Homepage of Harald Dimmelmeier

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linkPfeilExtern.gifRelativistic Hydrodynamics
linkPfeilExtern.gifGravitational Waveform Catalog


Since May 2008 I am working as an expert for safety analysis of nuclear reactors for the company AREVA NP GmbH in Erlangen, Germany. Previously, I was a Marie Curie fellow at the linkPfeilExtern.gifSection of Astrophysics, Astronomy & Mechanics of the linkPfeilExtern.gifAristotle University of Thessaloniki in Greece. Before that I was a postdoctoral researcher in the linkRelativistic Hydrodynamics Group of the linkMax Planck Institute for Astrophysics in Garching.

Until January 2007, I was also a member of the German research network linkPfeilExtern.gifSFB Transregio 7 "Gravitational Wave Astronomy", I was a former member of the German research network linkPfeilExtern.gifSFB 375 "Astro-Particle Physics", and I was a previous informal member of the European Union linkPfeilExtern.gifResearch and Training Network "Sources of Gravitational Waves".

My research interest was on relativistic hydrodynamics and numerical relativity, with particular focus on compact sources of gravitational waves, numerical methods in computational fluid dynamics, and applications of such methods in simulations of stellar gravitational collapse and rotating neutron star models. A very useful external resource on this subject is the linkPfeilExtern.gifStellar Collapse Website.

Numerical simulations of stellar gravitational collapse are usually performed on parallel supercomputers like for instance the ones at the linkPfeilExtern.gifGarching Computing Center of the Max Planck Society, the linkPfeilExtern.gifLeibniz Computing Center of the Bavarian Academy of Sciences, or the linkPfeilExtern.gifNational Computing Center of Supercomputing Applications of the linkPfeilExtern.gifUniversity of Illinois at Urbana-Champaign.

Such simulations are based on methods also utilized in the field of acoustics, aerodynamics, combustion theory, hydrology, geology, automotive safety, and even the financing sector. For this schemes are employed which are specificly tailored for the use in astrophysics and general relativity, and for example accomodate for the fact that in a strong gravitational field spacetime is curved.

The investigated scenarios are a promising source of gravitational radiation. These distortions of spacetime are planned to be measured by laser interferometers or resonant bar detectors in the near future. Such experiments (like linkPfeilExtern.gifGEO 600, linkPfeilExtern.gifLIGO, linkPfeilExtern.gifVIRGO, linkPfeilExtern.gifLISA, or linkPfeilExtern.gifIGEC) have recently started very sensitive measurements. Many of my projects involve providing the data analysis groups of these detectors with templates of the expected waveforms, which are crucial for a successful detection of the signals.

In the development of numerical codes for simulations of general relativistic hydrodynamics (like the powerful, modern and robust three-dimensional linkPfeil.gifCoCoNuT code which has been used for many projects I have been involved in), I closely collaborated with scientists from the linkPfeilExtern.gifDepartamento de Astronomía y Astrofísica at the linkPfeilExtern.gifUniversidad de Valencia in Spain, from the linkPfeilExtern.gifLaboratoire de l'Univers et de ses Théories at the linkPfeilExtern.gifObservatoire de Paris in France, and from the linkPfeilExtern.gifNumerical Relativity Group at the linkPfeilExtern.gifMax Planck Institute for Gravitational Physics in Potsdam, Germany.

In addition, I was the technical editor of the online journal linkPfeilExtern.gifLiving Reviews in Relativity, which is a peer reviewed journal offered by the linkPfeilExtern.gifMax Planck Institute for Gravitational Physics in Potsdam. It publishes reviews of research in the theory of relativity as a free service to the scientific community. This journal is one of three journals of the linkPfeilExtern.gifLiving Reviews journal family, which is hosted and supported by the linkPfeilExtern.gifHeinz Nixdorf Center for Information Management of the linkPfeilExtern.gifMax Planck Society.

top Projects:

This is a selection of previous and current projects pursued by me and my collaborators.

  • linkPfeilExtern.gifSimulations of the Accretion-Induced Gravitational Collapse of White Dwarfs

    E.B. Abdikamalov, C.D. Ott, L. Rezzolla, L. Dessart, H. Dimmelmeier, A. Marek, H.-T. Janka

    Accretion of matter from a companion star may trigger the collapse of a white dwarf to a proto-neutron star. We have found that this process is accompanied by the emission of gravitational radiation with a particular signal structure. The signal waveform could also give information about the occurence of rotational instabilities in the nascent proto-neutron star.

