Long-chain molecules in polymers are responsible for flow-induced nucleation (FIN). The role of a short-chain matrix in FIN was investigated using bidisperse blends of polyethylenelike high molecular weight long chains in short-chain polymer matrices. It was found that the critical specific work, $w_c$, measured for the onset of FIN in the blends has a power law dependence on the molecular weight of the matrix polymer with $w_c\propto M_w^{2.59\pm 0.27}$ indicating that the matrix can affect the stretching of the long chains and limit their ability to act as nucleation sites for flow-induced crystallization.

Information theory tells us that if the rate of sending information across a noisy channel were above the capacity of that channel, then the transmission would necessarily be unreliable. For classical information sent over classical or quantum channels, one could, under certain conditions, make a stronger statement that the reliability of the transmission shall decay exponentially to zero with the number of channel uses, and the proof of this statement typically relies on a certain fundamental bound on the reliability of the transmission. Such a statement or the bound has never been given for sending quantum information. We give this bound and then use it to give the first example where the reliability of sending quantum information at rates above the capacity decays exponentially to zero. We also show that our framework can be used for proving generalized bounds on the reliability.

Implementations of solid-state quantum optics provide us with devices where qubits are placed at fixed positions in photonic or plasmonic one-dimensional waveguides. We show that solely by controlling the position of the qubits and with the help of a coherent driving, collective spontaneous decay may be engineered to yield an entangled mesoscopic steady state. Our scheme relies on the realization of pure superradiant Dicke models by a destructive interference that cancels dipole-dipole interactions in one dimension.

A fluctuation relation for aging systems is introduced and verified by extensive numerical simulations. It is based on the hypothesis of partial equilibration over phase-space regions in a scenario of entropy-driven relaxation. The relation provides a simple alternative method, amenable of experimental implementation, to measure replica symmetry breaking parameters in aging systems. The connection with the effective temperatures obtained from the fluctuation-dissipation theorem is discussed.

Results are presented from a search for the pair production of third-generation scalar and vector leptoquarks, as well as for top squarks in $R$-parity-violating supersymmetric models. In either scenario, the new, heavy particle decays into a $\tau$ lepton and a $b$ quark. The search is based on a data sample of $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$, which is collected by the CMS detector at the LHC and corresponds to an integrated luminosity of $4.8{\mathrm{fb}}^{-1}$. The number of observed events is found to be in agreement with the standard model prediction, and exclusion limits on mass parameters are obtained at the 95% confidence level. Vector leptoquarks with masses below 760 GeV are excluded and, if the branching fraction of the scalar leptoquark decay to a $\tau$ lepton and a $b$ quark is assumed to be unity, third-generation scalar leptoquarks with masses below 525 GeV are ruled out. Top squarks with masses below 453 GeV are excluded for a typical benchmark scenario, and limits on the coupling between the top squark, $\tau$ lepton, and $b$ quark, ${\lambda }_{333}^{\prime }$ are obtained. These results are the most stringent for these scenarios to date.

The polarizations of the ${\rm Y}(1S)$, ${\rm Y}(2S)$, and ${\rm Y}(3S)$ mesons are measured in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$, using a data sample of ${\rm Y}(nS)\to {\mu }^{+}{\mu }^{-}$ decays collected by the CMS experiment, corresponding to an integrated luminosity of $4.9{\mathrm{fb}}^{-1}$. The dimuon decay angular distributions are analyzed in three different polarization frames. The polarization parameters ${\lambda }_{\vartheta }$, ${\lambda }_{\phi }$, and ${\lambda }_{\vartheta \phi }$, as well as the frame-invariant quantity $\tilde{\lambda }$, are presented as a function of the ${\rm Y}(nS)$ transverse momentum between 10 and 50 GeV, in the rapidity ranges $|y|<0.6$ and $0.6<|y|<1.2$. No evidence of large transverse or longitudinal polarizations is seen in the explored kinematic region.

We develop a framework for a systematic resummation of the transverse momentum distribution of top-quark pairs produced at hadron colliders based on effective field theory. Compared to Drell-Yan and Higgs production, a novel soft function matrix is required to account for the soft gluon emissions from the final states. We calculate this soft function at the next-to-leading order, and perform the resummation at the next-to-next-to-leading logarithmic accuracy. We compare our results with parton shower programs and with the experimental data at the Tevatron and the LHC. We also discuss the implications for the top quark charge asymmetry.

