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*From*: John Denker <jsd@av8n.com>*Date*: Wed, 20 Oct 2010 19:41:13 -0400

On 10/20/2010 06:42 PM, Derek McKenzie wrote:

I would be interested to know if my thinking is confused on either of

these points, but at the moment I'm wondering if plain old vanilla

'mass' would be a better term.

Mass is undoubtedly the preferred term.

...... the term 'invariant mass' seems to me to conflict

with a genuine geometric model of spacetime. In particular we must

ask 'invariant with respect to what?'. Presumably, the invariance is

with respect to a particular class of coordinate systems, but mass

transcends these coordinate systems.

Like mass itself, the notion of Lorentz invariance transcends any

"particular class of coordinate systems" ... so I think we are

entirely safe when we say things like

-- Mass is Lorentz invariant.

-- Mass is a Lorentz scalar.

I don't see any conflict with a fully geometric approach to special

relativity.

It is shorthand to say "mass is invariant" ... but usually it is

obvious from context that Lorentz invariance is intended. If this

is not obvious from context, for instance if something unusual

like isospin invariance is being discussed, I would hope that

authors would have enough sense to avoid this kind of shorthand.

**References**:**[Phys-l] Rest mass again?***From:*"Espinosa, James" <JEspinosa@mail.twu.edu>

**Re: [Phys-l] Rest mass again?***From:*John Denker <jsd@av8n.com>

**Re: [Phys-l] Rest mass again?***From:*Derek McKenzie <derek_s_mckenzie@hotmail.com>

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