Contact: Roland Triay (CPT) – triay[at]cpt.univ-mrs.fr
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I will share some personal thoughts prompted by the recent experimental confirmations of the standard model of particle physics and of the so-called concordance model of cosmology.
In the past 20 years, the Standard Model (SM) of elementary particles and their interactions has provided an unfailing and remarkably accurate description of all experiments with and without high-energy accelerators, establishing that we understand the physics of the very small up to energy scales of 100 GeV. The Large Hadron Collider of CERN, and its experiments, were conceived to probe the physics of the next frontier, that of the TeV energy scale. True to their charge, the experiments have delivered hundreds of significant and often beautiful measurements, along with the discovery of what looks like the first fundamental scalar particle. The triumph of the Standard Model is complete, especially since no new signal has emerged from the intense searches for “new physics” — yet. The field is now at a crossroads: the existence of a Higgs boson opens a new set of questions, while the evidence, both direct and indirect, that there physics beyond the SM does exist, is still strong and convincing. The talk will present a broad-brush picture of how Run 1 of the LHC has shaped the field of High Energy Physics; along with why expectations are still so very high.
Much effort has been devoted to the study of weak scale particles, e.g. supersymmeteric neutralinos, which have a relic abundance from thermal equilibrium in the early universe matching that of the dark matter. This does not however provide any connection to the comparable abundance of asymmetric baryons, which must have a non-thermal origin. `Dark baryons' from a hidden sector with a similar asymmetry and mass of ~GeV would naturally provide the dark matter. Low-threshold direct detection experiments are required to find such particles, while monojet searches at colliders provide a complementary probe.
Sketched out in 1992, selected by ESA in 1996, launched in 2009, Planck delivered on March 21st its first full sky maps of the millimetric emission at 9 frequencies, as well as those which follow from them, and in particular Planck map of the anisotropies of the Cosmic Microwave Background (CMB). The later displays minuscule variations as a function of the observing direction of the temperature of the fossile radiation around its mean temperature of 2.725K. I will briefly describe how these high resolution maps with a precision of a few parts in a million have been obtained, from collection to analysis of the first 500 billion samples of our HFI instrument.
CMB anisotropies reveal the imprint of the primordial fluctuations which initiate the growth of the large scale structures of the Universe, as transformed by their evolution, in particular during the first 370 000 years, i.e. till the Universe became transparent and the forming of the image we record today. The statistical characteristics of these anisotropies allow constraining jointly the physics of the creation of the primordial fluctuations and that of their evolution. They teach us the possible value of the parameters of the models which we confront to data. I will describe Planck estimates of the density of the constituents of the Universe (usual matter, cold dark matter or CDM, dark energy...), and their implication in terms of derived quantities like the expansion rate or the spatial curvature. I will review what we learnt on the generation of the fluctuation, and wil discuss extensions of the standard cosmological model, so called “Lambda-CDM”, both in term of non minimal physical models – multi-field inflation for instance, or additional constituents - like cosmic strings or a fourth neutrino.
Finally, it will briefly describe other promising results on the matter distribution which is travelled through by the CMB image on its long 13.7 billion years trip towards us. I will mention in particular what we can learn on the dark matter distribution - which is detected through its distorting effet of the CMB image by gravitationnal lensing, or that of hot gaz, which is revealed by the spectral distortion it induces.
The two main messages from the LHC, after its first phase, are the discovery of the Higgs-like particle and no evidence for any BSM physics. This stunning, continuous, success of the SM up to the mass scales of order 0(1 TeV) is very puzzling. Although with the discovery of the Higgs particle, the SM is a consistent theory that can be extrapolated up to the Planck scale, it leaves unanswered several well known experimental and theoretical questions. In particular, the naturalness of the weak scale as the guiding principle for BSM physics is now somewhat challanged. From the historical perspective, the concept of naturalness in particle physics is a crucial issue and it should not be abandoned too quickly. After the lessons from the LHC, supersymmetry still remains to be the leading candidate for BSM physics. Other BSM scenarios and the near term experimental prospects for discovering supersymmetric or non-supersymmetric BSM physics will also be briefly reviewed.
I give a general overview of the developments in Loop Quantum Gravity and I describe a recent idea for a possible novel window of observation of quantum gravitational phenomena: Planck stars.
