We show that three-dimensional general relativity, augmented with two vector fields, allows for a nonrelativistic limit, different from the standard limit leading to Newtonian gravity, that results in a well-defined action which is of the Chern-Simons type. We show that this three-dimensional “extended Bargmann gravity,” after coupling to matter, leads to equations of motion allowing a wider class of background geometries than the ones that one encounters in Newtonian gravity. We give the supersymmetric generalization of these results and point out an important application in the context of calculating partition functions of nonrelativistic field theories using localization techniques.

We develop a framework for studying the well-known universal term in the Rényi entropy for an arbitrary entangling region in four-dimensional conformal field theories that are holographically dual to gravitational theories. The shape dependence of the Rényi entropy $S_n$ is described by two coefficients: $f_b(n)$ for traceless extrinsic curvature deformations and $f_c(n)$ for Weyl tensor deformations. We provide the first calculation of the coefficient $f_b(n)$ in interacting theories by relating it to the stress tensor one-point function in a deformed hyperboloid background. The latter is then determined by a straightforward holographic calculation. Our results show that a previous conjecture $f_b(n)=f_c(n)$, motivated by surprising evidence from a variety of free field theories and studies of conical defects, fails holographically.

We present a new class of models of lepton flavor in the composite Higgs framework. Following the concept of minimality, they lead to a rich phenomenology in good agreement with the current experimental picture. Because of a unification of the right-handed leptons, our scenario is very predictive and can naturally lead to a violation of lepton-flavor universality in neutral current interactions. We will show that, in particular, the anomaly in $R_K=\mathcal{B}(B\to K{\mu }^{+}{\mu }^{-})/\mathcal{B}(B\to K{e}^{+}{e}^{-})$, found by LHCb, can be addressed, while other constraints from quark- and lepton-flavor physics are met. In fact, the minimal structure of the setup allows for the implementation of a very powerful flavor protection, which avoids the appearance of new sources of flavor-changing neutral currents to very good approximation. Finally, the new lepton sector provides a parametrically enhanced correction to the Higgs mass, such that the need for ultralight top partners is weakened considerably, linking the mass of the latter with the size of the neutrino masses.

A search for radiative decays of the $P$-wave spin singlet charmonium resonance $h_c$ is performed based on $4.48\times {10}^8$ ${\psi }^{\prime }$ events collected with the BESIII detector operating at the BEPCII storage ring. Events of the reaction channels $h_c\to \gamma {\eta }^{\prime }$ and $\gamma \eta$ are observed with a statistical significance of $8.4\sigma$ and $4.0\sigma$, respectively, for the first time. The branching fractions of $h_c\to \gamma {\eta }^{\prime }$ and $h_c\to \gamma \eta$ are measured to be $\mathcal{B}(h_c\to \gamma {\eta }^{\prime })=(1.52\pm 0.27\pm 0.29)\times {10}^{-3}$ and $\mathcal{B}(h_c\to \gamma \eta )=(4.7\pm 1.5\pm 1.4)\times {10}^{-4}$, respectively, where the first errors are statistical and the second are systematic uncertainties.

High $p_T>10\mathrm{GeV}$ elliptic flow, which is experimentally measured via the correlation between soft and hard hadrons, receives competing contributions from event-by-event fluctuations of the low-$p_T$ elliptic flow and event-plane angle fluctuations in the soft sector. In this Letter, a proper account of these event-by-event fluctuations in the soft sector, modeled via viscous hydrodynamics, is combined with a jet-energy-loss model to reveal that the positive contribution from low-$p_T$ $v_2$ fluctuations overwhelms the negative contributions from event-plane fluctuations. This leads to an enhancement of high-$p_T>10\mathrm{GeV}$ elliptic flow in comparison to previous calculations and provides a natural solution to the decade-long high-$p_T$ $R_{AA}\otimes v_2$ puzzle. We also present the first theoretical calculation of high-$p_T$ $v_3$, which is shown to be compatible with current LHC data. Furthermore, we discuss how short-wavelength jet-medium physics can be deconvoluted from the physics of soft, bulk event-by-event flow observables using event-shape engineering techniques.

