90 research outputs found
Holographic Dark Energy Characterized by the Total Comoving Horizon and Insights to Cosmological Constant and Coincidence Problem
The observed acceleration of the present universe is shown to be well
explained by the holographic dark energy characterized by the total comoving
horizon of the universe (HDE). It is of interest to notice that the very
large primordial part of the comoving horizon generated by the inflation of
early universe makes the HDE behave like a cosmological constant. As a
consequence, both the fine-tuning problem and the coincidence problem can
reasonably be understood with the inflationary universe and holographical
principle. We present a systematic analysis and obtain a consistent
cosmological constraint on the HDE model based on the recent cosmological
observations. It is found that the HDE model gives the best-fit result
() and the minimal
which is compatible with for the CDM model.Comment: 17 pages, 4 figures, two eqs. (26)(27) added for the consistent
approximate solution of dark energy in early universe, references added,
published version in PR
Thermodynamical description of the interacting new agegraphic dark energy
We describe the thermodynamical interpretation of the interaction between new
agegraphic dark energy and dark matter in a non-flat universe. When new
agegraphic dark energy and dark matter evolve separately, each of them remains
in thermodynamic equilibrium. As soon as an interaction between them is taken
into account, their thermodynamical interpretation changes by a stable thermal
fluctuation. We obtain a relation between the interaction term of the dark
components and this thermal fluctuation.Comment: 11 pages, accepted for publication in MPLA (2010
Brane-Bulk energy exchange and agegraphic dark energy
We consider the agegraphic models of dark energy in a braneworld scenario
with brane-bulk energy exchange. We assume that the adiabatic equation for the
dark matter is satisfied while it is violated for the agegraphic dark energy
due to the energy exchange between the brane and the bulk. Our study shows that
with the brane-bulk interaction, the equation of state parameter of agegraphic
dark energy on the brane, , can have a transition from normal state where
to the phantom regime where , while the effective equation
of state for dark energy always satisfies .Comment: 13 pages, to appear in IJMP
Agegraphic Chaplygin gas model of dark energy
We establish a connection between the agegraphic models of dark energy and
Chaplygin gas energy density in non-flat universe. We reconstruct the potential
of the agegraphic scalar field as well as the dynamics of the scalar field
according to the evolution of the agegraphic dark energy. We also extend our
study to the interacting agegraphic generalized Chaplygin gas dark energy
model.Comment: 8 page
Cosmological Constraint and Analysis on Holographic Dark Energy Model Characterized by the Conformal-age-like Length
We present a best-fit analysis on the single-parameter holographic dark
energy model characterized by the conformal-age-like length,
. Based on the Union2 compilation of
557 supernova Ia data, the baryon acoustic oscillation results from the SDSS
DR7 and the cosmic microwave background radiation data from the WMAP7, we show
that the model gives the minimal , which is comparable to
for the CDM model. The single
parameter concerned in the model is found to be . Since the fractional density of dark energy at
, the fraction of dark energy is naturally negligible in the early
universe, at . The resulting constraints on the
present fractional energy density of matter and the equation of state are
\Omega_{m0}=0.286^{+0.019}_{-0.018}^{+0.032}_{-0.028} and
w_{de0}=-1.240^{+0.027}_{-0.027}^{+0.045}_{-0.044} respectively. The model
leads to a slightly larger fraction of matter comparing to the CDM
model. We also provide a systematic analysis on the cosmic evolutions of the
fractional energy density of dark energy, the equation of state of dark energy,
the deceleration parameter and the statefinder. It is noticed that the equation
of state crosses from to , the universe transits from
decelerated expansion () to accelerated expansion () recently, and
the statefinder may serve as a sensitive diagnostic to distinguish the CHDE
model with the CDM model.Comment: 17 pages, 5 figures, minor changes for the fitting data, references
adde
Interacting HDE and NADE in Brans-Dicke Chameleon Cosmology
Motivated by the recent work of one of us [1], we generalize this work to the
case where the pressureless dark matter and the holographic dark energy do not
conserve separately but interact with each other. We investigate the
cosmological applications of interacting holographic dark energy in Brans-Dicke
theory with chameleon scalar field which is non-minimally coupled to the matter
field. We find out that in this model the phantom crossing can be constructed
if the model parameters are chosen suitably. We also perform the study for the
new agegraphic dark energy model and calculate some relevant cosmological
parameters and their evolution.Comment: 13 pages, version accepted at Phys. Lett.
Probing spacetime foam with extragalactic sources
Due to quantum fluctuations, spacetime is probably ``foamy'' on very small
scales. We propose to detect this texture of spacetime foam by looking for
core-halo structures in the images of distant quasars. We find that the Very
Large Telescope interferometer will be on the verge of being able to probe the
fabric of spacetime when it reaches its design performance. Our method also
allows us to use spacetime foam physics and physics of computation to infer the
existence of dark energy/matter, independent of the evidence from recent
cosmological observations.Comment: LaTeX, 11 pages, 1 figure; version submitted to PRL; several
references added; very useful comments and suggestions by Eric Perlman
incorporate
Models of wave-function collapse, underlying theories, and experimental tests
We describe the state of the art in preparing, manipulating and detecting coherent molecular matter. We focus on experimental methods for handling the quantum motion of compound systems from diatomic molecules to clusters or biomolecules.Molecular quantum optics offers many challenges and innovative prospects: already the combination of two atoms into one molecule takes several well-established methods from atomic physics, such as for instance laser cooling, to their limits. The enormous internal complexity that arises when hundreds or thousands of atoms are bound in a single organic molecule, cluster or nanocrystal provides a richness that can only be tackled by combining methods from atomic physics, chemistry, cluster physics, nanotechnology and the life sciences.We review various molecular beam sources and their suitability for matter-wave experiments. We discuss numerous molecular detection schemes and give an overview over diffraction and interference experiments that have already been performed with molecules or clusters.Applications of de Broglie studies with composite systems range from fundamental tests of physics up to quantum-enhanced metrology in physical chemistry, biophysics and the surface sciences.Nanoparticle quantum optics is a growing field, which will intrigue researchers still for many years to come. This review can, therefore, only be a snapshot of a very dynamical process
Interacting agegraphic tachyon model of dark energy
Scalar-field dark energy models like tachyon are often regarded as an
effective description of an underlying theory of dark energy. In this Letter,
we implement the interacting agegraphic dark energy models with tachyon field.
We demonstrate that the interacting agegraphic evolution of the universe can be
described completely by a single tachyon scalar field. We thus reconstruct the
potential as well as the dynamics of the tachyon field according to the
evolutionary behavior of interacting agegraphic dark energy.Comment: 11 pages, to appear in Phys. Lett.
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