I will present the root of the quantization of geometry in the framework of loop quantum gravity. Then I will review some of the key theoretical implications of this prediction and its possible relevance for cosmology.

Understanding the motion of nanoparticles in polymer solutions and melts is a problem of broad importance, with applications to many different fields, such as material science, biophysics, and medicine. If the nanoparticles are larger than the polymer's radius of gyration, their structure and dynamics can be well described in terms of effective pair potentials. However, much remains to be understood in the so-called “protein limit”, where the size of the nanoparticles becomes comparable to or smaller than that of the polymers. Moreover, most of the previous study considering this size range have only focused on the dilute nanoparticle regime, which is easier to handle since inter-nanoparticle interaction can be neglected and the properties of the polymer solution/melt are expected to be unchanged.

Using molecular dynamics simulations, we study the dynamic and structural properties of a semidilute polymer solution containing well dispersed spherical nanoparticles of size smaller than the polymer's radius of gyration. We consider various nanoparticle diameters and a broad range of nanoparticle volume fractions, up to values for which the inter-nanoparticle interaction becomes important.

Four decades after its prediction the axion remains the most compelling solution to the strong CP problem and a well motivated dark matter candidate, inspiring several ultrasensitive experiments based on axion-photon mixing. After reviewing the axion solution of the strong CP problem and the experimental landscape of axion searches, I will focus on some recent developments in axion model building which suggest that the QCD axion parameter space is much larger than what traditionally thought. The implications for astrophysical limits and future detection experiments will be discussed as well.

While systems of uniform particles (colloids, nanoparticles, atoms) and discrete mixtures (binary, ternary) have traditionally been well studied, much less is known about particles with a continuous distribution in sizes and shapes. Such disperse particle systems are natural outcomes of syntheses or can develop dynamically through exchange of mass or charge or mechanical forces between neighboring particles. Theoretical research over the last 20 years pointed towards a fractionation mechanism involving multiple face-centered cubic crystals with narrower size distributions in each crystal than the size distribution of the fluid. However, experiments were unable to confirm such a behavior. Only recently, first evidence appeared that dispersity can be responsible for novel crystallization phenomena. We confirm this view with the help of computer simulations of a simple model system – size-disperse hard spheres [1]. We can now unambiguously state: particles with dispersity eventually do crystallize, even for high values of dispersity, and they do so in unexpected ways. Our findings suggest that crystallization of size-disperse colloids closely mimics crystallization in binary mixtures into AB2 and AB13 crystals and alloys by favoring Frank-Kasper phases. We obtain this result with the help of an algorithm that combines event-driven molecular dynamics with particle swap move (static dispersity) or particle resize moves (dynamic dispersity).

Reference:
[1] P.K. Bommineni, N.R. Varela-Rosales, M. Klement, M. Engel, Complex Crystals from Size-Disperse Spheres, Phys. Rev. Lett., in press (2019).

Light new states which are singlet under the Standard Model gauge group and have mass below the electroweak scale have interesting connections with many new physics solutions of Standard Model puzzles. Exploiting one or more of these connections enable us to pinpoint a particular mass range and/or coupling structure of the light state to the Standard Model. I will briefly review some of these connections and discuss the phenomenological challenges of probing light new states. My main focus will be the parameter range within the reach of colliders, i.e. both the LHC and the different flavor experiments. I will give a taste of a vast physics program which is quickly developing to improve the reach on light new physics at these facilities. As an example in this direction, I will present my recent works on new probes of axion solutions to the strong CP problem and on muonic forces addressing the muon g-2 anomaly together with Dark Matter freeze-out.

Metallic nanoparticles or nanocrystals are one of the most important families of functional materials. Their remarkable properties, due to their nanometric dimension, combined with their chemical composition and morphology, have contributed to the increasing development of their use in fields as diverse as electronics, data storage, catalysis, optics, bio-medical etc.

