S. Bauer - Universität Duisburg-Essen

S. Bauer
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S. Bauer
Universität Duisburg-Essen

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Mathematics - Mathematical Physics (8)
Mathematical Physics (8)
Instrumentation and Methods for Astrophysics (6)
Physics - Instrumentation and Detectors (5)
Solar and Stellar Astrophysics (5)
Mathematics - Analysis of PDEs (5)
Astrophysics (4)
Physics - Materials Science (4)
Statistics - Machine Learning (4)
Computer Science - Software Engineering (3)
Mathematics - Geometric Topology (3)
Physics - Mesoscopic Systems and Quantum Hall Effect (2)
Computer Science - Logic in Computer Science (2)
Computer Science - Computer Vision and Pattern Recognition (2)
Mathematics - Numerical Analysis (2)
Physics - Atmospheric and Oceanic Physics (2)
Physics - Geophysics (2)
Physics - Optics (2)
Mathematics - Algebraic Topology (1)
Mathematics - Differential Geometry (1)
Physics - Medical Physics (1)
Computer Science - Computational Engineering; Finance; and Science (1)
Nuclear Experiment (1)
Mathematics - Statistics (1)
Quantitative Biology - Quantitative Methods (1)
Computer Science - Numerical Analysis (1)
Earth and Planetary Astrophysics (1)
Statistics - Applications (1)
Computer Science - Learning (1)
Quantitative Biology - Tissues and Organs (1)
Mathematics - Functional Analysis (1)
High Energy Physics - Experiment (1)
Statistics - Theory (1)
Physics - Chemical Physics (1)

Publications Authored By S. Bauer

Gradient matching is a promising tool for learning parameters and state dynamics of ordinary differential equations. It is a grid free inference approach which for fully observable systems is at times competitive with numerical integration. However for many real-world applications, only sparse observations are available or even unobserved variables are included in the model description. Read More

The most common reason for spinal surgery in elderly patients is lumbar spinal stenosis(LSS). For LSS, treatment decisions based on clinical and radiological information as well as personal experience of the surgeon shows large variance. Thus a standardized support system is of high value for a more objective and reproducible decision. Read More

Stimulated by the discovery of a number of close-in low-density planets, we generalise the Jeans escape parameter taking hydrodynamic and Roche lobe effects into account. We furthermore define $\Lambda$ as the value of the Jeans escape parameter calculated at the observed planetary radius and mass for the planet's equilibrium temperature and considering atomic hydrogen, independently of the atmospheric temperature profile. We consider 5 and 10 $M_{\oplus}$ planets with an equilibrium temperature of 500 and 1000 K, orbiting early G-, K-, and M-type stars. Read More

Gradient matching with Gaussian processes is a promising tool for learning parameters of ordinary differential equations (ODE's). The essence of gradient matching is to model the prior over state variables as a Gaussian process which implies that the joint distribution given the ODE's and GP kernels is also Gaussian distributed. The state-derivatives are integrated out analytically since they are modelled as latent variables. Read More

Gaussian processes are powerful, yet analytically tractable models for supervised learning. A Gaussian process is characterized by a mean function and a covariance function (kernel), which are determined by a model selection criterion. The functions to be compared do not just differ in their parametrization but in their fundamental structure. Read More

Matrix-free finite element implementations of massively parallel geometric multigrid save memory and are often significantly faster than implementations using classical sparse matrix techniques. They are especially well suited for hierarchical hybrid grids on polyhedral domains. In the case of constant coefficients all fine grid node stencils in the interior of a coarse macro element are equal. Read More

After having demonstrated that an IFU, attached to a microscope rather than to a telescope, is capable of differentiating complex organic tissue with spatially resolved Raman spectroscopy, we have launched a clinical validation program that utilizes a novel optimized fiber-coupled multi-channel spectrograph whose layout is based on the modular MUSE spectrograph concept. The new design features a telecentric input and has an extended blue performance, but otherwise maintains the properties of high throughput and excellent image quality over an octave of wavelength coverage with modest spectral resolution. We present the opto-mechanical layout and details of its optical performance. Read More

