Higgs cosmology

In the case of a metastable electroweak vacuum the quantum corrected effective potential plays a crucial role in the potential instability of the Standard Model. In the Early Universe, in particular during inflation and reheating, this instability can be triggered leading to catastrophic vacuum decay. In this talk Markkanen discusses in detail how the large spacetime curvature of the Early Universe can be incorporated in the calculation and in many cases significantly modify the flat space prediction. The two key new elements are the unavoidable generation of the non-minimal coupling between the Higgs field and the scalar curvature of gravity and a curvature induced contribution to the running of the constants. For the minimal set up of the Standard Model and a decoupled inflation sector Markkanen shows how a metastable vacuum can lead to very tight bounds for the non-minimal coupling.

Dr Tommi Markkanen, King's College London, UK

Dr Tommi Markkanen, King's College London, UK

Tommi Markkanen completed his PhD in theoretical physics at the University of Helsinki in 2015. His thesis focused on applying the framework of quantum field theory on a curved background to models of cosmological inflation. He has then been a visitor at Imperial College London and is currently a postdoc at King's College London. His research interests broadly lie in the area of particle cosmology, in particular electroweak vacuum stability in the early Universe.

Data from LHC experiments suggest that the standard model is in a near-critical regime, offering the possibility that the physical electroweak vacuum state is unstable. Gies’ group critically re-examine conventional perturbative arguments and show that the stability bound on the Higgs mass depend on the largely unknown details of the short distance physics within the standard model. The group determine new standard model stability bounds from nonperturbative RG flows as a functional of the short-distance action, relaxing conventional stability bounds. Gies shows that a metastability of the Higgs potential also has to be encoded in the short distance properties of the standard model. Studying the nonperturbative RG flow of metastable potentials gives us access to the quantum phase diagram of the model as well as to the interplay of false vacuum decay and convexity of the effective potential.

Professor Holger Gies, Friedrich-Schiller-Universität Jena, Germany

Professor Holger Gies, Friedrich-Schiller-Universität Jena, Germany

Holger Gies’s work focuses on quantum field theory and its applications to particle physics, many-body physics and gravity. He is specifically interested in the question of how long-range properties of physical systems arise from quantum fluctuations of microscopic degrees of freedom of the underlying theory. Holger Gies is a professor of quantum theory at the University of Jena, where he is also a member of the Helmholtz Institute Jena. Previous to this, he was heading an Emmy Noether research group at the University of Heidelberg. Gies also worked as an Emmy Noether fellow at CERN. He obtained his PhD (in 1999) and his physics diploma studies at the University of Tübingen.

Electroweak baryogenesis is an extremely testable framework. Its most popular realizations, in the MSSM and in general two Higgs doublet models, are either excluded or pushed to such a small corner of parameter space as to strain credibility. One might wonder whether it is still possible to design robust working models in light of new LHC constraints. Professor Cline will address this question, with emphasis on a model that can also provide the dark matter.

Professor James Cline, McGill University, Canada

Professor James Cline, McGill University, Canada

James Cline is a Professor of Physics at McGill University. After his PhD from Caltech, he held postdoctoral positions at Ohio State University, McGill, and University of Minnesota. His interests lie at the interface of particle physics and cosmology, including theories of early universe inflation, the asymmetry of matter over antimatter, and dark matter.

The recent measurement of the Higgs boson mass implies a relatively slow rise of the Standard Model Higgs potential at large scales. This allows the Higgs field to develop a large vacuum expectation value during inflation. The relaxation of the Higgs field from its large postinflationary value to the minimum of the effective potential represents an interesting new stage in the evolution of the universe. The matter-antimatter asymmetry could be generated during this epoch.

Professor Alexander Kusenko, University of California Los Angeles, USA & Kavli IPMU, University of Tokyo, Japan

Professor Alexander Kusenko, University of California Los Angeles, USA & Kavli IPMU, University of Tokyo, Japan

Professor Kusenko grew up in the Soviet Union and obtained his undergraduate education at Moscow State University.  He received his PhD degree from Stony Brook University in the USA in 1994.  After that, he worked at the University of Pennsylvania (1994-1996) and at CERN (1996-1998), and joined University of California, Los Angeles in 1998.  In addition to his professorial appointment at UCLA he has held positions of a RIKEN Fellow at Brookhaven National Laboratory (1999-2014) and of a Senior Scientist at Kavli IPMU, University of Tokyo (2007-present). In 2008 Professor Kusenko was elected an APS Fellow, and in 2012 he was awarded an Outstanding Referee Award by American Physical Society. He has served on the board of Aspen Center for Physics since 2004, and has recently been re-elected for a third 5-year term.

