In this paper we study the sensitivity of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project to the determination of cosmological parameters, employing the Monte Carlo Markov Chains (MCMC) method. For comparison, we first analyze the constraints on cosmological parameters from current observational data, including WMAP, SDSS and SN Ia. We then simulate the 3D matter power spectrum data expected from LAMOST, together with the simulated CMB data for PLANCK and the SN Ia from 5-year Supernovae Legacy Survey (SNLS). With the simulated data, we investigate the future improvement on cosmological parameter constraints, emphasizing the role of LAMOST. Our results show the potential of LAMOST in probing for the cosmological parameters, especially in constraining the equation-of-state (EoS) of the dark energy and the neutrino mass.
The Large Area Multi-Object Spectroscopic Telescope (LAMOST) is a dedicated spectroscopic survey telescope being built in China, with an effective aperture of 4 meters and equiped with 4000 fibers. Using the LAMOST telescope, one could make redshift survey of the large scale structure (LSS). The baryon acoustic oscillation (BAO) features in the LSS power spectrum provide standard rulers for measuring dark energy and other cosmological parameters. In this paper we investigate the meaurement precision achievable for a few possible surveys: (1) a magnitude limited survey of all galaxies, (2) a su…
It is commonly believed that our Universe has experienced two different stages of accelerated expansion. The early stage is known as inflation and the current acceleration is driven by dark energy. Observing inflation and dark energy dynamics are among the most important aspects of the current cosmological research. In this paper we make a first detailed probe of possible degeneracies between dynamical inflation and dark energy in light of current cosmological observations. We find the inclusion of inflation and dark energy parameters together make the parameter spaces broader, but interesting…
In the previous papers we derived cosmological equations for models with Gurzadyan-Xue dark energy, have performed their qualitative analysis and, particularly, have revealed a remarkable hidden invariance in the models with respect to the separatrix $Ω_{sep}$ in their phase portraits. Now, new analytic solutions for these models are obtained, showing additional symmetries at various curvatures. The likelihood analysis with supernovae and radio galaxies data and their characteristics (age, the deceleration parameter), again demonstrate the crucial role of the $Ω_{sep}$ for all models, in spite…
In light of the recent finding of the narrow clustering of the geometrically-corrected gamma-ray energies emitted by Gamma Ray Bursts (GRBs), we investigate the possibility to use these sources as standard candles to probe cosmological parameters such as the matter density Omega_m and the cosmological constant energy density Omega_Lambda. By simulating different samples of gamma-ray bursts, based on recent observational results, we find that Omega_m (with the prior Omega_m + Omega_Lambda = 1) can be determined with accuracy ~7% with data from 300 GRBs, provided a local calibration of the stand…
Using the values of the cosmological parameters obtained from Wilkinson Microwave Anisotropy Probe (WMAP) and the cosmological chemical clock observed by high-redshift quasars, it is shown that star formation should have started by the redshift $z_F > 9.5$, and that $z_F$ is sensitive only to $\omegamz h^2$ in flat $Λ$CDM cosmology.
We show that the baryonic oscillations expected in the galaxy power spectrum may be used as a "standard cosmological ruler'' to facilitate accurate measurement of the cosmological equation of state. Our approach involves a straight-forward measurement of the oscillation "wavelength'' in Fourier space, which is fixed by fundamental linear physics in the early Universe and hence is highly model-independent. We quantify the ability of future large-scale galaxy redshift surveys with mean redshifts z~1 and z~3 to delineate the baryonic peaks in the power spectrum, and derive corresponding constrain…
In recent years, the possibility of measuring the cosmological constant $Ω_Λ$ through the application of the Alcock-Paczynski test to the Lyman Alpha (Ly$α$) forest has been suggested (McDonald et al. 1999; Hui et al. 1999). Despite the theoretical uncertainties due to a few other cosmological parameters, some of the greatest difficulties we encounter concern the huge uncertainties due to cosmic variance and noise. In this paper, we propose a maximum likelihood estimation (MLE) method to deal with cosmic variance and noise using synthetic spectra of quasistellar objects (QSOs) from our cosmolo…
I show that neutral lithium couples strongly to the cosmic microwave background (CMB) through its 6708A resonant transition after it recombines at z~500. At observed wavelengths of <335 micron, the CMB anisotropies are significantly altered since the optical depth for resonant scattering by neutral lithium is substantial, of order 0.5. The scattering would suppress the original anisotropies, but will generate strong new anisotropies in the CMB temperature and polarization on sub-degree scales (l>100). Observations at different wavelengths in this spectral regime can probe different thin slices…
