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Search Results: 1 - 10 of 11824 matches for " Andreas Schmitt-Sody "
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High-Power Hybrid Mode-Locked External Cavity Semiconductor Laser Using Tapered Amplifier with Large Tunability
Andreas Schmitt-Sody,Andreas Velten,Ye Liu,Ladan Arissian,Jean-Claude Diels
International Journal of Optics , 2008, DOI: 10.1155/2008/865092
Abstract: We report on hybrid mode-locked laser operation of a tapered semiconductor amplifier in an external ring cavity, generating pulses as short as 0.5 ps at 88.1 MHz with an average power of 60 mW. The mode locking is achieved through a combination of a multiple quantum well saturable absorber (>10% modulation depth) and an RF current modulation. This designed laser has 20 nm tuning bandwidth in continuous wave and 10 nm tuning bandwidth in mode locking around 786 nm center wavelength at constant temperature.
Generation of multi-terawatt vortex laser beams
Craig Ament,Lee Johnson,Andreas Schmitt-Sody,Adrian Lucero,Thomas Milster,Pavel Polynkin
Physics , 2014, DOI: 10.1364/AO.53.003355
Abstract: We report the fabrication of large-area phase masks on thin fused-silica substrates that are suitable for shaping multi-terawatt femtosecond laser beams. We apply these phase masks for the generation of intense femtosecond optical vortices. We further quantify distortions of the vortex beam patterns that result from several common types of mask defects.
Spin-one Color Superconductivity in Cold and Dense Quark Matter
Andreas Schmitt
Physics , 2004,
Abstract: In this thesis, several color-superconducting phases where quarks of the same flavor form Cooper pairs are investigated. In these phases, a Cooper pair carries total spin one. A systematic classification of theoretically possible phases, discriminated by the color-spin structure of the order parameter and the respective symmetry breaking pattern, is presented. In the weak-coupling limit, i.e., for asymptotically high densities, a universal form of the QCD gap equation is derived, applicable to arbitrary color-superconducting phases. It is applied to several spin-one and spin-zero phases in order to determine their energy gaps and critical temperatures. In some of the spin-one phases the resulting gap function is anisotropic and has point or line nodes. It is shown that the phases with two different gaps violate the well-known BCS relation between the critical temperature and the zero-temperature gap. Moreover, the screening properties of color superconductors regarding gluons and photons are discussed. In particular, it turns out that, contrary to spin-zero color superconductors, spin-one color superconductors exhibit an electromagnetic Meissner effect. This property is proven by symmetry arguments as well as by an explicit calculation of the gluon and photon Meissner masses.
Dense matter in compact stars - A pedagogical introduction
Andreas Schmitt
Physics , 2010, DOI: 10.1007/978-3-642-12866-0
Abstract: Cold and dense nuclear and/or quark matter can be found in the interior of compact stars. It is very challenging to determine the ground state and properties of this matter because of the strong-coupling nature of QCD. I give a pedagogical introduction to microscopic calculations based on phenomenological models, effective theories, and perturbative QCD. I discuss how the results of these calculations can be related to astrophysical observations to potentially rule out or confirm candidate phases of dense matter.
Supercurrents in color-superconducting quark matter
Andreas Schmitt
Physics , 2008, DOI: 10.1016/j.nuclphysa.2009.01.018
Abstract: We review the basic properties of the currCFL-K^0 phase in dense quark matter. At asymptotically large densities, three-flavor quark matter is in the color-flavor locked (CFL) state. The currCFL-K^0 state is a way to respond to ``stress'' on the quark Cooper pairing, imposed at more moderate densities by the strange quark mass and the conditions of electric and color neutrality. We show how a kaon supercurrent is incorporated in a purely fermionic formalism, and show that the net current vanishes due to cancellation of fermion and charge-conjugate fermion contributions.
Superfluid two-stream instability in a microscopic model
Andreas Schmitt
Physics , 2013, DOI: 10.1103/PhysRevD.89.065024
Abstract: The superflow in a superfluid is bounded from above by Landau's critical velocity. Within a microscopic bosonic model, I show that below this critical velocity there is a dynamical instability that manifests itself in an imaginary sound velocity and that is reminiscent of the two-stream instability in electromagnetic plasmas. I compute the onset of this instability and its full angular structure in a relativistic, uniform superfluid for all temperatures. At weak coupling, the instability only operates in a very small region in the phase diagram of temperature and superflow. Varying the coupling of the model suggests that the effect is more prominent at strong coupling and thus could be important for superfluids in compact stars and in the laboratory.
