COSMIC DEFECT COSMOLOGY

2009 ◽  
Vol 24 (08n09) ◽  
pp. 1620-1624
Author(s):  
A. TARTAGLIA
Keyword(s):  
Phase Space ◽  
Cold Dark Matter ◽  
Displacement Vector ◽  
Empty Space ◽  
Space Time ◽  
Point Particle ◽  
Accelerated Expansion ◽  
Displacement Vector Field ◽  
Type Ia ◽  
Ia Supernovae

The accelerated expansion of the universe is interpreted as an effect of a defect in space-time treated as a four-dimensional continuum endowed with physical properties. The analogy is with texture defects in material continua, like dislocations and disclinations, described in terms of a singular displacement vector field. A Lagrangian for empty space-time is proposed exploiting one further analogy between the phase space of a Robertson-Walker universe and the phase space of a point particle moving across an homogeneous isotropic medium. The model, named Cosmic Defect theory, produces, as a byproduct, also inflation near the initial singularity. The theory has been applied to fit the luminosity data of 192 type Ia supernovae. The results are satisfying and comparable with the ones obtained by means of the Λ Cold Dark Matter standard model.

A DARKLESS SPACE–TIME

2008 ◽  
Vol 17 (02) ◽  
pp. 275-299 ◽  
Author(s):  
ANGELO TARTAGLIA ◽  
MONICA CAPONE
Keyword(s):  
Vector Field ◽  
Displacement Vector ◽  
Lagrange Equation ◽  
Empty Space ◽  
Space Time ◽  
Accelerated Expansion ◽  
Displacement Vector Field ◽  
The One ◽  
Internal Viscosity ◽  
The Universe

In cosmology it has become usual to introduce new entities as dark matter and dark energy in order to explain otherwise unexplained observational facts. Here, we propose a different approach treating space–time as a continuum endowed with properties similar to those of ordinary material continua, such as internal viscosity and strain distributions originated by defects in the texture. A Lagrangian modeled on the one valid for simple dissipative phenomena in fluids is built and used for empty space–time. The internal "viscosity" is shown to correspond to a four-vector field. The vector field is shown to be connected with the displacement vector field induced by a point defect in a four-dimensional continuum. Using the known symmetry of the universe, assuming the vector field to be divergenceless and solving the corresponding Euler–Lagrange equation, we directly obtain inflation and a phase of accelerated expansion of space–time. The only parameter in the theory is the "strength" of the defect. We show that it is possible to fix it in such a way as to also quantitatively reproduce the acceleration of the universe. We have finally verified that the addition of ordinary matter does not change the general behavior of the model and that the proper Newtonian limit exists.

scholarly journals Dynamic of the Accelerated Expansion of the Universe in the DGP Model

2011 ◽  
Vol 21 (3) ◽  
pp. 253 ◽  
Author(s):  
Vo Quoc Phong
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Cold Dark Matter ◽  
Growth Index ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Density Parameter ◽  
Type Ia ◽  
Age Of The Universe ◽  
The Universe

According to experimental data of SNe Ia (Supernovae type Ia), we will discuss in detial dynamics of the DGP model and introduce a simple parametrization of matter $\omega$, in order to analyze scenarios of the expanding universe and the evolution of the scale factor. We find that the dimensionless matter density parameter at the present epoch $\Omega^0_m=0.3$, the age of the universe $t_0= 12.48$ Gyr, $\frac{a}{a_0}=-2.4e^{\frac{-t}{25.56}}+2.45$. The next we study the linear growth of matter perturbations, and we assume a definition of the growth rate, $f \equiv \frac{dln\delta}{dlna}$. As many authors for many years, we have been using a good approximation to the growth rate $f \approx \Omega^{\gamma(z)}_m$, we also find that the best fit of the growth index, $\gamma(z)\approx 0.687 - \frac{40.67}{1 + e^{1.7. (4.48 + z)}}$, or $\gamma(z)= 0.667 + 0.033z$ when $z\ll1$. We also compare the age of the universe and the growth index with other models and experimental data. We can see that the DGP model describes the cosmic acceleration as well as other models that usually refers to dark energy and Cold Dark Matter (CDM).

scholarly journals MULTIDIMENSIONAL GRAVITATIONAL MODEL WITH ANISOTROPIC PRESSURE

