quintic type