  • linkPfeilExtern.gifReconstruction of Gravitational Wave Burst Signals with Bayesian Inference Techniques

    C. Röver, M.-A. Bizouard, N. Christensen, H. Dimmelmeier, I.S. Heng, R. Meyer

    The gravitational waveform burst emitted during the formation of the proto-neutron star in a stellar core collapse has a complicated structure. To be able to employ efficient filtering techniques in the search pipelines of wave detectors, we have proposed a statistical method to accurately reconstruct such waveforms using a small set of basis vectors only.

  • linkPfeilExtern.gifDynamic Migration of Rotating Neutron Stars due to a Phase Transition Instability

    H. Dimmelmeier, M. Bejger, P. Haensel, J.L. Zdunik

    In their early life, rapidly rotating neutron stars (like e.g. magnetars) can possibly encounter an instability that results in a dynamic migration to a new stable equilibrium after a collapse and a sequence of ring-down pulsations. Using fully dynamical numerical simulations, we have investigated such a scenario, where also strong gravitational waves with a complicated frequency spectrum could be emitted.

  • linkPfeilExtern.gifA Solution for the Nonuniqueness Problem of the Spacetime Constraint Equations

    I. Cordero-Carrión, P. Cerdá-Durán, H. Dimmelmeier, J.L. Jaramillo, J. Novak, E. Gourgoulhon

    The otherwise very successful CFC scheme for approximating the Einstein equations in simulations of compact astrophysical objects fail at very high densities. We have found a reformulation which solves this problem and extends the applicability of CFC to e.g. black hole formation.

  • linkPfeilExtern.gifPhase-Transition-Induced Collapse of a Rotating Neutron Star to a Hybrid Quark Star

    E.B. Abdikamalov, H. Dimmelmeier, L. Rezzolla, J.C. Miller

    If rotating neutron stars undergo a phase transition from regular matter to quarks in their core, the subsequent collapse can be a strong source of gravitational waves. We have performed the first-ever general relativistic simulations of this scenario, and find that resonance effects can even enhance the emission of gravitational radiation.

  • linkPfeilExtern.gifSimulations of Rotational Stellar Core Collapse in General Relativity with Microphysics

    H. Dimmelmeier, C.D. Ott, H.-T. Janka, A. Marek, I. Hawke, B. Zink, E. Schnetter, and E. Müller

    We have performed the first 2D and 3D simulations of rotating stellar core collapse to a neutron star in general relativity with microphysics. We have found that the resulting gravitational wave signals are much more generic than previously anticipated.

  • linkPfeilExtern.gifNonlinear Axisymmetric Pulsations of Rotating Relativistic Stars

    H. Dimmelmeier, N. Stergioulas, J.A. Font

    With the axisymmetric version of the linkPfeil.gif"Mariage des Maillages" code we have for the first time simulated pulsations in uniformly and differentially rotating neutron star models in general relativistic gravity and identified important nonlinear effects. We have also investigated the issue of detectability of gravitational wave emitted by such oscillations.

  • linkPfeilExtern.gifGravitational Radiation from Relativistic Rotational Core Collapse

    H. Dimmelmeier, J.A. Font, E. Müller

    We have succeeded for the first time to simulate the collapse of a rotating stellar core to a neutron star including the effects of general relativity, making a major step forward towards realistic predictions of gravitational wave signals.

top Professional Experience:

Over the years, I have acquired professional experience in a number of fields, including

  • computational fluid dynamics in astrophysics and nuclear engineering,
  • electronic publishing,
  • system administration, and
  • research and development in automotive safety.

More on my expertise in these fields can be found in a linkPfeil.gifdetailed description.

top Curriculum Vitae:

My curriculum vitae can be downloaded in linkPfeil.gifPDF format and linkPfeil.gifgzipped PS format.

top List of Publications:

Here is a linkPfeil.giflist of my scientific publication track record.

top List of Attendance at Scientific Conferences, Invited Seminar Talks, and Summer Schools:

Here is a linkPfeil.giflist of my attendance at scientific conferences and summer schools, and invited seminar talks.

topComments to: Harald Dimmelmeier