Direct or Eley-Rideal reactions between energetic ${\mathrm{N}}^{+}$ and ${\mathrm{O}}^{+}$ projectiles and O atoms, adsorbed onto Pt and Pd surfaces, are studied experimentally at incidence energies between 20 and 200 eV. The exit energies of the diatomic molecular products NO and ${\mathrm{O}}_2$ depend linearly on the incidence energy of the corresponding projectiles. A reaction mechanism is proposed, where the incident projectile collides with a single metal atom on the surface, linked to an adsorbed O atom. At the apsis point, a high-energy transient state is formed between the projectile, substrate, and adsorbate atoms. As the projectile begins to rebound, the transient state decomposes into a diatomic molecule, consisting of the original projectile and the adsorbed O atom, which exits the surface with memory of the incidence energy. Energy and momentum conservation during this single-bounce event (atom in, molecule out) accurately predict the exit energy of the molecular product, thus capturing the kinematics of the direct reaction.

Quantum interference arising from the superposition of states is striking evidence of the validity of quantum mechanics, confirmed in many experiments and also exploited in applications. However, as for any scientific theory, quantum mechanics is valid within the limits in which it has been experimentally verified. In order to extend such limits, it is necessary to observe quantum interference in unexplored conditions such as moving terminals at large distances in space. Here, we experimentally demonstrate single photon interference at a ground station due to the coherent superposition of two temporal modes reflected by a rapidly moving satellite a thousand kilometers away. The relative speed of the satellite induces a varying modulation in the interference pattern. The measurement of the satellite distance in real time by laser ranging allows us to precisely predict the instantaneous value of the interference phase. We then observed the interference patterns with a visibility up to 67% with three different satellites and with a path length up to 5000 km. Our results attest to the viability of photon temporal modes for fundamental tests of physics and quantum communication in space.

We report the broadband characterization of the propagation of light through a multiple scattering medium by means of its multispectral transmission matrix. Using a single spatial light modulator, our approach enables the full control of both the spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in sensing, coherent control, and imaging.

Self-organized spatial structures in the light emission from the ion-ion capacitive rf plasma of a strongly electronegative gas (${\mathrm{CF}}_4$) are observed experimentally for the first time. Their formation is analyzed and understood based on particle-based kinetic simulations. These “striations” are found to be generated by the resonance between the driving radio frequency and the eigenfrequency of the ion-ion plasma (derived from an analytical model) that establishes a modulation of the electric field, the ion densities, as well as the energy gain and loss processes of electrons in the plasma. The growth of the instability is followed by the numerical simulations.

We analyze the heavy ion components ($A>4\mathrm{amu}$) in collisionally young solar wind plasma and show that there is a clear, stable dependence of temperature on mass, probably reflecting the conditions in the solar corona. We consider both linear and power law forms for the dependence and find that a simple linear fit of the form $T_i/T_p=(1.35\pm .02)m_i/m_p$ describes the observations twice as well as the equivalent best fit power law of the form $T_i/T_p={(m_i/m_p)}^{1.07\pm .01}$. Most importantly we find that current model predictions based on turbulent transport and kinetic dissipation are in agreement with observed nonthermal heating in intermediate collisional age plasma for $m/q<3.5$, but are not in quantitative or qualitative agreement with the lowest collisional age results. These dependencies provide new constraints on the physics of ion heating in multispecies plasmas, along with predictions to be tested by the upcoming Solar Probe Plus and Solar Orbiter missions to the near-Sun environment.

We studied the electronic and magnetic dynamics of ferromagnetic insulating ${\mathrm{BaFeO}}_3$ thin films by using pump-probe time-resolved resonant x-ray reflectivity at the Fe $2p$ edge. By changing the excitation density, we found two distinctly different types of demagnetization with a clear threshold behavior. We assigned the demagnetization change from slow ($\sim 150\mathrm{ps}$) to fast ($<70\mathrm{ps}$) to a transition into a metallic state induced by laser excitation. These results provide a novel approach for locally tuning magnetic dynamics. In analogy to heat-assisted magnetic recording, metallization can locally tune the susceptibility for magnetic manipulation, allowing one to spatially encode magnetic information.

