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Markus Heusler - One of the best experts on this subject based on the ideXlab platform.

  • Stationary Black Holes: Uniqueness and Beyond
    Living Reviews in Relativity, 2012
    Co-Authors: Piotr T. Chruściel, João Lopes Costa, Markus Heusler
    Abstract:

    The spectrum of known black-hole solutions to the stationary Einstein equations has been steadily increasing, sometimes in unexpected ways. In particular, it has turned out that not all black-hole-equilibrium configurations are characterized by their mass, angular momentum and global charges. Moreover, the high degree of symmetry displayed by vacuum and electro-vacuum black-hole spacetimes ceases to exist in self-gravitating non-Linear Field theories. This text aims to review some developments in the subject and to discuss them in light of the uniqueness theorem for the Einstein-Maxwell system.

  • Stationary Black Holes: Uniqueness and Beyond
    Living Reviews in Relativity, 1998
    Co-Authors: Markus Heusler
    Abstract:

    The spectrum of known black hole solutions to the stationary Einstein equations has increased in an unexpected way during the last decade. In particular, it has turned out that not all black hole equilibrium configurations are characterized by their mass, angular momentum and global charges. Moreover, the high degree of symmetry displayed by vacuum and electro-vacuum black hole space-times ceases to exist in self-gravitating non-Linear Field theories. This text aims to review some of the recent developments and to discuss them in the light of the uniqueness theorem for the Einstein-Maxwell system.

Piotr T. Chruściel - One of the best experts on this subject based on the ideXlab platform.

  • Stationary Black Holes: Uniqueness and Beyond
    Living Reviews in Relativity, 2012
    Co-Authors: Piotr T. Chruściel, João Lopes Costa, Markus Heusler
    Abstract:

    The spectrum of known black-hole solutions to the stationary Einstein equations has been steadily increasing, sometimes in unexpected ways. In particular, it has turned out that not all black-hole-equilibrium configurations are characterized by their mass, angular momentum and global charges. Moreover, the high degree of symmetry displayed by vacuum and electro-vacuum black-hole spacetimes ceases to exist in self-gravitating non-Linear Field theories. This text aims to review some developments in the subject and to discuss them in light of the uniqueness theorem for the Einstein-Maxwell system.

Tong Yang - One of the best experts on this subject based on the ideXlab platform.

  • Construction method through forward and reverse ray tracing for a design of ultra-wide Linear Field-of-view off-axis freeform imaging systems
    Journal of Optics, 2015
    Co-Authors: Hou Wei, Tong Yang, Zhu Jun, Guofan Jin
    Abstract:

    In this paper, a construction method through forward and reverse ray tracing for a design of ultra-wide Linear Field-of-view (FOV) off-axis freeform systems is proposed. The freeform initial system is numerically constructed by a point-by-point calculation. This method begins with a spherical system solved by the paraxial optical theory. In this method, the primary mirror is calculated through the reverse ray tracing; hence, the size and position of the aperture stop is not affected by the changes of mirrors. The Fields in the reverse system are selected to cause certain beam overlaps on the primary mirror between adjacent Fields. These overlaps offer a more uniform distribution of data points, improving the calculation of this mirror. As an example, an off-axis freeform system with an ultra-wide Linear Field-of-view of 70? is designed by this method. The effective focal length of the system is 75 mm, and the F-number is 5.8. The diffraction-limited performance of this freeform system in the visible band and the near infrared and near ultraviolet bands validate the construction method presented in this paper.

  • design of freeform imaging systems with Linear Field of view using a construction and iteration process
    Optics Express, 2014
    Co-Authors: Tong Yang, Jun Zhu, Guofan Jin
    Abstract:

    In this paper, a design method based on a construction and iteration process is proposed for designing freeform imaging systems with Linear Field-of-view (FOV). The surface contours of the desired freeform surfaces in the tangential plane are firstly designed to control the tangential rays of multiple Field angles and different pupil coordinates. Then, the image quality is improved with an iterative process. The design result can be taken as a good starting point for further optimization. A freeform off-axis scanning system is designed as an example of the proposed method. The convergence ability of the construction and iteration process to design a freeform system from initial planes is validated. The MTF of the design result is close to the diffraction limit and the scanning error is less than 1 μm. This result proves that good image quality and scanning Linearity were achieved.

  • design method of surface contour for a freeform lens with wide Linear Field of view
    Optics Express, 2013
    Co-Authors: Tong Yang
    Abstract:

    In this paper, a design method of surface contour for a freeform imaging lens with a wide Linear Field-of-view (FOV) is developed. During the calculation of the data points on the unknown freeform surfaces, the aperture size and different Field angles of the system are both considered. Meanwhile, two special constraints are employed to find the appropriate points that can generate a smooth and accurate surface contour. The surfaces obtained can be taken as the starting point for further optimization. An f-θ single lens with a ± 60° Linear FOV has been designed as an example of the proposed method. After optimization with optical design software, the MTF of the lens is close to the diffraction limit and the scanning error is less than 1μm. This result proves that good image quality and scanning Linearity were achieved.

João Lopes Costa - One of the best experts on this subject based on the ideXlab platform.

  • Stationary Black Holes: Uniqueness and Beyond
    Living Reviews in Relativity, 2012
    Co-Authors: Piotr T. Chruściel, João Lopes Costa, Markus Heusler
    Abstract:

    The spectrum of known black-hole solutions to the stationary Einstein equations has been steadily increasing, sometimes in unexpected ways. In particular, it has turned out that not all black-hole-equilibrium configurations are characterized by their mass, angular momentum and global charges. Moreover, the high degree of symmetry displayed by vacuum and electro-vacuum black-hole spacetimes ceases to exist in self-gravitating non-Linear Field theories. This text aims to review some developments in the subject and to discuss them in light of the uniqueness theorem for the Einstein-Maxwell system.

Diptiman Sen - One of the best experts on this subject based on the ideXlab platform.

  • Non-Linear Field theory of a frustrated Heisenberg spin chain
    Nuclear Physics B, 1994
    Co-Authors: Sumathi Rao, Diptiman Sen
    Abstract:

    Abstract We derive a continuum Field theory for the Majumdar-Ghosh model in the large- S limit. The Field takes values in the manifold of the group SO(3) and the Field theory is not Lorentz-invariant. No topological term is induced in the action and the cases for integer spin and half-integer spin appear to be indistinguishable. A one-loop s-function calculation indicates that the theory flows towards a strong coupling (disordered) phase at long distances.