118327242
Inhomogeneous and Interacting Vacuum Energy
Vacuum energy is a simple model for dark energy driving an accelerated expansion of the universe. If the vacuum energy is inhomogeneous in spacetime then it must be interacting. We present the general equations for a spacetime-dependent vacuum energy in cosmology, including inhomogeneous perturbations. We show how any dark energy cosmology can be described by an interacting vacuum+matter. Different models for the interaction can lead to different behaviour (e.g., sound speed for dark energy perturbations) and hence could be distinguished by cosmological observations. As an example we present the cosmic microwave microwave background anisotropies and the matter power spectrum for two different versions of a generalised Chaplygin gas cosmology.
118465763
Current observational constraints to the holographic dark energy model with a new infrared cutoff via the Markov chain Monte Carlo method
In this paper, the holographic dark energy models with the new infrared cutoff for both the flat case and the nonflat case are confronted with the combined constraints of current cosmological observations: type Ia supernovae, baryon acoustic oscillations, current cosmic microwave background, and the observational Hubble data. By utilizing the Markov chain Monte Carlo method, we obtain the best fit values of the parameters with $1\ensuremath{\sigma}$, $2\ensuremath{\sigma}$ errors in the flat model: ${\ensuremath{\Omega}}_{b}{h}^{2}={0.0233}_{\ensuremath{-}0.0009\ensuremath{-}0.0014}^{+0.0009+0.0013}$, $\ensuremath{\alpha}={0.8502}_{\ensuremath{-}0.0875\ensuremath{-}0.1064}^{+0.0984+0.1299}$, $\ensuremath{\beta}={0.4817}_{\ensuremath{-}0.0773\ensuremath{-}0.0955}^{+0.0842+0.1176}$, ${\ensuremath{\Omega}}_{\mathrm{de}0}={0.7287}_{\ensuremath{-}0.0294\ensuremath{-}0.0429}^{+0.0296+0.0432}$, ${\ensuremath{\Omega}}_{m0}={0.2713}_{\ensuremath{-}0.0296\ensuremath{-}0.0432}^{+0.0294+0.0429}$, ${H}_{0}={66.35}_{\ensuremath{-}2.14\ensuremath{-}3.07}^{+2.38+3.35}$. In the nonflat model, the constraint results are found in $1\ensuremath{\sigma}$, $2\ensuremath{\sigma}$ regions: ${\ensuremath{\Omega}}_{b}{h}^{2}={0.0228}_{\ensuremath{-}0.0010\ensuremath{-}0.0014}^{+0.0010+0.0014}$, ${\ensuremath{\Omega}}_{k}={0.0305}_{\ensuremath{-}0.0134\ensuremath{-}0.0176}^{+0.0092+0.0140}$, $\ensuremath{\alpha}={0.8824}_{\ensuremath{-}0.1163\ensuremath{-}0.1378}^{+0.2180+0.2213}$, $\ensuremath{\beta}={0.5016}_{\ensuremath{-}0.0871\ensuremath{-}0.1102}^{+0.0973+0.1247}$, ${\ensuremath{\Omega}}_{\mathrm{de}0}={0.6934}_{\ensuremath{-}0.0304\ensuremath{-}0.0413}^{+0.0364+0.0495}$, ${\ensuremath{\Omega}}_{m0}={0.2762}_{\ensuremath{-}0.0302\ensuremath{-}0.0412}^{+0.0278+0.0402}$, ${H}_{0}={70.20}_{\ensuremath{-}3.17\ensuremath{-}4.00}^{+3.03+3.58}$. In the best fit holographic dark energy models, the equation of state of dark energy and the deceleration parameter at present are characterized by ${w}_{\mathrm{de}0}=\ensuremath{-}1.1414\ifmmode\pm\else\textpm\fi{}0.0608$, ${q}_{0}=\ensuremath{-}0.7476\ifmmode\pm\else\textpm\fi{}0.0466$ (flat case) and ${w}_{\mathrm{de}0}=\ensuremath{-}1.0653\ifmmode\pm\else\textpm\fi{}0.0661$, ${q}_{0}=\ensuremath{-}0.6231\ifmmode\pm\else\textpm\fi{}0.0569$ (nonflat case). Compared to the $\ensuremath{\Lambda}\mathrm{CDM}$ model, it is found the current combined data sets do not favor the holographic dark energy model over the $\ensuremath{\Lambda}\mathrm{CDM}$ model.
122323511
DIMENSION EMERGENCE, HOLOGRAPHY AND QUANTUM GRAVITY
In this paper, we try to give an alternative interpretation of the holography principle. We argue that the space or time may be regarded as emerging from quantum mechanics as an evolutive parameter. The lower D-dimensional theory is related to a corresponding (D+1)-theory by a mysterious quantum system. Then from the higher-dimensional theory, under a new dimension reduction mechanism we obtain the corresponding results. We also try to incorporate the gauge field into the reduction, roughly identifying Aμ with Nμ which is the shift vector in the ADM-like decomposition of space–time metric. In the end, we extend to the gravitational field, and obtain a relation $\tilde{M}^3 = \kappa M_{\rm Pl}^2$ with a cutoff factor κ, from a different view.
