Recent content by vld

Yes, of course, if one would neglect the structural complexity of the measuring and measured systems, then to interpret the results of observations one would require a theory containing an uncertainty constant because these results will be affected by a lot of factors (such as the sizes and...

There is no need in establishing the "just-let's-use-a-limit" approach because this approach is already in use based on the causality principle and the corresponding limit on the speed of interactions (usually called the speed of light). This limit automatically establishes the limits on the...

Does Cartan have something to do with metallurgy? As far as I know Einstein doesn't. Since in Einstein-Cartan's theory singularity is avoided because of negative pressure due to torsion, does this mean that it is more general then GR, which is known to have a limited domain of validity (failing...

One can study both spacetimes and fluids by using the same mathematical tools (e.g., differential geometry and topology). That is where the analogy comes from. But in fluid dynamics people study "particles" as being stable configuration patterns of fluid (like vortices). By analogy, one can...

I think there were many effects taken into account when processing the galactic red-shifts. A few years ago I asked the above question to Saul Perlmutter when he was giving a talk on the subject. The answer was "Yes, this effect was also taken into account".

The notion of singularity is usually invoked when a theory results in infinite values. For example, when spacetime curvature in GR becomes infinite the outcome is called a singularity. The infinite curvature means infinite energy concentrated in a point-like (zero-sized) object. Then I believe...

Better to say, in order to get it right, one has to be able to distinguish between the mathematical and physical objects. A zero-size point is obviously a mathematical object plagued with infinities. It can be succesfully used for idealisations when describing a physical object but it seems that...

The good thing in cristo's comment is that he is trying to separate "flies from the soup", i.e the singularity notion from those having physical meaning. Indeed, there are theorems saynig that a sufficiently massive object will collapse to a point. Then how can we deal with a physical object...

Many thanks, Chronos. Among the GLAST publications I have immediately found those which you have in mind, e.g. astro-ph/0610571 . :smile:

That's quite interesting. Please, could you give any details or references (perhaps it would be appropriate to open a new thread)? I know about specially organised observations of high-redshift objects to detect quantum fluctuations of space. But you are talking about something different: an...

It is probably the property of human mind to re-invent things. Ten years ago one of my friends secretly explained me his idea about what is now known as shutter glasses (for 3D computer vision). He was very excited saying that he is going to patent the device. And how much was he disappointed...

According to Zeldovitch and Novikov (in their book "The Structure and Evolution of the Universe"), the net mass of the universe is zero. However, if mass is equivalent to energy then, according to the current theories, locally vacuum contains enormous amounts of energy (hence - mass?)

I don't see any problem here: their motions can be described in the same way as the motions of vortices in liquid helium (incidentally, in fluid dynamics similar vortices are also called "particles"). This question cannot be answered before quantifying (within this framework) the strength...

(ict,x) The existence of various equivalent formulations of GR, including graviton scattering, torsion, polarisable medium, etc., means that the underlying physical reality might be richer than any of that theories. When we deal with something unknown, none of the working models has to be...

Of course, nothing can happen instantly, and in a real physical system one will need a finite time to measure a distance. But this artificial theoretical construction shows that you can use ANY amount of time to measure a distance, which is what actually means that such a measurement is...