An intriguing and elusive feature of the timelike hadron form factor is the possible presence of an imaginary part associated to rescattering processes. We find evidence of that in the recent and precise data on the proton timelike form factor measured by the BABAR Collaboration. By plotting these data as a function of the 3-momentum of the relative motion of the final proton and antiproton, a systematic sinusoidal modulation is highlighted in the near-threshold region. Our analysis attributes this pattern to rescattering processes at a relative distance of 0.7–1.5 fm between the centers of the forming hadrons. This distance implies a large fraction of inelastic processes in $\overline{p}p$ interactions, and a large imaginary part in the related $e^{+}{e}^{-}\to \overline{p}p$ reaction because of unitarity.

We report the first direct measurement of the ${}^{14}\mathrm{O}$ superallowed Fermi $\beta$-decay $Q_{EC}$ value, the last of the so-called “traditional nine” superallowed Fermi $\beta$ decays to be measured with Penning trap mass spectrometry. ${}^{14}\mathrm{O}$, along with the other low-$Z$ superallowed $\beta$ emitter, ${}^{10}\mathrm{C}$, is crucial for setting limits on the existence of possible scalar currents. The new ground state $Q_{EC}$ value, 5144.364(25) keV, when combined with the energy of the $0^{+}$ daughter state, $E_x(0^{+})=2312.798(11)\mathrm{keV}$ [, Nucl. Phys. A523, 1 (1991)], provides a new determination of the superallowed $\beta$-decay $Q_{EC}$ value, $Q_{EC}(\mathrm{sa})=2831.566(28)\mathrm{keV}$, with an order of magnitude improvement in precision, and a similar improvement to the calculated statistical rate function $f$. This is used to calculate an improved $\mathcal{F}t$ value of 3073.8(2.8) s.

The origin of nonlinear dynamics traces back to the study of the dynamics of planets with the seminal work of Poincaré at the end of the nineteenth century: Les Méthodes Nouvelles de la Mécanique Céleste, Vols. 1–3 (Gauthier Villars, Paris, 1899). In his work he introduced a methodology fruitful for investigating the dynamical properties of complex systems, which led to the so-called “Poincaré surface of section,” which allows one to capture the global dynamical properties of a system, characterized by fixed points and separatrices with respect to regular and chaotic motion. For two-dimensional phase space (one degree of freedom) this approach has been extremely useful and applied to particle accelerators for controlling their beam dynamics as of the second half of the twentieth century. We describe here an extension of the concept of 1D fixed points to fixed lines in two dimensions. These structures become the fundamental entities for characterizing the nonlinear motion in the four-dimensional phase space (two degrees of freedom).

We study the transport properties of long quantum wires by generalizing the Luttinger liquid approach to allow for the finite lifetime of the bosonic excitations. Our theory accounts for long-range disorder and strong electron interactions, both of which are common features of experiments with quantum wires. We obtain the electrical and thermal resistances and thermoelectric properties of such quantum wires and find a strong deviation from perfect conductance quantization. We cast our results in terms of the thermal conductivity and bulk viscosity of the electron liquid and give the temperature scale above which the transport can be described by classical hydrodynamics.

We observe geometric resonance features of composite fermions on the flanks of the even-denominator $\nu =1/2$ fractional quantum Hall state in high-mobility two-dimensional electron and hole systems confined to wide GaAs quantum wells and subjected to a weak, strain-induced, unidirectional periodic potential modulation. The features provide a measure of how close to $\nu =1/2$ the system stays single-component and supports a composite fermion Fermi sea before transitioning into a $\nu =1/2$ fractional quantum Hall state, presumably, the two-component ${\mathrm{\Psi }}_{331}$ state.

Inspired by the recent experimental observation of topological superconductivity in ferromagnetic chains, we consider a dilute 2D lattice of magnetic atoms deposited on top of a superconducting surface with a Rashba spin-orbit coupling. We show that the studied system supports a generalization of $p_x+i{p}_y$ superconductivity and that its topological phase diagram contains Chern numbers higher than $\xi /a(\gg 1)$, where $\xi$ is the superconducting coherence length and $a$ is the distance between the magnetic atoms. The signatures of nontrivial topology can be observed by STM spectroscopy in finite-size islands.

We study the effect of strong spin-orbit coupling (SOC) on bound states induced by impurities in superconductors. The presence of SOC breaks the SU(2)-spin symmetry and causes the superconducting order parameter to have generically both singlet ($s$-wave) and triplet ($p$-wave) components. We find that in the presence of SOC the spectrum of Yu-Shiba-Rusinov (YSR) states is qualitatively different in $s$-wave and $p$-wave superconductors, a fact that can be used to identify the superconducting pairing symmetry of the host system. We also predict that, in the presence of SOC, the spectrum of the impurity-induced bound states depends on the orientation of the magnetic moment $\mathbf{S}$ of the impurity and, in particular, that by changing the orientation of $\mathbf{S}$, the fermion-parity of the lowest energy bound state can be tuned. We then study the case of a dimer of magnetic impurities and show that, in this case, the YSR spectrum for a $p$-wave superconductor is qualitatively very different from the one for an $s$-wave superconductor even in the limit of vanishing SOC.

By means of detailed electronic structure calculations, we show that strained ${\mathrm{HgTe}}_x{\mathrm{S}}_{1-x}$ alloys show a surprisingly rich topological phase diagram. In the strong topological insulator phase, the spin chirality of the topological nontrivial surface states can be reversed by adjusting the alloy concentration $x$ and the strain. On top of this, we predict two semimetallic topological phases, namely, a Dirac semimetal and a Weyl semimetal. The topological phases are characterized by their ${\mathcal{Z}}_2$ invariants and their mirror Chern numbers.

