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Exact Solutions and Scalar Fields in Gravity - Instituto Avanzado de ...

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On Electromagnetic Thirr<strong>in</strong>g Problems 285<br />

The electromagnetic field tensor belong<strong>in</strong>g to the Reissner–Nordström<br />

metric (2) has only a radial component<br />

where is the Heavisi<strong>de</strong> function (the charge is concentrated<br />

solely on the <strong>in</strong>ner shell at ), <strong>and</strong> the potentials (5) or<br />

(6) have to be <strong>in</strong>serted <strong>in</strong> the respective regions. The charge <strong>de</strong>nsity<br />

of the <strong>in</strong>terior shell results from the <strong>in</strong>homogeneous Maxwell equation<br />

as<br />

3. FIRST ORDER ROTATION OF THE<br />

SHELLS<br />

Rotations of the shells from Sec. 2 <strong>in</strong> first or<strong>de</strong>r of angular velocity<br />

(<strong>de</strong>not<strong>in</strong>g the velocity of the <strong>in</strong>ner charged shell <strong>and</strong>/or the velocity<br />

of the exterior mass shell) are <strong>de</strong>scribed by an extension of the metric<br />

(2):<br />

with neglect of the By the very <strong>de</strong>f<strong>in</strong>ition of an angular velocity,<br />

a stationary rotat<strong>in</strong>g system is <strong>in</strong>variant un<strong>de</strong>r the common substitutions<br />

<strong>and</strong> <strong>and</strong> s<strong>in</strong>ce the metric functions U, V,<br />

<strong>and</strong> A are <strong>in</strong><strong>de</strong>pen<strong>de</strong>nt of they have to be even functions of Therefore,<br />

<strong>in</strong> first or<strong>de</strong>r of the functions U <strong>and</strong> V can be taken from Sec.<br />

2, <strong>and</strong> the function A is the only new metric function.<br />

(Centrifugal <strong>de</strong>formations of the spherical shells start only at or<strong>de</strong>r )<br />

The relevant E<strong>in</strong>ste<strong>in</strong> equation takes its simplest form <strong>in</strong> the variable<br />

with S<strong>in</strong>ce there are no electric currents <strong>in</strong> the <strong>and</strong><br />

<strong>in</strong> our mo<strong>de</strong>ls, the magnetic field component is<br />

zero, <strong>and</strong> there rema<strong>in</strong>s only one homogeneous Maxwell equation (with<br />

• <strong>de</strong>not<strong>in</strong>g the )

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