Recent content by Airsteve0

This question may be quite trivial but I was wondering if you were observing a galaxy that was say 10 arc seconds in diameter with a telescope whose diffraction limited resolution was 15 arc seconds would the galaxy appear completely unresolved or just "blurry".

Homework Statement Find, by comparison with exact trigonometry, the angle,  (provide a numerical value in degrees), above which the small angle approximation departs from the exact result by more than 1 percent. Homework Equations Approx.: d = s = rθ Exact: d = 2*r*Sin(θ/2) The...

If anyone on here uses Mathematica maybe you could help me with an issue I am having with computing the following: Solving for x in: Sinc[x] > (1/1.01) I am looking only at the positive values and not making any headway with the Solve or NSolve commands. I should also mention that this...

Say we were given an expression for the energy-momentum tensor (also assuming a perfect fluid), without getting into an expression with multiple derivatives of the metric, are there any cases where it would be possible to deduce the form of the metric?

I was wondering if someone wouldn't mind offering me an explanation as to the differences between a flat spacetime versus a conformally flat spacetime (if there even is a difference).

In my intro. to GR class we recently covered the Kruskal Szekeres diagram and trajectories within the diagram. My question comes from a comment made by my professor about time-like trajectories emerging from v=0 and that if an emitter sends a light signal to an observer it will be blue shifted...

In my general relativity course we recently covered the definition of a killing vector and their importance. However, I am not completely comfortable calculating the killing vectors for a given metric (in a particular case, the 2-sphere), and would like to know if anyone knows of a good...

Homework Statement Find all killing vectors of the 2-sphere.Homework Equations ds^2=dθ^2+(sinθ)^2d\phi^2The Attempt at a Solution The goal of this problem is pretty self-explanatory; however, I didn't feel that the topic of killing vectors was covered very well in my course. I was just...

Oh ok, so for example if the interior of a spherical region was vacuum and outside the sphere was a Robertson-Walker type spacetime? Are there any other interesting properties that the vanishing Weyl tensor can give rise to?

Vanishing of the Weyl tensor implies the spacetime cannot be a vacuum?

I was just wondering what physical conclusions could be made about a spacetime which possesses a vanishing Weyl curvature tensor, aside from the spacetime being conformally flat. By this question I am simply interested if any inferences can be made about the metric describing the spacetime, or...

Hi all, I was just interested in verification of a concept. If we are given the full Riemann tensor in the form which implies constant curvature (i.e. lambda multiplying metric components) does this imply that the Ricci tensor vanishes? The question stems from why the vacuum equations cannot be...

Hi, I was wondering if someone wouldn't mind breaking down the geometrical differences between the Riemann, Ricci, and Weyl tensor. My current understanding is that the Ricci tensor describes the change in volume of a n-dimensional object in curved space from flat Euclidean space and that if we...

Homework Statement In class we derived the Schwarzschild interior solution (constant density). Examine the behaviour of non-radial null geodesics in this spacetime.Homework Equations \Phi(r)=ln\left(\frac{3\sqrt{1-\frac{2M}{R}}}{2}-\frac{\sqrt{1-\frac{2Mr^2}{R^3}}}{2}\right)...

got it, thanks!