Practical and Structural Infinitary Expansions

Given a structure $M$ we introduce infinitary logic expansions, which generalise the Morleyisation. We show that these expansions are tame, in the sense that they preserve and reflect both the Embedding Ramsey Property (ERP) and the Modelling Property (MP). We then turn our attention to Scow's theorem connecting generalised indiscernibles with Ramsey classes and show that by passing through infinitary logic, one can obtain a stronger result, which does not require any technical assumptions. We also show that every structure with ERP, not necessarily countable, admits a linear order which is a union of quantifier-free types, effectively proving that any Ramsey structure is ``essentially'' ordered. We also introduce a version of ERP for classes of structures which are not necessarily finite (the finitary-ERP) and prove a strengthening of the Kechris-Pestov-Todorcevic correspondence for this notion.Comment: 22 pages. Minor corrections and rearrangement of sections. Section 8 of the previous version will appear in a separate pape

Generalised Indiscernibles, Dividing Lines, and Products of Structures

Generalised indiscernibles highlight a strong link between model theory and structural Ramsey theory. In this paper, we use generalised indiscernibles as tools to prove results in both these areas. More precisely, we first show that a reduct of an ultrahomogenous $\aleph_0$-categorical structure which has higher arity than the original structure cannot be Ramsey. In particular, the only nontrivial Ramsey reduct of the generically ordered random $k$-hypergraph is the linear order. We then turn our attention to model-theoretic dividing lines that are characterised by collapsing generalised indiscernibles, and prove, for these dividing lines, several transfer principles in (full and lexicographic) products of structures. As an application, we construct new algorithmically tame classes of graphs

Monadic NIP in Monotone Classes of Relational Structures

We prove that for any monotone class of finite relational structures, the first-order theory of the class is NIP in the sense of stability theory if, and only if, the collection of Gaifman graphs of structures in this class is nowhere dense. This generalises results previously known for graphs to relational structures and answers an open question posed by Adler and Adler (2014). The result is established by the application of Ramsey-theoretic techniques and shows that the property of being NIP is highly robust for monotone classes. We also show that the model-checking problem for first-order logic is intractable on any monotone class of structures that is not (monadically) NIP. This is a contribution towards the conjecture that the hereditary classes of structures admitting fixed-parameter tractable model-checking are precisely those that are monadically NIP

Stratégies d'ancêtre commun pour les réseaux RPL multi-chemins

National audienceThe IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) networks is designed for Internet of Things (IoT) networks to generate routes between devices with minimal processing. This protocol creates a DODAG (Destination Oriented Directed Acyclic Graph) network topology through the use of DODAG Information Object (DIO) control packets. The DODAG routes the data packets upstream to the destination device. In order to obtain a reliable network, we implement Packet Replication and Elimination (PRE) to perform multi-path data transmission via multiple parent devices. However, there is no standard way to select an alternative path. This document presents three types of Alternative Parent (AP) selection following a braided model. We focus on analyzing its performance in terms of delay and compromise between network traffic and reliability.Le protocole de routage IPv6 pour les réseaux à faible puissance et fort taux de pertes (RPL) est conçu pour les réseaux Internet des objets (IoT) afin de générer des itinéraires entre les appareils avec un traitement minimal. Ce protocole crée une topologie de réseau DODAG (Destination Oriented Directed Acyclic Graph) grâce à l'utilisation de paquets de contrôle DODAG Information Object (DIO). Le DODAG achemine les paquets de données en amont vers le périphérique de destination. Afin d'obtenir un réseau fiable, nous implémentons la réplication et l'élimination des paquets (PRE) pour effectuer une transmission de données à chemins multiples via plusieurs périphériques parents. Cependant, il n'existe aucun moyen standard de sélectionner un chemin alternatif. Ce document présente trois types de sélection de parent alternatif (AP) suivant un modèle triangulaire. Nous nous concentrons sur l'analyse de ses performances en termes de retard et de compromis entre trafic réseau et fiabilité

