356 reputation
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bio website maths.swan.ac.uk/staff/ejb
location Swansea, Wales
age
visits member for 2 years, 3 months
seen Mar 11 at 16:41

Mar
5
comment How rigid can a rigid object be in GR?
That is a good way of thinking about it - and may well give a method for finding the answer.
Mar
4
comment How rigid can a rigid object be in GR?
The problem is, what if we cannot start in flat space? What is the best that we can do with the coordinate system? The black hole is just an example of a localised curvature - the details are not important.
Mar
4
comment How rigid can a rigid object be in GR?
There is a coordinate system which is formed by taking a 3D space like submanifold, and declaring it to be time zero, and then taking the geodesic motion in 4D perpendicular to the submanifold, with time coordinate proper time. This gives a nicely behaved coordinate system, at least locally. If we can start in flat space, and then move into more complicated geometry, we can set an initial metric on the 3D slice to be the usual Euclidian metric.
Mar
4
comment How rigid can a rigid object be in GR?
The question is a bit ambiguous, but I was hoping that there was an existing body of literature, and I did not want to make it too restrictive.
Mar
3
asked How rigid can a rigid object be in GR?
Nov
3
asked model structure of noncommutative non-negatively graded DGAs
Oct
24
revised Second order term of the Fedosov quantised product
added tag
Oct
23
asked Second order term of the Fedosov quantised product
Jul
24
awarded  Tumbleweed
Jul
17
asked the push forward of the differential idea of sheaf
Jul
4
awarded  Yearling
Jul
4
asked allowing `discontinuous functions' into a C* algebra
Jul
2
awarded  Curious
Jun
26
comment complementary bundle for a divisor
More thought - the direct sum by preference, if not then any related construction would be welcome.
Jun
26
comment complementary bundle for a divisor
Honestly, I do not know which. Whichever works nicely I guess. I had thought of the first, but anything nice to say about the second would be welcome. Modules with connection in noncommutative geometry form an abelian category, so either approach could be used in noncommutative geometry.
Jun
26
asked complementary bundle for a divisor
Jun
10
comment When is the corner algebra $PM_n(A)P$ isomorphic to $A$?
Just got a copy of Brown's paper - I will read it!
Jun
10
comment When is the corner algebra $PM_n(A)P$ isomorphic to $A$?
That is a good point - hopefully there are other cases - there are classically line bundles not with the same K-theory class as the trivial bundle. (E.g. on the sphere.)
Jun
9
asked When is the corner algebra $PM_n(A)P$ isomorphic to $A$?
Jun
4
comment Universal unital $C^*$ algebra generated by the relations of an n by n projection
Thanks, that is just what I was looking for. Blackadar in turn refers to a paper by L. Brown "Ext of certain free product C* algebras", J. Operator Theory 6. I have some reading to do.