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From: Peter Schmitteckert (boost) (boost_at_[hidden])
Date: 2004-07-06 06:42:22


On Tuesday 06 July 2004 11:54, Matthias Troyer wrote:

> > You can now argues, wether this is still a vector, but in physics it
> > is called
> > a vector.
> As another theoretical physicist I want to disagree with this

Sorry for beeing unclear. I wanted to say, "in my special problem, it is a vector".
I didn't want to claim that in general.

> definition. I would call the object with four indices a linear
> operator, but not a matrix. Matrices for me are representation of
> linear operators with two indices.

As I said, that's a matter of taste, convention, education and notation,
and it's fine with me.

> You however point out an important requirement for generic algorithms
> on vector spaces: they should not require that a vector can be accessed
> with operator[] and a single subscript, or that once can construct a
> vector by passing just the size to the constructor. These too narrow
> requirements of the Iterative Template Library ITL, caused us to
> introduce the "vector space" concept in the our Iterative Eigenvalue
> Template Library IETL.

I agree.

Best wishes,

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