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Apr
12
answered Questions on redshift
Apr
11
comment galaxies fading away after time
Yes. Note that this is a technical limitation - if we could detect light of arbitrary wavelengths and intensity, we'd still be able to see them.
Apr
10
comment Does non-matter energy curve spacetime?
see this picture from wikipedia - anything that's in there has an effect on space-time geometry
Apr
10
revised How Are Galaxies Receding Faster Than Light Visible To Observers?
deleted 4 characters in body
Apr
10
answered How Are Galaxies Receding Faster Than Light Visible To Observers?
Apr
10
comment How Are Galaxies Receding Faster Than Light Visible To Observers?
actually, recession velocities may well exceed $c$ at time of emission and we may still be able to observe the galaxy; not the Hubble sphere, but the cosmic event horizon places bounds of the observational universe
Apr
10
awarded  Critic
Apr
10
comment Name this Mulltivariable Calculus Theorem
-1: you're looking for the Jacobian matrix, which is basically the differential; however, $H_\mu$ is not given by the differential - it just agrees with it at point $a$
Apr
9
awarded  Nice Answer
Apr
9
comment Singular wave function
@user119264: it's a valid space, but it won't help - the Lebesgue integral doesn't change if you just remove individual points (or any set of measure 0)
Apr
9
revised Trace in non-orthogonal basis?
use algebraic dual
Apr
9
answered Trace in non-orthogonal basis?
Apr
6
comment What are the spaces over spacetime points in which a field takes its values? Is it always the same?
slight correction: while the typical fiber of the principal bundle is the Lie group, the connection form (aka gauge field) as well its curvature form (aka field strength) take their values in the Lie algebra
Apr
5
comment Dark energy and conservation of energy
@Jim: we do not need global time translation symmetry in GR - the time-like vector field of your choice basically becomes a gauge parameter
Apr
5
awarded  Good Answer
Apr
5
comment Dark energy and conservation of energy
@JohnRennie: you can read more of Philip and Luboš in the comments of Philip's blog posts on energy conservation in GR ( blog.vixra.org/2010/08/06/energy-is-conserved blog.vixra.org/2010/08/08/energy-is-conserved-the-maths blog.vixra.org/2010/08/17/energy-is-conserved-in-cosmology )
Apr
5
comment Dark energy and conservation of energy
@JohnRennie: I disagree with energy not being conserved in FLRW cosmology; the relevant papers are linked from this comment
Apr
5
comment Dark energy and conservation of energy
Friedmann-type universes have zero total energy - the positive contributions by matter and dark energy are cancelled by the negative contribution due to gravitational energy
Apr
4
awarded  Nice Answer
Apr
4
comment How can water evaporate at room temperature?
@JohnRennie: I expanded the answer and made it community wiki - feel free to improve upon it as yous ee fit...