Ben Whale

ctypes, restype and arrays

Ben — Thu, 10 May 2012 00:50:43 +0000

I’ve been having some problems accessing, as python arrays, an array returned by C code via the ctypes module. The ctypes documentation is not great, but this is.

synctex + gedit + evince

Ben — Sun, 26 Jun 2011 22:29:03 +0000

Forward and backwards search for latex source and their compiled images is a must have feature for me.

I have to write literature too?

Ben — Fri, 29 Apr 2011 23:59:53 +0000

I wish to be a successful mathematician. I want my papers to be read, enjoyed, even eagerly anticipated. I struggle, however, to write well. Most of my posts are stream of consciousness. They are my thoughts, with only a little reflection thrown in. This I don’t mind. My blog isn’t to advertise myself, allow inclusion …

A theoretical language to study numerical computation?

Ben — Mon, 11 Apr 2011 05:18:44 +0000

I’ve just finished Jörg Frauendiener’s, “On the applicability of constrained symplectic integrators in general relativity”. It’s a readable paper (the necessary background is given in the paper) about numerical integration in Hamiltonian systems. The idea here is that if we have a symplectic manifold modelling the states of some system of ODE’s, along with a …

What do we really know about Dark Energy?

Ben — Tue, 05 Apr 2011 04:28:45 +0000

I refer you to Ruth Durrer’s very readable (and short) paper with the same title as above. The main point of the paper is that all evidence for Dark Energy comes from the measurement of luminosity distance as a function of redshift and that energy/matter content of the universe is then inferred from this measurement …

Hyperbolicity of BSSN

Ben — Wed, 23 Mar 2011 04:00:19 +0000

So, from what I understand it seems that strong and symmetric hyperbolicity of equations is only defined for systems with first order derivatives. The significance is that strong or symmetric hyperbolic systems of differential equations are “well posed” that is, roughly speaking, that they have unique solutions that depend continuously on the initial data (i.e. …

Analytic work on constraint quantities lacking?

Ben — Tue, 08 Mar 2011 21:01:18 +0000

The paper provides a general introduction to how to perform analysis of the attractors of some dynamical system (with specified initial conditions) and then applies this to a particular initial value formulation of Einstein's equations.

MOND v LambdaCDM

Ben — Wed, 02 Mar 2011 04:11:03 +0000

I have a soft spot for MOND. Yes, it’s a silly sounding name but I kind of like it. I must admit that this is because CDM feels a bit contrived. The CDM models requires dwarf galaxies to be missing approximately 99% of the baryons associated to their dark matter halo. A bit unnecessary perhaps? …

Summation by parts (SBP) operators and interface boundary treatments

Ben — Fri, 25 Feb 2011 04:42:58 +0000

Finished of Carpenter, Nordstrom and Gottlieb’s paper, “A stable and conservative interface treatment of arbitrary spatial accuracy”. I like papers like this. It ‘feels’ clean, organised self contained. Writing such papers takes work so when I find ones like this I take a bit more time over them. The crux of the paper is a …

Rate of convergence not affected by lower order convergence near boundaries

Ben — Fri, 25 Feb 2011 03:26:47 +0000

I’ve just finished up my second reading of Gustafsson’s, “The convergence rate for difference approximations to mixed initial boundary value problems” and I’m still abit confused. The paper is referenced by (what seems to me) almost everyone and their dog as justification that a finite difference scheme can have one order of convergence less on …