Speaker
Description
In recent works it has been claimed that "gravitomagnetism" and/or non-linear general relativistic effects can play a leading role in galactic dynamics, partially or totally replacing dark matter. Using the 1+3 "quasi-Maxwell" formalism, and generalizing it for null geodesics, we show, on general grounds, such hypothesis to be impossible. We demonstrate that (i) the observed gravitational lensing effects rule out any galactic model based on gravitomagnetism, and (ii) the non-linear contributions to the gravitational field actually weaken gravitational attraction, thereby only aggravating the need for dark matter.
Realistic examples of gravitomagnetic lensing effects will be displayed for a Kerr black hole, contrasting with the Schwarzschild case, in particular in what pertains to the Einstein rings.
