相关论文: Cosmic Acceleration from Elementary Interactions
Gamma rays trace accelerated particles, and the observed flux of extragalactic gamma rays therefore constrains the global efficiency for particle acceleration. Extragalactic jets in active galactic nuclei can account for the gamma ray…
These lecture notes cover some of the theoretical topics associated with cosmic acceleration. Plausible explanations to cosmic acceleration include dark energy, modified gravity and a violation of the Copernican principle. Each of these…
Generally making the cosmological scale factor $R$ be a function of the coordinate of the extra dimension $\sigma $ that is also a function of time $t$, we achieve a new kind of cosmic acceleration mechanism depending on extra dimension. We…
A new model of nonlinear electromagnetic fields possessing a dimensional parameter $\beta$ is proposed. Electromagnetic fields are considered as the source of the gravitation field and accelerated expansion of the universe is driven by…
Particles of the cosmic radiation, electrons and nuclei, transport a dominant positive electric charge. A tiny fraction of these particles of extremely high energies in favorable conditions overflow from galaxies. The overflowing of…
A web of interlocking observations has established that the expansion of the Universe is speeding up and not slowing, revealing the presence of some form of repulsive gravity. Within the context of general relativity the cause of cosmic…
We consider a simplified model of quantum gravity using a mini-superspace description of an isotropic and homogeneous universe with dust. We derive the corresponding Friedmann equations for the scale factor, which now contain a dependence…
We argue that the occurrence of late-time acceleration can conveniently be described by first-order general relativity covariantly coupled to fermions. Dark energy arises as a Bardeen-Cooper-Schrieffer condensate of fermions which forms in…
Observations of large-scale radio emissions prove the existence of shock accelerated cosmic-ray electrons in galaxy clusters, while the lack of detected $\gamma$-rays limits the acceleration of cosmic-ray protons in galaxy clusters. This…
This is a short overview of spatially flat (or open) four-dimensional accelerating cosmologies for some simple exponential potentials obtained by string or M theory compactification on some non-trivial curved spaces, which may lead to some…
Recent astrophysical observations indicate that the universe is composed of a large amount of dark energy (DE) responsible for an accelerated expansion of the universe, along with a sizeable amount of cold dark matter (CDM), responsible for…
Cosmology is undergoing an explosive period of activity, fueled both by new, accurate astrophysical data and by innovative theoretical developments. Cosmological parameters such as the total density of the Universe and the rate of…
It is shown that an accelerating expansion of the present-day Universe extracted from observed luminosity of the type Ia supernovae can be explained by quantum theory which takes into account feedback coupling between geometry and matter…
Laboratory experiments to explore plasma conditions and stimulated particle acceleration can illuminate aspects of the cosmic particle acceleration process. Here we discuss the cosmic-ray candidate source object variety, and what has been…
The accelerating expansion of the universe presents an exciting, fundamental challenge to the standard models of particle physics and cosmology. I highlight some of the outstanding challenges in both developing theoretical models and…
It is proved that in order to obtain a model of the accelerated cosmic expansion the thing one only need to do is to add a perturbation term to the Einstein-Hilbert Lagrangian. This term leads to some symmetry breaking terms in the fields…
Observations of distant supernovae indicate that the Universe is now in a phase of accelerated expansion the physical cause of which is a mystery. Formally, this requires the inclusion of a term acting as a negative pressure in the…
We discuss how a cosmological magnetic field could affect the expansion of the universe, through its interaction with the spacetime geometry. The tension of the field lines means that the magneto-curvature coupling tends to accelerate…
To describe dark energy we introduce a fluid model with no free parameter on the microscopic level. The constituents of this fluid are massless particles which are a dynamical realisation of the unextended $D=(3+1)$ Galilei algebra. These…
There is no single mechanism by which fast particles are accelerated in astrophysical environments, and it is now recognized that the data require a rich variety of different mechanisms operating under different conditions. The mechanisms…