9,919 research outputs found
Extended Holographic dark energy
The idea of relating the infrared and ultraviolet cutoffs is applied to
Brans-Dicke theory of gravitation. We find that extended holographic dark
energy from the Hubble scale or the particle horizon as the infrared cutoff
will not give accelerating expansion. The dynamical cosmological constant with
the event horizon as the infrared cutoff is a viable dark energy model.Comment: one reference is corrected, 3 pages, no figure,V3: minor correction
Adsorption, Segregation and Magnetization of a Single Mn Adatom on the GaAs (110) Surface
Density functional calculations with a large unit cell have been conducted to
investigate adsorption, segregation and magnetization of Mn monomer on
GaAs(110). The Mn adatom is rather mobile along the trench on GaAs(110), with
an energy barrier of 0.56 eV. The energy barrier for segregation across the
trenches is nevertheless very high, 1.67 eV. The plots of density of states
display a wide gap in the majority spin channel, but show plenty of
metal-induced gap states in the minority spin channel. The Mn atoms might be
invisibl in scanning tunneling microscope (STM) images taken with small biases,
due to the directional p-d hybridization. For example, one will more likely see
two bright spots on Mn/GaAs(110), despite the fact that there is only one Mn
adatom in the system
Effective generation of Ising interaction and cluster states in coupled microcavities
We propose a scheme for realizing the Ising spin-spin interaction and atomic
cluster states utilizing trapped atoms in coupled microcavities. It is shown
that the atoms can interact with each other via the exchange of virtual photons
of the cavities. Through suitably tuning the parameters, an effective Ising
spin-spin interaction can be generated in this optical system, which is used to
produce the cluster states. This scheme does not need the preparation of
initial states of atoms and cavity modes, and is insensitive to cavity decay.Comment: 11pages, 2 figures, Revtex
Limits from Weak Gravity Conjecture on Dark Energy Models
The weak gravity conjecture has been proposed as a criterion to distinguish
the landscape from the swampland in string theory. As an application in
cosmology of this conjecture, we use it to impose theoretical constraint on
parameters of two types of dark energy models. Our analysis indicates that the
Chaplygin-gas-type models realized in quintessence field are in the swampland,
whereas the power-low decay model of the variable cosmological constant can
be viable but the parameters are tightly constrained by the conjecture.Comment: Revtex4, 8 pages, 5 figures; References, minor corrections in
content, and acknowledgement adde
Holographic dark energy model with non-minimal coupling
We find that holographic dark energy model with non-minimally coupled scalar
field gives rise to an accelerating universe by choosing Hubble scale as IR
cutoff. We show viable range of a non-minimal coupling parameter in the
framework of this model.Comment: 7 pages, no figure, corrected some typos, to be published in
Europhys. Let
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