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# Activity for Volpinaâ€­

Type On... Excerpt Status Date
Edit Post #288293 Initial revision 11 months ago
Question Understand intuitively 4th boundary condition of gravitational wave
Suppose we have a gravitational wave which obeys the equation: $[G{tt}-c^{2}G{xx}]h{\mu\nu}=0$ Lets take the case where $h{\mu\nu}\ne0$ so we are left with the classical wave equation.Suppose for simplicity that the gravitational wave has a wavelength of 1m so we get the following boundary cond...
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11 months ago
Edit Post #288288 Post edited:
11 months ago
Edit Post #288288 Initial revision 11 months ago
Question How are gravitational waves derived?
Gravitational waves can be derived from the non-linear Einstein field equations and since they are by definition waves they must obey the wave equation: $u{tt}=c^{2}u{xx}$ but in General Relativity time and space are not fixed so how are $t$ and $x$ defined for a gravitational wave?
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11 months ago
Comment Post #288251 Just suppose we solve this problem as boundary condition problem,not by just solving the ODE in the "simplest" way
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12 months ago
Edit Post #288251 Post edited:
12 months ago
Edit Post #288251 Post edited:
12 months ago
Edit Post #288251 Initial revision 12 months ago
Question What do eigenfunctions and eigenvalues mean physically?
Lets say we have a mass connected to a spring.Assuming not any friction the ODE which describes the system is $m\frac{d^{2}x}{dt^{2}} = -kx$ We can set 2 Dirichlet boundary conditions $x(0)=0$ and $x(c)=0$ where $c$ will depend on $k,m$ If we solve the boundary condition problem we end up w...
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12 months ago