Real time simulations and the electroweak phase transition

We review recent developments in real-time simulations of SU(2)-Higgs theory near the electroweak transition and related topics.Comment: 6 pages, latex, 4 figures; to appear in the proceedings of LATTICE '9

Cold Electroweak Baryogenesis

We present arguments that the CKM CP-violation in the standard model may be sufficient for the generation of the baryon asymmetry, if the electroweak transition in the early universe was of the cold, tachyonic, type after electroweak-scale inflation. A model implementing this is described which complies with the CMB constraints and which is falsifiable with the LHC. Numerical simulations of the tachyonic transition with an effective CP-bias indicate that the observed baryon asymmetry can be generated this way.Comment: 10 pages, 4 figures, presented at Strong and ElectroWeak Matter 200

Simulations in Early Universe Theory

We give an impression of the type of results that have been obtained with numerical lattice simulations of field theory in the early universe.Comment: 19 pages, contribution to Lattice 200

Classical issues in electroweak baryogenesis

In one scenario of baryogenesis, the matter-antimatter asymmetry was generated in the early universe during a cold electroweak transition. We model this transition by changing the sign of the effective mass-squared parameter of the Higgs field from positive to negative. The resulting `tachyonic' instability leads to a rapid growth of occupation numbers, such that a classical approximation can be made in computing subsequent developments in real time. We solve the classical equations of motion in the SU(2)-Higgs model under the influence of effective CP-violation. The resulting baryon asymmetry follows from the generated Chern-Simons number using the anomaly equation. The `classical' difficulties with lattice implementations of these observables are avoided here because the fields are smooth on the lattice scale.Comment: Proceedings Lattice 2003 (Higgs), 3 pages; added reference

Simulations of Cold Electroweak Baryogenesis: Dependence on Higgs mass and strength of CP-violation

Cold electroweak baryogenesis was proposed as a scenario to bypass generic problems of electroweak baryogenesis within the Standard Model. In this scenario, baryogenesis takes place during an electroweak symmetry breaking transition, which is also responsible for preheating after inflation. In the simplest modelling of the scenario, only two parameters remain undetermined: The Higgs mass and the strength of CP violation. Using full real-time lattice simulations, we compute the dependence of the asymmetry on these parameters.Comment: 14 pages, 13 figure

Chern-Simons Diffusion Rate near the Electroweak Phase Transition for mH≈mWm_H \approx m_W

The rate of $B$-violation in the standard model at finite temperature is closely related to the diffusion rate $\Gamma$ of Chern-Simons number. We compute this rate for $m_H \approx m_W$ in the classical approximation in an effective SU(2)-Higgs model, using Krasnitz's algorithm. The parameters in the effective hamiltonian are determined by comparison with dimensional reduction. In the high temperature phase we find $\Gamma/V (\alpha_W T)^4 \approx 1$, neglecting a finite renormalization. In the low temperature phase near the transition we find the rate to be much larger than might be expected from previous analytic calculations based on the sphaleron.Comment: 23 pages, 8 Postscript figures, uses epsf.st

No strong coupling regime in the fermion-Higgs sector of the standard model

We present results for the renormalized quartic self-coupling \lm_R and the renormalized Yukawa coupling $y_R$ in a fermion-Higgs model with two SU(2) doublets, indicating that these couplings are not very strong.Comment: 4 pages, 4 postscript figures (appended), ITFA-92-32, HLRZ-92-92, UCSD/PTH 92-43, Contribution to the Conference Lattice'9

Chern-Simons number asymmetry from CP violation at electroweak tachyonic preheating

We consider the creation of non-zero Chern-Simons number in a model of the early Universe, where the Higgs field experiences a fast quench at the end of inflation and subsequently rolls down its potential barrier. Neglecting the expansion, we perform numerical lattice simulations in the Abelian Higgs model in 1+1 dimensions with an added phenomenological C and P violating term during this stage of so-called tachyonic preheating. The results suggest that even the sign of the Chern-Simons and thus baryon number is dependent on the ratio of the Higgs to W mass. We also discuss the appropriate choice of vacuum initial conditions for classical simulations.Comment: 24 pages, 17 figures, added references, published versio