Palaeomagnetic stratigraphy of pliocene continental deposits of the bolivian Altiplano

Les dépots fluviolacustres post-Miocène de l'Altiplans bolivien ont été échantillonnés sur une section de 400 m. dans les bassins de la Paz et de Ayo Ayo. Leur étude permet d'établir un schéma magnétostratigraphique pour des interprétations chonostratigraphiques

Warped Unification, Proton Stability and Dark Matter

Many extensions of the Standard Model have to face the problem of new unsuppressed baryon-number violating interactions. In supersymmetry, the simplest way to solve this problem is to assume R-parity conservation. As a result, the lightest supersymmetric particle becomes stable and a well-motivated dark matter candidate. In this paper, we show that solving the problem of baryon number violation in non supersymmetric grand unified theories (GUT's) in warped higher-dimensional spacetime can lead to a stable Kaluza-Klein particle. This exotic particle has gauge quantum numbers of a right-handed neutrino, but carries fractional baryon-number and is related to the top quark within the higher-dimensional GUT. A combination of baryon-number and SU(3) color ensures its stability. Its relic density can easily be of the right value for masses in the 10 GeV--few TeV range. An exciting aspect of these models is that the entire parameter space will be tested at near future dark matter direct detection experiments. Other exotic GUT partners of the top quark are also light and can be produced at high energy colliders with distinctive signatures.Comment: 4 pages, 4 figures; v2: some comments added, figures updated; v3: Final version to appear in Phys. Rev. Let

Gravitational Waves from Warped Spacetime

We argue that the RSI model can provide a strong signature in gravitational waves. This signal is a relic stochastic background generated during the cosmological phase transition from an AdS-Schwarschild phase to the RS1 geometry that should occur at a temperature in the TeV range. We estimate the amplitude of the signal in terms of the parameters of the potential stabilizing the radion and show that over much of the parameter region in which the phase transition completes, a signal should be detectable at the planned space interferometer, LISA.Comment: 18 pages, 15 figures; v2: discussion improved, in particular on the justification of the thick wall approximation. 6 figures added. 4 pi factor corrected in perturbativity bound. N-dependence displayed. Conclusions unchanged. JHEP versio

Dirac Neutrino Dark Matter

We investigate the possibility that dark matter is made of heavy Dirac neutrinos with mass in the range [O(1) GeV- a few TeV] and with suppressed but non-zero coupling to the Standard Model Z as well as a coupling to an additional Z' gauge boson. The first part of this paper provides a model-independent analysis for the relic density and direct detection in terms of four main parameters: the mass, the couplings to the Z, to the Z' and to the Higgs. These WIMP candidates arise naturally as Kaluza-Klein states in extra-dimensional models with extended electroweak gauge group SU(2)_L* SU(2)_R * U(1). They can be stable because of Kaluza-Klein parity or of other discrete symmetries related to baryon number for instance, or even, in the low mass and low coupling limits, just because of a phase-space-suppressed decay width. An interesting aspect of warped models is that the extra Z' typically couples only to the third generation, thus avoiding the usual experimental constraints. In the second part of the paper, we illustrate the situation in details in a warped GUT model.Comment: 35 pages, 25 figures; v2: JCAP version; presentation and plots improved, results unchange

Chiral Compactification on a Square

We study quantum field theory in six dimensions with two of them compactified on a square. A simple boundary condition is the identification of two pairs of adjacent sides of the square such that the values of a field at two identified points differ by an arbitrary phase. This allows a chiral fermion content for the four-dimensional theory obtained after integrating over the square. We find that nontrivial solutions for the field equations exist only when the phase is a multiple of \pi/2, so that this compactification turns out to be equivalent to a T^2/Z_4 orbifold associated with toroidal boundary conditions that are either periodic or anti-periodic. The equality of the Lagrangian densities at the identified points in conjunction with six-dimensional Lorentz invariance leads to an exact Z_8\times Z_2 symmetry, where the Z_2 parity ensures the stability of the lightest Kaluza-Klein particle.Comment: 28 pages, latex. References added. Clarifying remarks included in section 2. Minor corrections made in section

Effet de la matrice de l'eau sur l'élimination des micropolluants organiques par ozonation. Partie 1. Consommation spécifique de l'ozone dans un réacteur