Through an explicit calculation of massive scalar particle (e.g., Higgs boson) production in high energy $pA$ collisions up to one-loop order, we demonstrate, for the first time, that the Sudakov-type logarithms in hard processes in the small-$x$ saturation formalism can be systematically separated from the small-$x$ logarithms. The generic feature of the Sudakov logarithms and all order resummation is derived. This calculation shall provide us deep insights into the understanding of factorizations in the saturation formalism. We further comment on the phenomenological implications in the LHC energy regime and extension to other hard processes in small-$x$ calculations.

The double photoionization of Mg has been studied experimentally and theoretically in a kinematic where the two photoelectrons equally share the excess energy. The observation of a symmetrized gerade amplitude, which strongly deviates from the Gaussian ansatz, is explained by a two-electron interference predicted theoretically, but never before observed experimentally. Similar to the Cooper minima in the single photoionization cross section, the effect finds its origin in the radial extent and oscillation of the target wave function.

A high-storage efficiency and long-lived quantum memory for photons is an essential component in long-distance quantum communication and optical quantum computation. Here, we report a 78% storage efficiency of light pulses in a cold atomic medium based on the effect of electromagnetically induced transparency. At 50% storage efficiency, we obtain a fractional delay of 74, which is the best up-to-date record. The classical fidelity of the recalled pulse is better than 90% and nearly independent of the storage time, as confirmed by the direct measurement of phase evolution of the output light pulse with a beat-note interferometer. Such excellent phase coherence between the stored and recalled light pulses suggests that the current result may be readily applied to single photon wave packets. Our work significantly advances the technology of electromagnetically induced transparency–based optical memory and may find practical applications in long-distance quantum communication and optical quantum computation.

Carrier-envelope-phase- (CEP) stabilized 5 and 22 fs pulses of intense 800 nm light are used to probe the strong-field ionization dynamics of xenon and carbon disulfide. We compare ion yields obtained with and without CEP stabilization. With 8-cycle (22 fs) pulses, ${\mathrm{Xe}}^{6+}$ yields are suppressed (relative to ${\mathrm{Xe}}^{+}$) by 30%–50%, depending on phase, reflecting the phase dependence of nonsequential ionization and its contribution to the formation of higher charge states. Ion yields for ${\mathrm{Xe}}^{q+}$ ($q=2–4$) with CEP-stabilized pulses are enhanced (by up to 50%) compared to those with CEP-unstabilized pulses. Such enhancement is particularly pronounced with 2-cycle (5 fs) pulses and is distinctly phase dependent. Orbital shape and symmetry affect how ${\mathrm{CS}}_2$ responds to variations in optical field that are effected as CEP is altered, keeping intensity constant. Molecular fragmentation is found to depend on field strength (not intensity); the relative enhancement of fragmentation when CEP-stabilized 2-cycle pulses are used is found to be at the expense of molecular ionization.

A novel scheme to compress the radiation pulse in x-ray free electron lasers is proposed not only to shorten the pulse length but also to enhance the peak power of the radiation, by inducing a periodic current enhancement with an optical laser and applying a temporal shift between the optical and electron beams. Calculations show that a 10-keV x-ray pulse with a peak power of 5 TW and a pulse length of 50 asec can be generated by applying this scheme to an existing x-ray free electron laser facility.

The first experimental observation of a Korteweg–de Vries-type soliton wave train in intense electron beams is reported. A narrow, large-amplitude perturbation on a long-pulse beam is observed to steepen and spawn a soliton wave train. The pulse width and amplitude of each peak remain unchanged over a long propagation distance, and the amplitude is inversely proportional to the square of the width. Two such pulses are seen to pass through each other, emerging from the collision unchanged. The experimental results are reproduced by particle-in-cell simulations.

The formation of $\mathrm{R}8$ germanium is reported. The $\beta$-Sn phase is first induced by the indentation of amorphous germanium (a-Ge) and the resultant phases on pressure release are characterized by Raman scattering. The expected Raman line frequencies for the various phases of Ge are determined from first-principles calculations using density functional perturbation theory of the zone-center phonons in the diamond, ST12, BC8, and $\mathrm{R}8$ Ge phases. In addition to the $\mathrm{R}8$ phase, traces of BC8 may also be present following pressure release.