Accurate and robust cell nuclei classification is the cornerstone for a wider range of tasks in digital and Computational Pathology. However, most machine learning systems require extensive labeling from expert pathologists for each individual problem at hand, with no or limited abilities for knowledge transfer between datasets and organ sites. In this paper we implement and evaluate a variety of deep neural network models and model ensembles for nuclei classification in renal cell cancer (RCC) and prostate cancer (PCa). Read More

Tuning the band gap of semiconductors via quantum size effects launched a technological revolution in optoelectronics, advancing solar cells, quantum dot light-emitting displays, and solid state lasers. Next generation devices seek to employ low-cost, easily processable semiconductors. A promising class of such materials are metal-halide perovskites, currently propelling research on emerging photovoltaics. Read More

Autonomous driving is a rapidly evolving technology. Autonomous vehicles are capable of sensing their environment and navigating without human input through sensory information such as radar, lidar, GNSS, vehicle odometry, and computer vision. This sensory input provides a rich dataset that can be used in combination with machine learning models to tackle multiple problems in supervised settings. Read More

While a fully relativistic collisionless plasma is modeled by the Vlasov-Maxwell system a good approximation in the non-relativistic limit is given by the Vlasov-Poisson system. We modify the Vlasov-Poisson system so that damping due to the relativistic effect of radiation reaction is included. We prove the existence and uniqueness as well as the higher regularity of local classical solutions. Read More

Authors: M. Arenz, M. Babutzka, M. Bahr, J. P. Barrett, S. Bauer, M. Beck, A. Beglarian, J. Behrens, T. Bergmann, U. Besserer, J. Blümer, L. I. Bodine, K. Bokeloh, J. Bonn, B. Bornschein, L. Bornschein, S. Büsch, T. H. Burritt, S. Chilingaryan, T. J. Corona, L. De Viveiros, P. J. Doe, O. Dragoun, G. Drexlin, S. Dyba, S. Ebenhöch, K. Eitel, E. Ellinger, S. Enomoto, M. Erhard, D. Eversheim, M. Fedkevych, A. Felden, S. Fischer, J. A. Formaggio, F. Fränkle, D. Furse, M. Ghilea, W. Gil, F. Glück, A. Gonzalez Urena, S. Görhardt, S. Groh, S. Grohmann, R. Grössle, R. Gumbsheimer, M. Hackenjos, V. Hannen, F. Harms, N. Hauÿmann, F. Heizmann, K. Helbing, W. Herz, S. Hickford, D. Hilk, B. Hillen, T. Höhn, B. Holzapfel, M. Hötzel, M. A. Howe, A. Huber, A. Jansen, N. Kernert, L. Kippenbrock, M. Kleesiek, M. Klein, A. Kopmann, A. Kosmider, A. Kovalík, B. Krasch, M. Kraus, H. Krause, M. Krause, L. Kuckert, B. Kuffner, L. La Cascio, O. Lebeda, B. Leiber, J. Letnev, V. M. Lobashev, A. Lokhov, E. Malcherek, M. Mark, E. L. Martin, S. Mertens, S. Mirz, B. Monreal, K. Müller, M. Neuberger, H. Neumann, S. Niemes, M. Noe, N. S. Oblath, A. Off, H. -W. Ortjohann, A. Osipowicz, E. Otten, D. S. Parno, P. Plischke, A. W. P. Poon, M. Prall, F. Priester, P. C. -O. Ranitzsch, J. Reich, O. Rest, R. G. H. Robertson, M. Röllig, S. Rosendahl, S. Rupp, M. Rysavy, K. Schlösser, M. Schlösser, K. Schönung, M. Schrank, J. Schwarz, W. Seiler, H. Seitz-Moskaliuk, J. Sentkerestiova, A. Skasyrskaya, M. Slezak, A. Spalek, M. Steidl, N. Steinbrink, M. Sturm, M. Suesser, H. H. Telle, T. Thümmler, N. Titov, I. Tkachev, N. Trost, A. Unru, K. Valerius, D. Venos, R. Vianden, S. Vöcking, B. L. Wall, N. Wandkowsky, M. Weber, C. Weinheimer, C. Weiss, S. Welte, J. Wendel, K. L. Wierman, J. F. Wilkerson, D. Winzen, J. Wolf, S. Wüstling, M. Zacher, S. Zadoroghny, M. Zboril

