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Noether and Lie symmetries for charged perfect fluids. (English) Zbl 1217.83015

Summary: We study the underlying nonlinear partial differential equation that governs the behaviour of spherically symmetric charged fluids in general relativity. We investigate the conditions for the equation to admit a first integral or be reduced to quadratures using symmetry methods for differential equations. A general Noether first integral is found. We also undertake a comprehensive group analysis of the underlying equation using Lie point symmetries. The existence of a Lie symmetry is subject to solving an integro-differential equation in general; we investigate the conditions under which it can be reduced to quadratures. Earlier results for uncharged fluids and particular first integrals for charged matter are regained as special cases of our treatment.

MSC:

83C15 Exact solutions to problems in general relativity and gravitational theory
83C40 Gravitational energy and conservation laws; groups of motions
83C50 Electromagnetic fields in general relativity and gravitational theory
83C55 Macroscopic interaction of the gravitational field with matter (hydrodynamics, etc.)
35L15 Initial value problems for second-order hyperbolic equations
45K05 Integro-partial differential equations
35K55 Nonlinear parabolic equations
83C20 Classes of solutions; algebraically special solutions, metrics with symmetries for problems in general relativity and gravitational theory

Software:

LIE