3,954 research outputs found
Abnormal enhancement of electric field inside a thin permittivity-near-zero object in free space
It is found that the electric field can be enhanced strongly inside a
permittivity-near-zero object in free space, when the transverse cross section
of the object is small and the length along the propagation direction of the
incident wave is large enough as compared with the wavelength. The physical
mechanism is explained in details. The incident electromagnetic energy can only
flow almost normally through the outer surface into or out of the
permittivity-near-zero object, which leads to large energy stream density and
then strong electric field inside the object. Meanwhile, the magnetic field
inside the permittivity-near-zero object may be smaller than that of the
incident wave, which is also helpful for enhancing the electric field. Two
permittivity-near-zero objects of simple shapes, namely, a thin cylindrical
shell and a long thin rectangular bar, are chosen for numerical illustration.
The enhancement of the electric field becomes stronger when the
permittivity-near-zero object becomes thinner. The physical mechanism of the
field enhancement is completely different from the plasmonic resonance
enhancement at a metal surface
Dark information of black hole radiation raised by dark energy
The "lost" information of black hole through the Hawking radiation was
discovered being stored in the correlation among the non-thermally radiated
particles [Phys. Rev. Lett 85, 5042 (2000), Phys. Lett. B 675, 1 (2009)]. This
correlation information, which has not yet been proved locally observable in
principle, is named by dark information. In this paper, we systematically study
the influences of dark energy on black hole radiation, especially on the dark
information. Calculating the radiation spectrum in the existence of dark energy
by the approach of canonical typicality, which is reconfirmed by the quantum
tunneling method, we find that the dark energy will effectively lower the
Hawking temperature, and thus makes the black hole has longer life time. It is
also discovered that the non-thermal effect of the black hole radiation is
enhanced by dark energy so that the dark information of the radiation is
increased. Our observation shows that, besides the mechanical effect (e.g.,
gravitational lensing effect), the dark energy rises the the stored dark
information, which could be probed by a non-local coincidence measurement
similar to the coincidence counting of the Hanbury-Brown -Twiss experiment in
quantum optics.Comment: 21 pages, 3 figures, complete journal-info of Ref.[4] is added,
comments are welcome ([email protected]
Squeezing electromagnetic energy with a dielectric split ring inside a permeability-near-zero metamaterial
A novel electromagnetic energy squeezing mechanism is proposed based on the
special properties of permeability-near-zero metamaterials. Nearly no energy
stream can enter a conventional dielectric region positioned inside a
permeability-near-zero material. When a source is surrounded by a dielectric
split ring (encloser with a gap opened), the electromagnetic energy generated
by the source is forced to propagate through the gap. When the gap is narrow,
the energy stream density becomes very large and makes the magnetic field
enhanced drastically in the gap. The narrow gap can be long and bended. This
provides us a method to obtain strong magnetic field without using resonance
enhancement.Comment: 17pages, 4 figure
Bi-Frobenius algebra structure on quantum complete intersections
This paper is to look for bi-Frobenius algebra structures on quantum complete
intersections. We find a class of comultiplications, such that if , then a quantum complete intersection becomes a bi-Frobenius algebra with
comultiplication of this form if and only if all the parameters . Also, it is proved that if then a quantum exterior algebra
in two variables admits a bi-Frobenius algebra structure if and only if the
parameter . While if , then the exterior algebra
with two variables admits no bi-Frobenius algebra structures. Since a quantum
complete intersection over a field of characteristic zero admits no bialgebra
structures, this gives a class of examples of bi-Frobenius algebras which are
not bialgebras (and hence not Hopf algebras). On the other hand, a quantum
exterior algebra admits a bialgebra structure if and only if . In commutative case, other two comultiplications on complete intersection
rings are given, such that they admit non-isomorphic bi-Frobenius algebra
structures
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