The KATRIN experiment will probe the neutrino mass by measuring the beta-electron energy spectrum near the endpoint of tritium beta-decay. An integral energy analysis will be performed by an electro-static spectrometer (Main Spectrometer), an ultra-high vacuum vessel with a length of 23.2 m, a volume of 1240 m^3, and a complex inner electrode system with about 120000 individual parts. Read More

We prove that a time series satisfying a (linear) multivariate autoregressive moving average (VARMA) model satisfies the same model assumption in the reversed time direction, too, if all innovations are normally distributed. This reversibility breaks down if the innovations are non-Gaussian. This means that under the assumption of a VARMA process with non-Gaussian noise, the arrow of time becomes detectable. Read More

We prove that for bounded Lipschitz domains in $\mathbb{R}^N$ Korn's first inequality holds for vector fields satisfying homogeneous mixed normal and tangential boundary conditions. Read More

We report on the observation of a terahertz radiation induced photon drag effect in epitaxially grown $n$- and $p$-type (Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{3}$ three dimensional topological insulators with different antimony concentrations $x$ varying from 0 to 1. We demonstrate that the excitation with polarized terahertz radiation results in a $dc$ electric photocurrent. While at normal incidence a current arises due to the photogalvanic effect in the surface states, at oblique incidence it is outweighed by the trigonal photon drag effect. Read More

For a bounded weak Lipschitz domain we show the so called `Maxwell compactness property', that is, the space of square integrable vector fields having square integrable weak rotation and divergence and satisfying mixed tangential and normal boundary conditions is compactly embedded into the space of square integrable vector fields. We will also prove some canonical applications, such as Maxwell estimates, Helmholtz decompositions and a static solution theory. Furthermore, a Fredholm alternative for the underlying time-harmonic Maxwell problem and all corresponding and related results for exterior domains formulated in weighted Sobolev spaces are straight forward. Read More

PEPSI is the bench-mounted, two-arm, fibre-fed and stabilized Potsdam Echelle Polarimetric and Spectroscopic Instrument for the 2x8.4 m Large Binocular Telescope (LBT). Three spectral resolutions of either 43 000, 120 000 or 270 000 can cover the entire optical/red wavelength range from 383 to 907 nm in three exposures. Read More

We will prove that for piecewise smooth and concave domains Korn's first inequality holds for vector fields satisfying homogeneous normal or tangential boundary conditions with explicit Korn constant square root of 2. Read More

The KATRIN experiment is going to search for the average mass of the electron antineutrino with a sensitivity of 0.2 eV/c2. It uses a retardation spectrometer of MAC-E filter type to accurately measure the shape of the electron spectrum at the endpoint of tritium beta decay. Read More

During the past years there has been renewed interest in the wide-bandgap II-VI semiconductor ZnO, triggered by promising prospects for spintronic applications. First, ferromagnetism was predicted for dilute magnetic doping. In comprehensive investigation of ZnO:Co thin films based on the combined measurement of macroscopic and microscopic properties, we find no evidence for carrier-mediated itinerant ferromagnetism. Read More

The KATRIN (KArlsruhe TRItium Neutrino) experiment aims to determine the mass of the electron antineutrino with a sensitivity of 200meV by precisely measuring the electron spectrum of the tritium beta decay. This will be done by the use of a retarding spectrometer of the MAC-E-Filter type. To achieve the desired sensitivity the stability of the retarding potential of -18. Read More

In this paper we describe a new variant of null ellipsometry to determine thicknesses and optical properties of thin films on a substrate at cryogenic temperatures. In the PCSA arrangement of ellipsometry the polarizer and the compensator are placed before the substrate and the analyzer after it. Usually, the polarizer and the analyzer are rotated to find the intensity minimum searched for in null ellipsometry. Read More

For an n-dimensional bounded domain we derive some inequalities bounding the norm of a square tensor field. Concerning the Div-Dev-inequality the bound is given by the trace-free part and the divergence and the tensor. In the case of the DevSym-Curl-inequality the bound is given by the trace-free and symmetric part and the curl of the tensor. Read More

A previous dielectric, near-infrared (NIR), and nuclear magnetic resonance study on the hydrogen-bonded liquid 2-ethyl-1-hexanol [C. Gainaru et al., Phys. Read More

