The derivation of Bell inequalities requires an assumption of measurement independence, related to the amount of free will experimenters have in choosing measurement settings. Violation of these inequalities by singlet state correlations brings this assumption into question. A simple measure of the degree of measurement independence is defined for correlation models, and it is shown that all spin correlations of a singlet state can be modeled via giving up just 14% of measurement independence. The underlying model is deterministic and no signaling. It may thus be favorably compared with other underlying models of the singlet state, which require maximum indeterminism or maximum signaling. A local deterministic model is also given that achieves the maximum possible violation of the well-known Bell–Clauser-Horne-Shimony-Holt inequality, at a cost of only $1/3$ of measurement independence.

Bilayer graphene has attracted considerable interest due to the important role played by many-body effects, particularly at low energies. Here we report local compressibility measurements of a suspended graphene bilayer. We find that the energy gaps at filling factors $\nu =\pm 4$ do not vanish at low fields, but instead merge into an incompressible region near the charge neutrality point at zero electric and magnetic field. These results indicate the existence of a zero-field ordered state and are consistent with the formation of either an anomalous quantum Hall state or a nematic phase with broken rotational symmetry. At higher fields, we measure the intrinsic energy gaps of broken-symmetry states at $\nu =0$, $\pm 1$, and $\pm 2$, and find that they scale linearly with magnetic field, yet another manifestation of the strong Coulomb interactions in bilayer graphene.

A very exotic process of $\beta$-delayed fission of ${}^{180}\mathrm{Tl}$ is studied in detail by using resonant laser ionization with subsequent mass separation at ISOLDE (CERN). In contrast to common expectations, the fission-fragment mass distribution of the post-$\beta$-decay daughter nucleus ${}^{180}\mathrm{Hg}$ ($N/Z=1.25$) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two ${}^{90}\mathrm{Zr}$ fragments, with magic $N=50$ and semimagic $Z=40$. This is a new type of asymmetric fission, not caused by large shell effects related to fragment magic proton and neutron numbers, as observed in the actinide region. The newly measured branching ratio for $\beta$-delayed fission of ${}^{180}\mathrm{Tl}$ is $3.6(7)\times {10}^{-3}\%$, approximately 2 orders of magnitude larger than in an earlier study.

The first measurement of the charged-particle multiplicity density at midrapidity in Pb-Pb collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=2.76\mathrm{TeV}$ is presented. For an event sample corresponding to the most central 5% of the hadronic cross section, the pseudorapidity density of primary charged particles at midrapidity is $1584\pm 4(\mathrm{stat})\pm 76(\mathrm{syst})$, which corresponds to $8.3\pm 0.4(\mathrm{syst})$ per participating nucleon pair. This represents an increase of about a factor 1.9 relative to $pp$ collisions at similar collision energies, and about a factor 2.2 to central Au-Au collisions at $\sqrt{s_{NN}}=0.2\mathrm{TeV}$. This measurement provides the first experimental constraint for models of nucleus-nucleus collisions at LHC energies.

We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$ with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region ($|\eta |<0.8$) and transverse momentum range $0.2<p_t<5.0\mathrm{GeV}/c$. The elliptic flow signal $v_2$, measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is $0.087\pm 0.002(\mathrm{stat})\pm 0.003(\mathrm{syst})$ in the 40%–50% centrality class. The differential elliptic flow $v_2(p_t)$ reaches a maximum of 0.2 near $p_t=3\mathrm{GeV}/c$. Compared to RHIC Au-Au collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.

By using the ATLAS detector, observations have been made of a centrality-dependent dijet asymmetry in the collisions of lead ions at the Large Hadron Collider. In a sample of lead-lead events with a per-nucleon center of mass energy of 2.76 TeV, selected with a minimum bias trigger, jets are reconstructed in fine-grained, longitudinally segmented electromagnetic and hadronic calorimeters. The transverse energies of dijets in opposite hemispheres are observed to become systematically more unbalanced with increasing event centrality leading to a large number of events which contain highly asymmetric dijets. This is the first observation of an enhancement of events with such large dijet asymmetries, not observed in proton-proton collisions, which may point to an interpretation in terms of strong jet energy loss in a hot, dense medium.

The “island of inversion” nucleus ${}^{32}\mathrm{Mg}$ has been studied by a ($t$, $p$) two neutron transfer reaction in inverse kinematics at REX-ISOLDE. The shape coexistent excited $0^{+}$ state in ${}^{32}\mathrm{Mg}$ has been identified by the characteristic angular distribution of the protons of the $\Delta L=0$ transfer. The excitation energy of 1058 keV is much lower than predicted by any theoretical model. The low $\gamma$-ray intensity observed for the decay of this $0^{+}$ state indicates a lifetime of more than 10 ns. Deduced spectroscopic amplitudes are compared with occupation numbers from shell-model calculations.

We show experimentally for the first time that two mutually attracting flux ropes may bounce back instead of merging together, leading to a variety of dynamics not expected from a two-dimensional model. Attraction forces due to flux rope currents compete with repulsion from field line bending of in-plane and out-of-plane magnetic fields and elastic plasma compression. Bouncing dynamics occurs if the line-bending force due to an out-of-plane field dominates. Otherwise, the ropes merge. Further reduction in the field line-bending force results in violently erratic magnetic states.

We propose a topological order parameter for interacting topological insulators, expressed in terms of the full Green’s functions of the interacting system. We show that it is exactly quantized for a time-reversal invariant topological insulator, and it can be experimentally measured through the topological magneto-electric effect. This topological order parameter can be applied to both interacting and disordered systems, and used for determining their phase diagrams.