2013 ◽  
Vol 22 (13) ◽  
pp. 1350075 ◽  
Author(s):  
O. A. GRIGORIEVA ◽  
G. S. SHAROV
Keyword(s):  
Equations Of State ◽  
Einstein Equations ◽  
Accelerated Expansion ◽  
Anisotropic Pressure ◽  
Gravitational Model ◽  
Spatial Dimensions ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
Ia Supernovae ◽  
The Universe

We consider the gravitational model with additional spatial dimensions and anisotropic pressure which is nonzero only in these dimensions. Cosmological solutions of the Einstein equations in this model include accelerated expansion of the universe at late stage of its evolution and dynamical compactification of extra dimensions. This model describes observational data for Type Ia supernovae on the level or better than the ΛCDM model. We analyze two equations of state resulting in different predictions for further evolution, but in both variants the acceleration epoch is finite.

scholarly journals Accelerated Lyra's Cosmology Driven by Electromagnetic Field in Inhomogeneous Universe

2009 ◽  
Vol 2009 ◽  
pp. 1-20 ◽  
Author(s):  
Anirudh Pradhan ◽  
Padmini Yadav
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Displacement Vector ◽  
Fluid Distribution ◽  
Inhomogeneous Universe ◽  
Cylindrically Symmetric ◽  
Type Ia ◽  
Electromagnetic Field Tensor ◽  
Deterministic Solution ◽  
Ia Supernovae

A new class of cylindrically symmetric inhomogeneous cosmological models for perfect fluid distribution with electromagnetic field is obtained in the context of Lyra's geometry. We have obtained solutions by considering the time dependent displacement field. The source of the magnetic field is due to an electric current produced along thez-axis. OnlyF12is a nonvanishing component of electromagnetic field tensor. To get the deterministic solution, it has been assumed that the expansionθin the model is proportional to the shearσ. It has been found that the solutions are consistent with the recent observations of type Ia supernovae, and the displacement vectorβ(t)affects entropy. Physical and geometric aspects of the models are also discussed in presence and absence of magnetic field.

scholarly journals H0LiCOW – XIII. A 2.4 per cent measurement of H0 from lensed quasars: 5.3σ tension between early- and late-Universe probes

2019 ◽  
Vol 498 (1) ◽  
pp. 1420-1439 ◽  
Author(s):  
Kenneth C Wong ◽  
Sherry H Suyu ◽  
Geoff C-F Chen ◽  
Cristian E Rusu ◽  
Martin Millon ◽  
...  
Keyword(s):  
Time Delay ◽  
Cold Dark Matter ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Joint Analysis ◽  
Type Ia Supernovae ◽  
Acoustic Oscillations ◽  
Type Ia ◽  
Measured Time ◽  
Ia Supernovae

ABSTRACT We present a measurement of the Hubble constant (H0) and other cosmological parameters from a joint analysis of six gravitationally lensed quasars with measured time delays. All lenses except the first are analysed blindly with respect to the cosmological parameters. In a flat Λ cold dark matter (ΛCDM) cosmology, we find $H_{0} = 73.3_{-1.8}^{+1.7}~\mathrm{km~s^{-1}~Mpc^{-1}}$, a $2.4{{\ \rm per\ cent}}$ precision measurement, in agreement with local measurements of H0 from type Ia supernovae calibrated by the distance ladder, but in 3.1σ tension with Planck observations of the cosmic microwave background (CMB). This method is completely independent of both the supernovae and CMB analyses. A combination of time-delay cosmography and the distance ladder results is in 5.3σ tension with Planck CMB determinations of H0 in flat ΛCDM. We compute Bayes factors to verify that all lenses give statistically consistent results, showing that we are not underestimating our uncertainties and are able to control our systematics. We explore extensions to flat ΛCDM using constraints from time-delay cosmography alone, as well as combinations with other cosmological probes, including CMB observations from Planck, baryon acoustic oscillations, and type Ia supernovae. Time-delay cosmography improves the precision of the other probes, demonstrating the strong complementarity. Allowing for spatial curvature does not resolve the tension with Planck. Using the distance constraints from time-delay cosmography to anchor the type Ia supernova distance scale, we reduce the sensitivity of our H0 inference to cosmological model assumptions. For six different cosmological models, our combined inference on H0 ranges from ∼73 to 78 km s−1 Mpc−1, which is consistent with the local distance ladder constraints.

