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We predict the polarization of cosmic microwave background (CMB) photons that results from a cosmic bubble collision. The polarization is purely E-mode, symmetric around the axis pointing towards the collision bubble, and has several salient features in its radial dependence that can help distinguish it from a more conventional explanation for unusually cold or hot features in the CMB sky. The anomalous cold spot detected by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite is a candidate for a feature produced by such a collision, and the Planck satellite and other proposed surveys will measure the polarization on it in the near future. The detection of such a collision would provide compelling evidence for the string theory landscape.
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We study strongly supercooled cosmological phase transitions. We perform numerical lattice simulations of two-bubble collisions and demonstrate that, depending on the scalar potential, in the collision the field can either bounce to a false vacuum or remain oscillating around the true vacuum. We study if these cases can be distinguished from their gravitational wave signals and discuss the possibility of black hole formation in the bubble collisions.
We study the magnetic fields generation from the cosmological first-order electroweak phase transition. We calculate the magnetic field induced by the variation of the Higgs phase for two bubbles and three bubbles collisions. Our study shows that electromagnetic currents in the collision direction produce the ring-like magnetic field in the intersect regions of colliding bubbles, which may seed the primordial magnetic field that are constrained by intergalatic field observations.
We comprehensively study the effects of bubble wall thickness and speed on the gravitational wave emission spectrum of collisions of two vacuum bubbles. We numerically simulate a large dynamical range, making use of symmetry to reduce the dimensionality. The high-frequency slope of the gravitational wave spectrum is shown to depend on the thickness of the bubble wall, becoming steeper for thick-wall bubbles, in agreement with recent fully 3+1 dimensional lattice simulations of many-bubble collisions. This dependence is present, even for highly relativistic bubble wall collisions. We use the reduced dimensionality as an opportunity to investigate dynamical phenomena which may underlie the observed differences in the gravitational wave spectra. These phenomena include `trapping, which occurs most for thin-wall bubbles, and oscillations behind the bubble wall, which occur for thick-wall bubbles.
We study large scale structure in the cosmology of Coleman-de Luccia bubble collisions. Within a set of controlled approximations we calculate the effects on galaxy motion seen from inside a bubble which has undergone such a collision. We find that generically bubble collisions lead to a coherent bulk flow of galaxies on some part of our sky, the details of which depend on the initial conditions of the collision and redshift to the galaxy in question. With other parameters held fixed the effects weaken as the amount of inflation inside our bubble grows, but can produce measurable flows past the number of efolds required to solve the flatness and horizon problems.
We study the nucleation of a quark gluon plasma (QGP) phase in a hadron gas at low temperatures and high baryon densities. This kind of process will presumably happen very often in nuclear collisions at FAIR and NICA. When the appropriate energy densities (or baryon densities) and temperatures are reached the conversion of one phase into another is not instantaneous. It is a complex process, which involves the nucleation of bubbles of the new phase. One important element of this transition process is the rate of growth of a QGP bubble. In order to estimate it we solve the Relativistic Rayleigh$-$Plesset equation which governs the dynamics of a relativistic spherical bubble in a strongly interacting medium. The baryon rich hadron gas is represented by the nonlinear Walecka model and the QGP is described by the MIT bag model and also by a mean field model of QCD.
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