@article{ConfortiPraRoelly2015, author = {Conforti, Giovanni and Pra, Paolo Dai and Roelly, Sylvie}, title = {Reciprocal Class of Jump Processes}, series = {Journal of theoretical probability}, volume = {30}, journal = {Journal of theoretical probability}, publisher = {Springer}, address = {New York}, issn = {0894-9840}, doi = {10.1007/s10959-015-0655-3}, pages = {551 -- 580}, year = {2015}, abstract = {Processes having the same bridges as a given reference Markov process constitute its reciprocal class. In this paper we study the reciprocal class of compound Poisson processes whose jumps belong to a finite set . We propose a characterization of the reciprocal class as the unique set of probability measures on which a family of time and space transformations induces the same density, expressed in terms of the reciprocal invariants. The geometry of plays a crucial role in the design of the transformations, and we use tools from discrete geometry to obtain an optimal characterization. We deduce explicit conditions for two Markov jump processes to belong to the same class. Finally, we provide a natural interpretation of the invariants as short-time asymptotics for the probability that the reference process makes a cycle around its current state.}, language = {en} } @book{VanLeeuwenChengReich2015, author = {Van Leeuwen, Peter Jan and Cheng, Yuan and Reich, Sebastian}, title = {Nonlinear data assimilation}, series = {Frontiers in applied dynamical systems: reviews and tutorials ; 2}, journal = {Frontiers in applied dynamical systems: reviews and tutorials ; 2}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-18346-6}, doi = {10.1007/978-3-319-18347-3}, pages = {xii, 118}, year = {2015}, abstract = {This book contains two review articles on nonlinear data assimilation that deal with closely related topics but were written and can be read independently. Both contributions focus on so-called particle filters. The first contribution by Jan van Leeuwen focuses on the potential of proposal densities. It discusses the issues with present-day particle filters and explorers new ideas for proposal densities to solve them, converging to particle filters that work well in systems of any dimension, closing the contribution with a high-dimensional example. The second contribution by Cheng and Reich discusses a unified framework for ensemble-transform particle filters. This allows one to bridge successful ensemble Kalman filters with fully nonlinear particle filters, and allows a proper introduction of localization in particle filters, which has been lacking up to now.}, language = {en} } @incollection{KiyLuckeSass2015, author = {Kiy, Alexander and Lucke, Ulrike and Sass, K.}, title = {Gewusst was: Mit einer E-Learning-Toolbox die pers{\"o}nliche virtuelle Umgebung gestalten}, series = {DeLFI 2015 - die 13. E-Learning Fachtagung Informatik der Gesellschaft f{\"u}r Informatik e.V. : 1.-4. September 2015 M{\"u}nchen, Deutschland}, booktitle = {DeLFI 2015 - die 13. E-Learning Fachtagung Informatik der Gesellschaft f{\"u}r Informatik e.V. : 1.-4. September 2015 M{\"u}nchen, Deutschland}, number = {247}, editor = {Pongratz, Hans J. and Keil, R.}, publisher = {Gesellschaft f{\"u}r Informatik e.V.}, address = {Bonn}, isbn = {978-3-88579-641-1}, issn = {1617-5468}, publisher = {Universit{\"a}t Potsdam}, pages = {43 -- 55}, year = {2015}, language = {de} } @article{KiyDehneBussler2015, author = {Kiy, Alexander and Dehne, Julian and Bussler, Dirk}, title = {Aufbau einer Cloud-Speicherl{\"o}sung und Integration in bestehende IuK-Infrastrukturen am Beispiel ownCloud an der Universit{\"a}t Potsdam}, series = {Cloudspeicher im Hochschuleinsatz 2015: Proceedings der Tagung "Cloudspeicher im Hochschuleinsatz" am 07. und 08. Mai 2015 am IT-Service-Center (tubIT) der Technischen Universit{\"a}t Berlin}, journal = {Cloudspeicher im Hochschuleinsatz 2015: Proceedings der Tagung "Cloudspeicher im Hochschuleinsatz" am 07. und 08. Mai 2015 am IT-Service-Center (tubIT) der Technischen Universit{\"a}t Berlin}, publisher = {Universit{\"a}tsverlag der TU Berlin}, address = {Berlin}, isbn = {978-3-7983-2780-1}, pages = {61 -- 72}, year = {2015}, abstract = {In 2015 the second conference „Cloud Storage Deployment in Academics" took place. Interest regarding this issue was again high and topics established in 2014 like data security and scalability were complemented by new ones like federations or technical integration in existing infrastructures. This is caused by the advances in the establishment of cloud-based storage systems. This publication contains the contributions of the conference „Cloud Storage Deployment in Academics 2015", which took place in may 2015 at TU Berlin.}, language = {de} } @article{HoegeleRuffino2015, author = {Hoegele, Michael and Ruffino, Paulo}, title = {Averaging along foliated Levy diffusions}, series = {Nonlinear analysis : theory, methods \& applications ; an international multidisciplinary journal}, volume = {112}, journal = {Nonlinear analysis : theory, methods \& applications ; an international multidisciplinary journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0362-546X}, doi = {10.1016/j.na.2014.09.006}, pages = {1 -- 14}, year = {2015}, abstract = {This article studies the dynamics of the strong solution of a SDE driven by a discontinuous Levy process taking values in a smooth foliated manifold with compact leaves. It is assumed that it is foliated in the sense that its trajectories stay on the leaf of their initial value for all times almost surely. Under a generic ergodicity assumption for each leaf, we determine the effective behaviour of the system subject to a small smooth perturbation of order epsilon > 0, which acts transversal to the leaves. The main result states that, on average, the transversal component of the perturbed SDE converges uniformly to the solution of a deterministic ODE as e tends to zero. This transversal ODE is generated by the average of the perturbing vector field with respect to the invariant measures of the unperturbed system and varies with the transversal height of the leaves. We give upper bounds for the rates of convergence and illustrate these results for the random rotations on the circle. This article complements the results by Gonzales and Ruffino for SDEs of Stratonovich type to general Levy driven SDEs of Marcus type.