Using combined theoretical and experimental approaches, we demonstrate that the bond orientation of water at the water-vapor interface depends markedly on the water isotope (H-D) composition. While the interfacial water structures of ${\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{D}}_2\mathrm{O}$ are indistinguishable, the intramolecular symmetry breaking in HDO is directly reflected at the surface: the OD bonds preferably orient down towards the bulk water, whereas the OH bond tends to orient up into the vapor phase. Path integral molecular dynamics simulations show good agreement with surface-specific sum-frequency generation (SFG) spectroscopy results, revealing that the distinct interfacial bond orientations originate from nuclear quantum effects. The enhanced localization of the heavier D atom leads to stronger hydrogen bonds, giving rise to OD bonds pointing down into the bulk.

We have modulated the density of a trapped Bose-Einstein condensate by changing the trap stiffness, thereby modulating the speed of sound. We observe the creation of correlated excitations with equal and opposite momenta, and show that for a well-defined modulation frequency, the frequency of the excitations is half that of the trap modulation frequency.

The suppression of the individual ${\rm Y}(nS)$ states in PbPb collisions with respect to their yields in $pp$ data has been measured. The PbPb and $pp$ data sets used in the analysis correspond to integrated luminosities of $150\mu {\mathrm{b}}^{-1}$ and $230{\mathrm{nb}}^{-1}$, respectively, collected in 2011 by the CMS experiment at the LHC, at a center-of-mass energy per nucleon pair of 2.76 TeV. The ${\rm Y}(nS)$ yields are measured from the dimuon invariant mass spectra. The suppression of the ${\rm Y}(nS)$ yields in PbPb relative to the yields in $pp$, scaled by the number of nucleon-nucleon collisions, $R_{AA}$, is measured as a function of the collision centrality. Integrated over centrality, the $R_{AA}$ values are $0.56\pm 0.08(\mathrm{stat})\pm 0.07(\mathrm{syst})$, $0.12\pm 0.04(\mathrm{stat})\pm 0.02(\mathrm{syst})$, and lower than 0.10 (at 95% confidence level), for the ${\rm Y}(1S)$, ${\rm Y}(2S)$, and ${\rm Y}(3S)$ states, respectively. The results demonstrate the sequential suppression of the ${\rm Y}(nS)$ states in PbPb collisions at LHC energies.

The cooperative motion induced structural evolution of the liquid with microheterogeneity is investigated in quasi-2D dusty plasma liquids, through direct optical visualization. A novel bond-dynamics analysis is used to further classify the robust cooperative 2D clusters into static, rotating, and drifting patches, beyond the earlier findings of the cooperative hopping strings and bands. The relative motion between two adjacent clusters causes the formation of a fractal network with narrow shear strips along the cluster interface. The rotation of the large ordered patch through rupturing into multiple rotating patches followed by the healing process, and the growth to a larger ordered patch by aligning the different lattice orientations of the adjacent ordered domains through patch rupturing, rotation, drifting, and merging are the key processes for the microstructural evolution.

We experimentally investigate a recently proposed optical excitation scheme V. I. Yudin et al. [Phys. Rev. A 82, 011804(R) (2010)] that is a generalization of Ramsey’s method of separated oscillatory fields and consists of a sequence of three excitation pulses. The pulse sequence is tailored to produce a resonance signal that is immune to the light shift and other shifts of the transition frequency that are correlated with the interaction with the probe field. We investigate the scheme using a single trapped ${}^{171}\mathrm{Yb}^{+}$ ion and excite the highly forbidden ${}^{2}S_{1/2}-{}^{2}F_{7/2}$ electric-octupole transition under conditions where the light shift is much larger than the excitation linewidth, which is in the hertz range. The experiments demonstrate a suppression of the light shift by four orders of magnitude and an immunity against its fluctuations.

The NASA/ESA Cassini probe of Saturn analyzed the molecular composition of plumes emanating from one of its moons, Enceladus, and the upper atmosphere of another, Titan. However, interpretation of this data is complicated by the hypervelocity (HV) flybys of up to $\sim 18\mathrm{km}/\sec$ that cause substantial molecular fragmentation. To interpret this data we use quantum mechanical based reactive force fields to simulate the HV impact of various molecular species and ice clathrates on oxidized titanium surfaces mimicking those in Cassini’s neutral and ion mass spectrometer (INMS). The predicted velocity dependent fragmentation patterns and composition mixing ratios agree with INMS data providing the means for identifying the molecules in the plume. We used our simulations to predict the surface damage from the HV impacts on the INMS interior walls, which we suggest acts as a titanium sublimation pump that could alter the instrument’s readings. These results show how the theory can identify chemical events from hypervelocity impacts in space plumes and atmospheres, providing in turn clues to the internal structure of the corresponding sources (e.g., Enceladus). This may be valuable in steering modifications in future missions.

