[Faculty] Fwd: [CSRC-SDSU COLLOQUIUM]: Non-Spherical Models of Compact Stellar Objects. ---- A High-Order Dirac-Delta Regularization with Optimal Scaling in the Spectral Solution of One-Dimensional Singular Hyperbolic Conservation Laws.

[Jose Castillo]

*DATE:*  Friday, September 19, 2014

*TITLE:*

   1.              Non-Spherical Models of Compact Stellar Objects. (Omair
   Zubairi)
   2.              A High-Order Dirac-Delta Regularization with Optimal
   Scaling in the Spectral Solution of One-Dimensional Singular Hyperbolic
   Conservation Laws. (Jean Suarez)


*TIME:*  3:30 PM

*LOCATION:*  GMCS 214

*SPEAKER:*  Omair Zubairi. Jean P. Suarez. CSRC at SDSU

*ABSTRACTS:*  Conventionally, the structure of compact stellar objects such
as neutron or quark stars are modeled with the assumption that they are
perfect spheres. However, due to high magnetic fields, certain classes of
these compact stars (such as magnetars and neutron stars containing cores
of color-superconducting quark matter) are expected to be deformed
(non-spherical) making them ob-longed spheroids. In this work, we seek to
investigate the stellar properties of these deformed compact stars in the
framework of general relativity. Using a metric that describes a
non-spherical mass distribution, we derive the stellar structure equations
of these non-spherical compact objects. We then calculate stellar
properties such as mass and radii along with pressure and density profiles
and investigate any changes from the standard spherical models. (Omair
Zubairi)

The physics in a range of engineering problems are governed by hyperbolic
conservation laws with singular, Dirac delta sources, such as interfaces in
multi-phase flows and plasmas and jams in traffic flow. In numerical
approximations of these models, the singular sources require
regularization. In this talk, we discuss the development of a higher-order
resolution regularization technique that suppresses Gibb's oscillation near
singularities, while providing higher-order resolution in region away from
the regularization zone. We present a theorethical criterion that
determines an optimal scaling of the regularization zone while ensuring a
formal order of convergence of the numerical scheme. We validate the
theorem with numerical tests including a moving wave described by a linear
and nonlinear (Burgers) scalar advection equation with a singular source
using spectral methods; as well as, a shock-particle interaction problem
described by the nonlinear Euler equations with singular sources (system of
hyperbolic conservation laws governing compressible fluid dynamics) using a
high-order high-resolution multi-domain hybrid WENO-spectral scheme. (Jean
Suarez)

*HOST:*  Dr. Jose Castillo

For future events, please visit our website at:

http://www.csrc.sdsu.edu/colloquium.html

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Jose E. Castillo  Ph.D.

Director / Professor

Computational Science Research Center

5500 Campanile Dr

San Diego State University

San Diego CA 92182-1245

619 5947205/3430, Fax 619-594-2459

 http://www.csrc.sdsu.edu/mimetic-book/

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