The KATRIN experiment aims at the direct model-independent determination of the average electron neutrino mass via the measurement of the endpoint region of the tritium beta decay spectrum. The electron spectrometer of the MAC-E filter type is used, requiring very high stability of the electric filtering potential. This work proves the feasibility of implanted 83Rb/83mKr calibration electron sources which will be utilised in the additional monitor spectrometer sharing the high voltage with the main spectrometer of KATRIN. Read More

The second Betti number of a smooth, closed, connected and simply connected, four-dimensional spin manifold is greater or equal 11/8 times the abolute value of its signature. Read More

Specification theories as a tool in model-driven development processes of component-based software systems have recently attracted a considerable attention. Current specification theories are however qualitative in nature, and therefore fragile in the sense that the inevitable approximation of systems by models, combined with the fundamental unpredictability of hardware platforms, makes it difficult to transfer conclusions about the behavior, based on models, to the actual system. Hence this approach is arguably unsuited for modern software systems. Read More

In this review, we look back upon the literature, which had the GREGOR solar telescope project as its subject including science cases, telescope subsystems, and post-focus instruments. The articles date back to the year 2000, when the initial concepts for a new solar telescope on Tenerife were first presented at scientific meetings. This comprehensive bibliography contains literature until the year 2012, i. Read More

The GREGOR Fabry-P\'erot Interferometer (GFPI) is one of three first-light instruments of the German 1.5-meter GREGOR solar telescope at the Observatorio del Teide, Tenerife, Spain. The GFPI uses two tunable etalons in collimated mounting. Read More

Affiliations: 1Leibniz-Institut für Astrophysik Potsdam, 2Leibniz-Institut für Astrophysik Potsdam, 3Friedrich-Schiller-Universität Jena, 4Friedrich-Schiller-Universität Jena, 5Leibniz-Institut für Astrophysik Potsdam, 6Leibniz-Institut für Astrophysik Potsdam, 7Leibniz-Institut für Astrophysik Potsdam, 8Leibniz-Institut für Astrophysik Potsdam, 9Leibniz-Institut für Astrophysik Potsdam, 10Leibniz-Institut für Astrophysik Potsdam, 11Leibniz-Institut für Astrophysik Potsdam, 12Leibniz-Institut für Astrophysik Potsdam, 13HOT Hannover, 14Leibniz-Institut für Astrophysik Potsdam, 15Leibniz-Institut für Astrophysik Potsdam, 16Leibniz-Institut für Astrophysik Potsdam

Astronomical instrumentation is most of the time faced with challenging requirements in terms of sensitivity, stability, complexity, etc., and therefore leads to high performance developments that at first sight appear to be suitable only for the specific design application at the telescope. However, their usefulness in other disciplines and for other applications is not excluded. Read More

Affiliations: 1Ludwig-Maximilians-Universität München, Germany, 2University Paul Sabatier-Toulouse III, France

This volume contains the proceedings of the 4th workshop on Foundations of Interface Technologies (FIT 2012) which was collocated with ETAPS 2012 in Tallinn, Estonia, and took place on March 25, 2012. The aim of this workshop is to bring together researchers who are interested in the formal underpinnings of interface technologies. Read More

Affiliations: 1Institute for Surgical Technology and Biomechanics, University of Bern, Switzerland, 2Institute for Surgical Technology and Biomechanics, University of Bern, Switzerland, 3Institute for Surgical Technology and Biomechanics, University of Bern, Switzerland

Skull-stripping separates the skull region of the head from the soft brain tissues. In many cases of brain image analysis, this is an essential preprocessing step in order to improve the final result. This is true for both registration and segmentation tasks. Read More