Sliding friction across a thin soft lubricant film typically occurs by stick slip, the lubricant fully solidifying at stick, yielding and flowing at slip. The static friction force per unit area preceding slip is known from molecular dynamics (MD) simulations to decrease with increasing contact area. That makes the large-size fate of stick slip unclear and unknown; its possible vanishing is important as it would herald smooth sliding with a dramatic drop of kinetic friction at large size. Here we formulate a scaling law of the static friction force, which for a soft lubricant is predicted to decrease as $f_m+\Delta f/A^{\gamma }$ for increasing contact area $A$, with $\gamma >0$. Our main finding is that the value of $f_m$, controlling the survival of stick slip at large size, can be evaluated by simulations of comparably small size. MD simulations of soft lubricant sliding are presented, which verify this theory.

The $(\sqrt{3}\times \sqrt{3})R30°$ honeycomb of silicene monolayer on Ag(111) was found to undergo a phase transition to two types of mirror-symmetric boundary-separated rhombic phases at temperatures below 40 K by scanning tunneling microscopy. The first-principles calculations reveal that weak interactions between silicene and Ag(111) drive the spontaneous unusual buckling in the monolayer silicene, forming two energy-degenerate and mirror-symmetric $(\sqrt{3}\times \sqrt{3})R30°$ rhombic phases, in which the linear band dispersion near the Dirac point and a significant gap opening (150 meV) at the Dirac point were induced. The low transition barrier between these two phases enables them to be interchangeable through dynamic flip-flop motion, resulting in the $(\sqrt{3}\times \sqrt{3})R30°$ honeycomb structure observed at high temperature.

We study theoretically the onset of shear banding in the three most common time-dependent rheological protocols: step stress, finite strain ramp (a limit of which gives a step strain), and shear startup. By means of a linear stability analysis we provide a fluid-universal criterion for the onset of banding for each protocol, which depends only on the shape of the experimentally measured time-dependent rheological response function, independent of the constitutive law and internal state variables of the particular fluid in question. Our predictions thus have the same highly general status, in these time-dependent flows, as the widely known criterion for banding in steady state (of negatively sloping shear stress vs shear rate). We illustrate them with simulations of the Rolie-Poly model of polymer flows, and the soft glassy rheology model of disordered soft solids.

A first-principles model of the electrochemical double layer is applied to study surface energies and surface coverage under realistic electrochemical conditions and to determine the equilibrium shape of metal nanoparticles as a function of applied potential. The potential bias is directly controlled by adding electronic charge to the system, while total energy calculations and thermodynamic relations are used to predict electrodeposition curves and changes in surface energies and coverage. This approach is applied to Pt surfaces subject to hydrogen underpotential deposition. The shape of Pt nanoparticles under a cathodic scan is shown to undergo an octahedric-to-cubic transition, which is more pronounced in alkaline media due to the interaction energy of the $p\mathrm{H}$-dependent surface charge with the surface dipole.

We illustrate for a solid-liquid interface how local atomic order in a metallic melt (NiZr) transforms into a massive in-plane ordering at the surface of a crystal (bcc Zr) when commensurability is given between the solute-centered clusters of the melt and the periodic potential of the crystalline surface for a given orientation. Linking molecular dynamics simulation to phase-field modeling allows us to estimate quantitatively the influence of the surface effect on the growth kinetics. This study sheds new light on the relation between the undercooling ability (e.g., in the case of glass-forming alloys) and the pronounced local order in the melt.

We have used aberration corrected in situ transmission electron microscopy to study the interface between liquid Al and different sapphire facet planes, including quantitative analysis of the degree of residual contrast delocalization, ensuring that the experimental contrast perturbations can be associated with density perturbations in the liquid. The results confirm that the liquid is ordered at the interface, and the degree of ordering varies as a function of the sapphire facet planes, with a decreasing degree of order according to $\{0006\}>\{1\overline{2}10\}>\{10\overline{1}2\}\ge \{\overline{1}014\}$.