[Developers] HydroBase update

Werner Benger Werner.Benger at aei.mpg.de
Mon Dec 7 12:46:43 CST 2009


On Mon, 07 Dec 2009 09:49:30 -0600, Frank Loeffler <knarf at cct.lsu.edu> wrote:

> On Mon, Dec 07, 2009 at 09:32:45AM -0600, Allen Gabrielle wrote:
>> Just wonder about the parameter name, does vacuum imply anything outside the domain of the hydro variables (that is, could there be anything non-vacuum that is not coordinated by HydroBase).
>
> "vacuum" would only mean "without matter", if taken literally, this
> would not exclude all types of radiation (e.g. not electro-magnetic
> fields).
>
I'm used to the terminology that "vacuum" means vanishing energy-momentum tensor, whatever causes it, therefore Ricci tensor being zero.

Some of my professors in theoretical physics even called electro-magnetic fields "photo-matter" (zero rest mass), in contrast to "electro-matter" (non-zero rest mass).

    Werner



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