118677216
CMB Temperature and Matter Power Spectrum in a Decay Vacuum Dark Energy Model
In this paper, a decay vacuum model $\bar{\rho}_\Lambda=3\sigma M_p^2H_0 H$ is revisited by detailed analysis of background evolution and perturbation equations. We show the imprints on CMB temperature and matter power spectrum from the effective coupling terms between dark sectors by comparing to the standard cosmological constant model and observational data points (WMAP7 and SDSS DR7). We find that the decay vacuum model can describe the expansion rate at late times as well as the standard cosmological constant model but it fails to simultaneously reproduce the observed CMB and matter power spectrum. Its generalization $\bar{\rho}_\Lambda=3M_p^2(\xi_1 H_0 H+\xi_2 H^2)$ is also discussed. Detailed analysis of the background evolution shows that the dimensionless parameter $\xi_{2}$ would be zero to avoid the unnatural 'fine tuning' and to keep the positivity of energy density of dark matter and dark energy in the early epoch.
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.
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.
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 $B_{s}= 0.775_{-0.0161- 0.0338}^{+ 0.0161+ 0.0307}$.
115754528
GEM technical design report
15016676
A low temperature expansion for matrix quantum mechanics
A bstractWe analyze solutions to loop-truncated Schwinger-Dyson equations in massless N=2$$ \mathcal{N}=2 $$ and N=4$$ \mathcal{N}=4 $$ Wess-Zumino matrix quantum mechanics at finite temperature, where conventional perturbation theory breaks down due to IR divergences. We find a rather intricate low temperature expansion that involves fractional power scaling in the temperature, based on a consistent “soft collinear” approximation. We conjecture that at least in the N=4$$ \mathcal{N}=4 $$ matrix quantum mechanics, such scaling behavior holds to all perturbative orders in the 1/N expansion. We discuss some preliminary results in analyzing the gauged supersymmetric quantum mechanics using Schwinger-Dyson equations, and comment on the connection to metastable microstates of black holes in the holographic dual of BFSS matrix quantum mechanics.
119152267
Nontrivial geometries: Bounds on the curvature of the universe
Abstract Probing the geometry of the universe is one of the most important endevours in cosmology. Current observational data from the cosmic microwave background anisotropy (CMB), galaxy surveys and type Ia supernovae (SNe Ia) strongly constrain the curvature of the universe to be close to zero for a universe dominated by a cosmological constant or dark energy with a constant equation of state. Here we investigate the role of cosmic priors on deriving these tight bounds on geometry, by considering a landscape motivated scenario with an oscillating curvature term. We perform a likelihood analysis of current data under such a model of non-trivial geometry and find that the uncertainties on curvature, and correspondingly on parameters of the matter and dark energy sectors, are larger. Future dark energy experiments together with CMB data from experiments like Planck could dramatically improve our ability to constrain cosmic curvature under such models enabling us to probe possible imprints of quantum gravity.
51050412
AMBER/VLTI observations of the B[e] star MWC 300
Aims. We study the enigmatic B[e] star MWC 300 to investigate its disk and binary with milli-arcsecond-scale angular resolution. Methods. We observed MWC 300 with the VLTI/AMBER instrument in the H and K bands and compared these observations with temperature-gradient models to derive model parameters. Results. The measured low visibility values, wavelength dependence of the visibilities, and wavelength dependence of the closure phase directly suggest that MWC 300 consists of a resolved disk and a close binary. We present a model consisting of a binary and a temperature-gradient disk that is able to reproduce the visibilities, closure phases, and spectral energy distribution. This model allows us to constrain the projected binary separation (∼4.4 mas or ∼7.9 AU), the flux ratio of the binary components (∼2.2), the disk temperature power-law index, and other parameters.
121694828
Performance of prototypes for the ALICE electromagnetic calorimeter
Abstract The performance of prototypes for the ALICE electromagnetic sampling calorimeter has been studied in test beam measurements at FNAL and CERN. A 4 × 4 array of final design modules showed an energy resolution of about 11 % / E ( GeV ) ⊕ 1.7 % with a uniformity of the response to electrons of 1% and a good linearity in the energy range from 10 to 100 GeV. The electromagnetic shower position resolution was found to be described by 1.5 mm ⊕ 5.3 mm / E ( GeV ) . For an electron identification efficiency of 90% a hadron rejection factor of > 600 was obtained.
119247594
Investigate the interaction between dark matter and dark energy
In this paper we investigate the interaction between dark matter and dark energy by considering two different interacting scenarios, i.e. the cases of constant interaction function and variable interaction function. By fitting the current observational data to constrain the interacting models, it is found that the interacting strength is non-vanishing, but weak for the case of constant interaction function, and the interaction is not obvious for the case of variable interaction function. In addition, for seeing the influence from interaction we also investigate the evolutions of interaction function, effective state parameter for dark energy and energy density of dark matter. At last some geometrical quantities in the interacting scenarios are discussed.