scholarly journals Supernova constraints on higher-dimensional cosmology with a phantom field

2016 ◽  
Vol 25 (06) ◽  
pp. 1650069
Author(s):  
James Overduin ◽  
Nathan Prins ◽  
Joohan Lee
Keyword(s):  
Narrow Range ◽  
Accelerated Expansion ◽  
Higher Dimensional Cosmology ◽  
Higher Dimensional ◽  
Type Ia ◽  
Ia Supernovae ◽  
Energy Scalar ◽  
The Universe ◽  
Range Of Values ◽  
Rule Out

We use observational data on the magnitude-redshift relation for Type Ia supernovae (SNeIa) together with constraints on the ages of the oldest stars to rule out a higher-dimensional extension of General Relativity with a negative kinetic energy scalar field. This theory is of considerable physical interest because it produces accelerated expansion at both early and late times with a single new field, as in quintessential inflation scenarios. It is also of mathematical interest because it is characterized by an analytic expression for the macroscopic scale factor [Formula: see text]. We show that cosmological solutions of this theory can be usefully parametrized by a single quantity, the lookback time [Formula: see text] corresponding to the transition from deceleration to acceleration. Supernovae data from the recently released Supernova Cosmology Project (SCP) Union 2.1 compilation single out a narrow range of values for [Formula: see text]. In the context of the theory, however, these same values of [Formula: see text] imply that the universe is much older than the oldest observed stars.

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 “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 Dark Energy and Cosmological Constant

2018 ◽  
Vol 17 (1) ◽  
pp. 25-32
Author(s):  
Louise Rebecca ◽  
C Sivaram ◽  
Kenath Arun
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Mass Density ◽  
Critical Density ◽  
Accelerated Expansion ◽  
Microwave Background ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
Ia Supernovae ◽  
The Universe

One of the unresolved problems in cosmology is that the measured mass density of the universe has revealed a value that was about 30% of the critical density. Since the universe is very nearly spatially flat, as is indicated by measurements of the cosmic microwave background, about 70% of the energy density of the universe was left unaccounted for. Another observation seems to be connected to this mystery. Generally one would expect the rate of expansion to slow down once the universe started expanding. The measurements of Type Ia supernovae have revealed that the expansion of the universe is actually accelerating. This accelerated expansion is attributed to the so-called dark energy (DE).Here we give a brief overview on the observational basis for DE hypothesis and how cosmological constant, initially proposed by Einstein to obtain a static universe, can play the role of dark energy.

scholarly journals FITTING THE LUMINOSITY DATA FROM TYPE Ia SUPERNOVAE IN THE FRAME OF THE COSMIC DEFECT THEORY

2009 ◽  
Vol 18 (03) ◽  
pp. 501-512
Author(s):  
A. TARTAGLIA ◽  
M. CAPONE ◽  
V. CARDONE ◽  
N. RADICELLA
Keyword(s):  
Accelerated Expansion ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
The One ◽  
Ia Supernovae ◽  
The Universe ◽  
Good Agreement

The cosmic defect (CD) theory is reviewed and used to fit the data for the accelerated expansion of the universe, obtained from the apparent luminosity of 192 SnIa 's. The fit from the CD theory is compared with the one obtained by means of ΛCDM. The results from the two theories are in good agreement and the fits are satisfactory. The correspondence between the two approaches is discussed and interpreted.

scholarly journals Testing dissipative dark matter in causal thermodynamics

2020 ◽  
pp. 2150032
Author(s):  
Norman Cruz ◽  
Esteban González ◽  
Guillermo Palma
Keyword(s):  
Dark Matter ◽  
Accelerated Expansion ◽  
Model Parameters ◽  
Fitted Parameter ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
Viscous Pressure ◽  
Ia Supernovae ◽  
Parameter Values ◽  
The Universe

In this paper we study the consistency of a cosmological model representing a universe filled with a one-component dissipative dark matter fluid, in the framework of the causal Israel–Stewart theory, where a general expression arising from perturbation analysis for the relaxation time [Formula: see text] is used. This model is described by an exact analytic solution recently found in [N. Cruz, E. González and G. Palma, Gen. Relat. Gravit. 52, 62 (2020), which depends on several model parameters as well as integration constants, allowing the use of Type Ia Supernovae and Observational Hubble data to perform by an astringent observational tests. The constraint regions found for the parameters of the solution allow the existence of an accelerated expansion of the universe at late times, after the domination era of the viscous pressure, which holds without the need of including a cosmological constant. Nevertheless, the fitted parameter values lead to drawbacks as a very large non-adiabatic contribution to the speed of sound, and some inconsistencies, not totally conclusive, with the description of the dissipative dark matter as a fluid, which is nevertheless a common feature of these kind of models.

