The shear viscosity of a two-dimensional (2D) liquid was calculated using equilibrium molecular dynamics simulations with a Yukawa potential. The shear viscosity has a minimum, at a Coulomb coupling parameter Γ of about 17, arising from the temperature dependence of the kinetic and potential contributions. Previous calculations of 2D viscosity were less extensive, and for a different potential....

A new approximation formalism is applied to study the bound states of the Hellmann potential, which represents the superposition of the attractive Coulomb potential −a/r and the Yukawa potential b exp(−δr)/r of arbitrary strength b and screening parameter δ. Although the analytic expressions for the energy eigenvalues En,l yield quite accurate results for a wide range of n, l in the limit of ve...

Integrated forms of the one-loop evolution equations are given for the Yukawa couplings in the MSSM, valid for any value of tan β, generalizable to virtually any number of Yukawa fermions, and including all gauge couplings. These forms turn out to have nice mathematical convergence properties which we prove, and we determine the ensuing convergence criteria. Furthermore, they allow to write dow...

We investigate numerically on the lattice the interplay of universality classes of the threedimensional Yukawa model with U(1) chiral symmetry, using the Binder method of finite size scaling. At zero Yukawa coupling the scaling related to the magnetic Wilson–Fisher fixed point is confirmed. At sufficiently strong Yukawa coupling the dominance of the chiral fixed point associated with the 3D Gro...

The presence of an extra dimension of size R ≡ M−1 c introduces corrections of order (μ/Mc)α to the gauge and Yukawa couplings and accelerates their running at scales μ larger than Mc. This could result in a grand unification scale MX ≈ 20Mc. We study the corrections at the two-loop level. We find corrections of order (μ/Mc)α 2 for the gauge couplings and of order (μ/Mc) 2α2 for the Yukawa coup...

The minimal supersymmetric standard model with complete, partial or no Yukawa unification and radiative electroweak breaking with boundary conditions from the Hořava-Witten theory is considered. The parameters are restricted by constraining the lightest sparticle relic abundance by cold dark matter considerations and requiring the b-quark mass after supersym-metric corrections and the branching...

In the light of the gathering evidence for νμ − ντ neutrino oscillations, coming in particular from the Super-Kamiokande data on atmospheric neutrinos, we re-analyze the unification of gauge and Yukawa couplings within the minimal supersymmetric extension of the Standard Model (MSSM). Guided by a range of different grand-unified models, we stress the relevance of large mixing in the lepton sect...