We show that hard spheres confined between two parallel hard plates pack denser with periodic adaptive prismatic structures which are composed of alternating prisms of spheres. The internal structure of the prisms adapts to the slit height which results in close packings for a range of plate separations, just above the distance where three intersecting square layers fit exactly between the plates. The adaptive prism phases are also observed in real-space experiments on confined sterically stabilized colloids and in Monte Carlo simulations at finite pressure.

Motivated by new capabilities to realize artificial gauge fields in ultracold atomic systems, and by their potential to access correlated topological phases in lattice systems, we present a new strategy for designing topologically nontrivial band structures. Our approach is simple and direct: it amounts to considering tight-binding models directly in reciprocal space. These models naturally cause atoms to experience highly uniform magnetic flux density and lead to topological bands with very narrow dispersion, without fine-tuning of parameters. Further, our construction immediately yields instances of optical Chern lattices, as well as band structures with Chern numbers of magnitude larger than one.

Although $CP$ violation in the $B$ meson system has been well established by the $B$ factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral $B$ mesons into definite flavor states ($B^0$ or ${\overline{B}}^0$), and $J/\psi K_L^0$ or $c\overline{c}{K}_S^0$ final states (referred to as $B_{+}$ or $B_{-}$), allow comparisons between the probabilities of four pairs of $T$-conjugated transitions, for example, ${\overline{B}}^0\to B_{-}$ and $B_{-}\to {\overline{B}}^0$, as a function of the time difference between the two $B$ decays. Using $468\times {10}^6$ $B\overline{B}$ pairs produced in ${\rm Y}(4S)$ decays collected by the BABAR detector at SLAC, we measure $T$-violating parameters in the time evolution of neutral $B$ mesons, yielding $\Delta S_T^{+}=-1.37\pm 0.14(\mathrm{stat})\pm 0.06(\mathrm{syst})$ and $\Delta S_T^{-}=1.17\pm 0.18(\mathrm{stat})\pm 0.11(\mathrm{syst})$. These nonzero results represent the first direct observation of $T$ violation through the exchange of initial and final states in transitions that can only be connected by a $T$-symmetry transformation.

We have used torsional oscillators, containing disk-shaped slabs of superfluid ${}^3\mathrm{He}$-$A$, to probe the chiral orbital textures created by cooling into the superfluid state while continuously rotating. Comparing the observed flow-driven textural transitions with numerical simulations of possible textures shows that an oriented monodomain texture with $\widehat{\mathit{l}}$ antiparallel to the angular velocity ${\mathbf{\Omega }}_0$ is left behind after stopping rotation. The bias toward a particular chirality, while in the vortex state, is due to the inequivalence of energies of vortices of opposite circulation. When spun-up from rest, the critical velocity for vortex nucleation depends on the sense of rotation relative to that of $\widehat{\mathit{l}}$. A different type of vorticity, apparently linked to the slab’s rim by a domain wall, appears when the angular velocity, $\mathbf{\Omega }$, is parallel to $\widehat{\mathit{l}}$.

A fractal design is shown to be highly efficient both as a load bearing structure and as a general metamaterial. Through changing the hierarchical order of the structure, the scaling of material required for stability against loading can be manipulated. We show that the transition from solid to hollow beams changes the scaling in a manner analogous to increasing the hierarchical order by one. An example second order solid beam frame is constructed using rapid prototyping techniques. The optimal hierarchical order of the structure is found for different values of loading. Possible fabrication methods and applications are then discussed.

We introduce a novel photon production mechanism stemming from the conformal anomaly of $\mathrm{QCD}\times \mathrm{QED}$ and the existence of strong (electro)magnetic fields in heavy ion collisions. Using the hydrodynamical description of the bulk modes of QCD plasma, we show that this mechanism leads to the photon production yield that is comparable to the yield from conventional sources. This mechanism also provides a significant positive contribution to the azimuthal anisotropy of photons, $v_2$, as well as to the radial “flow.” We compare our results to the data from the PHENIX Collaboration.

We show that new families of diffraction-free nonparaxial accelerating optical beams can be generated by considering the symmetries of the underlying vectorial Helmholtz equation. Both two-dimensional transverse electric and magnetic accelerating wave fronts are possible, capable of moving along elliptic trajectories. Experimental results corroborate these predictions when these waves are launched from either the major or minor axis of the ellipse. In addition, three-dimensional spherical nondiffracting field configurations are presented along with their evolution dynamics. Finally, fully vectorial self-similar accelerating optical wave solutions are obtained via oblate-prolate spheroidal wave functions. In all occasions, these effects are illustrated via pertinent examples.