Nonvibrating energy strings as fundamental building blocks of space and particles

2019 ◽  
Vol 32 (3) ◽  
pp. 338-352
Author(s):  
Albert Zur (Albo)
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Displacement Vector ◽  
Building Blocks ◽  
Space Time ◽  
Accelerated Expansion ◽  
Absolute Space ◽  
Position Space ◽  
3D Space ◽  
The Universe

In the proposed Energy String (ES) theory, we assume the existence of fundamental energy strings forming a generally Euclidean four-dimensional fabric of empty space as well as forming all types of particles in the universe. The 4D space fabric is composed of space energy strings bearing dark-energy as well as a newly described dark-momentum. Particles are composed of particle energy strings which interact with space energy strings inducing three-dimensional space curvatures embedded in a flat fourth-space dimension. The induced space curvatures are responsible for gravity of particles and assign a longitudinal and a transverse direction to particles. The proposed ES theory yields an adapted model of the universe with remarkable teachings as follows: (1) The fabric of space and related dark-energy are associated with a newly defined dark-momentum. This dark momentum is the sole contributor to the cosmological constant Λ in Einstein's field equations which describes the accelerated expansion of the universe. The energy of the quantum vacuum becomes nonrelevant to the cosmological constant Λ, enabling a solution to the “Cosmological Constant Problem”; (2) All particles perform an equal distance of translatory displacement in 4D-space, reflecting a universal displacement rate of particles relative to an absolute generally Euclidean 4D-space. This universal principle is equivalent to Lorentz transformation of a fundamental four-displacement vector, representing a new model of Special Relativity with superior compatibility to quantum theories. (3) Time is a displacement property of mass particles in 4D-space. Frames of 3D-space+time are the perspective by which mass particles experience 4D-space. In this perspective, absolute space longitudinally displaces over mass particles experienced as proper time elapse. Temporal momentum is an inherent invariant property of mass particles. Frames of 3D-space+time are mixed domains: three spatial coordinates of position-space and a temporal coordinate of momentum-space, meaning the position-space in the temporal coordinate is totally inaccessible.

scholarly journals “Pure” Supernovae and Dark Energy

2011 ◽  
Vol 7 (S281) ◽  
pp. 17-20
Author(s):  
M. V. Pruzhinskaya ◽  
E. S. Gorbovskoy ◽  
V. M. Lipunov
Keyword(s):  
Dark Energy ◽  
Chemical Evolution ◽  
Special Class ◽  
Accelerated Expansion ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
Ia Supernovae ◽  
The Universe

AbstractA special class of Type Ia supernovae that is not subject to ordinary and additional intragalactic gray absorption and chemical evolution has been identified. Analysis of the Hubble diagrams constructed for these supernovae confirms the accelerated expansion of the Universe irrespective of the chemical evolution and possible gray absorption in galaxies.

scholarly journals A measurement of the Hubble constant from Type II supernovae

2020 ◽  
Vol 496 (3) ◽  
pp. 3402-3411 ◽  
Author(s):  
T de Jaeger ◽  
B E Stahl ◽  
W Zheng ◽  
A V Filippenko ◽  
A G Riess ◽  
...  
Keyword(s):  
Cold Dark Matter ◽  
Background Radiation ◽  
Hubble Constant ◽  
Systematic Errors ◽  
Host Galaxy ◽  
Microwave Background Radiation ◽  
Type Ia ◽  
Cepheid Variables ◽  
Red Giant ◽  
Ia Supernovae

ABSTRACT Progressive increases in the precision of the Hubble-constant measurement via Cepheid-calibrated Type Ia supernovae (SNe Ia) have shown a discrepancy of ∼4.4σ with the current value inferred from Planck satellite measurements of the cosmic microwave background radiation and the standard $\Lambda $cold dark matter (ΛCDM) cosmological model. This disagreement does not appear to be due to known systematic errors and may therefore be hinting at new fundamental physics. Although all of the current techniques have their own merits, further improvement in constraining the Hubble constant requires the development of as many independent methods as possible. In this work, we use SNe II as standardisable candles to obtain an independent measurement of the Hubble constant. Using seven SNe II with host-galaxy distances measured from Cepheid variables or the tip of the red giant branch, we derive H$_0= 75.8^{+5.2}_{-4.9}$ km s−1 Mpc−1 (statistical errors only). Our value favours that obtained from the conventional distance ladder (Cepheids + SNe Ia) and exhibits a difference of 8.4 km s−1 Mpc−1 from the Planck + ΛCDM value. Adding an estimate of the systematic errors (2.8 km s−1 Mpc−1) changes the ∼1.7σ discrepancy with Planck +ΛCDM to ∼1.4σ. Including the systematic errors and performing a bootstrap simulation, we confirm that the local H0 value exceeds the value from the early Universe with a confidence level of 95 per cent. As in this work, we only exchange SNe II for SNe Ia to measure extragalactic distances, we demonstrate that there is no evidence that SNe Ia are the source of the H0 tension.

