5 research outputs found
Breakdown of Universality in Random Matrix Models
We calculate smoothed correlators for a large random matrix model with a
potential containing products of two traces \tr W_1(M) \cdot \tr W_2(M) in
addition to a single trace \tr V(M). Connected correlation function of
density eigenvalues receives corrections besides the universal part derived by
Brezin and Zee and it is no longer universal in a strong sense.Comment: 16 pages, LaTex, references and footnote adde
Singular Vertices and the Triangulation Space of the D-sphere
By a sequence of numerical experiments we demonstrate that generic
triangulations of the sphere for contain one {\it singular}
simplex. The mean number of elementary simplices sharing this
simplex increases with the volume of the triangulation according to a simple
power law. The lower dimension subsimplices associated with this
simplex also show a singular behaviour. Possible consequences for the
DT model of four-dimensional quantum gravity are discussed.Comment: 15 pages, 9 figure
String Effects in the Wilson Loop: a high precision numerical test
We test numerically the effective string description of the infrared limit of
lattice gauge theories in the confining regime. We consider the 3d Z(2) lattice
gauge theory, and we define ratios of Wilson loops such that the predictions of
the effective string theory do not contain any adjustable parameters. In this
way we are able to obtain a degree of accuracy high enough to show
unambiguously that the flux--tube fluctuations are described, in the infrared
limit, by an effective bosonic string theory.Comment: 19 pages, LaTeX file + two .eps figure
Neutral Heavy Leptons and Electroweak Baryogenesis
We investigate the possibility that baryogenesis occurs during the weak phase
transition in a minimal extension of the Standard Model which contains extra
neutral leptons and conserves total lepton number. The necessary CP-violating
phases appear in the leptonic Yukawa couplings. We compute the CP-asymmetries
in both the neutral and the charged lepton fluxes reflected on the bubble wall.
Using present experimental bounds on the mixing angles and Standard Model
estimates for the parameters related to the scalar potential, we conclude that
it seems unlikely to produce the observed baryon to entropy ratio within this
type of models. We comment on the possibility that the constraints on the
mixings might be naturally relaxed due to small finite temperature effects.Comment: 21 pages (4 Figures
Electroweak baryogenesis and low energy supersymmetry
Electroweak baryogenesis is an interesting theoretical scenario, which
demands physics beyond the Standard Model at energy scales of the order of the
weak boson masses. It has been recently emphasized that, in the presence of
light stops, the electroweak phase transition can be strongly first order,
opening the window for electroweak baryogenesis in the MSSM. For the
realization of this scenario, the Higgs boson must be light, at the reach of
the LEP2 collider. In this article, we compute the baryon asymmetry assuming
the presence of non-trivial CP violating phases in the parameters associated
with the left-right stop mixing term and the Higgsino mass . We conclude
that a phase and Higgsino and gaugino mass
parameters , and of the order of the electroweak scale, are
necessary in order to generate the observed baryon asymmetry.Comment: 20 pages, latex + psfig, 3 figure