Spatial variability in mass change of glaciers in the Everest region, central Himalaya, between 2000 and 2015

The mass balance of the majority of Himalayan glaciers is currently negative, and has been for several decades. Region wide averaging of mass change estimates has masked any catchment or glacier scale variability in glacier recession, thus the role of a number of glaciological processes in glacier wastage remains poorly understood. In this study, we quantify surface lowering and mass loss rates for the ablation areas of 32 glaciers in different catchments across the Everest region, and specifically examine the role of glacial lakes in glacier mass change. We then assess how future ice loss is likely to differ depending on glacier hypsometry. Spatially variable ice loss is observed within and between the Dudh Koshi and Tama Koshi catchments and glaciers that flow onto the Tibetan Plateau. Surface lowering rates on glaciers flowing onto the Tibetan Plateau are 54 and 19 % greater than those flowing southward into the Dudh Koshi and Tama Koshi catchments, respectively. Surface lowering rates of up to −3.78 ± 0.26 m a-1 occurred on some lacustrine terminating glaciers, although glaciers with small lakes showed rates of lowering comparable with those that terminate on land. We suggest that such a range reflects glacial lakes at different stages of development, and that rates of mass loss are likely to increase as glacial lakes expand and deep water calving begins to occur. Hypsometric data reveal a coincidence of the altitude of maximum surface lowering and the main glacier hypsometry in the Dudh Koshi catchment, thus a large volume of ice is readily available for melt. Should predicted CMIP5 RCP 4.5 scenario warming (0.9–2.3 °C by 2100) occur in the study area, 19–30, 17–50 and 14–37 % increases in the total glacierised area below the Equilibrium Line Altitude will occur in the Dudh Koshi and Tama Koshi catchments, and on the Tibetan Plateau. Comparison of our data with a conceptual model of Himalayan glacier shrinkage confirms the presence of three distinct process regimes, with all glaciers in our sample now in a state of accelerating mass loss and meltwater storage

1+1 string with quarks at the ends revisited

The canonical description is presented for the string with pointlike masses at the ends in 1+1 dimensions in two different gauges: in the proper time gauge and in the light cone one. The classical canonical transformation is written out explicitly, which relates physical variables in both gauges, and equivalence of two classical theories is demonstrated in such a way. Both theories are quantized, and it is shown that quantum theories are not unitary equivalent. It happens due to the fact that the canonical transformation depends on interaction. The quantum Poincare algebra proves to be closed in both cases, so that the requirement of Poincare covariance is not able to distinguish between two versions of the theory.Comment: 9 pages, LaTeX 2.0

Finite strain viscoplasticity with nonlinear kinematic hardening: phenomenological modeling and time integration

This article deals with a viscoplastic material model of overstress type. The model is based on a multiplicative decomposition of the deformation gradient into elastic and inelastic part. An additional multiplicative decomposition of inelastic part is used to describe a nonlinear kinematic hardening of Armstrong-Frederick type. Two implicit time-stepping methods are adopted for numerical integration of evolution equations, such that the plastic incompressibility constraint is exactly satisfied. The first method is based on the tensor exponential. The second method is a modified Euler-Backward method. Special numerical tests show that both approaches yield similar results even for finite inelastic increments. The basic features of the material response, predicted by the material model, are illustrated with a series of numerical simulations.Comment: 29 pages, 7 figure

White Light Interferometry for Quantitative Surface Characterization in Ion Sputtering Experiments

