We present the results of our large scale 4-dimensional (4d) lattice simulations for the MSSM electroweak phase transition (EWPT). We carried out infinite volume and continuum limit extrapolations and found a transition whose strength agrees well with perturbation theory. We determined the properties of the bubble wall that are important for a successful baryogenesis.
We briefly describe the Poor Man's Supercomputer (PMS) project carried out at Eötvös University, Budapest. The goal was to construct a cost effective, scalable, fast parallel computer to perform numerical calculations of physical problems that can be implemented on a lattice with nearest neighbour interactions. To this end we developed the PMS architecture using PC components and designed a special, low cost communication hardware and the driver software for Linux OS. Our first implementation of PMS includes 32 nodes (PMS1). The performance of PMS1 was tested by Lattice Gauge Theory simulations. Using pure SU(3) gauge theory or the bosonic part of the minimal supersymmetric extention of the standard model (MSSM) on PMS1 we obtained 3$ / Mflops and 0.60$ / Mflops price-to-sustained performance ratio for double and single precision operations, respectively. The design of the special hardware and the communication driver are freely available upon request for non-profit organizations.
We present the results of our large scale 4-dimensional (4d) lattice simulations for the MSSM electroweak phase transition (EWPT).We carried out infinite volume and continuum limit extrapolations and found a transition whose strength agrees well with perturbation theory.We determined the properties of the bubble wall that are important for a successful baryogenesis.
The electroweak phase transition provides the most attractive framework to account for the baryon asymmetry of the universe. Comparing results of perturbative and nonperturbative studies is not straightforward, however, due to the different coupling constant definitions. The perturbative one stems from the M̅S̅ subtraction scheme, while the nonperturbative one uses the static quark potential. The momentum-space perturbative static potential is calculated in the SU(2)–Higgs model, and is Fourier transformed into coordinate space. Based on the connection between the coupling constants, two-loop perturbative and 4-dimensional lattice simulation results are contrasted. The thermodynamical parameters of the phase transition indicate that perturbative results are reliable only for low Higgs masses, far from the endpoint. The value of the endpoint can be refined to 72.1±1.4 GeV. The Higgs mass range for which dimensional reduction yields reliable results is identified. As an extension of the standard model, the MSSM is also studied. Some useful trends are indicated by a simple one-loop perturbative approach: baryogenesis requirements are more easily met if the stop is lighter thanthe top; colour-breaking phase transition may be possible, etc. In order to perform 4D nonperturbative studies the supercomputer PMS was built at Eötvös University. The results and the techniques of the simulations of the bosonic sector of the MSSM performed on PMS are presented. A phase diagram is given, the bubble wall is studied. The cosmologically relevant part of the parameter space is analysed. The results show that baryogenesis is possible within the MSSM if m_h≤ 103± 4 GeV.
The goal of the Poor Man's Supercomputer (PMS) project is to construct a cost effective, scalable, fast parallel computer to perform numerical calculations of physical problems that can be implemented on a lattice with nearest neighbour interactions. Our first implementation of PMS was tested by Lattice Gauge Theory simulations. We obtained 3$/Mflop price-to-sustained performance ratio for double precision operations.
We present a one-loop calculation of the static potential in the SU(2)-Higgs model. The connection to the coupling constant definition used in lattice simulations is clarified. The consequences in comparing lattice simulations and perturbative results for finite temperature applications are explored.
We present a one-loop calculation of the static potential in the SU(2)-Higgs model. The connection to the coupling constant definition used in lattice simulations is clarified. The consequences in comparing lattice simulations and perturbative results for finite temperature applications are explored.
