5,022 research outputs found
Utilizing the Updated Gamma-Ray Bursts and Type Ia Supernovae to Constrain the Cardassian Expansion Model and Dark Energy
We update gamma-ray burst (GRB) luminosity relations among certain spectral
and light-curve features with 139 GRBs. The distance modulus of 82 GRBs at
can be calibrated with the sample at by using the cubic
spline interpolation method from the Union2.1 Type Ia supernovae (SNe Ia) set.
We investigate the joint constraints on the Cardassian expansion model and dark
energy with 580 Union2.1 SNe Ia sample () and 82 calibrated GRBs data
(). In CDM, we find that adding 82 high-\emph{z} GRBs to
580 SNe Ia significantly improves the constrain on
plane. In the Cardassian expansion model, the
best fit is and
, which is consistent with the CDM cosmology in the
confidence region. We also discuss two dark energy models in which
the equation of state is parametrized as and
, respectively. Based on our analysis, we see that our
Universe at higher redshift up to is consistent with the concordance
model within confidence level.Comment: 17 pages, 6 figures, 2 tables; accepted for publication in Advances
in Astronomy, special issue on Gamma-Ray Burst in Swift and Fermi Era. arXiv
admin note: text overlap with arXiv:0802.4262, arXiv:0706.0938 by other
author
Illusion Media: Generating Virtual Objects Using Realizable Metamaterials
We propose a class of optical transformation media, illusion media, which
render the enclosed object invisible and generate one or more virtual objects
as desired. We apply the proposed media to design a microwave device, which
transforms an actual object into two virtual objects. Such an illusion device
exhibits unusual electromagnetic behavior as verified by full-wave simulations.
Different from the published illusion devices which are composed of left-handed
materials with simultaneously negative permittivity and permeability, the
proposed illusion media have finite and positive permittivity and permeability.
Hence the designed device could be realizable using artificial metamaterials.Comment: 9 pages, 4 figures, published in Appl. Phys. Lett
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