Yang-Yang (YY) and singular diameter critical anomalies arise in exactly soluble compressible cell gas (CCG) models that obey complete scaling with pressure mixing. Thus, on the critical isochore $\rho ={\rho }_c$, ${\tilde{C}}_{\mu }≔-T{d}^2\mu /d{T}^2$ diverges as $|t{|}^{-\alpha }$ when $t\propto T-T_c\to 0^{-}$ while ${\rho }_d-{\rho }_c\sim |t{|}^{2\beta }$ where ${\rho }_d(T)=\frac{1}{2}[{\rho }_{\text{liq}}+{\rho }_{\text{gas}}]$. When the discrete local CCG cell volumes fluctuate freely, the YY ratio ${\mathfrak{R}}_{\mu }={\tilde{C}}_{\mu }/C_V$ may take any value $-\infty <{\mathfrak{R}}_{\mu }<\frac{1}{2}$ but “anticorrelated” free volumes are needed for ${\mathfrak{R}}_{\mu }>0$. More general decorated CCGs, including “hydrogen bonding” water models, illuminate energy-volume coupling as relevant to ${\mathfrak{R}}_{\mu }$.

Gravitational collapse of a massless scalar field in spherically symmetric anti–de Sitter (AdS) spacetimes presents a new phenomenology with a series of critical points whose dynamics is discretely self-similar as in the asymptotically flat case. Each critical point is the limit of a branch of scalar field configurations that have bounced off the AdS boundary a fixed number of times before forming an apparent horizon. We present results from a numerical study that focus on the interfaces between branches. We find that there is a mass gap between branches and that subcritical configurations near the critical point form black holes with an apparent horizon mass that follows a power law of the form $M_{\mathrm{AH}}-M_g\propto (p_c-p{)}^{\xi }$, where $M_g$ is the mass gap and the exponent $\xi \simeq 0.7$ appears to be universal.

We report on measurements of the decays of $\overline{B}$ mesons into the semileptonic final states $\overline{B}\to D^{(*)}{\pi }^{+}{\pi }^{-}{\ell }^{-}\overline{\nu }$, where $D^{(*)}$ represents a $D$ or $D^{*}$ meson and ${\ell }^{-}$ is an electron or a muon. These measurements are based on $471\times {10}^6$ $B\overline{B}$ pairs recorded with the BABAR detector at the SLAC asymmetric $B$ factory PEP-II. We determine the branching fraction ratios $R_{{\pi }^{+}{\pi }^{-}}^{(*)}=\mathcal{B}(\overline{B}\to D^{(*)}{\pi }^{+}{\pi }^{-}{\ell }^{-}\overline{\nu })/\mathcal{B}(\overline{B}\to D^{(*)}{\ell }^{-}\overline{\nu })$ using events in which the second $B$ meson is fully reconstructed. We find $R_{{\pi }^{+}{\pi }^{-}}=0.067\pm 0.010\pm 0.008$ and $R_{{\pi }^{+}{\pi }^{-}}^{*}=0.019\pm 0.005\pm 0.004$, where the first uncertainty is statistical and the second is systematic. Based on these results and assuming isospin invariance, we estimate that $\overline{B}\to D^{(*)}\pi \pi {\ell }^{-}\overline{\nu }$ decays, where $\pi$ denotes either a ${\pi }^{\pm }$ and ${\pi }^0$ meson, account for up to half the difference between the measured inclusive semileptonic branching fraction to charm hadrons and the corresponding sum of previously measured exclusive branching fractions.

Electron-positron angular correlations were measured for the isovector magnetic dipole 17.6 MeV ($J^{\pi }=1^{+}$, $T=1$) $\text{state}\to \text{ground}$ state ($J^{\pi }=0^{+}$, $T=0$) and the isoscalar magnetic dipole 18.15 MeV ($J^{\pi }=1^{+}$, $T=0$) $\text{state}\to \text{ground}$ state transitions in ${}^8\mathrm{Be}$. Significant enhancement relative to the internal pair creation was observed at large angles in the angular correlation for the isoscalar transition with a confidence level of $>5\sigma$. This observation could possibly be due to nuclear reaction interference effects or might indicate that, in an intermediate step, a neutral isoscalar particle with a mass of $16.70\pm 0.35(\text{stat})\pm 0.5(\text{syst})\mathrm{MeV}/c^2$ and $J^{\pi }=1^{+}$ was created.