After more than three decades, the fractional quantum Hall effect still poses challenges to contemporary physics. Recent experiments point toward a fractal scenario for the Hall resistivity as a function of the magnetic field. Here, we consider the so-called thin-torus limit of the Hamiltonian describing interacting electrons in a strong magnetic field, restricted to the lowest Landau level, and we show that it can be mapped onto a one-dimensional lattice gas with repulsive interactions, with the magnetic field playing the role of the chemical potential. The statistical mechanics of such models leads us to interpret the sequence of Hall plateaux as a fractal phase diagram whose landscape shows a qualitative agreement with experiments.

We obtain the general conditions for the emergence of odd-frequency superconducting pairing in a two-dimensional (2D) electronic system proximity coupled to a superconductor, making minimal assumptions about both the 2D system and the superconductor. Using our general results we show that a simple heterostructure formed by a monolayer of a group VI transition metal dichalcogenide, such as molybdenum disulfide, and an $s$-wave superconductor with Rashba spin-orbit coupling exhibits odd-frequency superconducting pairing. Our results allow the identification of a new class of systems among van der Waals heterostructures in which odd-frequency superconductivity should be present.

Weak topological phases are usually described in terms of protection by the lattice translation symmetry. Their characterization explicitly relies on periodicity since weak invariants are expressed in terms of the momentum-space torus. We prove the compatibility of weak topological superconductors with aperiodic systems, such as quasicrystals. We go beyond usual descriptions of weak topological phases and introduce a novel, real-space formulation of the weak invariant, based on the Clifford pseudospectrum. A nontrivial value of this index implies a nontrivial bulk phase, which is robust against disorder and hosts localized zero-energy modes at the edge. Our recipe for determining the weak invariant is directly applicable to any finite-sized system, including disordered lattice models. This direct method enables a quantitative analysis of the level of disorder the topological protection can withstand.

Recently, theory has predicted a Majorana zero mode (MZM) to induce spin selective Andreev reflection (SSAR), a novel magnetic property which can be used to detect the MZM. Here, spin-polarized scanning tunneling microscopy or spectroscopy has been applied to probe SSAR of MZMs in a topological superconductor of the ${\mathrm{Bi}}_2{\mathrm{Te}}_3/{\mathrm{NbSe}}_2$ heterostructure. The zero-bias peak of the tunneling differential conductance at the vortex center is observed substantially higher when the tip polarization and the external magnetic field are parallel rather than antiparallel to each other. This spin dependent tunneling effect provides direct evidence of MZM and reveals its magnetic property in addition to the zero energy modes. Our work will stimulate MZM research on these novel physical properties and, hence, is a step towards experimental study of their statistics and application in quantum computing.

Effects of local lattice distortions on the spin ordering are investigated for the antiferromagnetic classical Heisenberg model on the pyrochlore lattice. It is found by Monte Carlo simulations that the spin-lattice coupling (SLC) originating from site phonons induces a first-order transition into two different types of collinear magnetic ordered states. The state realized at the stronger SLC is cubic symmetric characterized by the magnetic $(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ Bragg peaks, while that at the weaker SLC is tetragonal symmetric characterized by the (1,1,0) ones, each accompanied by the commensurate local lattice distortions. Experimental implications to chromium spinels are discussed.

Using femtosecond time-resolved resonant magnetic x-ray diffraction at the Ho $L_3$ absorption edge, we investigate the demagnetization dynamics in antiferromagnetically ordered metallic Ho after femtosecond optical excitation. Tuning the x-ray energy to the electric dipole ($E1$, $2p\to 5d$) or quadrupole ($E2$, $2p\to 4f$) transition allows us to selectively and independently study the spin dynamics of the itinerant $5d$ and localized $4f$ electronic subsystems via the suppression of the magnetic (2 1 $3\text{−}\tau$) satellite peak. We find demagnetization time scales very similar to ferromagnetic $4f$ systems, suggesting that the loss of magnetic order occurs via a similar spin-flip process in both cases. The simultaneous demagnetization of both subsystems demonstrates strong intra-atomic $4f\text{−}5d$ exchange coupling. In addition, an ultrafast lattice contraction due to the release of magneto-striction leads to a transient shift of the magnetic satellite peak.