I apply the well controlled Hydro-PM approximation of Gnedin & Hui to model the column density distribution of the Lyman-alpha forest for 25 different flat cosmological scenarios, including variants of the standard CDM, tilted CDM, CDM with a cosmological constant, and CHDM models. I show that within the accuracy of the HPM approximation the slope of the column density distribution reflects the degree of nonlinearity of the cosmic gas distribution and is a function of the rms linear density fluctuation at the characteristic filtering scale only. The amplitude of the column density distribution…
Supernova experiments to characterize dark energy require a well designed low redshift program; we consider this for both ongoing/near term (e.g. Supernova Legacy Survey) and comprehensive future (e.g. SNAP) experiments. The derived criteria are: a supernova sample centered near z=0.05 comprising 150-500 (in the former case) and 300-900 (in the latter case) well measured supernovae. Low redshift Type Ia supernovae play two important roles for cosmological use of the supernova distance-redshift relation: as an anchor for the Hubble diagram and as an indicator of possible systematics. An innate …
It has been recently argued that higher dimensional gravity theories may manifest themselves not only at short microscopic distances but also at large cosmological scales. We study the constraints that cosmic microwave background measurements set on such large distance modifications of the gravitational potential.
We develop and assess the potential of several powerful techniques, designed to investigate the details of reionization. First, we present a procedure to probe the neutral fraction, x_HI, using the Lyman alpha transmission statistics of high-redshift (z > 6) sources. We find that only tens of bright quasar spectra could distinguish between x_HI ~ 1 and x_HI < 0.01. A rudimentary application of such a technique on quasar SDSS J1030+0524 has yielded compelling evidence of a large neutral fraction (x_HI > 0.2) at z ~ 6. We also generate the observable, high-z supernovae (SNe) rates and quantify t…
We suggest to use the observationally measured and theoretically justified correlation between size and rotational velocity of galactic discs as a viable method to select a set of high redshift standard rods which may be used to explore the dark energy content of the universe via the classical angular-diameter test. Here we explore a new strategy for an optimal implementation of this test. We propose to use the rotation speed of high redshift galaxies as a standard size indicator and show how high resolution multi-object spectroscopy and ACS/HST high quality spatial images, may be combined to …
We use the newly released 182 Type Ia supernova data combined with the third-year Wilkinson Microwave Anisotropic Probe data (WMAP3) and large scale structure (LSS) information including SDSS and 2dFGRS to constrain the dark energy equation of state (EoS) as well as the curvature of universe $Ω_K$. Using the full dataset of Cosmic Microwave Background (CMB) and LSS rather than the shift parameter and linear growth factor, we make a Markov Chain Monte Carlo (MCMC) global fit, while paying particular attention to the dark energy perturbation. Parameterizing the EoS as $w_{DE}(a) = w_{0} + w_{1}(…
The phases as well as the amplitudes of baryonic acoustic oscillations can be extracted out of a galaxy power spectrum and used as a standard ruler in a cosmological test. A non-oscillating phenomenological fitting function is used to extract the oscillatory part of the galaxy power spectrum and to disentangle phase information from amplitude information. The method (FITEX) is tested with simulated data of the Hubble Volume Simulation to include redshift space effects, non-linear structure growth and biasing. A cosmological test is introduced, which compares the extracted oscillations against …
We consider compactification of extra dimensions and numerically calculate Casimir energy which is provided by the mass of Kaluza-Klein modes. For the extra space we consider a torus with shape moduli and show that the corresponding vacuum energy is represented as a function of the moduli parameter of the extra dimensions. By assuming that the Casimir energy may be identified with cosmological constant, we evaluate the size of extra dimensions in terms of the recent data given by the WMAP observation. We suggest that the observed cosmological constant may probe the shape moduli of the extra sp…
We show, through Monte Carlo simulations, that the Alcock-Paczynski test, as applied to quasar clustering, is a powerful tool to probe the cosmological density and equation of state parameters, Omega_{m0}, Omega_{x0} and w. By taking into account the effect of peculiar velocities upon the correlation function we obtain, for the Two-Degree Field QSO Redshift Survey (2QZ), the predicted confidence contours for the cosmological constant (w = -1) and spatially flat (Omega_{m0} + Omega_{x0}=1) cases. It turns out that, for w = -1, the test is especially sensitive to the difference Omega_{m0} - Omeg…