scholarly journals BAYESIAN ANALYSIS OF THE CHAPLYGIN GAS AND COSMOLOGICAL CONSTANT MODELS USING THE SNe Ia DATA

2004 ◽  
Vol 13 (04) ◽  
pp. 669-693 ◽  
Author(s):  
R. COLISTETE ◽  
J. C. FABRIS ◽  
S. V. B. GONÇALVES ◽  
P. E. DE SOUZA
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Confidence Level ◽  
Cold Dark Matter ◽  
Chaplygin Gas ◽  
Type Ia Supernovae ◽  
Λcdm Model ◽  
Type Ia ◽  
Ia Supernovae ◽  
The Universe

The type Ia supernovae observational data are used to estimate the parameters of a cosmological model with cold dark matter and the Chaplygin gas. This exotic gas, which is characterized by a negative pressure varying with the inverse of density, represents in this model the dark energy responsible for the acceleration of the Universe. The Chaplygin gas model depends essentially on four parameters: the Hubble constant, the velocity of the sound of the Chaplygin gas, the curvature of the Universe and the fraction density of the Chaplygin gas and the cold dark matter. The Bayesian parameter estimation yields [Formula: see text] and [Formula: see text]. These and other results indicate that a Universe completely dominated by the Chaplygin gas is favoured, what reinforces the idea that the Chaplygin gas may unify the description for dark matter and dark energy, at least as the type Ia supernovae data are concerned. A closed and accelerating Universe is also favoured. The Bayesian statistics indicates that the Chaplygin gas model is more likely than the standard cosmological constant (ΛCDM) model at 55.3% confidence level when an integration on all free parameters is performed. Assuming the spatially flat curvature, this percentage mounts to 65.3%. On the other hand, if the density of dark matter is fixed at zero value, the Chaplygin gas model becomes more preferred than the ΛCDM model at 91.8% confidence level. Finally, the hypothesis of flat Universe and baryonic matter (Ωb0=0.04) implies a Chaplygin gas model preferred over the ΛCDM at a confidence level of 99.4%.

Cosmological implications of the dark matter equation of state

2017 ◽  
Vol 26 (03) ◽  
pp. 1750013 ◽  
Author(s):  
Weiqiang Yang ◽  
Hang Li ◽  
Yabo Wu ◽  
Jianbo Lu
Keyword(s):  
Dark Matter ◽  
Equation Of State ◽  
Cold Dark Matter ◽  
Evolution Equations ◽  
State Parameter ◽  
Acoustic Oscillation ◽  
Text Data ◽  
Equation Of State Parameter ◽  
Type Ia ◽  
Ia Supernovae

In this paper, we study a model which is composed of the cosmological constant and dark matter with nonzero equation of state parameter, which could be called as [Formula: see text]wDM. In the synchronous gauge, we obtain the perturbation equations of dark matter, and deduce the evolution equations of growth factor about the dark matter and baryons. Based on the Markov Chain Monte Carlo (MCMC) method, we constrain this model by the recently available cosmic observations which include cosmic microwave background (CMB) radiation, baryon acoustic oscillation (BAO), type Ia supernovae (SNIa) and [Formula: see text] data points from redshift-space distortion (RSD). The results present a tighter constraint on the model than the case without [Formula: see text] data. In 3[Formula: see text] regions, we find the dark matter equation of state parameter [Formula: see text]. The currently available cosmic observations do not favor the nonzero dark matter equation of state parameter, no deviation from the lambda cold dark matter ([Formula: see text]CDM) model is found in 1[Formula: see text] region.

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