The measurement of a small deviation of the primordial spectrum of scalar (density) perturbations in the Universe from the exactly flat (Harrison-Zeldovich, ) one in the WMAP and Planck CMB experiments confirms the general prediction of the early Universe scenario with the de Sitter (inflationary) stage preceding the radiation dominated stage (the hot Big Bang) and strongly restricts the class of viable inflationary models .Thus, the status of the inflationary paradigm is changing from “proving” it in general and testing some of its simplest models to applying it for investigation of the actual history of the Universe in the remote past and particle physics at super-high energies using actual observational data. The announced discovery of primordial gravitational wave background through the measurement of the B-mode of the CMB linear polarization in the range of multipoles in the BISEP2 experiment  confirms another general prediction  of this scenario, as well as produces the direct evidence for the existence of a very strongly curved space-time with in the past of our Universe and the necessity of quantization of gravitational waves. Still the BISEP2 result is partially contaminated by foregrounds (mainly by polarized galactic dust emission) and requires confirmation of its blackbody character. Moreover, comparison of BISEP2 data with the temperature and E-mode polarization data earlier obtained in the WMAP and Planck experiments shows that the inflationary stage is not so simple and may not be described by a one-parametric model. In particular, the primordial spectrum of scalar perturbations generated during inflation is not of a power-law form , mainly due to the depression of the angular anisotropy power spectrum in the multipole range . A class of models describing this feature which implies existence of some scale (i.e. new physics) during inflation is proposed . Furthermore, account of additional wiggles in the spectrum at and requires further complication of the inflaton potential  by introducing sharp features of the type suggested by previous studies . While viable inflationary models with a smooth potential require the inflaton mass GeV, it has to increase up to GeV and may be larger near the feature. Thus, combination of CMB temperature anisotropy and polarization data helps to make a “tomographic” study of inflation and particle physics in this range of energies.
 P. A. R. Ade et al. [Planck Collaboration], arXiv:1303.5082.
 P. A. R. Ade et al. [BISEP2 Collaboration], arxiv:1403.3985.
 A. A. Starobinsky, JETP Lett. 30, 682 (1979).
 D. K. Hazra, A. Shafieloo, G. F. Smoot and A. A. Starobinsky. JCAP 1406, 061 (2014), arXiv:1403.7786.
 D. K. Hazra, A. Shafieloo, G. F. Smoot and A. A. Starobinsky, arXiv:1404.0360.
 D. K. Hazra, A. Shafieloo, G. F. Smoot and A. A. Starobinsky, arXiv:1405.2012.
 A. A. Starobinsky, JETP Lett. 55, 489 (1992).
Brief overview of the current status and prospects of cosmic ray studies is presented. Our Galaxy and extragalactic space are filled with cosmic rays, a relativistic gas of high-energy protons, electrons, and heavy nuclei. The directly measured cosmic ray energy spectrum extends from about MeV to energies above eV. The radio-astronomical, X-ray, gamma-ray and the first very high energy neutrino observations shed light on the origin of cosmic rays. The model of cosmic ray origin in supernova remnants (including pulsars), the interpretation of Voyager data on low energy particles, the structure of knee in cosmic ray spectrum at eV, and the energy limit of Galactic sources are discussed. The origin of cosmic rays with energies above to eV may be associated with the Active Galactic Nuclei, the progenitors of Gamma-Ray Bursts, the fast spinning newborn pulsars, the large-scale structure formation shocks and some other objects.
Since nearly two decades, a decline of interest in scientific studies has entailed the choice of new objectives for science teaching in many countries. To put it briefly, affective factors like motivation and the development of competencies, for instance critical analysis, have received much attention, as well as new approaches to teaching, like Inquiry Based Science Education. Although multiple learning benefits are invoked in each case, also for the future citizen, there is often, de facto, a trend toward less conceptual development and structuring, be it in teaching objectives or in students' achievements. I will briefly discuss the risks of oversimplification and teaching rituals in physics, and the need for developing a critical stance in students. I will then discuss, based on two investigations at upper secondary or university level (hot air balloon, radio carbon dating), the idea that a competence like critical analysis should not be envisaged separately from a minimum conceptual development. The final discussion will bear on implications for teaching.
A second part of this talk will be given in a session about physics education: From a subtractive to multiplicative approach, two concept-driven interactive pathways on the selective absorption of light.
The traditional view is that a theory is a conceptual framework providing predictions, and the results of experiments or observations decide whether the theory is right or wrong. It will be contrasted with the modern view that one must incorporate the conditions of applicability of a concept into the very meaning of the concept (measurability analysis), and that only a series of theories (scientific research program) can be said to be scientific or unscientific. This modern view will be applied to a number of questions in quantum mechanics (what is quantization?, states vs processes, open vs closed systems) and quantum field theory (particles and field quanta, bosons vs fermions), and to the search for a theory of quantum gravity (background independent vs fixed background theories).
The origin of the galaxies represents an important focus of current cosmological research, both observational and theoretical. Its resolution involves a comprehensive understanding of star formation and evolution, galaxy dynamics, supermassive black holes, and the cosmology of the very early universe. I will review our current understanding of galaxy formation and describe some of the challenges that lie ahead. Specific issues that I will address include the star formation rate in galaxies and the galaxy luminosity function, including the role of feedback.