Cross-correlation between the CMB and large-scale structure is a powerful probe of dark-energy and gravity on the largest physical scales. We introduce a novel estimator, the CMB-velocity correlation, that has most of his power on large scales and that, at low redshift, delivers up to factor of two higher signal-to-noise ratio than the recently detected CMB-dark matter density correlation expected from the Integrated Sachs-Wolfe effect. We propose to use a combination of peculiar velocities measured from supernovae type Ia and kinetic Sunyaev-Zeldovich cluster surveys to reveal this signal and…
We have run Monte Carlo simulations, for quasar clustering redshift distortions in the Two-Degree Field QSO Redshift Survey (2QZ), in order to elicit the power of redshift distortions (geometric Alcock-Paczynski and linear kinematic) to constrain the cosmological density and equation of state parameters, Omega_{m0}, Omega_{x0}, w, of a pressureless matter + dark energy model. It turns out that, for the cosmological constant case (w = -1), the test is especially sensitive to the difference Delta := Omega_{m0} - Omega_{Lambda 0}, whereas for the spatially flat case (k = 0), it is quite competiti…
We examine the transition of a particle across the singularity of the compactified Milne (CM) space. Quantization of the phase space of a particle and testing the quantum stability of its dynamics are consistent to one another. One type of transition of a quantum particle is described by a quantum state that is continuous at the singularity. It indicates the existence of a deterministic link between the propagation of a particle before and after crossing the singularity. Regularization of the CM space leads to the dynamics similar to the dynamics in the de Sitter space. The CM space is a promi…
We perform a double line of sight (DLOS) analysis of the Lyman-alpha forest structures that form and evolve in cosmological N-body/hydrodynamic simulations. Pairs of simulated spectra, extracted from lines of sight separated by distances from D=12.5kpc up to 800kpc, and a ``control sample'' of unrelated lines of sight, are analyzed at redshifts 3, 2, and 1. Coincident line samples are defined for HI column density thresholds of Nco = 10^{12.5}, 10^{13}, and 10^{14} per square cm. We find that: 1) Under the assumption of a single structure size, a Bayesian analysis yields sizes that are larger …
Superstring theory, models with extra dimensions and other SUSY models generically predict that the coupling constants are in fact vacuum expectation values of fields like the dilaton, moduli etc. Assuming some of these fields are light during inflation, we get generation of small classical inhomogeneities in these fields from inflation. Consequently, coupling constants inherit small inhomogeneities at scales much larger than the causal horizon in the early universe. After the moduli get pinned down to their minima, the spatial variations of coupling constants in the late time universe will be…
We discuss the possibility to constrain the relation between redshift and temperature of the cosmic microwave background (CMB) using multifrequency Sunyaev-Zeldovich (SZ) observations. We have simulated a catalog of clusters of galaxies detected through their SZ signature assuming the sensitivities that will be achieved by the {\it Planck} satellite at 100, 143 and 353 GHz, taking into account the instrumental noise and the contamination from the Cosmic Infrared Background and from unresolved radiosources. We have parametrized the cosmological temperature-redshift law as $T\propto (1+z)^{(1-a)…
We explore the effects of a positive cosmological constant on astrophysical and cosmological configurations described by a polytropic equation of state. We derive the conditions for equilibrium and stability of such configurations and consider some astrophysical examples where our analysis may be relevant. We show that in the presence of the cosmological constant the isothermal sphere is not a viable astrophysical model since the density in this model does not go asymptotically to zero. The cosmological constant implies that, for polytropic index smaller than five, the central density has to e…
String and M-theory compactifications generically have compact moduli which can potentially act as the QCD axion. However, as demonstrated here, such a compact modulus can not play the role of a QCD axion and solve the strong CP problem if gravitational waves interpreted as arising from inflation with Hubble constant $H_inf \gsim 10^{13}$ GeV are observed by the PLANCK polarimetry experiment. In this case axion fluctuations generated during inflation would leave a measurable isocurvature and/or non-Gaussian imprint in the spectrum of primordial temperature fluctuations. This conclusion is inde…
We assess the feasibility of probing dark energy with strong gravitational lensing systems. The capability of the method, which depends on the accuracy with which the lensing systems are modeled, is quantitatively investigated using the Fisher-matrix formalism. We show that this method might place useful constraints on the density parameter and the redshift evolution of the dark energy by combining it with a constraint from supernova measurements. For this purpose, the lens potential needs to be precisely reconstructed. We determine the required quality of data. We also briefly discuss the opt…
