相关论文: Shocks in the Early Universe
Scalar fields in the minimal supersymmetric standard model may have large field values during inflation. Because of approximate global symmetry, it is plausible that the phase directions of them are nearly massless during inflation and…
We study the uniqueness and robustness of acoustic signatures in the cosmic microwave background by allowing for the possibility that they are generated by some as yet unknown source of gravitational perturbations. The acoustic {\it…
Several mechanisms exist for generating a stochastic background of gravitational waves in the period following inflation. These mechanisms are generally classical in nature, with the gravitational waves being produced from inhomogeneities…
A stochastic background of gravitational waves can be generated during a cosmological first order phase transition, at least by two distinct mechanisms: collisions of true vacuum bubbles and turbulence in the cosmic fluid. I compare these…
Thermal gravitational waves can be generated in various sources such as, in the cores of stars, white dwarfs and neutron stars due to the fermion collisions in the dense degenerate Fermi gas. Such high frequency thermal gravitational waves…
We study the observable implications of an incomplete first order phase transition during inflation. In such a phase transition, the nucleated bubbles do not percolate and instead are continuously produced until the onset of reheating. The…
Although cosmological observations suggest that the fluctuations of seed fields are almost Gaussian, the possibility of a small deviation of their fields from Gaussianity is widely discussed. Theoretically, there exist numerous inflationary…
The power spectrum of the scalar-tensor inflation with a quadratic form Ricci scalar coupling function $\Omega(\phi)=1- 2\phi/\phi_c+(1+\delta^2)(\phi/\phi_c)^2$ can be enhanced enough to produce primordial black holes and generate…
We consider true vacuum bubbles generated in a first order phase transition occurring during the slow rolling era of a two field inflation: it is known that gravitational waves are produced by the collision of such bubbles. We find that the…
A thermal gravitational wave background can be produced in the early Universe if a radiation dominated epoch precedes the usual inflationary stage. This background provides a unique way to study the initial state of the Universe. We discuss…
Cosmological gravitational wave backgrounds (CGWBs) are the conglomeration of unresolved gravitational wave signals from early Universe sources, which make them a promising tool for cosmologists. Because gravitons decouple from the cosmic…
Spiral shocks are potentially a major source of turbulence in the interstellar medium. To address this problem quantitatively, we use numerical simulations to investigate gas flow across spiral arms in vertically stratified,…
We calculate the gravitational wave background produced from density perturbations in an early matter domination era where primordial black holes form. The formation of black holes requires perturbations out of the linear regime. Space with…
Vacuum bubbles may nucleate and expand during the cosmic inflation. When inflation ends, the bubbles run into the ambient plasma, producing strong shocks followed by underdensity waves, which propagate outwards. The bubbles themselves…
Particle acceleration is expected to take place at shocks that form during the process of large scale structure formation. Electrons accelerated at such shocks can upscatter a small fraction of the photons in the cosmic microwave background…
The primordial bispectrum has been considered in the past decade as a powerful probe of the physical processes taking place in the early Universe. Within the inflationary paradigm, the properties of the bispectrum are one of the keys that…
We consider the stochastic background of gravitational waves produced during the radiation-dominated hot big bang as a constraint on the primordial density perturbation on comoving length scales much smaller than those directly probed by…
The properties of cosmic shock waves are studied through numerical simulations in two cosmological scenarios (SCDM and LCDM). The scaling relations for the average radius and velocity associated with the accretion shocks are somewhat…
Turbulence and turbulent mixing in natural fluids begins with big bang turbulence powered by spinning combustible combinations of Planck particles and Planck antiparticles. Particle prograde accretions on a spinning pair releases 42% of the…
Cosmological inflation generates a spectrum of density perturbations that can seed the cosmic structures we observe today. These perturbations are usually computed as the result of the gravitationally-induced spontaneous creation of…