Recent content by nix00

In a d=4 space-time, gravitation is encoded in the metric gμε which is a 4 by 4 symmetric matrix, with therefore 6 degrees of freedom which have to be found by the Einstein's equation. That's great, because Gμε= 8 π G Tμε represent 6 equations due to the symmetry. If you consider only the trace...

I am not sure to understand your point harrylin. I was trying to answer the question by saying that naturally in an homogeneous and isotropic space-time, under the principles, it exists a maximal speed, and you get the Poincare transformations which relate two inertial frames, moving in an...

they are not broken, they are considered also in Newton's mechanics, in a weak form. The fact is that when you consider Newton's equations, in an absolute referential, they are invariant under the Galilean transformations, which is fine. But Maxwell's equations are invariant under Poincare...

In fact, we have a theory to explain this postulate, special relativity simply. The second postulate of Einstein for special relativity is a natural consequence of the others postulates (principle of relativity and causality) when considering an homogeneous and isotropic space-time : it can be...

Thanks, I am working on it.

That's the principle of equivalence from Galileo. You can see if you write the Newton's equation that the acceleration of an object in a gravitational field is independent of its mass, roughly speaking, in the vacuum, on Earth of mass M, with m the mass of any objects F = m a =\mathcal{G}...

If you assume the force derived from the gradient of a potential U, then the Newton's equation can be recasted as the Euler-Lagrange equation where you define the Lagrangian as \mathcal{L} = T - U. The Euler-Lagrange equation is really similar to a solution of the principle of the least...

The Big Bang by itself is not valid, it's a singularity showing where the theory of General Relativity cease to be valid. It corresponds to an epoch where quantum effects play also a large role and need to be considered in the theory. But yeah, this quantum era is really "short" comparing to the...

I am currently looking at this so-called quasi-Maxwell equations :smile: They are simply derived from a geometric point of view, without referring to the Einstein's equations, expressed either in terms of the spatial metric and its conjugate momentum (q_{ab}, P^{cd}) or in terms of the...

Thanks Robphy for your answer, but you may have misunderstood the meaning of E_{ab} which is not related here to the densitized triad used in the Ashtekar variables. It's true I can reexpress the components in terms of these variables, but I am still looking at an expression for the Poisson...

In order to understand how related are the theories of General Relativity and Electromagnetism, I am looking at the electric and magnetic parts of the Weyl tensor (in the ADM formalism) and compare them with the ones from Maxwell's theory. I have tried to look at the Poisson bracket, but the...