Publications (33)
Image distortion in non perturbative gravitational lensing
Simonetta Frittelli, Thomas P. Kling, Ezra T. Newman
We introduce the idea of {\it shape parameters} to describe the shape of the pencil of rays connecting an observer with a source lying on his past lightcone. On the basis of these…
A variational principle for time of arrival of null geodesics
Simonetta Frittelli, Ezra T. Newman
Normally the issue or question of the time of arrival of light rays at an observer coming from a given source is associated with Fermat's Principle of Least Time which yields paths…
Einstein boundary conditions for the Einstein equations in the conformal-traceless decomposition
Simonetta Frittelli, Roberto Gomez
In relation to the BSSN formulation of the Einstein equations, we write down the boundary conditions that result from the vanishing of the projection of the Einstein tensor normall…
First-order quasilinear canonical representation of the characteristic formulation of the Einstein equations
Roberto Gomez, Simonetta Frittelli
We prescribe a choice of 18 variables in all that casts the equations of the fully nonlinear characteristic formulation of general relativity in first--order quasi-linear canonical…
Fermat Potentials for Non-Perturbative Gravitational Lensing
Simonetta Frittelli, Thomas P. Kling, Ezra T. Newman
The images of many distant galaxies are displaced, distorted and often multiplied by the presence of foreground massive galaxies near the line of sight; the foreground galaxies act…
Estimates for the characteristic problem of the first-order reduction of the wave equation
Simonetta Frittelli
We calculate certain estimates for the solution of the characteristic problem of the wave equation reduced to first order, in terms of the free data prescribed on two transverse su…