Ref HAL: hal-02340141_v1
Ref Arxiv: 1909.08567
Ref INSPIRE: 1754713
DOI: 10.1140/epjc/s10052-019-7581-y
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7 Citations
Résumé:

We investigate new-physics contributions to $b\rightarrow s \ell \ell $ transitions in the context of an effective field theory extension of the Standard Model, including operator mixing at one loop. We identify the few scenarios where a single Wilson coefficient, $C/\Lambda ^2 \sim 1/\mathrm{TeV}^2$, induces a substantial shift in the lepton flavour universality ratios $R_K$ and $R_{K^*}$ at one loop, while evading Z-pole precision tests, collider bounds, and other flavour constraints. Novel fits to the present data are achieved by a left-handed current operator with quark-flavour indices (2, 2) or (3, 3). Interestingly, the running of the Standard Model Yukawa matrices gives the dominant effect for these scenarios. We match the favoured effective-theory scenarios to minimal, single-mediator models, which are subject to additional stringent constraints. Notably, we recognise three viable instances of a leptoquark with one coupling to fermions only. If the anomalies were confirmed, it appears that one-loop explanations have good prospects of being directly tested at the LHC.

Ref HAL: hal-02322855_v1
DOI: 10.1016/j.nuclphysbps.2019.11.013
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We made the hypothesis that, if spacetime is composed of small hypercubes of one Planck length edge, it exists elementary wavefunctions which are equal to √ 2 exp(ix j) if it corresponds to a space dimension or equal to √ 2 exp(it) if it corresponds to a time dimension. The masses of fermions belonging to the first family of fermions are equal to integer powers of 2 (in eV/c 2) [1]. We make the hypothesis that the fermions of the 2nd and 3rd families are excited states of the fermions of the 1st family. Indeed, the fermions of the 2nd and 3rd families have masses equal to 2 n .(p 2)/2 where n is an integer [1] calculated for the first family of fermions and p is another integer. p is an integer which corresponds to the excited states of the elementary wavefunctions (the energy of the excited elementary wave functions are equal to p 2 /2; using normalized units).

Commentaires: Talk given at 19th International Conference in Quantum Chromodynamics (QCD 19), 2 july – 5 july 2019, Montpellier – FR.

Ref HAL: hal-02313772_v1
Ref Arxiv: 1910.03098
DOI: 10.1007/s00220-020-03854-6
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Whenever available, refined BPS indices provide considerably more information on the spectrum of BPS states than their unrefined version. Extending earlier work on the modularity of generalized Donaldson-Thomas invariants counting D4-D2-D0 brane bound states in type IIA strings on a Calabi-Yau threefold $\mathfrak{Y}$, we construct the modular completion of generating functions of refined BPS indices supported on a divisor class. Although for compact $\mathfrak{Y}$ the refined indices are not protected, switching on the refinement considerably simplifies the construction of the modular completion. Furthermore, it leads to a non-commutative analogue of the TBA equations, which suggests a quantization of the moduli space consistent with S-duality. In contrast, for a local CY threefold given by the canonical bundle over a complex surface $S$, refined DT invariants are well-defined, and equal to Vafa-Witten invariants of $S$. Our construction provides a modular completion of the generating function of these refined invariants for arbitrary rank. In cases where all reducible components of the divisor class are collinear (which occurs e.g. when $b_2(\mathfrak{Y})=1$, or in the local case), we show that the holomorphic anomaly equation satisfied by the completed generating function truncates at quadratic order. In the local case, it agrees with an earlier proposal by Minahan et al for unrefined invariants, and extends it to the refined level using the afore-mentioned non-commutative structure. Finally, we show that these general predictions reproduce known results for $U(2)$ and $U(3)$ Vafa-Witten theory on $\mathrm{P}^2$, and make them explicit for $U(4)$.

Ref HAL: hal-02178711_v1
Ref Arxiv: 1906.05991
Ref INSPIRE: 1739993
DOI: 10.1093/mnras/staa633
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10 Citations
Résumé:

Using redshift space distortion data, we perform model-independent reconstructions of the growth history of matter inhomogeneity in the expanding Universe using two methods: crossing statistics and Gaussian processes. We then reconstruct the corresponding history of the Universe background expansion and fit it to Type Ia supernovae data, putting constraints on (Ω_m, 0, σ_8, 0). The results obtained are consistent with the concordance flat-ΛCDM model and General Relativity as the gravity theory given the current quality of the inhomogeneity growth data.

Ref HAL: hal-02116566_v1
DOI: 10.1016/j.micromeso.2018.09.033
WoS: WOS:000546913300003
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3 Citations
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The structural transformations of periodic structures are very often initiated by the dynamicalfluctuation of theequilibrium structure. The natural mechanical excitations in crystals are called phonons. If the energy of thesefluctuations is low, they can easily be transformed into static deformations which define new structural prop-erties of the materials. This is the case in so called gate opening transformations which modify the structure andthe adsorptive properties of porous solids. Using the example of three SOD-type zeolitic imidazolate frameworks(ZIFs) containing linker molecules with different substituents, we show that analysis of low-frequency phononsobtained from density-functional theory (DFT) calculations allows one to model the observed gate opening andto understand the microscopic mechanism of this structural transformation.

Ref HAL: hal-02116565_v1
DOI: 10.1016/j.micromeso.2018.12.024
WoS: WOS:000546913300007
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1 Citation
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Unlike macroscopic objects, any system of nanometric size shows characteristics that strongly depend on its sizeand geometric form. It is mainly because the major part of atoms (or molecules) of nano-object is located at itssurface, and their cohesive energy is smaller than for the atoms in the bulk. Here we show that when a fluid isconfined in nano-volume, delimited by non-attractive pore walls, its density is heterogeneous, in particular closeto the pore wall, and, on average, smaller than the density of bulk fluid. This effect progressively weakens whenthe pore size increases, and totally disappears for pores larger than 5 nm. The reported observation has nontrivialinfluence on evaluation of total and excess amount of fluid adsorbed in nanopores, as these quantities aretraditionally calculated assuming the known – and homogeneous –density of the bulk fluid. Additionally, wepropose a new method of the estimations of the accessible pore volume, based on the analysis of the density ofconfined fluid. The right estimation of both: pore volume and gas density is essential for quantitative interpretationof experimental adsorption isotherms: evaluation of pore size distribution and of the adsorbed amount.Although we analyze these problems taking an example of hydrogen at 77 K, our conclusions are general andapply to any fluid confined in nanopores.