The ground state in a spin-one color superconductor
Andreas Schmitt
Physics , 2004, DOI: 10.1103/PhysRevD.71.054016
Abstract: Color superconductors in which quarks of the same flavor form Cooper pairs are investigated. These Cooper pairs carry total spin one. A systematic group-theoretical classification of possible phases in a spin-one color superconductor is presented, revealing parallels and differences to the theory of superfluid $^3$He. General expressions for the gap parameter, the critical temperature, and the pressure are derived and evaluated for several spin-one phases, with special emphasis on the angular structure of the gap equation. It is shown that the (transverse) color-spin-locked phase is expected to be the ground state.
Introduction to superfluidity -- Field-theoretical approach and applications
Andreas Schmitt
Physics , 2014,
Abstract: In this pedagogical introduction, I discuss theoretical aspects of superfluidity and superconductivity, mostly using a field-theoretical formalism. While the emphasis is on general concepts and mechanisms behind superfluidity, I also discuss various applications in low-energy and high-energy physics. Besides some introductory and standard topics such as superfluid helium and superfluidity in a simple scalar field theory, the lecture notes also include more advanced chapters, for instance discussions of the covariant two-fluid formalism and Cooper pairing with mismatched Fermi surfaces.
A Review of Methods to Control Bleeding from Life-Threatening Traumatic Wounds  [PDF]
Sody Abby Naimer
Health (Health) , 2014, DOI: 10.4236/health.2014.66067
Abstract: The large selection of techniques and modalities for field treatment of the bleeding wound may appear as a potpourri of arbitrarily introduced devices. Nevertheless, if we analyze the various offered solutions systematically in an orderly approach, they can be differentiated into set categories. It is necessary to recognize the pros and cons of each available product in order to decide when and where each is the most applicable for any given clinical scenario. Identification, development and evaluation of new products and technologies capable of stopping life threatening hemorrhage are still ongoing. Despite paucity of research on this topic recently more and more information has accumulated to assist in supporting those techniques of superior efficacy. The objective of this review is to guide the reader through the diverse products according to mechanism of action and expose the important literature relevant to this topic. Justification is found for use of each of the categories: tourniquets, hemostatic agents and compression dressings however close scrutiny is needed to select the most appropriate choice in each group. Hopefully, continuing appraisal of these devices together with the growing experience of trauma teams and combat medics can assist to establish the superior products in each class for the benefit of all casualties and trauma victims.
Generativity as a Route to Active Ageing
Andreas Kruse,Eric Schmitt
Current Gerontology and Geriatrics Research , 2012, DOI: 10.1155/2012/647650
Abstract: We elucidate the significance of active ageing from an individual as well as from a societal perspective. Taking an individual perspective, maintaining activity in later years is linked to successful ageing because of empirical relationships to positive self-perception, satisfaction with life, and development of competences, whereas from a societal perspective, active ageing implies usage of older people’s life competences as a human capital of society—a societal imperative, particularly in times of demographic change but also more basically substantiated in an ethics of responsibility, intergenerational solidarity, and generation equity. We focus on the psychological construct of generativity which is interpreted as an aspect of the philosophical-anthropological category of joint responsibility. Our own research in Mexico and the Baltic States supports the notion that maintaining access to the public sphere and active engagement for others is a more basic individual concern than a life-stages specific developmental task. We report background and results of a Dialogue Forum Project Funding, a research cooperation between our institute and the Foundation Remembrance, Responsibility, and Future aimed to improve generativity in Belarus, Russia, and Ukraine by implementing and supporting local initiatives offering opportunities for intergenerational dialogue. 1. Active Ageing in Individual and Societal Perspective Associating successful ageing with maintenance of activity has a long tradition in gerontology. Already in the 1960s, in the context of the classical controversy on propositions of disengagement theory, decreases in social roles and functions were interpreted as primarily reflecting prevalent misconceptions of old age and ageing, ageist stereotypes, and attitudes that contaminate external perception as well as self-conceptions and development of competences [1–4]. Although this pointed line of reasoning obviously neglects the significance of economic, political, and social structures as well as interindividual differences, the hypothesized relationships between role activity, self-concept, and satisfaction with life are still important for understanding positive or successful ageing [5, 6]. More recent gerontological theories elucidate that role activity in younger ages is a significant moderator of the relationship between older people’s actual activity in specific social roles, satisfaction with these roles, and satisfaction with life. From the perspective of continuity theory [5] what predicts satisfaction and well-being is not the number of
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