Two spacecraft separated by $\sim 1\,\au$ and equipped with gamma-ray burst (GRB) detectors could detect or rule out a cosmological density of Massive Compact Halo Objects (MACHOs) in the mass range $10^{-15} M_{\odot}\lsim M \lsim 10^{-7} M_{\odot}$ provided that GRBs prove to be cosmological. Previously devised methods for detecting MACHOs have spanned the mass range $10^{-16} M_{\odot}\lsim M \lsim 10^{7} M_{\odot}$, but with a gap of several orders of magnitude near $10^{-9} M_{\odot}$. For MACHOs and sources both at a cosmological distance, the Einstein radius is $\sim 1\,\au\,(M/10^{-7} …
We explore the prospects for using future supernova observations to probe the dark energy. We focus on quintessence, an evolving scalar field that has been suggested as a candidate for the dark energy. After simulating the observations that would be expected from the proposed SuperNova / Acceleration Probe satellite (SNAP), we investigate two methods for extracting information about quintessence from such data. First, by expanding the quintessence equation of state as w_Q(z) = w_Q(0)-alpha*ln(1+z), to fit the data, it is possible to reconstruct the quintessence potential for a wide range of sm…
Gravitational lenses can provide crucial information on the geometry of the Universe, on the cosmological scenario of formation of its structures as well as on the history of its components with look-back time. In this review, I focus on the most recent results obtained during the last five years from the analysis of the weak lensing regime. The interest of weak lensing as a probe of dark matter and the for study of the coupling between light and mass on scales of clusters of galaxies, large scale structures and galaxies is discussed first. Then I present the impact of weak lensing for the stu…
We have reanalysed constraints on the equation of state parameter, w_Q = P/rho, of the dark energy, using several cosmological data sets and relaxing the usual constraint w_Q > -1. We find that combining Cosmic Microwave Background, large scale structure and Type Ia supernova data yields a non-trivial lower bound on w_Q. At 95.4% confidence we find, assuming a flat geometry of the universe, a bound of -2.68 < w_Q < -0.78 if w_Q is taken to be a completely free parameter. Reassuringly we also find that the constraint w_Q > -1 does not significantly bias the overall allowed region for w_Q. When …
We perform a new study of future sensitivities of galaxy redshift surveys to the free-streaming effect caused by neutrino masses, adding the information on cosmological parameters from measurements of primary anisotropies of the cosmic microwave background (CMB). Our reference cosmological scenario has nine parameters and three different neutrino masses, with a hierarchy imposed by oscillation experiments. Within the present decade, the combination of the Sloan Digital Sky Survey (SDSS) and CMB data from the PLANCK experiment will have a 2-sigma detection threshold on the total neutrino mass c…
The Lenses Structure and Dynamics (LSD) Survey aims at measuring the luminous and dark matter distribution of high redshift early-type galaxies by combining gravitational lens analysis with newly determined velocity dispersion profiles. Here we describe the first results from the LSD survey, a measurement of the internal structure of the lens galaxy in MG2016+112 (z=1.004). The relevance of this measurement to the cosmological model is briefly discussed, in particular in the context of E/S0 galaxy formation and evolution, the existence and shape of universal dark matter profiles, and the measu…
We show that the measurement of the baryonic acoustic oscillations in large high redshift galaxy surveys offers a precision route to the measurement of dark energy. The cosmic microwave background provides the scale of the oscillations as a standard ruler that can be measured in the clustering of galaxies, thereby yielding the Hubble parameter and angular diameter distance as a function of redshift. This, in turn, enables one to probe dark energy. We use a Fisher matrix formalism to study the statistical errors for redshift surveys up to z=3 and report errors on cosmography while marginalizing…
The Fisher matrix formalism has in recent times become the standard method for predicting the precision with which various cosmological parameters can be extracted from future data. This approach is fast, and generally returns accurate estimates for the parameter errors when the individual parameter likelihoods approximate a Gaussian distribution. However, where Gaussianity is not respected (due, for instance, to strong parameter degeneracies), the Fisher matrix formalism loses its reliability. In this paper, we compare the results of the Fisher matrix approach with those from Monte Carlo simu…