Using a combination of $Z$-contrast imaging and atomically resolved electron energy-loss spectroscopy on a scanning transmission electron microscope, we show that the chemical bonding of individual impurity atoms can be deduced experimentally. We find that when a Si atom is bonded with four atoms at a double-vacancy site in graphene, Si $3d$ orbitals contribute significantly to the bonding, resulting in a planar $s{p}^{2}d$-like hybridization, whereas threefold coordinated Si in graphene adopts the preferred $s{p}^3$ hybridization. The conclusions are confirmed by first-principles calculations and demonstrate that chemical bonding of two-dimensional materials can now be explored at the single impurity level.

We propose a method for quantization of Lagrangians for which the Hamiltonian, as a function of momentum, is a branched function, possibly with cusps. Appropriate boundary conditions, which we identify, ensure unitary time evolution. In special cases a dual (canonical) transformation maps the problem into a problem of quantum mechanics on singular spaces, which we also develop. Several possible applications are indicated.

Classical novae are important contributors to the abundances of key isotopes, such as the radioactive ${}^{18}\mathrm{F}$, whose observation by satellite missions could provide constraints on nucleosynthesis models in novae. The ${}^{17}\mathrm{O}(p,\gamma ){}^{18}\mathrm{F}$ reaction plays a critical role in the synthesis of both oxygen and fluorine isotopes, but its reaction rate is not well determined because of the lack of experimental data at energies relevant to novae explosions. In this study, the reaction cross section has been measured directly for the first time in a wide energy range $E_{\mathrm{c}.\mathrm{m}.}\simeq 200–370\mathrm{keV}$ appropriate to hydrogen burning in classical novae. In addition, the $E_{\mathrm{c}.\mathrm{m}.}=183\mathrm{keV}$ resonance strength, $\omega \gamma =1.67\pm 0.12\mu \mathrm{eV}$, has been measured with the highest precision to date. The uncertainty on the ${}^{17}\mathrm{O}(p,\gamma ){}^{18}\mathrm{F}$ reaction rate has been reduced by a factor of 4, thus leading to firmer constraints on accurate models of novae nucleosynthesis.

When a granular system is tapped, its volume changes. Here, using a well-defined macroscopic protocol, we prepare an ensemble of granular systems and track the statistics of volume changes as a function of the number of taps. This is in contrast to previous studies, which have focused on single trajectories and assumed ergodicity. We devise a new method to assess the convergence properties of a sequence of ensemble volume histograms and introduce a reasonable approximate version of an invariant histogram. We then compare these invariant histograms with histograms generated by sampling a long trajectory for one system and observe nonergodicity, which we quantify. Finally, we use the overlapping histogram method to assess potential compatibility with Edwards’ canonical assumption. Our histograms are incompatible with this assumption.

We describe experiments and measurements on a trapped and laser-cooled single ion of ${}^{88}\mathrm{Sr}^{+}$ which, when probed on its reference $5s{}^{2}S_{1/2}\to 4d{}^{2}D_{5/2}$ transition at 445 THz, provides an optical frequency standard of evaluated accuracy outperforming the current realization of the SI second. Studies are presented showing that micromotion-associated shifts of the standard can be reduced to the ${10}^{-18}$ level and uncertainties in the blackbody-induced shifts for the current system are at the low ${10}^{-17}$ level due to the relatively well-known polarizability of the strontium ion system and careful choice of the trap structure. The current evaluated systematic shifts for the ion transition are at a fractional uncertainty of $2\times {10}^{-17}$. An absolute frequency measurement performed over a two-month period relative to a maser referenced to the SI second via Global Positioning System time transfer has determined the center frequency for the transition at ${\nu }_{SD}=444779044095485.5\pm 0.9\mathrm{Hz}$ ($1\sigma$).

A single multimode fiber is considered an ideal optical element for endoscopic imaging due to the possibility of direct image transmission via multiple spatial modes. However, the wave distortion induced by the mode dispersion has been a fundamental limitation. In this Letter, we propose a method for eliminating the effect of mode dispersion and therefore realize wide-field endoscopic imaging by using only a single multimode fiber with no scanner attached to the fiber. Our method will potentially revolutionize endoscopy in various fields encompassing medicine and industry.

Co-evolution exhibited by a network system, involving the intricate interplay between the dynamics of the network itself and the subsystems connected by it, is a key concept for understanding the self-organized, flexible nature of real-world network systems. We propose a simple model of such coevolving network dynamics, in which the diffusion of a resource over a weighted network and the resource-driven evolution of the link weights occur simultaneously. We demonstrate that, under feasible conditions, the network robustly acquires scale-free characteristics in the asymptotic state. Interestingly, in the case that the system includes dissipation, it asymptotically realizes a dynamical phase characterized by an organized scale-free network, in which the ranking of each node with respect to the quantity of the resource possessed thereby changes ceaselessly. Our model offers a unified framework for understanding some real-world diffusion-driven network systems of diverse types.