“…in an external magnetic field [10][11][12][13][14][15], with Weyl corrections [16][17][18], in Horava-Lifshitz gravity [19][20][21][22], Gauss-Bonnet gravity [7,9,12,[23][24][25][26][27][28][29][30][31][32][33][34][35][36], and f (R) gravity [37,38]. Some studies also include non-linear electrodynamics [13,14,30,31,[38][39][40][41][42][43][44][45]. In particular, Born-Infeld electrodynamics is especially interesting: it has finite self energies for charged point particles, and is the only non-linear electromagnetic theory that possesses invariance under electromagnetic duality and has no birefringence.…”