White light interferometry (WLI) can be used to obtain surface morphology information on dimensional scale of millimeters with lateral resolution as good as ~1 {\mu}m and depth resolution down to 1 nm. By performing true three-dimensional imaging of sample surfaces, the WLI technique enables accurate quantitative characterization of the geometry of surface features and compares favorably to scanning electron and atomic force microscopies by avoiding some of their drawbacks. In this paper, results of using the WLI imaging technique to characterize the products of ion sputtering experiments are reported. With a few figures, several example applications of the WLI method are illustrated when used for (i) sputtering yield measurements and time-to-depth conversion, (ii) optimizing ion beam current density profiles, the shapes of sputtered craters, and multiple ion beam superposition and (iii) quantitative characterization of surfaces processed with ions. In particular, for sputter depth profiling experiments of 25Mg, 44Ca and 53Cr ion implants in Si (implantation energy of 1 keV per nucleon), the depth calibration of the measured depth profile curves determined by the WLI method appeared to be self-consistent with TRIM simulations for such projectile-matrix systems. In addition, high depth resolution of the WLI method is demonstrated for a case of a Genesis solar wind Si collector surface processed by gas cluster ion beam: a 12.5 nm layer was removed from the processed surface, while the transition length between the processed and untreated areas was 150 {\mu}m.Comment: Applied Surface Science, accepted: 7 pages and 8 figure

Homogeneous photometry and star counts in the field of 9 Galactic star clusters

We present homogeneous $V,I$ CCD photometry of nine stellar fields in the two inner quadrants of the Galactic plane. The lines-of-view to most of these fields aim in the direction of the very inner Galaxy, where the Galactic field is very dense, and extinction is high and patchy. Our nine fields are, according to several catalogs, centred on Galactic star clusters, namely Trumpler 13, Trumpler 20, Lynga 4, Hogg 19, Lynga 12, Trumpler 25, Trumpler 26, Ruprecht 128, and Trumpler 34. Apart from their coordinates, and in some cases additional basic data (mainly from the 2MASS archive), their properties are poorly known. By means of star count techniques and field star decontaminated Color-Magnitude diagrams, the nature and size of these visual over-densities has been established; and, when possible, new cluster fundamental parameters have been derived. To strengthen our findings, we complement our data-set with JHK$_{s}$ photometry from the 2MASS archive, that we analyze using a suitably defined Q-parameter. Most clusters are projected towards the Carina-Sagittarium spiral arm. Because of that, we detect in the Color Magnitude Diagrams of most of the other fields several distinctive sequences produced by young population within the arm. All the clusters are of intermediate or old age. The most interesting cases detected by our study are, perhaps, that of Trumpler 20, which seems to be much older than previously believed, as indicated by its prominent -and double- red clump; and that of Hogg 19, a previously overlooked old open cluster, whose existence in such regions of the Milky Way is puzzling.Comment: 37 pages, 16 eps figures, in press in New Astronom

Real and Virtual Compton Scattering off the Nucleon

A review is given of the very recent developments in the fields of real and virtual Compton scattering off the nucleon. Both real and virtual Compton scattering reactions are discussed at low outgoing photon energy where one accesses polarizabilities of the nucleon. The real Compton scattering at large momentum transfer is discussed which is asymptotically a tool to obtain information on the valence quark wave function of the nucleon. The rapid developments in deeply virtual Compton scattering and associated meson electroproduction reactions at high energy, high photon virtuality and small momentum transfer to the nucleon are discussed. A unified theoretical description of those processes has emerged over the last few years, which gives access to new, generalized parton distributions. The experimental status and perspectives in these fields are also discussed.Comment: 25 pages, 17 figure

Non-universal gaugino masses: a signal-based analysis for the Large Hadron Collider

We discuss the signals at the Large Hadron Collider (LHC) for scenarios with non-universal gaugino masses in supersymmetric (SUSY) theories. We perform a multichannel analysis, and consider the ratios of event rates in different channels such as $jets + {E}_T/$, $same$ - and $opposite$-$sign dileptons$ $+jets+ {E}_T/$, as well as $single-lepton$ and $trilepton$ final states together with $jets + {E}_T/$ . Low-energy SUSY spectra corresponding to high-scale gaugino non-universality arising from different breaking schemes of SU(5) as well as SO(10) Grand Unified (GUT) SUSY models are considered, with both degenerate low-energy sfermion masses and those arising from a supergravity scenario. We present the numerical predictions over a wide range of the parameter space using the event generator {\tt Pythia}, specifying the event selection criteria and pointing out regions where signals are likely to be beset with backgrounds. Certain broad features emerge from the study, which may be useful in identifying the signatures of different GUT breaking schemes and distinguishing them from a situation with a universal gaugino mass at high scale. The absolute values of the predicted event rates for different scenarios are presented together with the various event ratios, so that these can also be used whenever necessary.Comment: 54 pages, 18 figure