However, due to their small size, the control of their properties depends crucially on the control of their morphology. This is even more critical for nanocrystals formed of several elements for which the chemical order (alloy, core-shell, demixed configuration, etc.) can also influence the morphology, which becomes extremely difficult to predict. For these reasons, many efforts are deployed today to understand, on the one hand, the mechanisms of formation of these objects and, on the other hand, the origin of the stability of the observed morphologies.

Through examples, I will show how, from atomistic modeling, it is possible to determine the way the growth conditions and the environment can influence the morphologies of metallic nanoparticles. I will also show that the morphology of a nanoparticle can be of paramount importance on its functionalization.

Dark Matter (DM) Direct detection aims at detecting the tiny nuclear recoils arising from non-relativistic DM-nucleus collisions. This talk is organised in three parts where I will present: i) the most useful approach to study signals in direct detection based on non-relativistic EFT; ii) how to match a non-complete set of high-energy effective operators to the non-relativistic EFT describing DM-nucleus collisions; iii) how the running of the SM couplings between the energy scale of the mass of the mediator and the nuclear energy scale generates operator mixing and, in turn, new interactions at low-energy. The inclusion of the running is not optional and gives rise to important phenomenological consequences that I'll discuss.

La théorie classique de l’électrodynamique, modifiée et développée depuis les années 30 pour prendre en compte les principes quantiques, a fait naître l’électrodynamique quantique. Cette théorie a été testée ex-périmentalement à maintes reprises avec une précision exceptionnelle. Néanmoins, il reste des phénomènes prédits par cette théorie mais encore jamais observés : ceux issus de l’interaction entre les fluctuations du vide et le photon seul. Ce type d’interaction photon-photon a été décrit par Heisenberg et Euler [1] dans les années 30. Sous l’e˙et de champs électriques ou magnétiques, le vide se polarise et de nombreux e˙ets non-linéaires sont alors possibles [2]. Parmi les phénomènes attendus mais jamais observés, on trouve l’e˙et de biréfringence induite dans le vide par un champ magnétique intense (Biréfringence Magnétique du Vide : BMV) aussi appelé e˙et Cotton-Mouton du vide, en relation avec les travaux e˙ectués au début du XXème siècle par les physiciens Cotton et Mouton dans les gaz. Dans le vide donc l’indice de réfraction n pour une lumière polarisée parallèlement au champ magnétique B est di˙érent de l’indice n⊥ vu par la lumière polarisée perpendiculairement à B donnant lieu à une biréfringence ∆nCM :

Thermometry at the Nanoscale: Light in Action
L. D. Carlos

Physics Department and CICECO-Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal

The emergence of luminescent nanothermometry during the last decade opened up the possibility of measure thermal flows at spatial scales below 1 μm, unreachable by conventional electrical methods [1]. In fact, diverse phosphors capable of providing a contactless thermal reading through their light emission properties have been examined, e.g., polymers, DNA or protein conjugated systems, organic dyes, quantum dots, and trivalent lanthanide ions incorporated in organic-inorganic hybrids, multifunctional heater-thermometer nanoplatforms, upconverting, downconverting and downshifting nanoparticles.

In the last couple of years, the focus of luminescence thermometry has gradually shifted from the fabrication of more sensitive nanoarchitectures towards the use of the technique as a tool for thermal bioimaging and for the unveiling of properties of the thermometers themselves and of their local surroundings [2-5].

After a general historical perspective of the work done on ratiometric luminescent nanothermometers since the explosion of the field at one decade ago, the lecture will be focused on recent examples illustrating the potential of the technology.

References

1 C. D. S. Brites, A. Millán, L. D. Carlos, in Handbook on the Physics and Chemistry of Rare Earths, J.-C. Bünzli, V. K. Pecharsky, Eds., Amsterdam: Elsevier Science B.V., Vol. 49 (2016), 339–427.
2 R. Piñol et al., ACS Nano 9 (2015) 3134–3142.
3 E. C. Ximendes et al., Nano Lett. 16 (2016) 1695–1703.
4 C. D. S. Brites et al., Nature Nanotech. 11 (2016) 851–857.
5. C. D. S. Brites et al., Nano Lett., 2017, 17, 4746-4752.