Pseudoscalar pole light-by-light contributions to the muon (g−2)(g-2) in Resonance Chiral Theory

We have studied the $P\to\gamma^\star\gamma^\star$ transition form-factors ($P=\pi^0,\eta,\eta'$) within a chiral invariant framework that allows us to relate the three form-factors and evaluate the corresponding contributions to the muon anomalous magnetic moment $a_\mu$, through pseudoscalar pole contributions. We use a chiral invariant Lagrangian to describe the interactions between the pseudo-Goldstones from the spontaneous chiral symmetry breaking and the massive meson resonances. We will consider just the lightest vector and pseudoscalar resonance multiplets. Photon interactions and flavor breaking effects are accounted for in this covariant framework. This article studies the most general corrections of order $m_P^2$ within this setting. Requiring short-distance constraints fixes most of the parameters entering the form-factors, consistent with previous determinations. The remaining ones are obtained from a fit of these form-factors to experimental measurements in the space-like ($q^2\le0$) region of photon momenta. The combination of data, chiral symmetry relations between form-factors and high-energy constraints allows us to determine with improved precision the on-shell $P$-pole contribution to the Hadronic Light-by-Light scattering of the muon anomalous magnetic moment: we obtain $a_{\mu}^{P,HLbL}=(8.47\pm 0.16)\cdot10^{-10}$ for our best fit. This result was obtained excluding BaBar $\pi^0$ data, which our analysis finds in conflict with the remaining experimental inputs. This study also allows us to determine the parameters describing the $\eta-\eta'$ system in the two-mixing angle scheme and their correlations. Finally, a preliminary rough estimate of the impact of loop corrections ($1/N_C$) and higher vector multiplets (asym) enlarges the uncertainty up to $a_\mu^{P,HLbL} = (8.47\pm 0.16_{\rm sta}\pm0.09_{1/N_C}{}^{+0.5}_{-0.0}{}_{\rm asym})\cdot 10^{-10}$.Comment: 43 pages, 5 figures. Accepted for publication in JHEP. New subsection involving error analysis and some minor change

Electronic transport through a parallel--coupled triple quantum dot molecule: Fano resonances and bound states in the continuum

The electronic transport through a triple quantum dot molecule attached in parallel to leads in presence of a magnetic flux is studied. Analytical expressions of the linear conductance and density of states for the molecule in equilibrium at zero temperature are obtained. As a consequence of quantum interference, the conductance exhibits in general a Breit--Wigner and two Fano resonances, the positions and widths of which are controlled by the magnetic field. Every two flux quanta, there is an inversion of roles of the bonding and antibonding states. For particular values of the magnetic flux and dot-lead couplings, one or even both Fano resonances collapse and bound states in the continuum (BIC's) are formed. The line broadenings of the molecular states are examined as a function of the Aharonov--Bohm phase around the condition for the formation of BIC's, finding resonances extremely narrow and robust against variations of the magnetic field.Comment: 15 pages, 7 figure

INTREPID Futures Initiative: Universities and Knowledge for Sustainable Urban Futures: as if inter and trans-disciplinarity mattered. 4th INTREPID REPORT

This London Workshop is meant to advance the agenda of “Universities and Knowledge for Sustainable Urban Futures: as if ID and TD mattered”, by helping to define the scope of the EU COST Action INTREPID contribution, and of the activities to be funded for 2017-2019. Intention statement: ‘To contribute to the shaping of tomorrow’s universities & their urban curricula: as if inter and transdisciplinary ways of knowing actually mattered’. For this purpose, the Workshop was a one-day gathering of experts and practitioners with diverse experience and disciplinary backgrounds. The report outlines the results obtained

Free expansion of impenetrable bosons on one-dimensional optical lattices

We review recent exact results for the free expansion of impenetrable bosons on one-dimensional lattices, after switching off a confining potential. When the system is initially in a superfluid state, far from the regime in which the Mott-insulator appears in the middle of the trap, the momentum distribution of the expanding bosons rapidly approaches the momentum distribution of noninteracting fermions. Remarkably, no loss in coherence is observed in the system as reflected by a large occupation of the lowest eigenstate of the one-particle density matrix. In the opposite limit, when the initial system is a pure Mott insulator with one particle per lattice site, the expansion leads to the emergence of quasicondensates at finite momentum. In this case, one-particle correlations like the ones shown to be universal in the equilibrium case develop in the system. We show that the out-of-equilibrium behavior of the Shannon information entropy in momentum space, and its contrast with the one of noninteracting fermions, allows to differentiate the two different regimes of interest. It also helps in understanding the crossover between them.Comment: 21 pages, 14 figures, invited brief revie

Disentangling the excitation conditions of the dense gas in M17 SW

We probe the chemical and energetic conditions in dense gas created by radiative feedback through observations of multiple CO, HCN and HCO$^+$ transitions toward the dense core of M17 SW. We used the dual band receiver GREAT on board the SOFIA airborne telescope to obtain maps of the $J=16-15$, $J=12-11$, and $J=11-10$ transitions of $^{12}$CO. We compare these maps with corresponding APEX and IRAM 30m telescope data for low- and mid-$J$ CO, HCN and HCO$^+$ emission lines, including maps of the HCN $J=8-7$ and HCO$^+$ $J=9-8$ transitions. The excitation conditions of $^{12}$CO, HCO$^+$ and HCN are estimated with a two-phase non-LTE radiative transfer model of the line spectral energy distributions (LSEDs) at four selected positions. The energy balance at these positions is also studied. We obtained extensive LSEDs for the CO, HCN and HCO$^+$ molecules toward M17 SW. The LSED shape, particularly the high-$J$ tail of the CO lines observed with SOFIA/GREAT, is distinctive for the underlying excitation conditions. The critical magnetic field criterion implies that the cold cloudlets at two positions are partially controlled by processes that create and dissipate internal motions. Supersonic but sub-Alfv\'enic velocities in the cold component at most selected positions indicates that internal motions are likely MHD waves. Magnetic pressure dominates thermal pressure in both gas components at all selected positions, assuming random orientation of the magnetic field. The magnetic pressure of a constant magnetic field throughout all the gas phases can support the total internal pressure of the cold components, but it cannot support the internal pressure of the warm components. If the magnetic field scales as $B \propto n^{2/3}$, then the evolution of the cold cloudlets at two selected positions, and the warm cloudlets at all selected positions, will be determined by ambipolar diffusion.Comment: 26 pages, 13 figures, A&A accepte