}, language = {en} } @article{EscribanoAkhmatskayaReichetal.2015, author = {Escribano, Bruno and Akhmatskaya, Elena and Reich, Sebastian and Azpiroz, Jon M.}, title = {Multiple-time-stepping generalized hybrid Monte Carlo methods}, series = {Journal of computational physics}, volume = {280}, journal = {Journal of computational physics}, publisher = {Elsevier}, address = {San Diego}, issn = {0021-9991}, doi = {10.1016/j.jcp.2014.08.052}, pages = {1 -- 20}, year = {2015}, abstract = {Performance of the generalized shadow hybrid Monte Carlo (GSHMC) method [1], which proved to be superior in sampling efficiency over its predecessors [2-4], molecular dynamics and hybrid Monte Carlo, can be further improved by combining it with multi-time-stepping (MTS) and mollification of slow forces. We demonstrate that the comparatively simple modifications of the method not only lead to better performance of GSHMC itself but also allow for beating the best performed methods, which use the similar force splitting schemes. In addition we show that the same ideas can be successfully applied to the conventional generalized hybrid Monte Carlo method (GHMC). The resulting methods, MTS-GHMC and MTS-GSHMC, provide accurate reproduction of thermodynamic and dynamical properties, exact temperature control during simulation and computational robustness and efficiency. MTS-GHMC uses a generalized momentum update to achieve weak stochastic stabilization to the molecular dynamics (MD) integrator. MTS-GSHMC adds the use of a shadow (modified) Hamiltonian to filter the MD trajectories in the HMC scheme. We introduce a new shadow Hamiltonian formulation adapted to force-splitting methods. The use of such Hamiltonians improves the acceptance rate of trajectories and has a strong impact on the sampling efficiency of the method. Both methods were implemented in the open-source MD package ProtoMol and were tested on a water and a protein systems. Results were compared to those obtained using a Langevin Molly (LM) method [5] on the same systems. The test results demonstrate the superiority of the new methods over LM in terms of stability, accuracy and sampling efficiency. This suggests that putting the MTS approach in the framework of hybrid Monte Carlo and using the natural stochasticity offered by the generalized hybrid Monte Carlo lead to improving stability of MTS and allow for achieving larger step sizes in the simulation of complex systems.}, language = {en} } @article{GraeterSperner2015, author = {Graeter, Joachim and Sperner, Robert P.}, title = {On embedding left-ordered groups into division rings}, series = {Forum mathematicum}, volume = {27}, journal = {Forum mathematicum}, number = {1}, publisher = {De Gruyter}, address = {Berlin}, issn = {0933-7741}, doi = {10.1515/forum-2012-0070}, pages = {485 -- 518}, year = {2015}, language = {en} } @article{Kroencke2015, author = {Kroencke, Klaus}, title = {On the stability of Einstein manifolds}, series = {Annals of global analysis and geometry}, volume = {47}, journal = {Annals of global analysis and geometry}, number = {1}, publisher = {Springer}, address = {Dordrecht}, issn = {0232-704X}, doi = {10.1007/s10455-014-9436-y}, pages = {81 -- 98}, year = {2015}, abstract = {Certain curvature conditions for the stability of Einstein manifolds with respect to the Einstein-Hilbert action are given. These conditions are given in terms of quantities involving the Weyl tensor and the Bochner tensor. In dimension six, a stability criterion involving the Euler characteristic is given.}, language = {en} } @article{AizingerKornGiorgettaetal.2015, author = {Aizinger, Vadym and Korn, Peter and Giorgetta, Marco and Reich, Sebastian}, title = {Large-scale turbulence modelling via alpha-regularisation for atmospheric simulations}, series = {Journal of turbulence}, volume = {16}, journal = {Journal of turbulence}, number = {4}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {1468-5248}, doi = {10.1080/14685248.2014.991443}, pages = {367 -- 391}, year = {2015}, abstract = {We study the possibility of obtaining a computational turbulence model by means of non-dissipative regularisation of the compressible atmospheric equations for climate-type applications. We use an -regularisation (Lagrangian averaging) of the atmospheric equations. For the hydrostatic and compressible atmospheric equations discretised using a finite volume method on unstructured grids, deterministic and non-deterministic numerical experiments are conducted to compare the individual solutions and the statistics of the regularised equations to those of the original model. The impact of the regularisation parameter is investigated. Our results confirm the principal compatibility of -regularisation with atmospheric dynamics and encourage further investigations within atmospheric model including complex physical parametrisations.}, language = {en} } @article{BagderinaTarkhanov2015, author = {Bagderina, Yulia Yu. and Tarkhanov, Nikolai Nikolaevich}, title = {Solution of the equivalence problem for the third Painleve equation}, series = {Journal of mathematical physics}, volume = {56}, journal = {Journal of mathematical physics}, number = {1}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0022-2488}, doi = {10.1063/1.4905383}, pages = {15}, year = {2015}, abstract = {We find necessary conditions for a second order ordinary differential equation to be equivalent to the Painleve III equation under a general point transformation. Their sufficiency is established by reduction to known results for the equations of the form y ' = f (x, y). We consider separately the generic case and the case of reducibility to an autonomous equation. The results are illustrated by the primary resonance equation.}, language = {en} }