In this paper,massive particles' Hawking radiation via tunneling from cosmological horizon of a(3+1)-dimensional de Sitter spacetime is investigated.According to Parikh's theory,when a particle tunnels across ...In this paper,massive particles' Hawking radiation via tunneling from cosmological horizon of a(3+1)-dimensional de Sitter spacetime is investigated.According to Parikh's theory,when a particle tunnels across the cos-mological horizon,the effective geometry is Schwarzschild-de Sitter spacetime.In this effective spacetime,a massiveparticle can be treated as a de Broglie S-wave.WKB method is used.The emission spectrum is obtained,and it takesthe same functional form as that of massless particles.展开更多
Recent type Ia supernovas data seemingly favor a dark energy model whose equation of state w（z） crosses -1 very recently, which is a much more amazing problem than the acceleration of the universe. In this paper we ...Recent type Ia supernovas data seemingly favor a dark energy model whose equation of state w（z） crosses -1 very recently, which is a much more amazing problem than the acceleration of the universe. In this paper we show that it is possible to realize such a crossing without introducing any phantom component in a Gauss-Bonnet brane worm with induced gravity, where a four-dimensional curvature scalar on the brahe and a five-dimensional Gauss-Bonnet term in the bu/k are present. In this realization, the Gauss-Bonnet term and the mass parameter in the bulk play a crucial role.展开更多
The quantum properties of O（2,2） string cosmology with a dilaton potential are studied in this paper. The cosmological solutions are obtained on three-dlmensional space-time. Moreover, the quantum probability of tra...The quantum properties of O（2,2） string cosmology with a dilaton potential are studied in this paper. The cosmological solutions are obtained on three-dlmensional space-time. Moreover, the quantum probability of transition between two duality universe is calculated through a Wheeler-De Witt approach.展开更多
From recent observational data two significant directions have been made in the field of theoretical cosmology recently. First, we are now able to make use of present observations, such as the Planck and BICEP2 data, ...From recent observational data two significant directions have been made in the field of theoretical cosmology recently. First, we are now able to make use of present observations, such as the Planck and BICEP2 data, to examine theoretical predictions from the standard inflationary ACDM which were made decades of years ago. Second, we can search for new cosmological signatures as a way to explore physics beyond the standard cosmic paradigm. In particular, a subset of early universe models admit a nonsingular bouncing solution that attempts to address the issue of the big bang singularity. These models have achieved a series of considerable developments in recent years, in particular in their perturbative frameworks, which made brand-new predictions of cosmological signatures that could be visible in current and forthcoming observations. Herein we present two representative paradigms of early universe physics. The first is the reputed new matter （or matter-ekpyrotic） bounce scenario in which the universe starts with a matter-dominated contraction phase and transitions into an ekpyrotic phase. In the setting of this paradigm, we have proposed some possible mechanisms of generating a red tilt for primordial curvature perturbations and confront the general predictions with recent cosmological observations. The second is the matter-bounce inflation scenario which can be viewed as an extension of inflationary cosmology with a matter contraction before inflation. We present a class of possible model constructions and review the implications on the current CMB experiments. Lastly a review of significant achievements of these paradigms beyond the inflationary ACDM model is made, which is expected to shed new light on the future direction of observational cosmology.展开更多
基金supported by National Natural Science Foundation of China under Grant Nos.10873003the National Basic Research Programm of China under Grant No.2007CB815405the Natural Science Foundation of Guangdong Province under Grant No.7301224
文摘In this paper,massive particles' Hawking radiation via tunneling from cosmological horizon of a(3+1)-dimensional de Sitter spacetime is investigated.According to Parikh's theory,when a particle tunnels across the cos-mological horizon,the effective geometry is Schwarzschild-de Sitter spacetime.In this effective spacetime,a massiveparticle can be treated as a de Broglie S-wave.WKB method is used.The emission spectrum is obtained,and it takesthe same functional form as that of massless particles.
文摘Recent type Ia supernovas data seemingly favor a dark energy model whose equation of state w（z） crosses -1 very recently, which is a much more amazing problem than the acceleration of the universe. In this paper we show that it is possible to realize such a crossing without introducing any phantom component in a Gauss-Bonnet brane worm with induced gravity, where a four-dimensional curvature scalar on the brahe and a five-dimensional Gauss-Bonnet term in the bu/k are present. In this realization, the Gauss-Bonnet term and the mass parameter in the bulk play a crucial role.
基金The project supported by the Natural Science Foundation of Sichuan Normal University
文摘The quantum properties of O（2,2） string cosmology with a dilaton potential are studied in this paper. The cosmological solutions are obtained on three-dlmensional space-time. Moreover, the quantum probability of transition between two duality universe is calculated through a Wheeler-De Witt approach.
基金supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Department of Physics at McGill
文摘From recent observational data two significant directions have been made in the field of theoretical cosmology recently. First, we are now able to make use of present observations, such as the Planck and BICEP2 data, to examine theoretical predictions from the standard inflationary ACDM which were made decades of years ago. Second, we can search for new cosmological signatures as a way to explore physics beyond the standard cosmic paradigm. In particular, a subset of early universe models admit a nonsingular bouncing solution that attempts to address the issue of the big bang singularity. These models have achieved a series of considerable developments in recent years, in particular in their perturbative frameworks, which made brand-new predictions of cosmological signatures that could be visible in current and forthcoming observations. Herein we present two representative paradigms of early universe physics. The first is the reputed new matter （or matter-ekpyrotic） bounce scenario in which the universe starts with a matter-dominated contraction phase and transitions into an ekpyrotic phase. In the setting of this paradigm, we have proposed some possible mechanisms of generating a red tilt for primordial curvature perturbations and confront the general predictions with recent cosmological observations. The second is the matter-bounce inflation scenario which can be viewed as an extension of inflationary cosmology with a matter contraction before inflation. We present a class of possible model constructions and review the implications on the current CMB experiments. Lastly a review of significant achievements of these paradigms beyond the inflationary ACDM model is made, which is expected to shed new light on the future direction of observational cosmology.
