Basic questions about raising and lowering indices

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In summary: It was mistake. My guess was ##T_{\mu \nu}*g^{\mu \nu}##. My question is: Can ##T_\mu^\mu## be written into form where T has only lower indices?No, it cannot be written that way.
  • #36
olgerm said:
try to understand my notation.
I can't even count the number of brackets you've used without computer support, let alone see if you've nested them correctly. Neither can you, which is why you are asking for help. Shouldn't that tell you something about your method?
 
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  • #37
olgerm said:
I like that form. maybe after simplifiyng it more it becomes sipmler. the form that includes Ricci tensor and other things that I do not know has jus no intuitive meaning to me.
would like to know whether I used correctly.

Although you may be reducing the field equation written as a single tensor equation
in terms of more primitive terms involving the metric and coordinate-dependent Christoffel symbols,
I don't think simpler-as-more-primitive
is more intuitive than simpler-as-tensors[-as-stuctures]
because you are missing sight of all of the symmetries and structures that went into the tensor formulation.

Those primitives are needed to build up the structures.
But it's the structures that provide the intuition behind the field equations.

Yes, you'll need to know how the Einstein tensor is built and what it means
in terms of the more primitive ideas.
But I don't think it's helpful, especially as a first step,
to write it out fully in terms of metrics and Christoffel symbols.
Trust us,... you won't gain any intuition by doing this.

That's why we don't write down Maxwell's Equations in its original form (as 20 coupled PDEs
https://en.wikipedia.org/wiki/Histo...Dynamical_Theory_of_the_Electromagnetic_Fieldhttps://en.wikisource.org/wiki/A_Dynamical_Theory_of_the_Electromagnetic_Field/Part_III) but we instead use the vector calculus notation of Heaviside... or, fancier, a tensor equation
... or even more fancy: with differential forms, or with geometric-algebra
https://en.wikipedia.org/wiki/Mathematical_descriptions_of_the_electromagnetic_fieldTensor notation was partially designed to avoid seeing explicit summation signs.
Sub-subscripts [itex]x_{i_1}y_{i_2}[/itex] (or indices-with-indices) are unnecessarily taxing on the reader,
unless there are important relations among the indices being suggested.Possibly useful advice:
https://aapt.scitation.org/doi/abs/10.1119/1.5111838?journalCode=ajp"Low-entropy expressions"
American Journal of Physics 87, 613 (2019); https://doi.org/10.1119/1.5111838
Sanjoy Mahajan

Possibly more useful use of time and effort:
http://pages.pomona.edu/~tmoore/LesHouches/DiagMetric.pdf
 
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  • #38
I still want to see this equation in form that includes more easily comprihensable quantities.

I remove sum symbols if it is easier for you:

##g^{\mu m_1}*g^{\nu m_2} g^{j_1 m_3}(\frac{\partial \Gamma_{m_3 m_2 m_1}}{\partial x^{j_1}}-\frac{{\partial \Gamma_{m_3 j_1 m_1}}}{\partial x^{m_2}}+g^{j_2 m_4}({\Gamma_{m_3 j_1 j_2}}{\Gamma_{m_4 m_2 m_1}}-{\Gamma_{m_3 m_2 j_2}}{\Gamma_{m_4 j_1 m_1}}))+
(\Lambda-\frac{1}{2}*g_{i_1i_2}*g^{i_1m_1}*g^{i_2m_2}*g^{m_3 j_1}(\frac{\partial{\Gamma}_{m_3 m_2 m_1}}{\partial x^{j_1}}-\frac{\partial \Gamma_{m_3 j_1 m_1}}{\partial x^{m_2}}+g^{j_2m_4}(\Gamma_{m_3 j_1 j_2}\Gamma_{m_4 m_2 m_1 }-\Gamma_{m_3 m_2 j_2} \Gamma_{m_4 j_1 m_1})))*g^{\mu \nu}=\frac{8*\pi*G}{c^4}*T^{\mu \nu}##

maybe it is easier understand my notation without sum symbols. is the equation correct? it is same equation as last equation in post26. Have any recomendations to simplify einstein fild equation füther?
 
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  • #39
olgerm said:
I still want to see this equation in form that includes more easily comprihensable quantities.

The standard form of the equation is already more comprehensible to everyone except you.

olgerm said:
maybe it is easier understand my notation without sum symbols. is the equation correct?

It's still too much of a mess for me to tell whether it's correct.

olgerm said:
Have any recomendations to simplify einstein fild equation füther?

What you are doing is not "simplifying" to anyone except you. To everyone else, the standard form of the equation is the "simple" one.
 
  • #40
This thread is going nowhere and is now closed.
 
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