The acceleration of the expansion of the universe arises from unknown physical processes involving either new fields in high energy physics or modifications of gravitation theory. It is crucial for our understanding to characterize the properties of the dark energy or gravity through cosmological observations and compare and distinguish between them. In fact, close consistencies exist between a dark energy equation of state function w(z) and changes to the framework of the Friedmann cosmological equations as well as direct spacetime geometry quantities involving the acceleration, such as ``geo…
I review the observational prospects to constrain the equation of state parameter of dark energy and I discuss the potential of future imaging and redshift surveys. Bayesian model selection is used to address the question of the level of accuracy on the equation of state parameter that is required before explanations alternative to a cosmological constant become very implausible. I discuss results in the prediction space of dark energy models. If no significant departure from w=-1 is detected, a precision on w of order 1% will translate into strong evidence against fluid-like dark energy, whil…
The relationship between the metric and nonrelativistic matter distribution depends on the theory of gravity and additional fields, providing a possible way of distinguishing competing theories. With the assumption that the geometry and kinematics of the homogeneous universe have been measured to sufficient accuracy, we present a procedure for understanding and testing the relationship between the cosmological matter distribution and metric perturbations (along with their respective evolution) using the ratio of the physical size of the perturbation to the size of the horizon as our small expa…
We discuss to which extent the present experiments of direct search for WIMPs, when interpreted in terms of relic neutralinos, probe interesting regions of the supersymmetric parameter space, which are also being progressively explored at accelerators. Our analysis is performed in a number of different supersymmetric schemes. We derive the relevant neutralino cosmological properties, locally and on the average in the universe. We prove that part of the susy configurations probed by current WIMP experiments entail relic neutralinos of cosmological interest. The main astrophysical and particle p…
We investigate the constraints on cosmological parameters especially for EoS of dark energy, inflationary parameters, neutrino mass and curvature of universe using simulated Planck data. Firstly we determine cosmological parameters with current observations including ESSENCE, WMAP3, Boomerang-2K2, CBI, VSA, ACBAR, SDSS LRG and 2dFGRS, and take best-fit model as the fiducial model in simulations. In simulations we pay attention to the effects of dynamical dark energy in determination of cosmological parameters. We add simulated SNAP data to do all the simulations. Using present data, we find Qu…
In this paper we discuss the possibility to measure the Hubble parameter and the slope of galaxy density profiles using future supernova data. With future supernova surveys such as SNAP, large numbers of core collapse supernovae will be discovered, a small fraction of which will be multiply imaged. Measurements of the image separation, flux-ratio, time-delay and lensing foreground galaxy for these systems will provide tight constraints on the slope of galactic halos as well as providing complementary and independent information to other cosmological tests with respect to the Hubble parameter.
If general relativity is the correct theory of physics on large scales, then there is a differential equation that relates the Hubble expansion function, inferred from measurements of angular diameter distance and luminosity distance, to the growth rate of large scale structure. For a dark energy fluid without couplings or an unusual sound speed, deviations from this consistency relationship could be the signature of modified gravity on cosmological scales. We propose a procedure based on this consistency relation in order to distinguish between some dark energy models and modified gravity mod…
Development of fundamental physics relies on the constancy of various fundamental quantities such as the fine structure constant. Detecting or constraining the possible time variations of these fundamental physical quantities is an important step toward a complete understanding of basic physics. Here we present the results from a detailed many-multiplet analysis performed using high signal-to-noise ratio, high spectral resolution observations of 23 Mg II systems detected toward 18 QSOs in the redshift range 0.4<z<2.3 obtained using UVES at the VLT. We validate our procedure and define the sele…
The cosmic acceleration is one of the most significant cosmological discoveries over the last century. The two categories of explanation are exotic component (dark energy) and modified gravity. We constrain the two types of model by a joint analysis with perturbation growth and direct $H(z)$ data. Though the minimal $χ^2$ of the $Λ$CDM is almost the same as that of DGP, in the sense of consistency we find that the dark energy ($Λ$CDM) model is more favored through a detailed comparison with the corresponding parameters fitted by expansion data.
