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Jay R. Yablon wrote:
Many of the widely-studied solutions to Einstein's field equations are taken in vacuo, that is, at events where the energy momentum tensor T^uv=0. This includes Schwarzchild and Kerr geometries, for example. Have there been many exact solutions found where T^uv not= 0? $$ No. I am speaking of analytical solutions where the differential equations are solved exactly, *not* numerical approximations. $$ YABsolutely no. Maxwell's energy tensor of electrodynamics T^u_v = (1/4pi) [F^ut F_vt - (1/4) lambda^u_v F^st F_st]. -=- ..interested in solutions where F^uv_u=0 (free space) -=- ..and where F^uv_u=J^v (space with current sources). Conditions of interest include static spherical symmetry in the nature of Schwarzchild, and rotation with spherical symmetry about the z-axis in the nature of Kerr. --Jay R Yablon. To be clear, I am *not* looking for solutions where the metric is assumed to be a Minkowski metric. Lots of analyses assume a flat-space background for electrodynamics. Rather, I am looking for *exact* solutions, to the extent that such solutions are known, which derive a curved spacetime metric from the electromagnetic field strength tensor, that is, which derive g_uv = g_uv(F^uv) via the Maxwell tensor T^u_v, whereby T^u_v(g_uv, F_uv) simply becomes T^u_v(F_uv) once the g_uv(F^uv) are found. $$ Maxwell used REAL "flat" plates in air to derive his equations. $$ This is why GR is only "approximately" flat, at-great-distance. $$ Even a dot has extreme "curvature", so you can imagine a point. $$ GR is a "point-SURFACE manifold" at the end of it's WORLD-line. $$ This is why GR is NOT a "local" theory (where it's all Newton). $$ This is why GR is a "far-field" theory (where it's all Newton). $$ [ The "SURFACE" of a GR-"POiNT" is "FLAT-at-a-GREAT-distance ]. $$ $$ Tom R ought derive a set from lab work ..using "CURVED" plates. $$ [Just let the PLATEs be M1 and m1 and the air as the "AEther"]. $$ $$ Hope this helps, ```Brian A M Stuckless, Ph.T (Tivity). GR CUT OFF it's own WORLD-line, having DECLARED no PRiOR geometry. p.s. A GR-"geodesic" is *NOT* Uncle Al's "OTHER LONGER way round". Thanks. Jay R. Yablon Email: Solution to Einstein's Field Equations where T^uv not= 0?. |
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