Gravitational waves from a supercooled electroweak phase transition and their detection with pulsar timing arrays

We investigate the properties of a stochastic gravitational wave background produced by a first-order electroweak phase transition in the regime of extreme supercooling. We study a scenario whereby the percolation temperature that signifies the completion of the transition, $T_p$, can be as low as a few MeV (nucleosynthesis temperature), while most of the true vacuum bubbles are formed much earlier at the nucleation temperature, $T_n\sim 50$ GeV. This implies that the gravitational wave spectrum is mainly produced by the collisions of large bubbles and characterised by a large amplitude and a peak frequency as low as $f \sim 10^{-9}-10^{-7}$ Hz. We show that such a scenario can occur in (but not limited to) a model based on a non-linear realisation of the electroweak gauge group, such that the Higgs vacuum configuration is altered by a cubic coupling. In order to carefully quantify the evolution of the phase transition of this model over such a wide temperature range, we go beyond the usual fast transition approximation, taking into account the expansion of the Universe as well as the behaviour of the nucleation probability at low temperatures. Our computation shows that there exists a range of parameters for which the gravitational wave spectrum lies at the edge between the exclusion limits of current pulsar timing array experiments and the detection band of the future Square Kilometre Array observatory.Comment: 20 pages, 3 figures. V2: references added and corrections to match published versio

Low temperature electroweak phase transition in the Standard Model with hidden scale invariance

We discuss a cosmological phase transition within the Standard Model which incorporates spontaneously broken scale invariance as a low-energy theory. In addition to the Standard Model fields, the minimal model involves a light dilaton, which acquires a large vacuum expectation value (VEV) through the mechanism of dimensional transmutation. Under the assumption of the cancellation of the vacuum energy, the dilaton develops a very small mass at 2-loop order. As a result, a flat direction is present in the classical dilaton-Higgs potential at zero temperature while the quantum potential admits two (almost) degenerate local minima with unbroken and broken eletroweak symmetry. We found that the cosmological electroweak phase transition in this model can only be triggered by a QCD chiral symmetry breaking phase transition at low temperatures, $T\lesssim 132$ MeV. Furthermore, unlike the standard case, the universe settles into the chiral symmetry breaking vacuum via a first-order phase transition which gives rise to a stochastic gravitational background with a peak frequency $\sim 10^{-8}$ Hz as well as triggers the production of approximately solar mass primordial black holes. The observation of these signatures of cosmological phase transitions together with the detection of a light dilaton would provide a strong hint of the fundamental role of scale invariance in particle physics

Intégration d'éoliennes dans le GridLab

Intégration du modèle d’éolienne de l’HES-SO au Gridlab afin d’étudier l’injection d’énergie dans le réseau BT. Pilotage du modèle d’éolienne en temps réel par l’application de mesures physiques

Two new species of Distaplia (Tunicata: Ascidiacea) from the SW Atlantic, Argentina

The ascidian fauna from the Southwestern Atlantic (Argentine Sea) have scarcely been studied and have rarely been sampled. The existing scanty ascidian records are from specimens collected by dredging many decades ago. During samplings in the San Matias Gulf (Río Negro, Patagonia), two new Distaplia species were found. Distaplia naufragii sp. nov. was collected in the subtidal zone attached to a shipwreck, while the other species, Distaplia fortuita sp. nov. was found released by the tides in the sandy intertidal zone. These two new species differ deeply from each other in the size and morphology of their zooids. They represent one third of the known species belonging to the family Holozoidae in the SW Atlantic. These results reinforce the importance of new studies in this extensive but little explored area that is, in addition, susceptible to invasion by non-native species.Fil: Lagger, Cristian Fabian. Universidad Nacional de Cordoba. Facultad de Cs.exactas Fisicas y Naturales. Departamento de Diversidad Biologica y Ecologica. Cat.de Ecologia Marina; ArgentinaFil: Tatian, Marcos. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Instituto de Diversidad y Ecologia Animal; Argentin

Egg-guarding behaviour in the Antarctic bathydraconid dragonfish Parachaenichthys charcoti

This paper provides the first photographic evidence of nest-guarding posture in the Antarctic bathydraconid Parachaenichthys charcoti in its natural habitat. Because bathydraconids are not monophyletic and P. charcoti is included in a different clade than Gymnodraco acuticeps, there is now documentation of nest guarding in all major clades of Antarctic notothenioids except for the Artedidraconidae.Fil: Barrera Oro, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Lagger, Cristian Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentin

