Problème de la hiérarchie

Résumé

En physique théorique, le problème de la hiérarchie concerne la divergence considérable entre les propriétés de la force faible et celles de la force gravitationnelle. Il n'y a aucun consensus scientifique sur ses causes, par exemple pourquoi la force faible est 10 fois plus intense que la gravitation ? Définition technique Un problème de hiérarchie apparaît quand la valeur fondamentale d'un paramètre physique, tel qu'une constante de couplage ou une masse, dans un lagrangien est profondément différente de sa valeur mesurée (dite « effective ») lors d'une expérience. Ceci est dû au fait que la valeur effective est reliée à la valeur fondamentale par le principe de renormalisation, qui lui applique des corrections quantiques. En général, la valeur renormalisée des paramètres physiques est proche de la valeur fondamentale, mais dans certains cas, il arrive que la correction quantique donne un résultat incohérent avec cette valeur fondamentale. Les problèmes de hiérarchie so

Source officielle

https://fr.wikipedia.org/wiki/Probl%C3%A8me_de_la_hi%C3%A9rarchie

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (23)

Publications associées

Chargement

Personnes associées (2)

Personnes associées

Chargement

Unités associées (2)

Unités associées

Chargement

Concepts associés (37)

Concepts associés

Chargement

Cours associés (5)

Presentation of the electroweak and strong interaction theories that constitute the Standard Model of particle physics. The course also discusses the new theories proposed to solve the problems of the Standard Model.

Supersymmetry is the unique quantum extension of the symmetry principles of relativity. This course offers a first but broad introduction covering the role of Supersymmetry in our understanding of both physics beyond the Standard Model and non-perturbative phenomena in quantum field theory.

The goal of this course is to explain the conceptual and mathematical bases of the Standard Model of fundamental interactions and to illustrate in detail its phenomenological consequences.

Afficher plus

Cours associés

Chargement

Séances de cours associées (6)

Séances de cours associées

Chargement

Asymptotic scale invariance and its consequences

Kengo Shimada

Scale invariance supplemented by the requirement of the absence of new heavy particles may play an important role in addressing the hierarchy problem. We discuss how the Standard Model may become scale invariant at the quantum level above a certain value of the Higgs field value without addition of new degrees of freedom and analyze phenomenological and cosmological consequences of this setup, in particular, possible metastability of the electroweak vacuum and Higgs inflation.

AMER PHYSICAL SOC2019

Chargement

Naturalness and Neutral Naturalness in the LHC Era

Davide Greco

We present two different approaches to solve the hierarchy problem of the Standard Model and to provide a consistent dynamical mechanism for electroweak symmetry breaking. As a first scenario, we follow the naturalness paradigm as realized in Composite Higgs theories, which conceive the Higgs particle as a bound state of a new strongly interacting sector confining at the TeV scale. We present a minimal implementation of the model and study in detail the phenomenology of vector resonances, which are predicted as states excited from the vacuum by the conserved currents of the new strong dynamics. This analysis allows us to derive constraints on the parameter space of Composite Higgs models from the presently available LHC data and to confront naturalness with experimental results. Motivated by the rising tension between theoretical expectations and the absence of new physics signals at the LHC, we consider as a second possibility the neutral naturalness paradigm and address the hierarchy problem by posing the existence of a mirror copy of the Standard Model, as realized in Twin Higgs theories. This new color-blind sector is the main actor in protecting the Higgs mass from large radiative corrections and is un-discoverable at the LHC, allowing us to push far in the ultraviolet the scale where the Standard Model effective theory breaks down and colored resonances appear. We present an implementation of the Twin Higgs program into a composite model and discuss the requirements for uplifting the symmetry protection mechanism also to the ultraviolet theory. After introducing a consistent Composite Twin Higgs model, we consider the constraints imposed on the scale where colored resonances are expected by the determination of the Higgs mass at three loops order, electroweak precision tests and perturbativity of the ultraviolet-complete model. We show that, although allowing in principle the new physics scale to lie far out of the LHC reach, these constructions need the existence of light colored top partners, with a mass of around 2-4 TeV, to comply with indirect observations. Neutral naturalness models may then evade detection at the LHC, but they can be probed and falsified at future colliders.

EPFL2017

Chargement

In theories with a large number N of particle species, black hole physics imposes an upper bound on the mass of the species equal to M-Planck/root N. This bound suggests a novel solution to the hierarchy problem in which there are N approximate to 10(32) gravitationally coupled species, for example 10(32) copies of the standard model. The black hole bound forces them to be at the weak scale, hence providing a stable hierarchy. We present various arguments, that in such theories the effective gravitational cutoff is reduced to Lambda(G)approximate to M-Planck/root N and a new description is needed around this scale. In particular, black holes smaller than Lambda(-1)(G) are already no longer semiclassical. The nature of the completion is model dependent. One natural possibility is that Lambda(G) is the quantum gravity scale. We provide evidence that within this type of scenarios, contrary to the standard intuition, micro-black-holes have a (slowly fading) memory of the species of origin. Consequently, the black holes produced at LHC will predominantly decay into the standard model particles, and negligibly into the other species.

2008

Chargement

Naturalness and Neutral Naturalness in the LHC Era

Davide Greco

EPFL2017