Geodesic Transport of Small 2D Surface on 3D Manifold

dismachaerus
Messages
9
Reaction score
0
Hello,
I've just read and I think I have understood the following result :
If we were to geodesically transport all points of a small 2D surface, so small that it would be flat for all purposes, in a direction vertically above it, and if this surface belongs in an arbitrary 3D manifold, then in general both its area and its shape will change. It is impossible to achieve a change in shape without its area to dwindle or expand simultaneously. And this is a property of the so-called Weyl tensor.
I can somehow visualize how this is happening without recourse to advanced maths, but what a great result this is!
In a 4D manifold, it is also true that the object can retain its volume even if the tidal forces (curvature) change its shape, but not in any lower dimension than 4.
I have nothing more to ask, just to verify if this is true. What a great result! If it is true, it is a moment of revelation and enlightening for me.
 
Physics news on Phys.org
dismachaerus said:
Hello,
I've just read and I think I have understood the following result :
If we were to geodesically transport all points of a small 2D surface, so small that it would be flat for all purposes, in a direction vertically above it, and if this surface belongs in an arbitrary 3D manifold, then in general both its area and its shape will change. It is impossible to achieve a change in shape without its area to dwindle or expand simultaneously. And this is a property of the so-called Weyl tensor.
I can somehow visualize how this is happening without recourse to advanced maths, but what a great result this is!
In a 4D manifold, it is also true that the object can retain its volume even if the tidal forces (curvature) change its shape, but not in any lower dimension than 4.
I have nothing more to ask, just to verify if this is true. What a great result! If it is true, it is a moment of revelation and enlightening for me.
Yes, but where did you read it ?
 
In Philippe G. Ciarlet's book 'An introduction to differential geometry', He gives the integrability conditions of the differential equations like this: $$ \partial_{i} F_{lj}=L^p_{ij} F_{lp},\,\,\,F_{ij}(x_0)=F^0_{ij}. $$ The integrability conditions for the existence of a global solution ##F_{lj}## is: $$ R^i_{jkl}\equiv\partial_k L^i_{jl}-\partial_l L^i_{jk}+L^h_{jl} L^i_{hk}-L^h_{jk} L^i_{hl}=0 $$ Then from the equation: $$\nabla_b e_a= \Gamma^c_{ab} e_c$$ Using cartesian basis ## e_I...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. The Relativator was sold by (as printed) Atomic Laboratories, Inc. 3086 Claremont Ave, Berkeley 5, California , which seems to be a division of Cenco Instruments (Central Scientific Company)... Source: https://www.physicsforums.com/insights/relativator-circular-slide-rule-simulated-with-desmos/ by @robphy
Abstract The gravitational-wave signal GW250114 was observed by the two LIGO detectors with a network matched-filter signal-to-noise ratio of 80. The signal was emitted by the coalescence of two black holes with near-equal masses ## m_1=33.6_{-0.8}^{+1.2} M_{⊙} ## and ## m_2=32.2_{-1. 3}^{+0.8} M_{⊙}##, and small spins ##\chi_{1,2}\leq 0.26 ## (90% credibility) and negligible eccentricity ##e⁢\leq 0.03.## Postmerger data excluding the peak region are consistent with the dominant quadrupolar...
Back
Top