@article{HoegelePavlyukevich2015, author = {H{\"o}gele, Michael and Pavlyukevich, Ilya}, title = {Metastability in a class of hyperbolic dynamical systems perturbed by heavy-tailed Levy type noise}, series = {Stochastics and dynamic}, volume = {15}, journal = {Stochastics and dynamic}, number = {3}, publisher = {World Scientific}, address = {Singapore}, issn = {0219-4937}, doi = {10.1142/S0219493715500197}, pages = {26}, year = {2015}, abstract = {We consider a finite dimensional deterministic dynamical system with finitely many local attractors K-iota, each of which supports a unique ergodic probability measure P-iota, perturbed by a multiplicative non-Gaussian heavy-tailed Levy noise of small intensity epsilon > 0. We show that the random system exhibits a metastable behavior: there exists a unique epsilon-dependent time scale on which the system reminds of a continuous time Markov chain on the set of the invariant measures P-iota. In particular our approach covers the case of dynamical systems of Morse-Smale type, whose attractors consist of points and limit cycles, perturbed by multiplicative alpha-stable Levy noise in the Ito, Stratonovich and Marcus sense. As examples we consider alpha-stable Levy perturbations of the Duffing equation and Pareto perturbations of a biochemical birhythmic system with two nested limit cycles.}, language = {en} } @article{Pirhayati2015, author = {Pirhayati, Mohammad}, title = {Boundary symbols in the cone algebra}, series = {Journal of pseudo-differential operators and applications}, volume = {6}, journal = {Journal of pseudo-differential operators and applications}, number = {3}, publisher = {Springer}, address = {Basel}, issn = {1662-9981}, doi = {10.1007/s11868-015-0123-y}, pages = {307 -- 339}, year = {2015}, abstract = {Boundary value problems on a smooth manifold X with boundary have the structure of edge problems. Operators A are described in terms of a principal symbolic hierarchy, namely, according to the stratification of X, with the interior and the boundary We focus here on operators with and without the transmission property and establish a new relationship between boundary symbols and operators in the cone calculus transversal to the boundary.}, language = {en} } @article{LyuQianSchulze2015, author = {Lyu, Xiaojing and Qian, Tao and Schulze, Bert-Wolfgang}, title = {Order filtrations of the edge algebra}, series = {Journal of pseudo-differential operators and applications}, volume = {6}, journal = {Journal of pseudo-differential operators and applications}, number = {3}, publisher = {Springer}, address = {Basel}, issn = {1662-9981}, doi = {10.1007/s11868-015-0126-8}, pages = {279 -- 305}, year = {2015}, abstract = {By edge algebra we understand a pseudo-differential calculus on a manifold with edge. The operators have a two-component principal symbolic hierarchy which determines operators up to lower order terms. Those belong to a filtration of the corresponding operator spaces. We give a new characterisation of this structure, based on an alternative representation of edge amplitude functions only containing holomorphic edge-degenerate Mellin symbols.}, language = {en} } @article{Ludewig2015, author = {Ludewig, Matthias}, title = {A semiclassical heat kernel proof of the Poincare-Hopf theorem}, series = {Manuscripta mathematica}, volume = {148}, journal = {Manuscripta mathematica}, number = {1-2}, publisher = {Springer}, address = {Heidelberg}, issn = {0025-2611}, doi = {10.1007/s00229-015-0741-y}, pages = {29 -- 58}, year = {2015}, abstract = {We consider the semiclassical asymptotic expansion of the heat kernel coming from Witten's perturbation of the de Rham complex by a given function. For the index, one obtains a time-dependent integral formula which is evaluated by the method of stationary phase to derive the Poincare-Hopf theorem. We show how this method is related to approaches using the Thom form of Mathai and Quillen. Afterwards, we use a more general version of the stationary phase approximation in the case that the perturbing function has critical submanifolds to derive a degenerate version of the Poincare-Hopf theorem.}, language = {en} } @article{AsariWardinski2015, author = {Asari, Seiki and Wardinski, Ingo}, title = {On magnetic estimation of Earth's core angular momentum variation}, series = {Journal of geophysical research : Solid earth}, volume = {120}, journal = {Journal of geophysical research : Solid earth}, number = {10}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9313}, doi = {10.1002/2014JB011458}, pages = {6740 -- 6757}, year = {2015}, abstract = {We study systematically the estimation of Earth's core angular momentum (CAM) variation between 1962.0 and 2008.0 by using core surface flow models derived from the recent geomagnetic field model C(3)FM2. Various flow models are derived by changing four parameters that control the least squares flow inversion. The parameters include the spherical harmonic (SH) truncation degree of the flow models and two Lagrange multipliers that control the weights of two additional constraints. The first constraint forces the energy spectrum of the flow solution to follow a power law l-p, where l is the SH degree and p is the fourth parameter. The second allows to modulate the solution continuously between the dynamical states of tangential geostrophy (TG) and tangential magnetostrophy (TM). The calculated CAM variations are examined in reference to two features of the observed length-of-day (LOD) variation, namely, its secular trend and 6year oscillation. We find flow models in either TG or TM state for which the estimated CAM trends agree with the LOD trend. It is necessary for TM models to have their flows dominate at planetary scales, whereas TG models should not be of this scale; otherwise, their CAM trends are too steep. These two distinct types of flow model appear to correspond to the separate regimes of previous numerical dynamos that are thought to be applicable to the Earth's core. The phase of the subdecadal CAM variation is coherently determined from flow models obtained with extensively varying inversion settings. Multiple sources of model ambiguity need to be allowed for in discussing whether these phase estimates properly represent that of Earth's CAM as an origin of the observed 6year LOD oscillation.