User: knarf Date: 2011/11/24 02:37 PM

Added: /seminars/ index.php /seminars/2011_11_28/ Zachariah_Etienne.jpg, index.php

Log: test seminars pge

Directory Changes:

Directory: /svn:executable/ ===========================

+ * Directory: /svn:mime-type/ ==========================

+ application/octet-stream

File Changes:

Directory: /seminars/2011_11_28/ ================================

File [added]: Zachariah_Etienne.jpg Delta lines: +0 -0 =================================================================== (Binary files differ)

Property changes on: seminars/2011_11_28/Zachariah_Etienne.jpg ___________________________________________________________________

File [added]: index.php Delta lines: +40 -0 =================================================================== --- seminars/2011_11_28/index.php (rev 0) +++ seminars/2011_11_28/index.php 2011-11-24 20:37:15 UTC (rev 749) @@ -0,0 +1,40 @@ +<?php $title='Einstein Toolkit Seminars'; +include_once($_SERVER['DOCUMENT_ROOT'].'/global/header.php');?> + +<h2>Improved EM Gauge Condition for GRMHD Simulations with AMR</h2> + +<h3>Abstract</h3> +<p> +We recently developed a new GRMHD code with AMR that evolves the +electromagnetic (EM) vector potential A_i instead of the magnetic fields +directly. Evolving A_i enables one to use any interpolation scheme on +refinement level boundaries and still guarantee that the magnetic field remains +divergenceless. As in classical EM, a gauge choice must be made when evolving +A_i, and we originally chose a straightforward ``algebraic'' gauge condition +to simplify the A_i evolution equation. However, magnetized black +hole-neutron star (BHNS) simulations in this gauge exhibit unphysical behavior, +including the spurious appearance of strong magnetic fields on refinement level +boundaries. This spurious behavior is exacerbated when matter crosses +refinement boundaries during tidal disruption of the NS. We demonstrate via an +eigenvalue analysis and a numerical study that zero-speed modes in the +algebraic gauge, coupled with the frequency filtering that occurs on refinement +level boundaries, are responsible for the creation of spurious magnetic fields. +We show that the EM Lorenz gauge exhibits no zero-speed modes, and as a +consequence, spurious magnetic effects are quickly propagated away, allowing +for long-term, stable magnetized BHNS evolutions. +</p> + +<h3>Presenter: Zachariah Etienne</h3> +<img href="Zachariah_Etienne.jpg" width="20%" alt="Zachariah Etienne"> +<p> +NSF Astronomy <&amp> Astrophysics Postdoctoral Fellow, University of Illinois +</p> +<p> +Numerical Relativity Group Research interests: My research interests span all +of computational astrophysics. Much of my past work has focused on simulating +the mergers of compact binary systems, including BHNS, BHBH, WDNS, and NSNS. My +current work focuses on BHBH mergers, as well as studying MHD effects in BHNS +mergers. +</p> + +<?php include_once($_SERVER['DOCUMENT_ROOT'].'/global/footer.php');?>

Property changes on: seminars/2011_11_28/index.php ___________________________________________________________________

Directory: /seminars/ =====================

File [added]: index.php Delta lines: +9 -0 =================================================================== --- seminars/index.php (rev 0) +++ seminars/index.php 2011-11-24 20:37:15 UTC (rev 749) @@ -0,0 +1,9 @@ +<?php $title='Einstein Toolkit Seminars'; +include_once($_SERVER['DOCUMENT_ROOT'].'/global/header.php');?> + +<p>The Einstein Toolkit (irregularly at the moment) hosts seminars on topics of +interest to the numerical relativity community. Date, time and (virtual) +location are, besides here, announced on the Einstein Toolkit mailing list. +</p> + +<?php include_once($_SERVER['DOCUMENT_ROOT'].'/global/footer.php');?>

Property changes on: seminars/index.php ___________________________________________________________________