@phdthesis{Bruegmann1996,
  author    = {Br{\"u}gmann, Bernd},
  title     = {Quantum gravity in four dimensions : canonical quantization and dynamical triangulations},
  pages     = {17 S.},
  year      = {1996},
  language  = {en}
}
@article{PoudelTichyBruegmannetal.2020,
  author    = {Poudel, Amit and Tichy, Wolfgang and Br{\"u}gmann, Bernd and Dietrich, Tim},
  title     = {Increasing the accuracy of binary neutron star simulations with an improved vacuum treatment},
  series = {Physical review : D, Particles, fields, gravitation, and cosmology},
  volume    = {102},
  journal   = {Physical review : D, Particles, fields, gravitation, and cosmology},
  number    = {10},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2470-0010},
  doi       = {10.1103/PhysRevD.102.104014},
  pages     = {16},
  year      = {2020},
  abstract  = {Numerical-relativity simulations are essential for studying the last stages of the binary neutron star coalescence. Unfortunately, for stable simulations there is the need to add an artificial low-density atmosphere. Here we discuss a new framework in which we can effectively set the density surrounding the neutron stars to zero to ensure a more accurate simulation. We test our method with a number of single star test cases and for an equal-mass binary neutron star simulation. While the bulk motion of the system is not influenced, and hence there is no improvement with respect to the emitted gravitational-wave signal, we find that the new approach is superior with respect to mass conservation and it allows a much better tracking of outward moving material. This will allow a more accurate simulation of the ejected material and supports the interpretation of present and future multimessenger observations with more accurate numerical-relativity simulations.},
  language  = {en}
}
@article{DudiDietrichRashtietal.2022,
  author    = {Dudi, Reetika and Dietrich, Tim and Rashti, Alireza and Br{\"u}gmann, Bernd and Steinhoff, Jan and Tichy, Wolfgang},
  title     = {High-accuracy simulations of highly spinning binary neutron star systems},
  series = {Physical review : D, Particles, fields, gravitation, and cosmology},
  volume    = {105},
  journal   = {Physical review : D, Particles, fields, gravitation, and cosmology},
  number    = {6},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2470-0010},
  doi       = {10.1103/PhysRevD.105.064050},
  pages     = {13},
  year      = {2022},
  abstract  = {With an increasing number of expected gravitational-wave detections of binary neutron star mergers, it is essential that gravitational-wave models employed for the analysis of observational data are able to describe generic compact binary systems. This includes systems in which the individual neutron stars are millisecond pulsars for which spin effects become essential. In this work, we perform numerical-relativity simulations of binary neutron stars with aligned and antialigned spins within a range of dimensionless spins of chi similar to [-0.28, 0.58]. The simulations are performed with multiple resolutions, show a clear convergence order and, consequently, can be used to test existing waveform approximants. We find that for very high spins gravitational-wave models that have been employed for the interpretation of GW170817 and GW190425 arc not capable of describing our numerical-relativity dataset. We verify through a full parameter estimation study in which clear biases in the estimate of the tidal deformability and effective spin are present. We hope that in preparation of the next gravitational-wave observing run of the Advanced LIGO and Advanced Virgo detectors our new set of numerical-relativity data can be used to support future developments of new gravitational-wave models.},
  language  = {en}
}
@article{KoelschDietrichUjevicetal.2022,
  author    = {K{\"o}lsch, Maximilian and Dietrich, Tim and Ujevic, Maximiliano and Br{\"u}gmann, Bernd},
  title     = {Investigating the mass-ratio dependence of the prompt-collapse threshold with numerical-relativity simulations},
  series = {Physical review : D, Particles, fields, gravitation, and cosmology},
  volume    = {106},
  journal   = {Physical review : D, Particles, fields, gravitation, and cosmology},
  number    = {4},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2470-0010},
  doi       = {10.1103/PhysRevD.106.044026},
  pages     = {27},
  year      = {2022},
  abstract  = {The next observing runs of advanced gravitational-wave detectors will lead to a variety of binary neutron star detections and numerous possibilities for multimessenger observations of binary neutron star systems. In this context a clear understanding of the merger process and the possibility of prompt black hole formation after merger is important, as the amount of ejected material strongly depends on the merger dynamics. These dynamics are primarily affected by the total mass of the binary, however, the mass ratio also influences the postmerger evolution. To determine the effect of the mass ratio, we investigate the parameter space around the prompt-collapse threshold with a new set of fully relativistic simulations. The simulations cover three equations of state and seven mass ratios in the range of 1.0 <= q <= 1.75, with five to seven simulations of binary systems of different total mass in each case. The threshold mass is determined through an empirical relation based on the collapse time, which allows us to investigate effects of the mass ratio on the threshold mass and also on the properties of the remnant system. Furthermore, we model effects of mass ratio and equation of state on tidal parameters of threshold configurations.},
  language  = {en}
}
@article{DudiAdhikariBruegmannetal.2022,
  author    = {Dudi, Reetika and Adhikari, Ananya and Br{\"u}gmann, Bernd and Dietrich, Tim and Hayashi, Kota and Kawaguchi, Kyohei and Kiuchi, Kenta and Kyutoku, Koutarou and Shibata, Masaru and Tichy, Wolfgang},
  title     = {Investigating GW190425 with numerical-relativity simulations},
  series = {Physical review : D, Particles, fields, gravitation, and cosmology},
  volume    = {106},
  journal   = {Physical review : D, Particles, fields, gravitation, and cosmology},
  number    = {8},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2470-0010},
  doi       = {10.1103/PhysRevD.106.084039},
  pages     = {11},
  year      = {2022},
  abstract  = {The third observing run of the LIGO-Virgo Collaboration has resulted in many gravitational wave detections, including the binary neutron star merger GW190425. However, none of these events have been accompanied with an electromagnetic transient found during extensive follow-up searches. In this article, we perform new numerical-relativity simulations of binary neutron star and black hole-neutron star systems that have a chirp mass consistent with GW190425. Assuming that the GW190425's sky location was covered with sufficient accuracy during the electromagnetic follow-up searches, we investigate whether the nondetection of the kilonova is compatible with the source parameters estimated through the gravitational -wave analysis and how one can use this information to place constraints on the properties of the system. Our simulations suggest that GW190425 is incompatible with an unequal mass binary neutron star merger with a mass ratio q < 0.8 when considering stiff or moderately stiff equations of state if the binary was face on and covered by the observation. Our analysis shows that a detailed observational result for kilonovae will be useful to constrain the mass ratio of binary neutron stars in future events.},
  language  = {en}
}