We investigate the dissociation of ${{\mathrm{H}}_2}^{+}$ into a proton and a ${\mathrm{H}}^0$ after single ionization with photons of an energy close to the threshold. We find that the $p^{+}$ and the ${\mathrm{H}}^0$ do not emerge symmetrically in the case of the ${{\mathrm{H}}_2}^{+}$ dissociating along the $1s{\sigma }_g$ ground state. Instead, a preference for the ejection of the $p^{+}$ in the direction of the escaping photoelectron can be observed. This symmetry breaking is strongest for very small electron energies. Our experiment is consistent with a recent prediction by Serov and Kheifets [Phys. Rev. A 89, 031402 (2014)]. In their model, which treats the photoelectron classically, the symmetry breaking is induced by the retroaction of the long-range Coulomb potential onto the dissociating ${{\mathrm{H}}_2}^{+}$.

We demonstrate Doppler cooling of trapped magnesium ions using a frequency comb at 280 nm obtained from a frequency tripled Ti:sapphire laser. A comb line cools on the $3s_{1/2}-3p_{3/2}$ transition, while the nearest blue-detuned comb line contributes negligible heating. We observe the cooling-heating transition and long-term cooling of ion chains with several sympathetically cooled ions. Spatial thermometry shows that the ion is cooled to near the Doppler limit. Doppler cooling with frequency combs has the potential to open many additional atomic species to laser cooling by reaching further into the vacuum and extreme ultraviolet via high-harmonic generation and by providing a broad bandwidth from which multiple excitation sidebands can be obtained.

Phase-control techniques of chaos aim to extract periodic behaviors from chaotic systems by applying weak harmonic perturbations with a suitably chosen phase. However, little is known about the best strategy for selecting adequate perturbations to reach desired states. Here we use experimental measures and numerical simulations to assess the benefits of controlling individually the three terms of a Duffing oscillator. Using a real-time analog indicator able to discriminate on-the-fly periodic behaviors from chaos, we reconstruct experimentally the phase versus perturbation strength stability areas when periodic perturbations are applied to different terms governing the oscillator. We verify the system to be more sensitive to perturbations applied to the quadratic term of the double-well Duffing oscillator and to the quartic term of the single-well Duffing oscillator.

In this work, the manipulation of an electrically charged droplet bouncing on a vertically vibrated bath is investigated. When a horizontal, uniform, and static electric field is applied to it, a motion is induced. The droplet is accelerated when the droplet is small. On the other hand, large droplets appear to move with a constant speed that depends linearly on the applied electrical field. In the latter regime, high-speed imaging of one bounce reveals that the droplet experiences an acceleration due to the electrical force during the flight and decelerates to 0 when interacting with the surface of the bath. Thus, the droplet moves with a constant average speed on a large time scale. We propose a criterion based on the force necessary to move a charged droplet at the surface of the bath to discriminate between constant speed and accelerated droplet regimes.

A unique feature of ultracold atoms is the separation of length scales, $r_0\ll k_F^{-1}$, where $k_F$ and $r_0$ are the Fermi momentum characterizing the average particle distance and the range of interaction between atoms, respectively. For $s$-wave scattering, Shina Tan discovered that such diluteness leads to universal thermodynamic relations governed by contact. Here, we show that the concept of contact can be generalized to an arbitrary partial-wave scattering. Contact of all partial-wave scatterings forms a contact spectrum, which establishes universal thermodynamic relations with notable differences from those in the presence of $s$-wave scattering alone. Such a contact spectrum is particularly useful for characterizing many-body correlations in atomic quantum Hall states (QHSs). It has an interesting connection with a special bipartite entanglement spectrum of QHSs and enables an intrinsic probe of atomic QHSs using short-range two-body correlations.

