Kostik
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- His proof is hard to follow, can someone help?
Weinberg ("Gravitation and Cosmology") defines the energy-momentum tensor ##T^{\mu\nu}## in equations (2.8.1)-(2.8.2). He proves $${T^{\mu\nu}}_{,\nu}=0$$ on page 44. But:
(1) Why does he have a minus sign at the very beginning; see the equation which starts $$\frac{\partial}{\partial x^i}T^{\alpha i}(x,t) =$$ when there is no such minus sign in (2.8.2)?
(2) How does he do what looks like an integration by parts (third equality) when there is no integration?
What makes his work more confusing is that on pp. 43-44 he alternately uses the notation ##({\bf{x}}t)##, ##(x)##, ##(x,t)## and ##({\bf{x}},t)##.
(1) Why does he have a minus sign at the very beginning; see the equation which starts $$\frac{\partial}{\partial x^i}T^{\alpha i}(x,t) =$$ when there is no such minus sign in (2.8.2)?
(2) How does he do what looks like an integration by parts (third equality) when there is no integration?
What makes his work more confusing is that on pp. 43-44 he alternately uses the notation ##({\bf{x}}t)##, ##(x)##, ##(x,t)## and ##({\bf{x}},t)##.