}, language = {en} } @article{SamarasNicolaeBoeckmannetal.2015, author = {Samaras, Stefanos and Nicolae, Doina and B{\"o}ckmann, Christine and Vasilescu, Jeni and Binietoglou, Ioannis and Labzovskii, Lev and Toanca, Florica and Papayannis, Alexandros}, title = {Using Raman-lidar-based regularized microphysical retrievals and Aerosol Mass Spectrometer measurements for the characterization of biomass burning aerosols}, series = {Journal of computational physics}, volume = {299}, journal = {Journal of computational physics}, publisher = {Elsevier}, address = {San Diego}, issn = {0021-9991}, doi = {10.1016/j.jcp.2015.06.045}, pages = {156 -- 174}, year = {2015}, abstract = {In this work we extract the microphysical properties of aerosols for a collection of measurement cases with low volume depolarization ratio originating from fire sources captured by the Raman lidar located at the National Institute of Optoelectronics (INOE) in Bucharest. Our algorithm was tested not only for pure smoke but also for mixed smoke and urban aerosols of variable age and growth. Applying a sensitivity analysis on initial parameter settings of our retrieval code was proved vital for producing semi-automatized retrievals with a hybrid regularization method developed at the Institute of Mathematics of Potsdam University. A direct quantitative comparison of the retrieved microphysical properties with measurements from a Compact Time of Flight Aerosol Mass Spectrometer (CToF-AMS) is used to validate our algorithm. Microphysical retrievals performed with sun photometer data are also used to explore our results. Focusing on the fine mode we observed remarkable similarities between the retrieved size distribution and the one measured by the AMS. More complicated atmospheric structures and the factor of absorption appear to depend more on particle radius being subject to variation. A good correlation was found between the aerosol effective radius and particle age, using the ratio of lidar ratios (LR: aerosol extinction to backscatter ratios) as an indicator for the latter. Finally, the dependence on relative humidity of aerosol effective radii measured on the ground and within the layers aloft show similar patterns. (C) 2015 Elsevier Inc. All rights reserved.}, language = {en} } @article{FedchenkoTarkhanov2015, author = {Fedchenko, Dmitry and Tarkhanov, Nikolai Nikolaevich}, title = {A Class of Toeplitz Operators in Several Variables}, series = {Advances in applied Clifford algebras}, volume = {25}, journal = {Advances in applied Clifford algebras}, number = {4}, publisher = {Springer}, address = {Basel}, issn = {0188-7009}, doi = {10.1007/s00006-015-0546-9}, pages = {811 -- 828}, year = {2015}, abstract = {We introduce the concept of Toeplitz operator associated with the Laplace-Beltrami operator on a compact Riemannian manifold with boundary. We characterise those Toeplitz operators which are Fredholm, thus initiating the index theory.}, language = {en} } @article{FedchenkoTarkhanov2015, author = {Fedchenko, Dmitri and Tarkhanov, Nikolai Nikolaevich}, title = {An index formula for Toeplitz operators}, series = {Complex variables and elliptic equations}, volume = {60}, journal = {Complex variables and elliptic equations}, number = {12}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {1747-6933}, doi = {10.1080/17476933.2015.1050007}, pages = {1764 -- 1787}, year = {2015}, abstract = {We prove a Fedosov index formula for the index of Toeplitz operators connected with the Hardy space of solutions to an elliptic system of first-order partial differential equations in a bounded domain in R-n with smooth boundary.}, language = {en} } @article{MoestaAnderssonMetzgeretal.2015, author = {Moesta, Philip and Andersson, Lars and Metzger, Jan and Szilagyi, Bela and Winicour, Jeffrey}, title = {The merger of small and large black holes}, series = {Classical and quantum gravit}, volume = {32}, journal = {Classical and quantum gravit}, number = {23}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0264-9381}, doi = {10.1088/0264-9381/32/23/235003}, pages = {20}, year = {2015}, abstract = {We present simulations of binary black-hole mergers in which, after the common outer horizon has formed, the marginally outer trapped surfaces (MOTSs) corresponding to the individual black holes continue to approach and eventually penetrate each other. This has very interesting consequences according to recent results in the theory of MOTSs. Uniqueness and stability theorems imply that two MOTSs which touch with a common outer normal must be identical. This suggests a possible dramatic consequence of the collision between a small and large black hole. If the penetration were to continue to completion, then the two MOTSs would have to coalesce, by some combination of the small one growing and the big one shrinking. Here we explore the relationship between theory and numerical simulations, in which a small black hole has halfway penetrated a large one.}, language = {en} }