Checking Properties Described by State Machines: On Synergy of Instrumentation, Slicing, and Symbolic Execution

We introduce a novel technique for checking properties described by finite state machines. The technique is based on a synergy of three well-known methods: instrumentation, program slicing, and symbolic execution. More precisely, we instrument a given program with a code that tracks runs of state machines representing various properties. Next we slice the program to reduce its size without affecting runs of state machines. And then we symbolically execute the sliced program to find real violations of the checked properties, i.e. real bugs. Depending on the kind of symbolic execution, the technique can be applied as a stand-alone bug finding technique, or to weed out some false positives from an output of another bug-finding tool. We provide several examples demonstrating the practical applicability of our technique.Představujeme novou techniku pro ověřování vlastností popsaných konečně-stavovými stroji. Tato technika je založena na synergii tří známých metod: instrumentace, prořezání programu a symbolické vykonání. Přesněji, instrumentujeme daný program kódem, který sleduje běh stavových strojů představujících různé vlastnosti. Dále program prořežeme, abychom zmenšili jeho velikost při zachování běhů stavových strojů. Nakonec prořezaný program symbolicky vykonáme, abychom našli skutečné porušení ověřovaných vlastností, t.j. skutečné chyby. Podle použitého druhu symbolického vykonání může být tato technika použita jako samostatná metoda pro detekci chyb nebo k vytřídění některých falešných hlášení z výstupu jiných nástrojů pro detekci chyb. Poskytujeme několik příkladů, které dokumentují praktickou použitelnost naší techniky

The structure and dynamics of young star clusters: King 16, NGC 1931, NGC 637 and NGC 189

In this paper, using 2MASS photometry, we study the structural and dynamical properties of four young star clusters viz. King 16, NGC 1931, NGC 637 and NGC 189. For the clusters King 16, NGC 1931, NGC 637 and NGC 189, we obtain the limiting radii of 7', 12', 6' and 5' which correspond to linear radii of 3.6 pc, 8.85 pc, 3.96 pc and 2.8 pc respectively. The reddening values $E(B-V)$ obtained for the clusters are 0.85, 0.65--0.85, 0.6 and 0.53 and their true distances are 1786 pc, 3062 pc, 2270 pc and 912 pc respectively. Ages of the clusters are 6 Myr, 4 Myr, 4 Myr and 10 Myr respectively. We compare their structures, luminosity functions and mass functions ($\phi(M) = dN/dM \propto M^{-(1+\chi)}$) to the parameter $\tau = t_{age}/t_{relax}$ to study the star formation process and the dynamical evolution of these clusters. We find that, for our sample, mass seggregation is observed in clusters or their cores only when the ages of the clusters are comparable to their relaxation times ($\tau \geq 1$). These results suggest mass seggregation due to dynamical effects. The values of $\chi$, which characterise the overall mass functions for the clusters are 0.96 $\pm$ 0.11, 1.16 $\pm$ 0.18, 0.55 $\pm$ 0.14 and 0.66 $\pm$ 0.31 respectively. The change in $\chi$ as a function of radius is a good indicator of the dynamical state of clusters.Comment: Accepted for publication in Astrophysics & Space Scienc

The spectrum of BPS branes on a noncompact Calabi-Yau

We begin the study of the spectrum of BPS branes and its variation on lines of marginal stability on O_P^2(-3), a Calabi-Yau ALE space asymptotic to C^3/Z_3. We show how to get the complete spectrum near the large volume limit and near the orbifold point, and find a striking similarity between the descriptions of holomorphic bundles and BPS branes in these two limits. We use these results to develop a general picture of the spectrum. We also suggest a generalization of some of the ideas to the quintic Calabi-Yau.Comment: harvmac, 45 pp. (v2: added references