We report on the temperature dependent electron transport in graphene at different carrier densities $n$. Employing an electrolytic gate, we demonstrate that $n$ can be adjusted up to $4\times {10}^{14}{\mathrm{cm}}^{-2}$ for both electrons and holes. The measured sample resistivity $\rho$ increases linearly with temperature $T$ in the high temperature limit, indicating that a quasiclassical phonon distribution is responsible for the electron scattering. As $T$ decreases, the resistivity decreases more rapidly following $\rho (T)\sim T^4$. This low temperature behavior can be described by a Bloch-Grüneisen model taking into account the quantum distribution of the two-dimensional acoustic phonons in graphene. We map out the density dependence of the characteristic temperature ${\Theta }_{\mathrm{BG}}$ defining the crossover between the two distinct regimes, and show that, for all $n$, $\rho (T)$ scales as a universal function of the normalized temperature $T/{\Theta }_{\mathrm{BG}}$.

New precise results of a measurement of the elastic electron-proton scattering cross section performed at the Mainz Microtron MAMI are presented. About 1400 cross sections were measured with negative four-momentum transfers squared up to $Q^2=1(\mathrm{GeV}/c{)}^2$ with statistical errors below 0.2%. The electric and magnetic form factors of the proton were extracted by fits of a large variety of form factor models directly to the cross sections. The form factors show some features at the scale of the pion cloud. The charge and magnetic radii are determined to be $⟨r_E^2{⟩}^{1/2}=0.879(5{)}_{\mathrm{stat}}(4{)}_{\mathrm{syst}}(2{)}_{\mathrm{model}}(4{)}_{\mathrm{group}}\mathrm{fm}$ and $⟨r_M^2{⟩}^{1/2}=0.777(13{)}_{\mathrm{stat}}(9{)}_{\mathrm{syst}}(5{)}_{\mathrm{model}}(2{)}_{\mathrm{group}}\mathrm{fm}$.

We study evolution driven by spatial heterogeneity in a stochastic model of source-sink ecologies. A sink is a habitat where mortality exceeds reproduction so that a local population persists only due to immigration from a source. Immigrants can, however, adapt to conditions in the sink by mutation. To characterize the adaptation rate, we derive expressions for the first arrival time of adapted mutants. The joint effects of migration, mutation, birth, and death result in two distinct parameter regimes. These results may pertain to the rapid evolution of drug-resistant pathogens and insects.

We report here the first successful synthesis of cold antihydrogen atoms employing a cusp trap, which consists of a superconducting anti-Helmholtz coil and a stack of multiple ring electrodes. This success opens a new path to make a stringent test of the CPT symmetry via high precision microwave spectroscopy of ground-state hyperfine transitions of antihydrogen atoms.

Optical absorption of circularly polarized light is well known to yield an electron spin polarization in direct band gap semiconductors. We demonstrate that electron spins can even be generated with high efficiency by absorption of linearly polarized light in ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$. By changing the incident linear polarization direction we can selectively excite spins in both polar and transverse directions. These directions can be identified by the phase during spin precession using time-resolved Faraday rotation. We show that the spin orientations do not depend on the crystal axes suggesting an extrinsic excitation mechanism.

We present a 4D ($x$; $y$; $z$; $t$) force map of Dictyostelium cells crawling on a soft gel substrate. Vertical forces are of the same order as the tangential ones. The cells pull the substratum upward along the cell, medium, or substratum contact line and push it downward under the cell except for the pseudopods. We demonstrate quantitatively that the variations in the asymmetry in cortical forces correlates with the variations of the direction and speed of cell displacement.

We note that the essential idea of inflation, that the Universe underwent a brief period of accelerated expansion followed by a long period of decelerated expansion, can be encapsulated in a “closure condition” which relates the amount of accelerated expansion during inflation to the amount of decelerated expansion afterward. We present a protocol for systematically testing the validity of this condition observationally.

The ac conductivity spectra of $x\mathrm{AgI}\mathrm{\text{−}}(1-x){\mathrm{AgPO}}_3$ fast-ion conducting glasses spanning the flexible, intermediate (isostatically rigid), and stressed rigid phases are analyzed. The rescaled frequency-dependent spectra are mapped into time-dependent mean-square displacements out of which a typical length scale characterizing the spatial extent $\sqrt{⟨{\tilde{R}}^2(\infty )⟩}$ of nonrandom subdiffusive regions of ionic motions is computed. The latter quantity is studied as a function of AgI compositions, and is found to display a maximum isostatic compositions, providing the first clear evidence of a typical length scale of a dynamical nature when a system becomes isostatically rigid and enters that phase.

We introduce a new method to measure the elastic constants of globular proteins. Gold nanoparticles, tethered to a gold surface by the protein, are driven by an ac electric field while their displacement is synchronously detected by evanescent wave scattering, yielding the mechanical response function of the macromolecular sample in the frequency domain. We apply the method to measure the stiffening of an enzyme upon binding its substrate.

We experimentally demonstrate the first metamaterial “illusion optics” device—an “invisible gateway” by using a transmission-line medium. The device contains an open channel that can block waves at a particular frequency range. We also demonstrate that such a device can work in a broad frequency range.

We study the transversal motion of paramagnetic particles on a uniaxial garnet film, exhibiting a longitudinal ratchet effect in the presence of an oscillating magnetic field. Without the field, the thermal diffusion coefficient obtained by video microscopy is $D_0\approx 3\times {10}^{-4}\mu {\mathrm{m}}^2/\mathrm{s}$. With the field, the transversal diffusion exhibits a giant enhancement by almost four decades and a pronounced maximum as a function of the driving frequency. We explain the experimental findings with a theoretical interpretation in terms of random disorder effects within the magnetic film.