arXiv subjects

Carlos R. Paiva

Publications and source records attributed to Carlos R. Paiva.

3 recordsLinked to original sources

arXiv2015

Asymmetric Band Diagrams in Photonic Crystals with a Spontaneous Nonreciprocal Response

We study the propagation of electromagnetic waves in layered photonic crystals formed by materials with a spontaneous nonreciprocal response, such as Tellegen (axion) media or topological insulators. Surprisingly, it is proven that stratified Tellegen photonic crystals that break simultaneously the space inversion and time reversal symmetries have always symmetric dispersion diagrams. Interestingly, we show that by combining chiral and nonreciprocal materials the photonic band diagrams can exhibit a spectral asymmetry such that . Furthermore, it is demonstrated that in some conditions two juxtaposed Tellegen medium layers have an electromagnetic response analogous to that of a biased ferrite slab.

physics.optics↗

arXiv2005

Generalized relativistic velocity addition with spacetime algebra

Using spacetime algebra, the geometric algebra of spacetime, the general problem of relativistic addition of velocities is addressed. The successive application of non-collinear Lorentz boosts is then studied in Minkowski spacetime. Even spatial vectors, such as the relative velocity of two reference frames, are analyzed in their proper setting: as vectors belonging to a four-dimensional spacetime manifold and not as vectors in ordinary three-dimensional (Euclidean) space. This is a clear and physical result that illustrates the fact that Lorentz boosts do not form a group. The entire derivation is carried through without using the second postulate on the speed of light, thereby stressing that the framework of special relativity does not depend on electromagnetism.

physics.class-ph↗

arXiv2005

Passive Lorentz transformations with spacetime algebra

In special relativity, spacetime algebra (STA) provides a powerful and insightful approach to an invariant formulation of physics. However, in this geometric algebra of spacetime, relativistic physics is usually considered a misnomer: STA provides us with an invariant (coordinate-free) formulation and hence it seems that (passive) Lorentz transformations are misplaced. However, in order to interpret experimental results, it is important to relate invariant physical quantities to some reference frame. In this paper, passive Lorentz transformations are derived using STA but without the second postulate on the speed of light used by Einstein. This derivation sheds light on the physical background of STA and, at the same time, clarifies Lorentz transformations in the proper setting of (Minkowski) four-dimensional spacetime.

physics.ed-ph↗