On the High TT Phase Transition in the Gauged SU(2)SU(2) Higgs Model

We study the effective field theory of a weakly coupled 3+1d gauged $\phi^4$ type model at high temperature. Our model has $4N$ real scalars ($N$ complex Higgs doublets) and a gauge group $SU(2)$ which is spontaneously broken by a nonzero scalar field $vev$ at zero temperature. We find, for sufficiently large $N$, that the transition from the high temperature symmetry restoring phase to the low temperature phase can be either first order or second order depending on the ratio of the gauge coupling to the scalar self coupling.Comment: 16 pages. 1 Figure, not include

The complete radiative corrections to the gaugino and Higgsino masses in the Minimal Supersymmetric Model

We determine the radiative corrections to the masses of the gauginos and Higgsinos in the MSSM, including all sectors of the theory in a one-loop calculation in the on-mass-shell renormalization scheme. We find that a gluino which is massless at tree level receives a mass of between 0 and 3 GeV, primarily due to the top/stop contribution. This radiatively generated mass depends directly on the off-diagonal element of the squark mass matrix. In the case of a massive gluino, its mass receives typically large corrections, as large as 40\% for a 125 GeV gluino. We find that the contributions to the neutralino and chargino mass corrections from the gauge/Higgs/gaugino/Higgsino sector are typically +-1%. The lightest neutralino, which can receive corrections larger than 25%, receives 5% corrections over most of the parameter space. We combine our results with the results of LEP and CDF searches to obtain the lower bounds on the neutralino and chargino masses at one-loop. We also demonstrate how the radiative corrections affect the presently excluded region of parameter space.Comment: 16 pages, JHU-TIPAC-940001, PURD-TH-94-04. 6 uuencoded postscript figures included. Uncomment the line "%\input epsf" to embed the figures in the tex

First Order Phase Transition in a Two Higgs-doublet Model with Mh>MWM_{h}>M_{W}

We study the 3d effective field theory of a weakly coupled two Higgs-doublet scalar model at high temperature. Our model has three scalar quartic couplings and an $O(4)$ symmetry which is spontaneously broken by a nonzero scalar field $vev$ at zero temperature. Using high temperature perturbation theory, renormalization group arguments in $4-\epsilon$ dimensions, as well as $1/N$ expansion techniques in 3 dimensions, we argue that the transition from the high temperature symmetry restoring phase to the low temperature phase is first order for a range of scalar couplings. This result is not due to gauge couplings. We discuss the implications of our results for baryogenesis in the two Higgs-doublet electroweak model, especially when the lightest neutral Higgs is heavier than the W--bosons.Comment: 15 page

Radiative Corrections to Neutralino and Chargino Masses in the Minimal Supersymmetric Model

We determine the neutralino and chargino masses in the MSSM at one-loop. We perform a Feynman diagram calculation in the on-shell renormalization scheme, including quark/squark and lepton/slepton loops. We find generically the corrections are of order 6%. For a 20 GeV neutralino the corrections can be larger than 20%. The corrections change the region of $\mu,\ M_2,\ \tan\beta$ parameter space which is ruled out by LEP data. We demonstrate that, e.g., for a given $\mu$ and $\tan\beta$ the lower limit on the parameter $M_2$ can shift by 20 GeV.Comment: 11 pages, JHU-TIPAC-930030, PURD-TH-93-13, uses epsf.sty, 6 uuencoded postscript figures, added one sentence and a referenc

Radiative corrections to the Higgs boson decay rate Γ(H→ZZ)\Gamma(H\rightarrow ZZ) in the minimal supersymmetric model

We consider radiative corrections to the decay rate $\Gamma(H\rightarrow ZZ)$ of the heavy {\it CP}-even Higgs boson of the minimal supersymmetric model to two $Z$ bosons. We perform a one loop Feynman diagram calculation in the on-mass-shell renormalization scheme, and include the third generation of quarks and squarks. The tree level rate is suppressed by a mixing angle factor and decreases as $1/M_H$ for large $M_H$. The corrected rate overcomes this suppression and increases with $M_H$ for $M_H > 500$~GeV. The corrections can be very large and depend in detail on the top squark masses and $A$-term, as well as the supersymmetric Higgs mass parameter $\mu$.Comment: 22 pages, 9 figures available from authors, UCB-PTH-92/23 and LBL-3249