Static Quantities of the W bosons in the MSSM

I discuss the static quantities of the W boson, magnetic dipole and electric quadrupole moments, in the context of the minimal supersymmetric standard model, in which supersymmetry is broken by soft terms $A_o,\, m_o,\, M_{1/2}$. Following a renormalization group analysis it is found that the supersymmetric values of $\Delta k_{\gamma}$ and $\Delta Q_{\gamma}$ can be largely different, in some cases, from the standard model predictions but of the same order of magnitude for values of \quad $A_0,m_0,M_{1/2} \leq {\cal O}(1 TeV)$. Therefore possible supersymmetric structure can be probed provided the accuracy of measurements for $\Delta k_{\gamma}$, $\Delta Q_{\gamma}$ reaches $10^{-2}-10^{-3}$ and hence hard to be detected at LEP2. In cases where $M_{1/2} \ll A_0,m_0$, the charginos and neutralinos may give substantial contributions saturating the LEP2 sensitivity limits. This occurs when their masses $m_{\tilde C},m_{\tilde Z}$ turn out to be both light satisfying $m_{\tilde C}+m_{\tilde Z} \simeq M_W$. However these extreme cases are perturbatively untrustworthy and besides unnatural for they occupy a small region in the parameter space.Comment: 14 pages+2 figures , Latex, uses revtex[aps,aipbook,floats,epsfig] (The two figures in a separate uuencode file ). Talk given at the International Symposium on Gauge Boson self-interactions, UCLA, February 1-3, 1995 Los Angele

Inflation in no-scale supergravity

$R+R^2$ Supergravity is known to be equivalent to standard Supergravity coupled to two chiral supermultiples with a no-scale K\"ahler potential. Within this framework, that can accomodate vanishing vacuum energy and spontaneous supersymmetry breaking, we consider modifications of the associated superpotential and study the resulting models, which, viewed as generalizations of the Starobinsky model, for a range of the superpotential parameters, describe viable single-field slow-roll inflation. In all models studied in this work the tensor to scalar ratio is found to be small, well below the upper bound established by the very recent PLANCK and BICEP2 data.Comment: 15 pages, 6 figures, references and comments adde

Non-critical String Cosmologies

Non-critical String Cosmologies are offered as an alternative to Standard Big Bang Cosmology. The new features encompassed within the dilaton dependent non-critical terms affect the dynamics of the Universe\'s evolution in an unconventional manner being in agreement with the cosmological data. Non-criticality is responsible for a late transition to acceleration at redshifts z=0.2. The role of the uncoupled rolling dilaton to relic abundance calculations is discussed. The uncoupled rolling dilaton dilutes the neutralino relic densities in supersymmetric theories by factors of ten, relaxing considerably the severe WMAP Dark Matter constraints, while at the same time leaves almost unaffected the baryon density in agreement with primordial Nucleosynthesis.Comment: 16 pages, 7 figures, conference tal

Dilaton dominance in the early Universe dilutes Dark Matter relic abundances

The role of the dilaton field and its coupling to matter may result to a dilution of Dark Matter (DM) relic densities. This is to be contrasted with quintessence scenarios in which relic densities are augmented, due to modification of the expansion rate, since Universe is not radiation dominated at DM decoupling. Dilaton field, besides this, affects relic densities through its coupling to dust which tends to decrease relic abundances. Thus two separate mechanisms compete each other resulting, in general, to a decrease of the relic density. This feature may be welcome and can rescue the situation if Direct Dark Matter experiments point towards small neutralino-nucleon cross sections, implying small neutralino annihilation rates and hence large relic densities, at least in the popular supersymmetric scenarios. In the presence of a diluting mechanism both experimental constraints can be met. The role of the dilaton for this mechanism has been studied in the context of the non-critical string theory but in this work we follow a rather general approach assuming that the dilaton dominates only at early eras long before Big Bang Nucleosynthesis.Comment: 11 pages, Latex, 4 figures: Comments and references added, version to appear in Phys. Rev.

Static and non-static quantum effects in two-dimensional dilaton gravity

We study backreaction effects in two-dimensional dilaton gravity. The backreaction comes from an $R^2$ term which is a part of the one-loop effective action arising from massive scalar field quantization in a certain approximation. The peculiarity of this term is that it does not contribute to the Hawking radiation of the classical black hole solution of the field equations. In the static case we examine the horizon and the physical singularity of the new black hole solutions. Studying the possibility of time dependence we see the generation of a new singularity. The particular solution found still has the structure of a black hole, indicating that non-thermal effects cannot lead, at least in this approximation, to black hole evaporation.Comment: 10 pages, no figure

Weak and electromagnetic interactions in the quarkbarton model

This thesis deals with the naive quark parton model as means of explaining deep inelastic scattering phenomena. The formalism of the quark model is reviewed as is the parton model and its main results. The Kuti-Weisskopf quark parton model is introduced and used to make predictions for charged and neutral current neutrino experiments. An attempt is made to improve the Kuti-Weisskopf model predictions and we propose a model in which new hadronic constituents, besides the p,n,λ and charmed p' quarks participate. In this model the new particles are classified in SU(2) triplets of the Weinberg model. Wu an.ilyee charged and neutral current neutrino experiments and construct a model which is a modification of a quark model proposed by R.Mc. Elhaney and S.F. Tuan. In the light of recent work on nonleptonic interactions of the electron we consider both electron positron annihilation and deepinelastic scattering. Finally, we propose a scheme in which "naive quark parton model' techniques can give (logs)(^2) behaviour for the hadronic total cross sections