@skillpatrol
I only know of 4 distinct types:
1. Units, which determines how physical quantities affected by scaling. This type is most relevant in dimensional analysis
2. Parameters, which can be thought of as degrees of freedom in some abstract or mathematical space
3. (I don't know the umbrella term for this) the physical ones such as space (xyz, compactified spatial dimensions in string theory and other unified theories) and time, which together formed the continuum called spacetime)
4. Dimensions in the context of linear algebra, which is the size of a basis

@Slereah
but why there are only two types: Space and Time. What prevent a 3rd type of dimension to exist without end up becoming something that live in an abstract space?

@skillpatrol
My memory is very hazy on that one, but from what I learnt in my analytical chemistry and a bit of first year physics. Measurement (not talking about the quantum mech one) is basically any quantity obtained that has a value and an uncertainty associated with it

For measurement in quantum systems, it is what happens when the wavefunction of the system get evolved into the eigenstate of some operator due to th…

@David Z. Hmm, makes sense (and using conclusions from a few months ago with Danu and Slereah, the value of q in a metric signature for a general metric (p,q,r), which count the number of 0 eigenvalues, does not have physical consequences in those directions because they are degenerate (not exact phrase, will dig that phrase up in the h bar later))

@Slereah I am not sure how to respond to that answer, as I know nothing about gauge bundles, thus I don't know if that sense of "can contain something" is present in the concept "gauge bundles"

https://en.wikipedia.org/wiki/Metric_signature

If zero is the zero tensor, then it probably have metric signature of (0,q,0) where q= dimension of the tensor

According to Acuriousmind and Danu, the metric tensors we use in GR are always symmetric and real and nondegenerate.

There are some guys who do work with degenerate metric tensors
http://arxiv.org/pdf/1105.0201.pdf, http://publica-sbi.if.usp.br/PDFs/pd1193.pdf

and some ones who worked with complex valued metrics, as I just dug up from google

I wonder if we can ever unravel the underlying mechanism of these intermediate states

It seems particle physics is kinda like photochemistry (both have notions of branching ratios, decay channels, reaction barriers etc.) , except that it is relativistic, and that intermediate states does not need to be a combination of some constituents, unlike in chemistry where the transition states and intermediates always involve the atoms in the products and reactants

Perhaps, the analogous quantity in particle physics to atoms in photochemistry will be those conservation laws (e.g. color charge, iso…

Using the answers there (and the discussion with h bar throughout these months) I wonder, if entanglement can be interpreted as follows (combining nonlocality and nonrealism):

Suppose we have two photons which can have two different polarisations: Clockwise(+) and anticlockwise(-)

We first prepared two photons of opposite polarisations
$$\lvert + \rangle and \lvert - \rangle$$
Next we brought them closer together and then interact them using some machine (which its interaction is included in the hamiltonian as usual). This prepared the following entangled state