Browsing by Subject "FALSE VACUUM"

Sort by: Order: Results:

Now showing items 1-7 of 7
  • Henriksson, Oscar (2022)
    We study the process of black brane evaporation through the emission of D-branes. Black branes in asymptotically anti-de Sitter spacetimes, holographically dual to field theory states at finite temperature and density, have previously been found to exhibit an instability due to brane nucleation. Working in the setting of D3-branes on the conifold, we construct static Euclidean solutions describing this nucleation to leading order-D3-branes bubbling off the horizon. Furthermore, we analyze the late-time dynamics of such a D3-brane bubble as it expands and find a steady-state solution including the wall profile and its speed.
  • Ares, Feanor Reuben; Henriksson, Oscar; Hindmarsh, Mark; Hoyos, Carlos; Jokela, Niko (2022)
    We discuss the computation of the quantum effective action of strongly interacting field theories using holographic duality and its use to determine quasiequilibrium parameters of first-order phase transitions relevant for gravitational wave production. A particularly simple holographic model is introduced, containing only the metric and a free massive scalar field. Despite the simplicity, the model contains a rich phase diagram, including first-order phase transitions at nonzero temperature, due to various multitrace deformations. We obtain the leading terms in the effective action from homogeneous black brane solutions in the gravity dual and linearized perturbations around them. We then employ the effective action to construct bubble and domain wall solutions in the field theory side and study their properties. In particular, we show how the scaling of the effective action with the effective number of degrees of freedom of the quantum field theory determines the corresponding scaling of gravitational wave parameters.
  • Ares, Feanor Reuben; Henriksson, Oscar; Hindmarsh, Mark; Hoyos, Carlos; Jokela, Niko (2022)
    Using a holographic derivation of a quantum effective action for a scalar operator at strong coupling, we compute quasiequilibrium parameters relevant for the gravitational wave signal from a first-order phase transition in a simple dual model. We discuss how the parameters of the phase transition vary with the effective number of degrees of freedom of the dual field theory. Our model can produce an observable signal at LISA if the critical temperature is around a TeV, in a parameter region where the field theory has an approximate conformal symmetry.
  • Cutting, Daniel; Hindmarsh, Mark; Weir, David J. (2018)
    We conduct large scale numerical simulations of gravitational wave production at a first-order vacuum phase transition. We find a power law for the gravitational wave power spectrum at high wave number which falls off as k(-1.5) rather than the k(-1) produced by the envelope approximation. The peak of the power spectrum is shifted to slightly lower wave numbers from that of the envelope approximation. The envelope approximation reproduces our results for the peak power less well, agreeing only to within an order of magnitude. After the bubbles finish colliding, the scalar field oscillates around the true vacuum. An additional feature is produced in the UV of the gravitational wave power spectrum, and this continues to grow linearly until the end of our simulation. The additional feature peaks at a length scale close to the bubble wall thickness and is shown to have a negligible contribution to the energy in gravitational waves, providing the scalar field mass is much smaller than the Planck mass.
  • Cutting, Daniel; Granados Escartin, Elba Sofia; Hindmarsh, Mark; Weir, David (2021)
    In a vacuum first-order phase transition, gravitational waves are generated from collision of bubbles of the true vacuum. The spectrum from such collisions takes the form of a broken power law. We consider a toy model for such a phase transition, where the dynamics of the scalar field depends on a single parameter (lambda) over bar, which controls how thin the bubble wall is at nucleation and how close to degenerate the vacua are relative to the barrier. We extend on our previous work by performing a series of simulations with a range of (lambda) over bar. The peak of the gravitational-wave power spectrum varies by up to a factor of 1.3, which is probably an unobservable effect. We find that the UV power law in the gravitational-wave spectrum becomes steeper as (lambda) over bar -> 0, varying between k(-1.4) and k(-2.2) for the (lambda) over bar. considered. This provides some evidence that the form of the underlying effective potential of a vacuum first-order phase transition could be determined from the gravitational-wave spectrum it produces.
  • Gould, Oliver; Ho, David L. -J.; Rajantie, Arttu (2019)
    Magnetic monopoles may be produced by the Schwinger effect in the strong magnetic fields of peripheral heavy-ion collisions. We review the form of the electromagnetic fields in such collisions and calculate from first principles the cross section for monopole pair production. Using the worldline instanton method, we work to all orders in the magnetic charge, and hence are not hampered by the breakdown of perturbation theory. Our result depends on the spacetime inhomogeneity through a single dimensionless parameter, the Keldysh parameter, which is independent of collision energy for a given monopole mass. For realistic heavy-ion collisions, the computational cost of the calculation becomes prohibitive and the finite size of the monopoles needs to be taken into account, and therefore our current results are not applicable to them-we indicate methods of overcoming these limitations, to be addressed in further work. Nonetheless, our results show that the spacetime dependence enhances the production cross section and would therefore lead to stronger monopole mass bounds than in the constant-field case.
  • Gould, Oliver; Sukuvaara, Satumaaria; Weir, David (2021)
    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.