Recent content by say_cheese

Very strange that someone would think I would not know the solution to the simple harmonic motion equation. You have not watched the physics behind it, the explanation for this is beautifully described in Peebles book, This has to do with the fact that if the Universe is a balloon, we are...

page 67, Peebles book - gravitational instabilty subsection in book, 1993. "if the mass density were lower than the critical value, the Universe would expand". The equations aare also from the same subsection. Also, I feel vindicated. There is actually a theoretical paper proposing this which...

My question does not qualify as a hand waving reasoning. Certainly not a dummy here. I quoted the math behind with references therein and asked a hard question.(See above). It takes a bit of time and not answer from the hip. Please pick up Peebles book and go through it. It is amazing in its...

The paper- https://royalsocietypublishing.org/doi/10.1098/rspa.2016.0887

Found it! This is not a wrong question. There is a current theory that uses this conjecture to explain the accelerated expansion without dark energy...

Also, in words, Einstein had to introduce the Cosmological Constant to adjust for a static Universe. He abandoned it because that would lead to a Gravitational Instability. So why cant we take the CC to be zero and explain the accelerated expansion as the instability?

The solution to the above Gravitational Stability equation (initial perturbation is e) gives the growth of perturbation The time constant then is

Ref: Principles of Physical Cosmology by P.J.E. Peoples, Princeton Univ. Press This question is likely fully answered somewhere, but I cant find it. Hubble obtained (1926) the mean mass density of the Universe as 10^-31 g/c.c. The gravitational stability equation gives (McCrea, Milne (1934))...

is there a simpler expansion of ((∇xA).∇)(∇xA). This is a common term in fluid equations.

Good questions. My present mesh sizes are about 5% of the variation length of the driving term A. The driving term is sinusoidal in theta and phi with a mild radial dependence. (180,50,50) mesh. There is a sharper variation in one area and I have remeshed there 5 times. It is quite possible...

One way to look at it is that it is the momentum imparted through the electromagnetic force, Momentum wikipedia - The classical Hamiltonian ℋ for a particle in any field equals the total energy of the system – the kinetic energy T = p2/2m (where p2 = p · p, see dot product) plus the potential...

I will try this, but that is only one term in (v.∇)v. The parameters have 3 components and the components of the equation have other component terms such as vr∂vθ/∂r.

The theta and phi coordinates are cyclic (v(0)=v(2*pi)), v=0, dv/dr=0 at v=0 and a.

I need to solve the well known momentum equation in 3D cylindrical coordinates: ρ(∂v/∂t +(v.∇)v)=A where A and the velocity v are both local vector variables. I am actually looking for the stationary solution to the equation, i.e. no ∂/∂t term) I have tried evolving the velocity and tried...

I hope someone with a deep conceptual understanding of terminologies would help me out here. I am having starting problems in understanding the approach of gauge theories. I have read suggested threads and I am still at a loss. I am an experimental physicist and know basics of electrodynamics...