We study indented spherical colloids, interacting via depletion forces. These systems exhibit liquid-vapor phase transitions whose properties are determined by a combination of strong “lock-and-key” bonds and weaker nonspecific interactions. As the propensity for lock-and-key binding increases, the critical point moves to significantly lower density, and the coexisting phases change their structure. In particular, the liquid phase is porous, exhibiting large percolating voids. The properties of this system depend strongly on the topological structure of an underlying bond network: we comment on the implications of this fact for the assembly of equilibrium states with controlled porous structures.

Standard evolutionary theories of aging and mortality, implicitly based on mean-field assumptions, hold that programed mortality is untenable, as it opposes direct individual benefit. We show that in spatial models with local reproduction, programed deaths instead robustly result in long-term benefit to a lineage, by reducing local environmental resource depletion via spatiotemporal patterns causing feedback over many generations. Results are robust to model variations, implying that direct selection for shorter life span may be quite widespread in nature.

New data are reported from the operation of a 2 liter ${\mathrm{C}}_3{\mathrm{F}}_8$ bubble chamber in the SNOLAB underground laboratory, with a total exposure of 211.5 kg days at four different energy thresholds below 10 keV. These data show that ${\mathrm{C}}_3{\mathrm{F}}_8$ provides excellent electron-recoil and alpha rejection capabilities at very low thresholds. The chamber exhibits an electron-recoil sensitivity of $<3.5\times 10^{-10}$ and an alpha rejection factor of $>98.2\%$. These data also include the first observation of a dependence of acoustic signal on alpha energy. Twelve single nuclear recoil event candidates were observed during the run. The candidate events exhibit timing characteristics that are not consistent with the hypothesis of a uniform time distribution, and no evidence for a dark matter signal is claimed. These data provide the most sensitive direct detection constraints on WIMP-proton spin-dependent scattering to date, with significant sensitivity at low WIMP masses for spin-independent WIMP-nucleon scattering.

Metal atoms have proved to be sensitive probes of the properties of superfluid helium nanodroplets. To date, all experiments on the doping of helium droplets have concentrated on the attachment of metal atoms in their ground electronic states. Here we report the first examples of metal atoms in excited states becoming attached to helium nanodroplets. The atoms in question are aluminum, and they have been generated by laser ablation in a metastable quartet state, which attaches to and remains on the surface of helium droplets. Evidence for a surface location comes from electronic spectra, which consist of very narrow absorption profiles that show very small spectral shifts. Supporting ab initio calculations show there to be an energy incentive for a metastable Al atom to remain on the surface of a helium droplet rather than move to the interior. The results suggest that helium droplets may provide a method for the capture and transport of metastable excited atomic and molecular species.

We measure the quantum speed of the state evolution of the field in a weakly driven optical cavity QED system. To this end, the mode of the electromagnetic field is considered as a quantum system of interest with a preferential coupling to a tunable environment: the atoms. By controlling the environment, i.e., changing the number of atoms coupled to the optical cavity mode, an environment-assisted speed-up is realized: the quantum speed of the state repopulation in the optical cavity increases with the coupling strength between the optical cavity mode and this non-Markovian environment (the number of atoms).

We explore the unusual electromagnetic response of ultrathin anisotropic $\sigma$-near-zero uniaxial metasurfaces, demonstrating extreme topological transitions—from closed elliptical to open hyperbolic—for surface plasmon propagation, associated with a dramatic tailoring of the local density of states. The proposed metasurfaces may be implemented using nanostructured graphene monolayers and open unprecedented venues for extreme light confinement and unusual propagation and guidance, combined with large tunability via electric bias.

Self-sustained reaction fronts in a disordered medium subject to an external flow display self-affine roughening, pinning, and depinning transitions. We measure spatial and temporal fluctuations of the front in $1+1$ dimensions, controlled by a single parameter, the mean flow velocity. Three distinct universality classes are observed, consistent with the Kardar-Parisi-Zhang (KPZ) class for fast advancing or receding fronts, the quenched KPZ class (positive-qKPZ) when the mean flow approximately cancels the reaction rate, and the negative-qKPZ class for slowly receding fronts. Both qKPZ classes exhibit distinct depinning transitions, in agreement with the theory.

A model equation for the Reynolds number dependence of the dimensionless dissipation rate in freely decaying homogeneous magnetohydrodynamic turbulence in the absence of a mean magnetic field is derived from the real-space energy balance equation, leading to $C_{ϵ}=C_{ϵ,\infty }+C/R_{-}+O(1/R_{-}^2)$, where $R_{-}$ is a generalized Reynolds number. The constant $C_{ϵ,\infty }$ describes the total energy transfer flux. This flux depends on magnetic and cross helicities, because these affect the nonlinear transfer of energy, suggesting that the value of $C_{ϵ,\infty }$ is not universal. Direct numerical simulations were conducted on up to ${2048}^3$ grid points, showing good agreement between data and the model. The model suggests that the magnitude of cosmological-scale magnetic fields is controlled by the values of the vector field correlations. The ideas introduced here can be used to derive similar model equations for other turbulent systems.

Using resonant soft-x-ray scattering as a function of both temperature and magnetic field, we reveal a large number of almost degenerate magnetic orders in ${\mathrm{SrCo}}_6{\mathrm{O}}_{11}$. The Ising-like spins in this frustrated material in fact exhibit a so-called magnetic devil’s staircase. It is demonstrated how a magnetic field induces transitions between different microscopic spin configurations, which is responsible for the magnetoresistance of ${\mathrm{SrCo}}_6{\mathrm{O}}_{11}$. This material therefore constitutes a unique combination of a magnetic devil’s staircase and spin-valve effects, yielding a novel type of magnetoresistance system.