Electroweak Baryogenesis with Cosmic Strings ?

I report on a critical analysis of the scenario of electroweak baryogenesis mediated by nonsuperconducting cosmic strings. This mechanism relies upon electroweak symmetry restoration in a region around cosmic strings, where sphalerons would be unsuppressed. I discuss the various problems this scenario has to face, presenting a careful computation of the sphaleron rates inside the strings, of the chemical potential for chiral number and of the efficiency of baryogenesis in different regimes of string networks. The conclusion is that the asymmetry in baryon number generated by this scenario is smaller than the observed value by at least 10 orders of magnitude.Comment: 5 pages, uses sprocl.sty. Talk given at SEWM98, Dec.98, Copenhage

A Fresh Look at the Calculation of Tunneling Actions including Gravitational Effects

Recently, the calculation of tunneling actions, that control the exponential suppression of the decay of metastable vacua, has been reformulated as an elementary variational problem in field space. This paper extends this formalism to include the effect of gravity. Considering tunneling potentials $V_t(\phi)$ that go from the false vacuum $\phi_+$ to some $\phi_0$ on the stable basin of the scalar potential $V(\phi)$, the tunneling action is the minimum of the functional $S_E[V_t]=6 \pi^2m_P^4\int_{\phi_+}^{\phi_0}(D+V_t')^2/(V_t^2D)d\phi$, where $D\equiv [(V_t')^2+6(V-V_t)V_t/m_P^2]^{1/2}$, $V_t'=dV_t/d\phi$ and $m_P$ is the reduced Planck mass. This one-line simple result applies equally to AdS, Minkowski or dS vacua decays and reproduces the Hawking-Moss action in the appropriate cases. This formalism provides new handles for the theoretical understanding of different features of vacuum decay in the presence of gravity.Comment: 12 pages in double-column format. 8 figures. Small changes, errata fixe

New limits on the mass of neutral Higgses in General Models

In general electroweak models with weakly coupled (and otherwise arbitrary) Higgs sector there always exists in the spectrum a scalar state with mass controlled by the electroweak scale. A new and simple recipe to compute an analytical tree-level upper bound on the mass of this light scalar is given. We compare this new bound with similar ones existing in the literature and show how to extract extra information on heavier neutral scalars in the spectrum from the interplay of independent bounds. Production of these states at future colliders is addressed and the implications for the decoupling limit in which only one Higgs is expected to remain light are discussed.Comment: 14 pages, LaTe

What is the upper limit on the lightest supersymmetric Higgs mass?

In this talk the question of what is the upper bound on the lightest supersymmetric Higgs mass, m_h is addressed. This question is relevant since experimental lower bounds on m_h might implement, in the near future, exclusion of supersymmetry. By imposing (perturbative) unification of the gauge couplings at some high scale \simgt 10^{17} GeV, we have found that for a top-quark mass M_t=175 GeV, and depending on the supersymmetric parameters, this bound can be as high as 205 GeV.Comment: 7 pages, 4 figures, Work presented at PASCOS-98, March 22-29 199