Affiliations: 1Didaktik der Physik, Universitaet Duisburg-Essen, 2Leibniz-Gymnasium Essen, 3Institut fuer Astrophysik, Georg-August-Universitaet Goettingen, 4Max-Planck-Gymnaisum Goettingen, 5Institut fuer Astrophysik, Georg-August-Universitaet Goettingen, 6Institut fuer Astrophysik, Georg-August-Universitaet Goettingen, 7Institut fuer Astrophysik, Georg-August-Universitaet Goettingen, 8Leibniz-Gymnasium Essen, 9Don Bosco-Gymnasium Essen, 10Evangelisches Gymnasium Lippstadt, 11Leibniz-Gymnasium Essen, 12Leibniz-Gymnasium Essen, 13Leibniz-Gymnasium Essen, 14Leibniz-Gymnasium Essen, 15Leibniz-Gymnasium Essen, 16Leibniz-Gymnasium Essen, 17Leibniz-Gymnasium Essen, 18Leibniz-Gymnasium Essen, 19Leibniz-Gymnasium Essen, 20Leibniz-Gymnasium Essen, 21Leibniz-Gymnasium Essen, 22Leibniz-Gymnasium Essen, 23Leibniz-Gymnasium Essen, 24Leibniz-Gymnasium Essen, 25Max-Planck-Gymnaisum Goettingen, 26Max-Planck-Gymnaisum Goettingen, 27Max-Planck-Gymnaisum Goettingen, 28Max-Planck-Gymnaisum Goettingen, 29Max-Planck-Gymnaisum Goettingen, 30Max-Planck-Gymnaisum Goettingen, 31Don Bosco-Gymnasium Essen, 32Don Bosco-Gymnasium Essen, 33Don Bosco-Gymnasium Essen, 34Don Bosco-Gymnasium Essen, 35Evangelisches Gymnasium Lippstadt, 36Evangelisches Gymnasium Lippstadt, 37Evangelisches Gymnasium Lippstadt, 38Evangelisches Gymnasium Lippstadt, 39Evangelisches Gymnasium Lippstadt, 40Evangelisches Gymnasium Lippstadt, 41Evangelisches Gymnasium Lippstadt, 42Evangelisches Gymnasium Lippstadt

As part of an ongoing collaboration between student groups at high schools and professional astronomers, we have searched for the presence of circum-binary planets in a bona-fide unbiased sample of twelve post-common envelope binaries (PCEBs) from the Catalina Sky Survey (CSS) and the Sloan Digital Sky Survey (SDSS). Although the present ephemerides are significantly more accurate than previous ones, we find no clear evidence for orbital period variations between 2005 and 2011 or during the 2011 observing season. The sparse long-term coverage still permits O-C variations with a period of years and an amplitude of tens of seconds, as found in other systems. Read More

Fabry-Perot interferometers have advantages over slit spectrographs because they allow fast narrow-band imaging and post-factum image reconstruction of spectropolarimetric data. Temperature, plasma velocity, and magnetic field maps can be derived from inversions of photospheric and chromospheric spectral lines, thus, advancing our understanding of the dynamic Sun and its magnetic fields at the smallest spatial scales. The GREGOR Fabry-Perot Interferometer (GFPI) is one of two firstlight instruments of the 1. Read More

Interface specifications play an important role in component-based software development. An interface theory is a formal framework supporting composition, refinement and compatibility of interface specifications. We present different interface theories which use modal I/O-transition systems as their underlying domain for interface specifications: synchronous interface theories, which employ a synchronous communication schema, as well as a novel interface theory for asynchronous communication where components communicate via FIFO-buffers. Read More

Pervasive user-centric applications are systems which are meant to sense the presence, mood, and intentions of users in order to optimize user comfort and performance. Building such applications requires not only state-of-the art techniques from artificial intelligence but also sound software engineering methods for facilitating modular design, runtime adaptation and verification of critical system requirements. In this paper we focus on high-level design and analysis, and use the algebraic rewriting language Real-Time Maude for specifying applications in a real-time setting. Read More

The existence of semiconductors exhibiting long-range ferromagnetic ordering at room temperature still is controversial. One particularly important issue is the presence of secondary magnetic phases such as clusters, segregations, etc.. Read More

We investigate the issue of "dangerous human-made interference with climate" using simulations with GISS modelE driven by measured or estimated forcings for 1880-2003 and extended to 2100 for IPCC greenhouse gas scenarios as well as the 'alternative' scenario of Hansen and Sato. Identification of 'dangerous' effects is partly subjective, but we find evidence that added global warming of more than 1 degree C above the level in 2000 has effects that may be highly disruptive. The alternative scenario, with peak added forcing ~1. Read More

We carry out climate simulations for 1880-2003 with GISS modelE driven by ten measured or estimated climate forcings. An ensemble of climate model runs is carried out for each forcing acting individually and for all forcing mechanisms acting together. We compare side-by-side simulated climate change for each forcing, all forcings, observations, unforced variability among model ensemble members, and, if available, observed variability. Read More