119217496
Revisiting generalized Chaplygin gas as a unified dark matter and dark energy model
In this paper, we revisit the generalized Chaplygin gas (GCG) model as a unified dark matter and dark energy model. The energy density of GCG model is given as ρGCG/ρGCG0=[Bs+(1−Bs)a−3(1+α)]1/(1+α), where α and Bs are two model parameters which will be constrained by type Ia supernova as standard candles, baryon acoustic oscillation as standard rulers and the seventh year full WMAP data points. In this paper, we will not separate GCG into dark matter and dark energy parts any more as adopted in the literature. By using the Markov Chain Monte Carlo method, we find the results $\alpha=0.00126_{-0.00126- 0.00126}^{+ 0.000970+ 0.00268}$ and $B_{s}= 0.775_{-0.0161- 0.0338}^{+ 0.0161+ 0.0307}$.
210001134
Reconstructing dark energy potentials from parameterized deceleration parameters
In this paper, the properties of dark energy are investigated according to the parameterized deceleration parameter q(z), which is used to describe the extent of the accelerating expansion of the universe. The potential of dark energy V() and the cosmological parameters, such as the dimensionless energy density ωo, Ωm, and the state parameter w, are connected to it. Concretely, by giving two kinds of parameterized deceleration parameters q(z) = a + bz/(1 + z) and q(z) = 1/2 + (az + b)/(1 + z)2, the evolution of these parameters and the reconstructed potentials V() are plotted and analysed. It is found that the potentials run away with the evolution of universe.
115754528
GEM technical design report
11259901
Present and future evidence for evolving dark energy
We compute the Bayesian evidences for one- and two-parameter models of evolving dark energy, and compare them to the evidence for a cosmological constant, using current data from Type Ia supernova, baryon acoustic oscillations, and the cosmic microwave background. We use only distance information, ignoring dark energy perturbations. We find that, under various priors on the dark energy parameters, LambdaCDM is currently favoured as compared to the dark energy models. We consider the parameter constraints that arise under Bayesian model averaging, and discuss the implication of our results for future dark energy projects seeking to detect dark energy evolution. The model selection approach complements and extends the figure-of-merit approach of the Dark Energy Task Force in assessing future experiments, and suggests a significantly-modified interpretation of that statistic.
119188783
Probing interaction and spatial curvature in the holographic dark energy model
In this paper we place observational constraints on the interaction and spatial curvature in the holographic dark energy model. We consider three kinds of phenomenological interactions between holographic dark energy and matter, i.e., the interaction term Q is proportional to the energy densities of dark energy (rho(A)), matter (p(m)), and matter plus dark energy (p(m) + p(A)). For probing the interaction and spatial curvature in the holographic dark energy model, we use the latest observational data including the type la supernovae (SNIa) Constitution data, the shift parameter of the cosmic microwave background (CMB) given by the five-year Wilkinson Microwave Anisotropy Probe (WMAP5) observations, and the baryon acoustic oscillation (BAO) measurement, from the Sloan Digital Sky Survey (SDSS). Our results show that, the interaction and spatial curvature in the holographic dark energy model are both rather small. Besides, it is interesting to find that there exists significant degeneracy between the phenomenological interaction and the spatial curvature in the holographic dark energy model.
64774799
Preliminary results of the Moon shadow using ARGO-YBJ detector
ARGO-YBJ is a “full coverage” air shower detector consisting of Resistive Plate Chambers(RPCs) at the Yangbajing High Altitude Cosmic Ray Laboratory (Tibet, China) at 4300 m a.s.l. (lat=30.11° N, long=90.53° E). Using the data collected with a carpet of RPCs (1900 m 2 , about 1/3 of the whole ARGO-YBJ detector), the cosmic ray shadowing effect due to the Moon was studied. The 50% angular resolution is found to be ∼1.2° with the Chess-board method and the Moon shadow with a significance of 4.9 σ is found displaced by 0.7° westward and 0.5° northward with respect to the expected position by the equi-zenith angle Method.
50843980
The BES-III experiment at the high luminosity Tau-Charm factory
Interesting results from BES-II and other experiments raised actually many new questions which shall be answered by its upgrade program, BEPCII and BES-III. The design and current status of BEPCII and BES-III are reported.
118092974
Particle acceleration and the origin of gamma-ray emission from Fermi Bubbles
Fermi LAT has discovered two extended gamma-ray bubbles above and below the galactic plane. We propose that their origin is due to the permanent energy release in the Galactic center (GC) as a result of star accretion onto the central black hole. Shocks generated by these processes propagate into the Galactic halo and accelerate particles there. We show that electrons accelerated up to ∼ 10 TeV may be responsible for the observed gamma-ray emission of the bubbles as a result of inverse Compton (IC) scattering on the relic photons. We suggest that the Bubble could generate the flux of CR protons at energies > 10 15 eV because the shocks in the Bubble have much larger length scales and longer