12 research outputs found
Nonlinear electrodynamics as a symmetric hyperbolic system
Nonlinear theories generalizing Maxwell's electromagnetism and arising from a
Lagrangian formalism have dispersion relations in which propagation planes
factor into null planes corresponding to two effective metrics which depend on
the point-wise values of the electromagnetic field. These effective Lorentzian
metrics share the null (generically two) directions of the electromagnetic
field. We show that, the theory is symmetric hyperbolic if and only if the
cones these metrics give rise to have a non-empty intersection. Namely that
there exist families of symmetrizers in the sense of Geroch which are positive
definite for all covectors in the interior of the cones intersection. Thus, for
these theories, the initial value problem is well-posed. We illustrate the
power of this approach with several nonlinear models of physical interest such
as Born-Infeld, Gauss-Bonnet and Euler-Heisenberg
Light propagation in (2+1)-dimensional electrodynamics: the case of nonlinear constitutive laws
We scrutinize the geometrical properties of light propagation inside a
nonlinear medium modeled by a fully covariant electromagnetic theory in
-dimensions. After setting the nonlinear constitutive relations, the phase
velocity and the polarization of waves are derived and three special cases are
analyzed in details. In spite of the dimensional reduction, our model still
presents phenomena like one-way propagation, controlled opacity among others
for a large class of dielectric and magneto-electric parameters.Comment: 9 pages, 7 figure
A classification of the effective metric in nonlinear electrodynamics
We show that only two types of effective metrics are possible in certain
nonlinear electromagnetic theories. This is achieved by using the dependence of
the effective metric on the energy-momentum tensor of the background along with
the Segr\`e classification of the latter. Each of these forms is completely
determined by single scalar function, which characterizes the light cone of the
nonlinear theory. We compare this light cone with that of Minkowski in two
examples.Comment: Accepted for publication in Classical & Quantum Gravit
Malignant lung PEComa (clear cell tumor): rare case report and literature review
Clear cell tumors of the lung (CCTL), or “sugar tumors” of lung, are very uncommon lesions and are mostly benign perivascular epithelioid cell (PEC) tumors with no specific morphologic features. Fewer than 100 cases have been reported; the aggressive nature demonstrated in sporadic reports has rarely been described in the literature. Although the course is generally described as benign, eight reported cases showed malignant behavior. We report a case of a PEC with a malignant presentation in a young man, correlating the main characteristics of the tumor with other cases reported in the literature to better elucidate this rare presentation. We also performed a literature review of reports on benign and malignant CCTL cases, with a focus on clinical, imaging, and immunohistochemical differentiation. CCTLs are rare tumors that require histopathological and immunohistochemical confirmation; to date, criteria that can predict malignant evolution are lacking
From disformal electrodynamics to exotic spacetime singularities
We study different types of spacetime singularities which emerge in the
context of disformal electrodynamics. The latter is characterized by
transformations of the background metric which preserve regular (non-null)
solutions of Maxwell equations in vacuum. Restricting ourselves to the case of
electrostatic fields created by charged point particles along a line, we show
that exotic types of singularities arise.Comment: 18 pages, 4 figure