An odd Seiberg-Witten invariant imposes bounds on the signature of a closed, almost complex 4-manifold with vanishing first Chern class. This applies in particular to symplectic 4-manifolds of Kodaira dimension zero. Read More

VIRUS is a planned integral-field instrument for the Hobby-Eberly Telescope (HET). In order to achieve a large field-of-view and high grasp at reasonable costs, the approach is to replicate integral-field units (IFU) and medium sized spectrographs many times. The Astrophysical Institute Potsdam (AIP) contributes to VIRUS with the development and testing of the IFU prototype. Read More

We study the dynamics of many charges interacting with the Maxwell field. The particles are modeled by means of non-negative distribution functions $f^+$ and $f^-$ representing two species of charged matter with positive and negative charge, respectively. If their initial velocities are small compared to the speed of light, $c$, then in lowest order, the Newtonian or classical limit, their motion is governed by the Vlasov-Poisson system. Read More

PPak is a new fiber-based Integral Field Unit (IFU), developed at the Astrophysical Institute Potsdam, implemented as a module into the existing PMAS spectrograph. The purpose of PPak is to provide both an extended field-of-view with a large light collecting power for each spatial element, as well as an adequate spectral resolution. The PPak system consists of a fiber bundle with 331 object, 36 sky and 15 calibration fibers. Read More

Affiliations: 1Universität Duisburg-Essen, 2Universität Duisburg-Essen, 3Universität Bayreuth, 4Max-Planck-Institut für Gravitationsphysik, Golm

We consider the relativistic Vlasov-Maxwell and Vlasov-Nordstr\"om systems which describe large particle ensembles interacting by either electromagnetic fields or a relativistic scalar gravity model. For both systems we derive a radiation formula analogous to the Einstein quadrupole formula in general relativity. Read More

Affiliations: 1Astrophysikalisches Institut Potsdam, Germany, 2Astrophysikalisches Institut Potsdam, Germany, 3Astrophysikalisches Institut Potsdam, Germany, 4Astrophysikalisches Institut Potsdam, Germany, 5Astrophysikalisches Institut Potsdam, Germany, 6Astrophysikalisches Institut Potsdam, Germany, 7Astrophysikalisches Institut Potsdam, Germany, 8Astrophysikalisches Institut Potsdam, Germany, 9Astrophysikalisches Institut Potsdam, Germany, 10Astrophysikalisches Institut Potsdam, Germany, 11Astrophysikalisches Institut Potsdam, Germany, 12Astrophysikalisches Institut Potsdam, Germany, 13Astronomical Instrument Group, Dept. of Physics, University of Durham, U.K, 14Landessternwarte Tautenburg, Germany, 15Konstruktionsbuero Altmann, Passau, Germany
Category: Astrophysics

We describe the design, manufacture, commissioning, and performance of PMAS, the Potsdam Multi-Aperture Spectrophotometer. PMAS is a dedicated integral field spectrophotometer, optimized to cover the optical wavelength regime of 0.35--1um. Read More

We study the Nordstr\"om-Vlasov system which describes the dynamics of a self-gravitating ensemble of collisionless particles in the framework of the Nordstr\"om scalar theory of gravitation. If the speed of light $c$ is considered as a parameter, it is known that in the Newtonian limit $c\to\infty$ the Vlasov-Poisson system is obtained. In this paper we determine a higher approximation and establish a pointwise error estimate of order $O(c^{-4})$. Read More

We study the relativistic Vlasov-Maxwell system which describes large systems of particles interacting by means of their collectively generated forces. If the speed of light $c$ is considered as a parameter then it is known that in the Newtonian limit $c\to\infty$ the Vlasov-Poisson system is obtained. In this paper we determine the next order approximate system, which in the case of individual particles usually is called the Darwin approximation. Read More

This is a survey article on the stable cohomotopy refinement of Seiberg-Witten invariants containing also new results, for example: - Stable cohomotopy groups describe path components of certain mapping spaces. - Relation of stable cohomotopy invariants to Seiberg-Witten invariants without restriction on Betti numbers. - Theorem on connected sums along (-2)-spheres. Read More

The monopole map defines an element in an equivariant stable cohomotopy group refining the Seiberg-Witten invariant. This first of two articles presents the details of the definition of the stable cohomotopy invariant and discusses its relation to the integer valued Seiberg-Witten invariant. Read More