Djouadi discusses scenarios in which the particles that form the dark matter in the universe interact mainly or exclusively with Higgs bosons, either the one of the standard model of particle physics or those of its extensions. The case of scalar, fermionic and vector dark matter particles are considered. Present constraints from collider experiments like the LHC and astroparticle physics experiments that search directly or indirectly for these particles are summarised. The prospects for future studies are discussed.

Professor Abdelhak Djouadi, Université Paris-Sud, France

Professor Abdelhak Djouadi, Université Paris-Sud, France

Abdelhak Djouadi is a Director of Research at the French National Center of Scientific Research (CNRS), based at the Université Paris-Sud in Orsay, and a Research Associate at the European Organization for Nuclear Research (CERN) in Geneva. He is an expert of the phenomenology of the weak, electromagnetic and strong forces of elementary particles and worked on tests of the Standard Model that unifies these interactions in a unified framework and its new physics extensions at high-energy collider and dark matter experiments.

In particular, he did major work on the physics of the Higgs boson which has been discovered at CERN in 2012. He was awarded several distinctions like the Silver Medal of the CNRS and the Alexander von Humboldt Prize and received an Advanced Grant of the European Research Council for the project Higgs at LHC in 2012.

Servant will report how the CKM matrix can be the source of CP-violation for electroweak baryogenesis if Yukawa couplings vary at the same time as the Higgs is acquiring its vacuum expectation value, offering new avenues for electroweak baryogenesis. The advantage of this approach is that it circumvents the usual bounds from electric dipole moments. These ideas apply if the mechanism explaining the flavour structure of the Standard Model is connected to electroweak symmetry breaking, as motivated for instance in Randall–Sundrum or composite Higgs models. Servant will show how this can be compatible with experimental constraints and naturally leads to the correct amount of the baryon asymmetry.

Professor Geraldine Servant, DESY and the University of Hamburg, Germany

Professor Geraldine Servant, DESY and the University of Hamburg, Germany

Geraldine Servant got her PhD in 2001 from University Paris 11 for theoretical research conducted at CEA Saclay and McGill University in Montreal. After postdoc years at the University of Chicago she returned to CEA Saclay on a permanent position, and eventually moved to CERN's Theory group in 2006, first as a Fellow and then on a 5-year contract with an ERC Starting Grant. In 2013 she moved to Barcelona where she was appointed Research Professor at ICREA (Catalan Institution for Research and Advanced Studies). In 2015 she became DESY scientist and Professor at University of Hamburg.

Her major direction of research is on the particle-cosmology interplay, in particular on the dark matter and the origin of the matter-antimatter asymmetry of the universe, with special emphasis for cosmological consequences of the electroweak phase transition in the early universe.

The direct detection of gravitational waves by LIGO has led to heightened interest in other observable sources of gravitational waves, both astrophysical and primordial. There is also growing interest in proposed detectors such as LISA, scheduled for launch in 2034. In this talk, David will focus on one possible primordial source of gravitational waves: first order phase transitions in the early universe. The resulting gravitational wave signal is a good candidate for detection at next-generation gravitational wave detectors. An electroweak-scale first order phase transition could yield information about physics beyond the Standard Model that will otherwise remain out of reach of colliders for quite some time. David will discuss efforts to simulate and model the phase transition and the resulting production of gravitational waves.

Dr David Weir, University of Helsinki, Finland

Dr David Weir, University of Helsinki, Finland

David James Weir received his doctorate from Imperial College London in 2011, before moving to the University of Helsinki as a postdoc. In 2014 he was awarded a Marie Curie Fellowship at the University of Stavanger in Norway, before moving back to Helsinki in 2016. His work is principally on very large numerical studies of the physics of the early universe, including first-order electroweak phase transitions, topological defect formation and the end of inflation.