相关论文: The age problem in $\Lambda$CDM model

Cosmic chronometers may be used to measure the age difference between passively evolving galaxy populations to calculate the Hubble parameter H(z). The age estimator emerges from the relationship between the amplitude of the rest frame…

In the Large Magellanic Cloud (LMC), there have been very few clusters observed with ages between 4 and 11 Gyr. This phenomenon is sometimes referred to as the `LMC age gap'. We constructed a model of the cluster age distribution aimed at…

We report the results of a study exploring the stellar populations of 13 luminous (L>L*), spectroscopically confirmed, galaxies in the redshift interval 5.5<z<6.5, all with WFC3/IR and IRAC imaging from the HST/CANDELS and Spitzer/SEDS…

Models with variable-mass particles, called VAMPs, have been proposed as a solution to the cosmic coincidence problem that plagues dark energy models. In this contribution we make a short description of this class of models and explore some…

The standard $\Lambda$CDM model provides an excellent fit to current cosmological observations but suffers from a potentially serious Boltzmann Brain problem. If the universe enters a de Sitter vacuum phase that is truly eternal, there will…

If Omega_tot = 1 and structure formed from adiabatic initial conditions then the age of the Universe, as constrained by measurements of the cosmic microwave background (CMB), is t_0=14.0 +/- 0.5 Gyr. The uncertainty is surprisingly small…

We consider a cosmological model in which a fraction $f$ of the Dark Matter (DM) is allowed to decay in an invisible relativistic component, and compute the resulting constraints on both the decay width (or inverse lifetime) $\Gamma$ and…

We use the age measurements of 114 old astrophysical objects (OAO) in the redshift range $0\lesssim z\lesssim 8$ to explore the Hubble tension. The age of the Universe at any $z$ is inversely proportional to the Hubble constant, $H_0$, so…

Our intuitive understanding of cosmic structure formation works best in scales small enough so that bound, relaxed gravitating systems are no longer adjusting their radius; and large enough so that space and matter follow the average…

We discuss the cosmological degeneracy between the Hubble parameter H(z), the age of the universe and cosmological parameters describing simple variations from the minimal LCDM model. We show that independent determinations of the Hubble…

The ages of globular clusters inferred from observations depends sensitively on assumptions like the initial helium abundance and the mass loss rate. A high helium abundance (e.g., $Y\approx$0.28) or a mass loss rate of…

We analyze the stellar populations of the Canis Major stellar over-density, using quantitative color-magnitude diagram (CMD) fitting techniques. The analysis is based on photometry obtained with the Wide Field Imager at the 2.2m telescope…

We present a new method to compute stellar ages in Globular Clusters (GC) that is ten times more precise than the traditional isochrone fitting procedure. The method relies on accurate stellar evolutionary tracks and on photometry for GCs…

We present a new algorithm that can reconstruct the full distributions of metric components within the class of spherically symmetric dust universes that may include a cosmological constant. The algorithm is capable of confronting this…

The epoch of galaxy formation provides an important additional test of cosmological theories. Cold-dark-matter (CDM) models with cosmological constant ($\Lambda$) are designed to account for the observed excess power in galaxy distribution,…

The age of globular clusters inferred from observations depends sensitively on assumptions such as the initial helium abundance and the mass loss rate. A high helium abundance (e.g., $Y\approx$0.28), as well as an inclusion of helium…

From observations at low and high redshifts, it is well known that the bulk of dark matter (DM) has to be stable or at least very long-lived. However, the possibility that a small fraction of DM is unstable or that all DM decays with a…

The absence of guidance from fundamental physics about the mechanism behind cosmic acceleration has given rise to a number of alternative cosmological scenarios. These are based either on modifications of general relativistic gravitation…

In this paper, we combine the latest observational data, including the WMAP five-year data (WMAP5), BOOMERanG, CBI, VSA, ACBAR, as well as the Baryon Acoustic Oscillations (BAO) and Type Ia Supernoave (SN) "Union" compilation (307 sample)…

VAMP (variable-mass particles) scenarios, in which the mass of the cold dark matter particles is a function of the scalar field responsible for the present acceleration of the Universe, have been proposed as a solution to the cosmic…