Related papers: Supernova observations fit Einstein-deSitter expan…

The Hubble relation between distance and redshift is a purely cosmographic relation that depends only on the symmetries of a FLRW spacetime, but does not intrinsically make any dynamical assumptions. This suggests that it should be possible…

We derive for the first time the form of the spiral null geodesics around the photon sphere of the Reissner-Nordstrom black hole in the de Sitter expanding universe. Moreover, we obtain the principal parameter we need for deriving,…

The unexpected faintness of high-redshift Type Ia supernovae (SNe Ia), as measured by two teams, has been interpreted as evidence that the expansion of the Universe is accelerating. We review the current challenges to this interpretation…

The coming decade will be an exciting period for dark energy research, during which astronomers will address the question of what drives the accelerated cosmic expansion as first revealed by type Ia supernova (SN) distances, and confirmed…

I review the use of Type Ia supernovae (SNe Ia) for cosmological distance determinations. Low-redshift SNe Ia (z <~ 0.1) demonstrate that the Hubble expansion is linear, that H_0 = 65 +/- 2 (statistical) km/s/Mpc, and that the properties of…

Although big bang cosmology effectively models even the most puzzling observational data, it offers no insight into why the cosmological expansion should occur at all. In this paper it is suggested that a finite Universe poses particular…

The acceleration of the cosmic expansion is a fundamental challenge to standard models of particle physics and cosmology. The new physics of dark energy may lie in the nature of gravity, the quantum vacuum, or extra dimensions. I give a…

The large-scale dynamics of the universe is generally described in terms of the time-dependent scale factor $a(t)$. To make contact with observational data, the $a(t)$ function needs to be related to the observable $z(r)$ function, redshift…

The explanation of the accelerated expansion of the Universe poses one of the most fundamental questions in physics and cosmology today. If the acceleration is driven by some form of dark energy, one can try to constrain the parameters…

We perform a number of inter-related cosmographic fits to the legacy05 and gold06 supernova datasets. We pay particular attention to the influence of both statistical and systematic uncertainties, and also to the extent to which the choice…

The expansion of the Universe is accelerating, as testified by observations of supernovae of type Ia as a function of redshift. Explanations are of two types: modifications of Einstein gravity or new forms of energy, coined dark energy.The…

Several key relations are derived for Cosmological General Relativity which are used in standard observational cosmology. These include the luminosity distance, angular size, surface brightness and matter density. These relations are used…

Subject of this contribution is to demonstrate that the observed faintness of the supernovae at the high redshift can be considered as a manifestation of quantum effects at cosmological scales. We show that observed redshift distribution of…

Supernovae are bright luminous stellar objects observable up to redshifts close to z~1. They are used to probe the geometry of the Universe and its expansion rate by applying different methods. In this article, I review various approaches…

We extend and apply a model-independent analysis method developed earlier by Daly & Djorgovski to new samples of supernova standard candles, radio galaxy and cluster standard rulers, and use it to constrain physical properties of the dark…

Recent observations in cosmology indicate an accelerating expansion of the universe postulated to arise from some form of dark energy, the paradigm being positive cosmological constant. De Sitter spacetime is the well-known isotropic…

The discovery of cosmic acceleration is one of the most important developments in modern cosmology. The observation, thirteen years ago, that type Ia supernovae appear dimmer that they would have been in a decelerating universe followed by…

We consider ever-expanding Big Bang models with a cosmological constant, $\Lambda$, and investigate in detail the evolution of the observable part of the universe. We also discuss quintessence models from the same point of view. A new…

In this thesis the cosmological constant is investigated from two points of view. First, we study the influence of a time-dependent cosmological constant on the late-time expansion of the universe. Thereby, we consider several combinations…

Recent observations of high-redshift supernovae seem to suggest that the global geometry of the Universe may be affected by a `cosmological constant', which acts to accelerate the expansion rate with time. But these data by themselves still…