arXiv subjects

A. Brotas

Publications and source records attributed to A. Brotas.

6 recordsLinked to original sources

arXiv2006

Fishing in Black Holes

The coordinate system $(\bar{x},\bar{t})$ defined by $r = 2m + K\bar{x}- c K \bar{t}$ and $t=\bar{x}/cK - 1 /cK \int_{r_a}^r (1- 2m/r + K^2)^{1/2} (1 - 2m/r)^{-1}dr$ allow us to write the Schwarzschild metric in the form: \[ds^2=c^2 d\bar{t}^2 + (W^2/K^2 - 2W/K) d\bar{x}^2 + 2c (1 + W/K) d\bar{x}d\bar{t} - r^2 (dθ^2 + cos^2θdϕ^2)\] with $W=(1 - 2m/r + K^2)^{1/2}$, in which the coefficients' pathologies are moved to $r_K = 2m/(1+K^2)$. This new coordinate system is used to study the entrance into a black hole of a rigid line (a line in which the shock waves propagate with velocity c).

gr-qc↗

arXiv2006

Heat transfer in theory of relativity

The traditional Fourier equation just allows us to study the evolution of temperature in an "undeformable" bar. The search for its relativistic variant is a task which is expected to fail because in relativity there are no undeformable bars. Rigid bodies, in the sense of "as rigid as possible", are deformables. In this work we show how to write in relativity the system of equations necessary to study simultaneously deformation and temperature evolution along a rigid deformable bar. The solutions of the two simultaneous equations is discussed assuming convenient constitutive relations for the material. An application is presented.

physics.gen-ph↗

arXiv2004

La peche dans les trous noires

The problem of a thread whose extremity is beyond the Schwarzschild horizon is discussed. We present a new coordinate system allowing to write the Schwarzschild metric in all regions. The system of coordinates introduced appears to be particulary indicated to study the passage of extended bodies throuth the Schwarzschild horizon,as it is the case of a thread that continues to attach a fisherman to a fish that entered a black hole.

physics.gen-ph↗

arXiv2003

The Relativistic Elasticity of Rigid Bodies

In 1909 Born studied the "relativistic undeformable body" but made the mistake of calling it "rigid". The "rigid body" as one can find in Relativity books is, in fact, this Born "undeformable body". In Relativity it is necessary to distinguish between "rigid" and "undeformable". The "undeformable" body (in the sense of the most rigid possible) must be the "deformable" body where schock waves propagate with maximum speed c. We present in this text the elastic laws for rigid bodies. We think that these laws, which are ignored by the majority of relativists, should be taught in the elementary relativistic courses. With the approach of 2005, the centenary year of Relativity, we should like to appeal to all those who have some influence on these matters to avoid this mistake of repeatedly calling "rigid" to the "undeformable body".

physics.gen-ph↗

arXiv2003

Heat transmission in Relativity

The simultaneous study of deformation and heat transmission in a bar was ignored for about 150 years. The traditional Fourier equation just allows to study the evolution of temperature in a undeformable bar. The search for its relativistic variant is a task which must fail because in Relativity there are no undeformable bars. Rigid bodies, in the sense as rigid as possible, are deformables. In this work we show how to write in Relativity the system of equations necessary to study simultaneously deformation and temperature evolution along a rigid bar.

physics.gen-ph↗

arXiv1997

A Elasticidade Relativista

The purpose of this paper is to make clear the difference between rigid and undeformable bodies in Relativity. The error of confusing these two concepts has survived up to the present day treatises. We hope it will not persist in the XXI century treatises. The large majority of relativists do not know the formulae for the relativistic elasticity of rigid bodies (Mc Crea 1952,Brotas 1968). The paradoxes of the rotating disk and of the 3-degrees of freedom of rigidies bodies in Relativity are in the domain of relativistic elasticity.

physics.ed-ph↗