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Antonio S. de Castro

Publications and source records attributed to Antonio S. de Castro.

46 records · Page 3Linked to original sources
arXiv2003

Scattering of neutral fermions by a pseudoscalar potential step in two-dimensional space-time

The problem of scattering of neutral fermions in two-dimensional space-time is approached with a pseudoscalar potential step in the Dirac equation. Some unexpected aspects of the solutions beyond the absence of Klein\'{}s paradox are presented. An apparent paradox concerning the uncertainty principle is solved by introducing the concept of effective Compton wavelength. Added plausibility for the existence of bound-state solutions in a pseudoscalar double-step potential found in a recent Letter is given.

hep-th↗
arXiv2002

Comment on "Relativistic extension of shape-invariant potentials"

This comment directs attention to some fails of the Alhaidari approach to solve relativistic problems. It is shown that his gauge considerations are way off the mark and that the class of exactly solvable relativistic problems is not so enlarged as Alhaidari thinks it is.

hep-th↗
arXiv2001

An analytically solvable three-body problem

The problem of three particles interacting through harmonic forces is discussed within the Newtonian formalism. By means of a didactic approach, an exact analytical solution is found, and ways to extend it to the N-body case are pointed out.

physics.class-ph↗
arXiv2001

On the regular-geometric-figure solution to the N-body problem

The regular-geometric-figure solution to the $N$-body problem is presented in a very simple way. The Newtonian formalism is used without resorting to a more involved rotating coordinate system. Those configurations occur for other kinds of interactions beyond the gravitational ones for some special values of the parameters of the forces. For the harmonic oscillator, in particular, it is shown that the $N$-body problem is reduced to $N$ one-body problems.

physics.class-ph↗
arXiv2001

n+1 dimensional Dirac equation and the Klein paradox

The purpose of this comment is to clarify two points related to the Dirac equation. First, the Lorentz structure of the potential and its connection with the Klein paradox. Second, the connection between the number of space dimensions and the number of spinor components.

quant-ph↗
arXiv2000

Ideal Coinstraints - A Warning Note

A criticism against the conception adopted by some textbook's authors concerning ideal constraints is presented. The criticism is strengthen with two traditional examples.

physics.class-ph↗
arXiv1999

Exploring a rheonomic system

A simple and illustrative rheonomic system is explored in the Lagrangian formalism. The difference between Jacobi's integral and energy is highlighted. A sharp contrast with remarks found in the literature is pointed out. The non-conservative system possess a Lagrangian not explicitly dependent on time and consequently there is a Jacobi's integral. The Lagrange undetermined multiplier method is used as a complement to obtain a few interesting conclusions

physics.class-ph↗