arXiv subjects

H. A. Camargo

Publications and source records attributed to H. A. Camargo.

4 recordsLinked to original sources

arXiv2015

Weyl geometry, anti-De Sitter space, and $Φ^4$-theory

We study the Gaussian approximation to the quantum fluctuations of the metric of the four dimensional anti-De Sitter spacetime. The associated massless scalar field has a quartic self interaction, for which we construct the generating functional of the $n$-point correlation functions. The concomitant infrared divergence is cured by a mass renormalization provided by the cosmological constant, which is also responsible for the renormalization of the coupling constant of the field theory.

physics.gen-ph↗

arXiv2014

Rindler approximation to Kerr black hole

We show that the Rindler approximation to the time-radial part of the Kerr and Kerr-Newman metrics near their external $h_+$ and internal $h_-$ horizons {\bf only} holds {\bf outside} $h_+$ and {\bf inside} $h_-$, so respectively inside and outside the external and internal ergospheres, regions where, in Boyer-Lindquist coordinates, both $g_{tt}$ and $g_{rr}$ are negative, but preserving the Lorentzian character of the metric, and $r>0$ i.e. outside the region $r<0$ where closed timelike curves exist. At each point, the choice of Rindler coordinates is not trivial, but depends on the polar angle $θ$. The approximation, as is known, automatically gives the absolute values of the surface gravities $κ_\pm$ as the corresponding proper accelerations, and therefore the Hawking temperatures $τ_\pm$ at $h_\pm$.

gr-qc↗

arXiv2014

Proper time and length in Schwarzschild geometry

We study proper time ($τ$) intervals for observers at rest in the universe ($U$) and anti-universe ($\bar{U}$) sectors of the Kruskal-Schwarzschild eternal spacetime of mass $M$, and proper lengths ($ρ$) in the black hole (BH) and white hole (WH) sectors. The fact that in asymptotically flat regions, coordinate time $t$ at infinity is proper time, leads to a past directed Kruskal time $T$ in $\bar{U}$. In the BH and WH sectors maximal proper lengths coincide with maximal proper time intervals, $πM$, in these regions, i.e. with the proper time of radial free falling (ejection) to (from) the singularity starting (ending) from (at) rest at the horizon.

physics.gen-ph↗

arXiv2014

Newman-Janis Algorithm Revisited

The purpose of the present article is to show that the Newman-Janis and Newman et al algorithm used to derive the Kerr and Kerr-Newman metrics respectively, automatically leads to the extension of the initial non negative polar radial coordinate r to a cartesian coordinate r' running from -\infty to +\infty, thus introducing in a natural way the region -\infty < r' < 0 in the above spacetimes. Using Boyer-Lindquist and ellipsoidal coordinates, we discuss some geometrical aspects of the positive and negative regions of r', like horizons, ergosurfaces, and foliation structures.

gr-qc↗