guenter

I have posted my question in the sub forum "Relativity".

Hi, my question fits probably better to the sub forum "Relativity". The article I had in mind shows in Fig. 1.1 The propagation of spacetime curvature oscillating light ray triangles. So, according to the phase of the wave the (Weyl?) curvature is negative, zero or positiv. 1. However in which plane? Do these triangles show the curvature in the x-y-plane or parallel to the z-direction? 2. To make the light ray triangles is very fast compared to the period of the gravitational wave. Can one say that the triangles measure (almost) frozen states and not the dynamics of the wave? Supposed there is curvature in the x-y-plane, wouldn't that mean that laser interferometer measurements are disturbed by shapiro delays? I have never heard about that, but perhaps it's marginal if not zero. Any help to better understand these things, especially the meaning of the Weyl curvature in otherwise flat space, is appreciated. Please use layman language and correct my reasoning, if wrong.

Hi everybody, hopefully I can improve my knowledge about the universe, the physics behind it. There are many popular books and articles dealing with that. However even good books stay on the surface, naturally, and some even suggest wrong notions to the reader. I have got a degree in physical chemistry long time ago. Please note, that english is not my mother language. Hope for good discussions! Regards, guenter

While Ricci curvature vanishes in the absence of matter (flat space) there is still Weyl curvature propagating with gravitational waves. To my understanding the Weyl tensor is responsible for tidal effects (stretching, shrinking) in the x-y-plane (the wave propagates in z-direction). This is only true for small fields (plan wave solution). But I wonder whatelse the Weyl curvature is responisble for. Is the x-y-plane flat like Minkowski-spacetime? If not, are triangles in this plane oszillating from concave to convex or whatelse would characterize this curvature? I have seen something like this but wasn't sure about the meaning and will search for it. It would be great, if you could clarify this question.

Ok, so the string theory does'nt say much about masses. Then I am not optimistic that it sheds light on my next question: The standard model can't explain why the charge of the elektron equals that of the proton (with the exception of the sign). Why is the H-Atom neutral? The Gut's are dealing with that. But also a theory which aims to be a ToE, like the string theory, should answer such questions, right? But it might well be, that I have a wrong imagination of what the string theory should be able to predict. The predictions of General Relativity include the predictions of Newtonian gravity. With the right simplifications one can arrive at Newton starting from GR. From this my reasoning is: Shouldn't a ToE predict the predictions of the sub theories, QM, the standard model, the GUT's?

Hi, to my (very basic) knowledge, string theory does'nt predict the masses of the elementary particles. However are there any hints about the relation of masses? For example the masses of electron/proton or constituent quark mass / current quark mass? And further, does the string theory predict, which particles have rest mass and which not? In this context, how about the neutrino? regards, guenter