Welcome, Traveler!

I am a research scientist at the Center for Computation & Technology and in the Department of Physics & Astronomy at Louisiana State University in Baton Rouge. I work in relativistic astrophysics, general relativity, and in computational physics; these fields overlap in numerical relativity. I work also in computer science, focussing on high performance computing.

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News

• December 3, 2007: We have finished designing and implementing our new GRMHD code, built on our multi-patch infrastructure. We test it on fixed backgrounds in an arXiv.org preprint:

  • Burkhard Zink, Erik Schnetter, Manuel Tiglio,
    Multi-patch methods in general relativistic astrophysics - I. Hydrodynamical flows on fixed backgrounds,
    arXiv:0712.0353 [astro-ph].

  We expect this code to be significantly more accurate than Cartesian codes in near-spherical situations, such as in collapse or accretion scenarios.

• August 29, 2007: We computed the inspiral and merger of a large set of binary black hole configurations with spins aligned with the orbital angular momentum, as this may be the preferred end state of such systems. We consider both equal mass (arXiv:0708.3999 [gr-qc]) and unequal mass (arXiv:0710.3345 [gr-qc]) systems. We have derived analytic expressions which fit our data points, and which we also chose carefully to have the correct extreme mass ratio limit. These formulae suggest a maximum recoil velocity of about 440 km/s for systems with a₁ = -a₂ = 1, and a maximum final spin a_fin = 0.96 for systems with a₁ = a₂.

• August 15, 2007: I hear that my proposal Cactus tools for Application Level Profiling And Correctness Analysis (Alpaca) will be funded by NSF's SDCI programme for three years. The Alpaca project will research tools helping to develop complex, collaborative scientific applications, appropriate for highly scalable hardware architectures, and provide fault tolerance, advanced debugging, and transparency against new developments in communication, programming, and execution models. Alpaca will address this at the application level, i.e., these tools will interact with the Cactus framework instead of using the traditional approach of examining an application from the outside.

• July 31, 2007: I am happy to hear that our proposal XiRel: Cyberinfrastructure for Numerical Relativity will be funded by NSF's PIF programme for three years. XiRel is collaborative proposal by LSU, PSU, UTB (now RIT), and AEI. The central goal of XiRel is the development of a highly scalable, efficient, and accurate adaptive mesh refinement layer based on the current Carpet driver, which will be fully integrated and supported in Cactus and optimised for numerical relativity.

• July 20, 2007: We developed and implemented a new method to fill excised regions with smooth (C²) data, called turduckening. A Turducken is a Cajun speciality consisting of a turkey, stuffed with a duck, itself stuffed with a chicken. We describe our method in Phys. Rev. D 76, 081503(R) (2007), arXiv:0707.3101 [gr-qc].
  
  [Image by David Scott Follin]

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Current Projects and Collaborations

I am working in the LSU Relativity Group on various topics in numerical relativity. My current focus is on binary black hole interactions and the gravitational waves emitted by such systems. The CCT has a close collaboration with the AEI Numerical Relativity Group led by Luciano Rezzolla.

In a collaboration with Christian D. Ott, Manuel Tiglio, and Burkhard Zink, we are developing a new GRMHD code based on our multi-patch infrastructure. Using multiple patches allows us to have near-spherical coordinates with all their advantages over Cartesian coordinates, but avoids the coordinate singularities near the z axis and at the origin. Such a code will be far more accurate in near-spherical configurations, such as in single-star or in collapse scenarios.

The Einstein Toolkit is a collection of Cactus thorns for numerical relativity. The Cactus group at AEI and CCT maintains a set of core thorns (the CactusEinstein arrangement) ensuring interoperability. Many people and groups worldwide have contributed to the Einstein Toolkit over the years, which contains today a set of high-quality evolution methods, initial data solvers, apparent and event horizon finders, and wave extraction methods.

I develop and maintain the Carpet mesh refinement infrastructure for the Cactus framework. Carpet supports adaptive mesh refinement (AMR), multiple grid patches, is parallelised using MPI, and runs on virtually all computer architectures since it is built in Cactus. An experimental version supports hybrid parallelisation combining MPI and OpenMP in support of the modern multi-core architectures.

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Recent Publications and Talks

[List of publications] -- [all publications in ADS] -- [refereed publications in ADS]

On December 9, 2007, I had 47 publications and 517 citations reported by ADS.

• Burkhard Zink, Erik Schnetter, Manuel Tiglio,
  Multi-patch methods in general relativistic astrophysics - I. Hydrodynamical flows on fixed backgrounds,
  arXiv:0712.0353 [astro-ph].

• Luciano Rezzolla, Peter Diener, Ernst Nils Dorband, Denis Pollney, Christian Reisswig, Erik Schnetter, Jennifer Seiler,
  The final spin from the coalescence of aligned-spin black-hole binaries,
  arXiv:0710.3345 [gr-qc].

• Maria C. Babiuc, Sascha Husa, Ian Hinder, Christiane Lechner, Erik Schnetter, Béla Szilagyi, Yosef Zlochower, Nils Dorband, Denis Pollney, Jeff Winicour,
  Implementation of standard testbeds for numerical relativity,
  arXiv:0709.3559 [gr-qc].

• Luciano Rezzolla, Ernst Nils Dorband, Christian Reisswig, Peter Diener, Denis Pollney, Erik Schnetter, Béla Szilágyi,
  Spin Diagrams for Equal-Mass Black-Hole Binaries with Aligned Spins,
  arXiv:0708.3999 [gr-qc].

• David Brown, Olivier Sarbach, Erik Schnetter, Manuel Tiglio, Peter Diener, Ian Hawke, Denis Pollney,
  Excision without excision,
  Phys. Rev. D 76, 081503(R) (2007),
  arXiv:0707.3101 [gr-qc].

• Erik Schnetter,
  Introduction to Numerical Relativity,
  Lectures at the KISTI Numerical Relativity Summer School in Pohang, South Korea, July 2007.

  1. The Einstein Equations (Formulations and Gauge Conditions) (PDF, 4.7 MB)

  2. Analysis Methods (Horizons and Gravitational Waves) (PDF, 5.5 MB)

  3. Numerical Methods (Cactus and Mesh Refinement) (PDF, 2.2 MB)

• Denis Pollney, Christian Reisswig, Luciano Rezzolla, Béla Szilágyi, Marcus Ansorg, Barrett Deris, Peter Diener, Ernst Nils Dorband, Michael Koppitz, Alessandro Nagar, Erik Schnetter,
  Recoil velocities from equal-mass binary black-hole mergers: a systematic investigation of spin-orbit aligned configurations,
  Phys. Rev. D (2007) (accepted for publication),
  arXiv:0707.2559 [gr-qc].

• Erik Schnetter, Christian D. Ott, Gabrielle Allen, Peter Diener, Tom Goodale, Thomas Radke, Edward Seidel, John Shalf,
  Cactus Framework: Black Holes to Gamma Ray Bursts,
  arXiv:0707.1607 [cs.DC].

• Erik Schnetter,
  Singularity replacement for black hole evolutions,
  invited talk given at the Instituto de Física y Matemáticas of the Universidad Michoacana de San Nicolás de Hidalgo in Morelia, Mexico, June 2007,
  (PDF, 1.2 MB).

• John Shalf, Erik Schnetter, Gabrielle Allen, Edward Seidel,
  Cactus as Benchmarking Platform,
  Technical Report, Louisiana State University, Center for Computation & Technology (2007), CCT-TR-2006-3.