Hari Sriskantha

I am a third-year Mathematics PhD student at the University of Edinburgh, under the supervision of Dr. Max Ruffert. My research interests are in computational astrophysics: I work on numerical simulations of compact star mergers (black holes and neutron stars), in order to investigate whether they result in short-duration gamma-ray bursts. I am currently in the process of adding the effect of magnetic fields to the simulation. Previously, I completed a BSc in Physics (2009) and an MSc in Scientific Computing (2010) at the University of Warwick.

Research Background

An Introduction to Gamma-Ray Bursts

Gamma-ray bursts (GRBs) are extremely energetic bursts of high energy radiation. In fact, they are the brightest known events since the big bang: a single GRB can outshine the rest of the observable universe in gamma-rays. Although they were discovered in the late 1960s, they remained mostly enigmatic until the launch of the Compton Gamma-Ray Observatory in 1991. This captured data on 2,704 bursts over nine years, and showed that there are at least two types of GRBs: short-duration (which last less than two seconds) and long-duration (which last longer, typically several minutes).


Short-Duration Gamma-Ray Bursts

My research is interested in what causes short-duration GRBs. The most popular model for their origin is the merger of two compact objects in a binary system: either two neutron stars, or a neutron star and a black hole. The in-spiral and coalescence of such systems is due to the emission of gravitational waves, which carry angular momentum away from the system. This results in a black hole, surrounded by a dense, accreting torus. It is such black hole-torus systems which are thought to be the central engines of all GRBs. By running numerical simulations of these systems, we can investigate whether they can explain explanation for the short-duration bursts.




The Simulation: This ray-traced picture shows typical initial conditions for a merger simulation. The black hole is represented by the larger, black sphere, while the neutron star is represented by the smaller, coloured sphere. The colours represent different densities, with purple for the dense core and red for the 'atmosphere'. The neutron star was initially constructed as a perfect sphere, but you can see that it is already being distorted by the strong gravitational pull of the black hole.

Teaching and Talks

Undergraduate Tutoring, 2012-2013

  • Numerical Ordinary Differential Equations
    • Including Matlab
  • Mathematical Computation and Communication
    • Including Maple and LaTeX
  • Mathematics for Science and Engineering (2)

Undergraduate Tutoring, 2011-2012

  • Mathematical Computation and Communication
  • Mathematics for Electrical and Mechanical Engineers

Undergraduate Tutoring, 2010-2011

  • Applicable Mathematics (1 and 2)
  • Mathematical Methods (1 and 2)

    • Other Teaching

    Summers of 2011 and 2012: I assisted with various Higher Maths revision classes, organised by the School of Mathematics, for local secondary school students (including the 'LEAPS' programme).


    Talks and Presentations

    • How to Simulate Gamma-ray Bursts
      Nuclear Physics Seminar, 10th Nov 2011
    • How to Design Great Talks
      Postgraduate Colloquium, 29th Sept 2011
      • Versions of this also given at a Presentations Workshop (ICMS, 12th Oct 2011) and the PG Colloquium (4th Oct 2012)
    • Simulations of Compact Object Mergers
      First Year Presentation, July 2011
    • Making Pictures: An Introduction to Realistic Image Synthesis
      Postgraduate Colloquium, March 2011

    Other Projects

    GitHub

    Whenever possible, I will upload some of the smaller projects that I've been working on to my GitHub profile:


    • Neutron Star Generator: this code generates a neutron star profile for a (tabulated) equation of state (EOS), for use in scientific numerical simulations. It uses the fourth-order Runge-Kutta scheme to solve the equations of hydrostatic equilibrium, and hence obtain values for the pressure and contained mass as a function of radius. It then uses these to estimate the mass density and the proton fraction, also as a function of radius.