scholarly journals COSMOLOGICAL CONSTRAINTS FOR THE COSMIC DEFECT THEORY

2011 ◽  
Vol 20 (06) ◽  
pp. 1039-1051 ◽  
Author(s):  
NINFA RADICELLA ◽  
MAURO SERENO ◽  
ANGELO TARTAGLIA
Keyword(s):  
Large Scale ◽  
Hubble Constant ◽  
Big Bang ◽  
Nuclear Species ◽  
Type Ia ◽  
Species Abundances ◽  
Age Of The Universe ◽  
Ia Supernovae ◽  
The Big Bang ◽  
The Universe

The cosmic defect theory has been confronted with four observational constraints: primordial nuclear species abundances emerging from the big bang nucleosynthesis; large scale structure formation in the Universe; cosmic microwave background acoustic scale; luminosity distances of type Ia supernovae. The test has been based on a statistical analysis of the a posteriori probabilities for three parameters of the theory. The result has been quite satisfactory and such that the performance of the theory is not distinguishable from that of the ΛCDM theory. The use of the optimal values of the parameters for the calculation of the Hubble constant and the age of the Universe confirms the compatibility of the cosmic defect approach with observations.

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 Model-independent cosmic acceleration and redshift-dependent intrinsic luminosity in type-Ia supernovae

2019 ◽  
Vol 625 ◽  
pp. A15 ◽  
Author(s):  
I. Tutusaus ◽  
B. Lamine ◽  
A. Blanchard
Keyword(s):  
Spline Interpolation ◽  
High Redshift ◽  
Cosmic Acceleration ◽  
Expansion Rate ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Model Independent ◽  
Ia Supernovae ◽  
The Universe ◽  
Intrinsic Luminosity

Context. The cosmological concordance model (ΛCDM) is the current standard model in cosmology thanks to its ability to reproduce the observations. The first observational evidence for this model appeared roughly 20 years ago from the type-Ia supernovae (SNIa) Hubble diagram from two different groups. However, there has been some debate in the literature concerning the statistical treatment of SNIa, and their stature as proof of cosmic acceleration. Aims. In this paper we relax the standard assumption that SNIa intrinsic luminosity is independent of redshift, and examine whether it may have an impact on our cosmological knowledge and more precisely on the accelerated nature of the expansion of the universe. Methods. To maximise the scope of this study, we do not specify a given cosmological model, but we reconstruct the expansion rate of the universe through a cubic spline interpolation fitting the observations of the different cosmological probes: SNIa, baryon acoustic oscillations (BAO), and the high-redshift information from the cosmic microwave background (CMB). Results. We show that when SNIa intrinsic luminosity is not allowed to vary as a function of redshift, cosmic acceleration is definitely proven in a model-independent approach. However, allowing for redshift dependence, a nonaccelerated reconstruction of the expansion rate is able to fit, at the same level of ΛCDM, the combination of SNIa and BAO data, both treating the BAO standard ruler rd as a free parameter (not entering on the physics governing the BAO), and adding the recently published prior from CMB observations. We further extend the analysis by including the CMB data. In this case we also consider a third way to combine the different probes by explicitly computing rd from the physics of the early universe, and we show that a nonaccelerated reconstruction is able to nicely fit this combination of low- and high-redshift data. We also check that this reconstruction is compatible with the latest measurements of the growth rate of matter perturbations. We finally show that the value of the Hubble constant (H0) predicted by this reconstruction is in tension with model-independent measurements. Conclusions. We present a model-independent reconstruction of a nonaccelerated expansion rate of the universe that is able to fit all the main background cosmological probes nicely. However, the predicted value of H0 is in tension with recent direct measurements. Our analysis points out that a final reliable and consensual value for H0 is critical to definitively prove cosmic acceleration in a model-independent way.

The Berkeley-AAO Distant Supernova Search

1991 ◽  
Vol 9 (2) ◽  
pp. 261-265 ◽  
Author(s):  
W. J. Couch ◽  
S. Perlmutter ◽  
H. J. M. Newburg ◽  
C. Pennypacker ◽  
G. Goldhaber ◽  
...  
Keyword(s):  
Mass Density ◽  
Type Ia Supernovae ◽  
Standard Candle ◽  
Type Ia ◽  
Ia Supernovae ◽  
The Universe

AbstractA search for Type Ia supernovae at cosmological distances is being undertaken in an attempt to exploit their standard candle property to constrain the mass density of the universe. We describe the rationale for such a program, the observational approach and strategy taken, and the progress made to date. The science that is being generated by the project in additional to supernova detection is also discussed briefly.

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