The global phase diagram of wetting in the two-dimensional Ising model is obtained through the exact calculation of the surface excess free energy. In addition to a surface field for inducing wetting, a surface-coupling enhancement is also included. The wetting transition (of second order) is critical for any finite ratio of surface coupling $J_s$ to bulk coupling $J$, and becomes of first order in the limit $J_s/J\to \infty$. However, for $J_s/J\gg 1$, the critical region is exponentially small and is practically invisible to numerical studies. A distinct preasymptotic regime exists in which the transition displays first-order character. In this regime, surprisingly, the surface susceptibility and surface specific heat develop a divergence and show anomalous scaling with an exponent equal to $3/2$.

We propose to realize and observe Chern Kondo insulators in an optical superlattice with laser-assisted $s$ and $p$ orbital hybridization and a synthetic gauge field, which can be engineered based on the recent cold atom experiments. Considering a double-well square optical lattice, the localized $s$ orbitals are decoupled from itinerant $p$ bands and are driven into a Mott insulator due to the strong Hubbard interaction. Raman laser beams are then applied to induce tunnelings between $s$ and $p$ orbitals, and generate a staggered flux simultaneously. Because of the strong Hubbard interaction of $s$ orbital states, we predict the existence of a critical Raman laser-assisted coupling, beyond which the Kondo screening is achieved, and then a fully gapped Chern Kondo phase emerges, with the topology characterized by integer Chern numbers. Being a strongly correlated topological state, the Chern Kondo phase is different from the single-particle quantum anomalous Hall state, and can be identified by measuring the band topology and double occupancy of $s$ orbitals. The experimental realization and detection of the predicted Chern Kondo insulator are also proposed.

Several recent experiments have reported an anomalous temperature dependence of the Coulomb drag effect in electron-hole bilayers. Motivated by these puzzling data, we study theoretically a low-density electron-hole bilayer, where electrons and holes avoid quantum degeneracy by forming excitons. We describe the ionization-recombination crossover between the electron-hole plasma and exciton gas and calculate both the intralayer and drag resistivity as a function of temperature. The latter exhibits a minimum followed by a sharp upturn at low temperatures, in qualitative agreement with the experimental observations [see, e.g., J. A. Seamons et al., Phys. Rev. Lett. 102, 026804 (2009)]. Importantly, the drag resistivity in the proposed scenario is found to be rather insensitive to a mismatch in electron and hole concentrations, in sharp contrast to the scenario of electron-hole Cooper pairing.

Motile and driven particles confined in microfluidic channels exhibit interesting emergent behavior, from propagating density bands to density shock waves. A deeper understanding of the physical mechanisms responsible for these emergent structures is relevant to a number of physical and biomedical applications. Here, we study the formation of density shock waves in the context of an idealized model of microswimmers confined in a narrow channel and subject to a uniform external flow. Interestingly, these density shock waves exhibit a transition from “subsonic” with compression at the back to “supersonic” with compression at the front of the population as the intensity of the external flow increases. This behavior is the result of a nontrivial interplay between hydrodynamic interactions and geometric confinement, and it is confirmed by a novel quasilinear wave model that properly captures the dependence of the shock formation on the external flow. These findings can be used to guide the development of novel mechanisms for controlling the emergent density distribution and the average population speed, with potentially profound implications on various processes in industry and biotechnology, such as the transport and sorting of cells in flow channels.

The charge formation at interfaces involving electrolyte solutions is due to the chemical equilibrium between the surface reactive groups and the potential determining ions in the solution (i.e., charge regulation). In this Letter we report our findings that this equilibrium is strongly coupled to the precise molecular structure of the solution near the charged interface. The neutral solvent molecules dominate this structure due to their overwhelmingly large number. Treating the solvent as a structureless continuum leads to a fundamentally inadequate physical picture of charged interfaces. We show that a proper account of the solvent effect leads to an unexpected and complex system behavior that is affected by the molecular and ionic excluded volumes and van der Waals interactions.

Having analytical instances of the eigenstate thermalization hypothesis (ETH) is of obvious interest, both for fundamental and applied reasons. This is generally a hard task, due to the belief that nonlinear interactions are basic ingredients of the thermalization mechanism. In this article we prove that random Gaussian-free fermions satisfy ETH in the multiparticle sector, by analytically computing the correlations and entanglement entropies of the theory. With the explicit construction at hand, we finally comment on the differences between fully random Hamiltonians and random Gaussian systems, providing a physically motivated notion of randomness of the microscopic quantum state.