Cosmological phase transitions in the Standard Model with hidden scale invariance

The Standard Model of particle physics is minimally extended by a dilaton field. This field expresses the spontaneous breaking of scale invariance of an unspecified ultraviolet complete theory. While being manifestly scale invariant at the classical level, the low energy theory admits quantum scale anomaly responsible for the generation of mass scales. In addition to predicting a very small dilaton mass, this model has important consequences for the cosmology of the early universe. The electroweak phase transition can only be triggered by the QCD chiral phase transition occurring around 132 MeV. Since the QCD transition is expected to be first order in this picture, such a scenario gives rise to the production of stochastic gravitational waves with a peak frequency around ∼ 10−8 Hz

Der Beitrag von evangelischen Religionslehrerinnen und Religionslehrern zur Friedenserziehung

Friedensbildung steht im engen Zusammenhang mit Friedenserziehung und Friedenspädagogik. Die Vorteile der Einführung des Begriffs Friedensbildung in die pädagogische Diskussion werden dargestellt und in der Charakterisierung von fünf Dimensionen von Friedensbildung Subjektorientierung, Prozessorientierung, Dialogorientierung, Sachorientierung und Kompetenzorientierung – zusammengefasst. Die Internationalen Dekaden der Vereinten Nationen und des Ökumenischen Rates der Kirchen sollen eine Kultur des Friedens nachhaltig beeinflussen. Die Vorstellung der Intentionen und Materialien bieten Anknüpfungspunkte für friedensbildendes Lernen. Im Bereich der schulischen Bildung sind aktuell Bildungsstandards und Kompetenzen in Entwicklung, welche die Lernergebnisse und erworbenen Fähigkeiten, Fertigkeiten, von Schülerinnen und Schülern beschreiben. Auch die religiöse Kompetenz kommt dabei in den Blick und bietet bereits erste Forschungsergebnisse aus Deutschland. Der Erwerb von Friedenskompetenz wird als bedeutender Anteil religiöser Bildung herausgearbeitet. Der Beitrag des Evangelischen Religionsunterrichts zur Friedensbildung wird durch die Betrachtung und Erörterung von besonderen Organisationsmodellen im Religionsunterricht und von Rahmenbedingungen wie Lehrplan und Lehrerbildung dargestellt. Friedensbildungsstandards für den Evangelischen Religionsunterricht in Österreich werden für die 4., 8. und 12. Schulstufe erarbeitet und vorgelegt. Die fünf Dimensionen von Friedensbildung bilden die Grundlage dafür. Der Evangelische Religionsunterricht dient als Beispiel für demokratische Schulkultur ohne strukturelle Gewalt und fördert eine Kultur des Friedens.Peace-education distinguishes two different words in German; “Friedenserziehung” and “Friedenspädagogik”. Both don’t express the meaning. The advantages of the introduction of a new term “Friedensbildung” into the pedagogical discussion were exposed and comprised in characterizing five dimensions of peace-education: subject-orientation, process-orientation, dialog-orientation, content-orientation and competence-orientation. The international decades of the United Nations and the Ecumenical Council of the Churches should influence a culture of peace sustainable. The presentation of the intentions and the materials offer starting-points for peaceful education. Actually in the field of school-building are standards and competences in formation, which describe the outcomes and outputs of students. Also the religious competence comes into the view and offers already first results from research in Germany. Peace-competence is generated as important part of religious education. The contribution to peace-education of Protestant Religious Education is presented by the consideration and discussion of special models of Religious Education and structural conditions like curriculum and teacher education. Standards for peace-building for Protestant Religious Education in Austria at stage 4, 8 and 12 were elaborated and submitted. The five dimensions of peace-education are the basis therefore. The Protestant Religious Education serves as an example for democratic school-culture without structural violence and promotes a culture of peace

Magnetization models for particle-based simulations of magnetorheological fluids

In this study, three-dimensional particle-based simulations are used to model magnetorheological fluids. The numerical model of the MRF is implemented in the framework of the Discrete Element Method (DEM) and takes into account the coupling of the magnetic dipoles, the hydrodynamic drag forces and steric forces between particles. To accurately treat the magnetic interaction between particles, the magnetic field at the particles’ position is computed and an appropriate magnetization model is implemented. DEM simulations with different volume fractions of the MRF are carried out and the resulting magnetization curves are put in comparison with experimental data