The effective potential and the renormalisation group

We discuss renormalisation group improvement of the effective potential both in general and in the context of $O(N)$ scalar \p^4 and the Standard Model. In the latter case we find that absolute stability of the electroweak vacuum implies that $m_H\geq 1.95m_t-189~GeV$, for \as (M_Z) = 0.11. We point out that the lower bound on $m_H$ {\it decreases\/} if \as (M_Z) is increased.Comment: 22 pages plus three PostScript figures (appended), Liverpool preprint LTH 288, University of Michigan preprint UM-TH-92-2

Can the Electroweak Symmetry-breaking Sector Be Hidden?

In a recent paper, Chivukula and Golden claimed that the electroweak symmetry--breaking sector could be hidden if there were many inelastic channels in the longitudinal $WW$ scattering process. They presented a model in which the $W$'s couple to pseudo--Goldstone bosons, which may be difficult to detect experimentally. Because of these inelastic channels, the $WW$ interactions do not become strong in the TeV region. We demonstrate that, despite the reduced $WW$ elastic amplitudes in this model, the total event rate ($\sim 5000$ extra longitudinal $W^+W^-$ pairs produced in one standard SSC year) does not decrease with an increasing number of inelastic channels, and is roughly the same as in a model with a broad high--energy resonance and no inelastic channels.Comment: 10 pages, phyzzx, JHU-TIPAC-92001

Multi-scale Renormalization

The Standard MS renormalization prescription is inadequate for dealing with multi-scale problems. To illustrate this we consider the computation of the effective potential in the Higgs-Yukawa model. It is argued that it is natural to employ a two-scale renormalization group. We give a modified version of a two-scale scheme introduced by Einhorn and Jones. In such schemes the beta functions necessarily contain potentially large logarithms of the RG scale ratios. For credible perturbation theory one must implement a large logarithms resumation on the beta functions themselves. We show how the integrability condition for the two RG equations allows one to perform this resummation.Comment: 8 pages, Standard LaTe

Rigid invariance as derived from BRS invariance: The abelian Higgs model

Consequences of a symmetry, e.g.\ relations amongst Green functions, are renormalization scheme independently expressed in terms of a rigid Ward identity. The corresponding local version yields information on the respective current. In the case of spontaneous breakdown one has to define the theory via the BRS invariance and thus to construct rigid and current Ward identity non-trivially in accordance with it. We performed this construction to all orders of perturbation theory in the abelian Higgs model as a prelude to the standard model. A technical tool of interest in itself is the use of a doublet of external scalar ``background'' fields. The Callan-Symanzik equation has an interesting form and follows easily once the rigid invariance is established.Comment: 33 pages, Plain Te

K\"ahler-driven Tribrid Inflation

We discuss a new class of tribrid inflation models in supergravity, where the shape of the inflaton potential is dominated by effects from the K\"ahler potential. Tribrid inflation is a variant of hybrid inflation which is particularly suited for connecting inflation with particle physics, since the inflaton can be a D-flat combination of charged fields from the matter sector. In models of tribrid inflation studied so far, the inflaton potential was dominated by either loop corrections or by mixing effects with the waterfall field (as in "pseudosmooth" tribrid inflation). Here we investigate the third possibility, namely that tribrid inflation is dominantly driven by effects from higher-dimensional operators of the K\"ahler potential. We specify for which superpotential parameters the new regime is realized and show how it can be experimentally distinguished from the other two (loop-driven and "pseudosmooth") regimes.Comment: 28 pages, v2: added some references, this version matches the publication in JCA

CP violation in gauge theories

We define the CP transformation properties of scalars, fermions and vectors in a gauge theory and show that only three types of interactions can lead to CP violation: scalar interactions, fermion-scalar interactions and $F \tilde F$ associated with the strong CP problem and which involve only the gauge fields. For technicolor theories this implies the absence of CP violation within perturbation theory.Comment: 5 pages, 1 figure, revtex and epsf require

A screening mechanism for extra W and Z gauge bosons

We generalize a previous construction of a fermiophobic model to the case of more than one extra $W$ and $Z$ gauge bosons. We focus in particular on the existence of screening configurations and their implication on the gauge boson mass spectrum. One of these configurations allows for the existence of a set of relatively light new gauge bosons, without violation of the quite restrictive bounds coming from the $\rho_{\rm NC}$ parameter. The links with Bess and degenerate Bess models are also discussed. Also the signal given here by this more traditional gauge extension of the SM could help to disentangle it from the towers of Kaluza-Klein states over $W$ and $Z$ gauge bosons in extra dimensions.Comment: 23 pages, 1 figure, extended discussion on precision tests. To appear in International Journal of Modern Physics

Instantons of Type IIB Supergravity in Ten Dimensions

A family of SO(10) symmetric instanton solutions in Type IIB supergravity is developed. The instanton of least action is a candidate for the low-energy, semiclassical approximation to the {D=--1} brane. Unlike a previously published solution,[GGP] this admits an interpretation as a tunneling amplitude between perturbatively degenerate asymptotic states, but with action twice that found previously. A number of associated issues are discussed such as the relation between the magnetic and electric pictures, an inversion symmetry of the dilaton and the metric, the $R\times S^9$ topology of the background, and some properties of the solution in an "instanton frame" corresponding to a Lagrangian in which the dilaton's kinetic energy vanishes.Comment: 15 pages, no figures; Version 2 has revised sections IV and V. Earlier equations are essentially unchanged, but interpretation changed, on advice of counse

Phytoalexines et réactions de défense de la tomate aux infections par PHYTOPHTHORA PARASITICA et VERTICILLIUM ALBO-ATRUM

Deux cultivars de tomates de phénotype Saint-Pierre, isogéniques pour la résistance à la verticilliose et différents par celle au mildiou (et à PHYTOPHTHORA PARASITICA Dast.), sont inoculés par P. PARASITICA et par VERTICILLIUM ALBO-ATRUM Reinke et Berth. Aux réactions de défense correspond l'accumulation, dans les tissus, de sesquiterpènes, de composés phénoliques, de tomatine et de dérivés oxygénés de linoléate de méthyle. Les synthèses de ces substances chez l'hôte sont modulées selon les cultivars et les parasites confrontés. Les études d'inhibition in vitro de P. PARASITICA révèlent une importante synergie entre des diénols d'une part, et des produits phénoliques et la tomatine d'autre part

Inflation with Non-minimal Gravitational Couplings and Supergravity

We explore in the supergravity context the possibility that a Higgs scalar may drive inflation via a non-minimal coupling to gravity characterised by a large dimensionless coupling constant. We find that this scenario is not compatible with the MSSM, but that adding a singlet field (NMSSM, or a variant thereof) can very naturally give rise to slow-roll inflation. The inflaton is necessarily contained in the doublet Higgs sector and occurs in the D-flat direction of the two Higgs doublets.Comment: 13 pages, 1 figur