A partir des réactions possibles entre l'ozone, les radicaux et les principaux composants d'une eau à potabiliser, des formules théoriques de formations de radicaux et de décomposition de l'ozone sont établies. La matière organique est schématisée par les composés qui réagissent avec l'ozone (Si), les initiateurs, les promoteurs et les inhibiteurs de la réaction radicalaire (SIi, Sp,i, Ss,i). La décomposition de l'ozone est ensuite mesurée pour 56 eaux naturelles caractérisées par les analyses suivantes (pH, Absorbance à 254 nm, COT, Alcalinité). En se basant sur les connaissances acquises et les valeurs expérimentales du taux spécifique de consommation de l'ozone w, l'équation théorique est simplifiée et on obtient:-(d[O3]/dt)=([O3](∑kDlSl,i)(∑klDP,i[SP,i])) / ([HCO3-](k9+k10 10pH-10,25))En prenant le COT comme représentatif des [Sp,i] (attaque radicalaire non sélective) et l'absorbance à 254 nm comme representative de SI,i (attaque directe sur les cycles aromatiques), une analyse multifactorielle permet d'obtenir l'expression:log10w = -3,93 + 0,24pH + 0,75 log10 Absorbance à 254 mm + 1,08 log10 COT - 0,19 log10 alcalinitéL'équation ainsi obtenue peut être utilisée dans tous les modèles prédictifs faisant appel aux bilans massiques sur l'oxydant.From the numerous reactions between ozone and other components of raw water in a drinking water plant, we obtain theoretical equations for hydroxy radical concentrations (1) and for the disappearance of ozone (2). Dissolved organic matter is divided in to four components: substances which react with ozone by a direct mechanism (Si), initiators, promotors, and scavengers ofradical reactions (SI,i, SP,i, SS,i). We also take into account the reactions between hydrogen peii*iâô. orThe, and free radicals to simulate advanced oxidation processes.[OH∘]= ([O3]{2k1∙10pH-14+2k2 10pH-11,6 [H2O2] + ∑kdl,i [Sl,i]}) / (klD[P]+[HCO3-] (k9+k10∙10pH-10,25)+∑klDS,i [Ss,i])   (1)-(d[O3])/(dt) = {kD[P]+∑kD,i[Si]+∑kDl,i[Sl,i]+3k110pH-14+k210pH-11,6H2O2]}[O3]+[OH∘]{k8[O3]+[H2O2](k210pH-11,6+K7)+∑klDP,i[SP,i]   (2)For 56 natural water samples, we measured the disappearence of ozone directly in a completely stirred batch reactor. Water samples were characterized by pH, TOC, 254 nm UV absorbance and alkalinity. Kinetics were first order with respect to ozone(d[O3])/(dt) = -w[O3]with w : specific ozone disappearence rate.Each term of equation 2 is discussed and, based on the experimental values of w, a simplified equation 3 obtained :-(d[O3])/(dt) = ([O3](∑kDISl,i)(∑klDP,i[SP,i))/([HCO3](k9+k10 10pH-10,25))The TOC parameter can represent [SP,i] because radical reactions are non selective, where as the 254 nm UV absorbance can represent [Si] because organic matter (Fulvic and Humic acid) can react directly with ozone via its constituent aromatic rings.Using the data set of 56 w values measured in natual water samples, mathematical correlations can be calculated :log10w = -3,93 + 0,24pH + 0,75 log10 Absorbance à 254 mm + 1,08 log10 COT - 0,19 log10 alcalinityA strong correlation between experimental measurements and predicted w values is obtained

Cosmological Expansion in the Presence of an Extra Dimension

It has recently been pointed out that global solutions of Einstein's equations for a 3-brane universe embedded in 4 spatial dimensions give rise to a Friedmann equation of the form H ~ rho on the brane, instead of the usual H ~ (rho)^{1/2}, which is inconsistent with cosmological observations. We remedy this problem by adding cosmological constants to the brane and the bulk, as in the recent scenario of Randall and Sundrum. Our observation allows for normal expansion during nucleosynthesis, but faster than normal expansion in the very early universe, which could be helpful for electroweak baryogenesis, for example.Comment: 4pp, latex, 1 figure; added and corrected references; revised incorrect argument about sign of action on brane; final version to be published in PR

TeV Symmetry and the Little Hierarchy Problem

Constraints from precision electroweak measurements reveal no evidence for new physics up to 5 - 7 TeV, whereas naturalness requires new particles at around 1 TeV to address the stability of the electroweak scale. We show that this "little hierarchy problem" can be cured by introducing a symmetry for new particles at the TeV scale. As an example, we construct a little Higgs model with this new symmetry, dubbed T-parity, which naturally solves the little hierarchy problem and, at the same time, stabilize the electroweak scale up to 10 TeV. The model has many important phenomenological consequences, including consistency with the precision data without any fine-tuning, a stable weakly-interacting particle as the dark matter candidate, as well as collider signals completely different from existing little Higgs models, but rather similar to the supersymmetric theories with conserved R-parity.Comment: 15 pages, 1 figure; v.2: typos corrected and various minor modifications/expansions on the presentations. now 16 pages and 1 figure. version to appear on JHE

An Introduction to Extra Dimensions

Models that involve extra dimensions have introduced completely new ways of looking up on old problems in theoretical physics. The aim of the present notes is to provide a brief introduction to the many uses that extra dimensions have found over the last few years, mainly following an effective field theory point of view. Most parts of the discussion are devoted to models with flat extra dimensions, covering both theoretical and phenomenological aspects. We also discuss some of the new ideas for model building where extra dimensions may play a role, including symmetry breaking by diverse new and old mechanisms. Some interesting applications of these ideas are discussed over the notes, including models for neutrino masses and proton stability. The last part of this review addresses some aspects of warped extra dimensions, and graviton localization.Comment: 39 pages. Two figures. Comments and references added. Lectures given at the XI Mexican School of Particles and Fields. Xalapa, Mexico, August 1-13, 200

Cosmological Consequences of Nearly Conformal Dynamics at the TeV scale

Nearly conformal dynamics at the TeV scale as motivated by the hierarchy problem can be characterized by a stage of significant supercooling at the electroweak epoch. This has important cosmological consequences. In particular, a common assumption about the history of the universe is that the reheating temperature is high, at least high enough to assume that TeV-mass particles were once in thermal equilibrium. However, as we discuss in this paper, this assumption is not well justified in some models of strong dynamics at the TeV scale. We then need to reexamine how to achieve baryogenesis in these theories as well as reconsider how the dark matter abundance is inherited. We argue that baryonic and dark matter abundances can be explained naturally in these setups where reheating takes place by bubble collisions at the end of the strongly first-order phase transition characterizing conformal symmetry breaking, even if the reheating temperature is below the electroweak scale $\sim 100$ GeV. We also discuss inflation as well as gravity wave smoking gun signatures of this class of models.Comment: 22 pages, 7 figure