2,215 research outputs found
Propagation of Bessel beams from a dielectric to a conducting medium
Recently, the use of Bessel beams in evaluating the possibility of using them
for a new generation of GPR (ground penetrating radar) systems has been
considered. Therefore, an analysis of the propagation of Bessel beam in
conducting media is worthwhile. We present here an analysis of this type.
Specifically, for normal incidence we analyze the propagation of a Bessel beam
coming from a perfect dielectric and impinging on a conducting medium, i.e. the
propagation of a Bessel beam generated by refracted inhomogeneous waves. The
remarkable and unexpected result is that the incident Bessel beam does not
change its shape even when propagating in the conducting medium.Comment: To be publishe
Passage of a Bessel beam through a classically forbidden region
The motion of an electromagnetic wave, through a classically-forbidden
region, has recently attracted renewed interest because of its implication with
regard to the theoretical and experimental problems of superluminality. From an
experimental point of view, many papers provide an evidence of superluminality
in different physical systems. Theoretically, the problem of a passage through
a forbidden gap has been treated by considering plane waves at oblique
incidence into a plane parallel layer of a medium with a refractive index
smaller than the index of the surrounding medium, and also confined (Gaussian)
beams, still at oblique incidence. In the present paper the case of a Bessel
beam is examined, at normal incidence into the layer (Secs. II and III), in the
scalar approximation (Sec. IV) and by developing also a vectorial treatment
(Sec. V). Conclusions are reported in Sic. VI
Bessel beam through a dielectric slab at oblique incidence: the case of total reflection
The oblique incidence of a Bessel beam on a dielectric slab with refractive
index n1 surrounded by a medium of a refractive index n>n1 may be studied
simply by expanding the Bessel beam into a set of plane waves forming the same
angle with the axis of the beam. In the present paper we examine a Bessel beam
that impinges at oblique incidence onto a layer in such a way that each
plane-wave component impinges with an angle larger than the critical angle.Comment: 10 pages, 6 figure
Gamma-convergence results for phase-field approximations of the 2D-Euler Elastica Functional
We establish some new results about the -limit, with respect to the
-topology, of two different (but related) phase-field approximations of
the so-called Euler's Elastica Bending Energy for curves in the plane
Superluminal behavior and the Minkowski space-time
Bessel X-waves, or Bessel beams, have been extensively studied in last years,
especially with regard to the topic of superluminality in the propagation of a
signal. However, in spite of many efforts devoted to this subject, no definite
answer has been found, mainly for lack of an exact definition of signal
velocity. The purpose of the present work is to investigate the field of
existence of Bessel beams in order to overcome the specific question related to
the definition of signal velocity. Quite surprisingly, this field of existence
can be represented in the Minkowski space-time by a Super-Light Cone which
wraps itself around the well-known Light Cone. So, the change in the upper
limit of the light velocity does not modify the fundamental low of the
relativity and the causal principle.Comment: 3 pages, 2 figure
Approximation of the Helfrich's functional via Diffuse Interfaces
We give a rigorous proof of the approximability of the so-called Helfrich's
functional via diffuse interfaces, under a constraint on the ratio between the
bending rigidity and the Gauss-rigidity
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