We show that Euclidean axion wormholes in theories of gravity coupled to a single axion have several independent inhomogeneous perturbations that lower the Euclidean action. Our analysis relies on a judiciously chosen gauge-invariant variable which makes the negative mode structure about axion wormholes transparent. Perturbations lowering the action are concentrated in the neck region and exist for wormholes in flat space and in AdS. Their presence means axion wormholes are not relevant saddle points of the functional integral in quantum gravity. This resolves the paradoxes associated with these solutions from the viewpoint of AdS/CFT.

We present the first-principles derivation of a weak-strong duality between the fishnet theory in four dimensions and a discretized stringlike model living in five dimensions. At strong coupling, the dual description becomes classical and we demonstrate explicitly the classical integrability of the model. We test our results by reproducing the strong coupling limit of the four-point correlator computed before nonperturbatively from the conformal partial wave expansion. Because of the extreme simplicity of our model, it could provide an ideal playground for holography with no supersymmetry. Furthermore, since the fishnet model and $\mathcal{N}=4$ super Yang-Mills theory are continuously linked, our consideration could shed light on the derivation of $\mathrm{AdS}/\mathrm{CFT}$ for the latter. For simplicity, in this Letter we restrict our considerations to a large subset of all states.

We propose to use the unique event topology and reconstruction capabilities of liquid argon time projection chambers to study sub-GeV atmospheric neutrinos. The detection of low energy recoiled protons in DUNE allows for a determination of the leptonic $CP$-violating phase independent from the accelerator neutrino measurement. Our findings indicate that this analysis can exclude a range of values of ${\delta }_{CP}$ beyond the $3\sigma$ level. Moreover, the determination of the sub-GeV atmospheric neutrino flux will have important consequences in the detection of diffuse supernova neutrinos and in dark matter experiments.

A time-dependent analysis of the $B_s^0\to \varphi \gamma$ decay rate is performed to determine the $CP$ -violating observables $S_{\varphi \gamma }$ and $C_{\varphi \gamma }$ and the mixing-induced observable ${\mathcal{A}}_{\varphi \gamma }^{\mathrm{\Delta }}$. The measurement is based on a sample of $pp$ collision data recorded with the LHCb detector, corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$ at center-of-mass energies of 7 and 8 TeV. The measured values are $S_{\varphi \gamma }=0.43\pm 0.30\pm 0.11$, $C_{\varphi \gamma }=0.11\pm 0.29\pm 0.11$, and ${\mathcal{A}}_{\varphi \gamma }^{\mathrm{\Delta }}=-{0.67}_{-0.41}^{+0.37}\pm 0.17$, where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables $S$ and $C$ in radiative $B_s^0$ decays. The results are consistent with the standard model predictions.

Apart from the difficulty of producing highly scattering samples, a major challenge in the observation of Anderson localization of 3D light is identifying an unambiguous signature of the phase transition in experimentally feasible situations. In this Letter, we establish a clear correspondence between the collapse of the conductance, the increase in intensity fluctuations at the localization transition and the scaling analysis results based on the Thouless number, thus connecting the macroscopic and microscopic approaches of localization. Furthermore, the transition thus inferred is fully compatible both with the results based on the eigenvalue analysis of the microscopic description and with the effective-medium Ioffe-Regel criterion.

Out-of-time-ordered correlators (OTOCs) describe information scrambling under unitary time evolution, and provide a useful probe of the emergence of quantum chaos. Here we calculate OTOCs for a model of disorder-free localization whose exact solubility allows us to study long-time behavior in large systems. Remarkably, we observe logarithmic spreading of correlations, qualitatively different to both thermalizing and Anderson localized systems. Rather, such behavior is normally taken as a signature of many-body localization, so that our findings for an essentially noninteracting model are surprising. We provide an explanation for this unusual behavior, and suggest a novel Loschmidt echo protocol as a probe of correlation spreading. We show that the logarithmic spreading of correlations probed by this protocol is a generic feature of localized systems, with or without interactions.

The reflection of electrons at noncollinear magnetic surfaces is investigated by spin-polarized scanning tunneling microscopy and spectroscopy on unoccupied resonance states located in vacuo. Even for energies up to 20 eV above the Fermi level, the resonance states are found to be spin split, exhibiting the same local spin quantization axis as the underlying spin texture. Mapping the spin-dependent electron phase shift upon reflection at the surface on the atomic scale demonstrates the relevance of all magnetic ground state interactions for the scattering of spin-polarized low-energy electrons.

We provide a framework for understanding the gapless Kitaev spin liquid (KSL) in the language of the tensor network (TN). Without introducing a Majorana fermion, most of the features of the KSL, including the symmetries, gauge structure, criticality, and vortex freeness, are explained in a compact TN representation. Our construction reveals a hidden string gas structure of the KSL. With only two variational parameters to adjust, we obtain an accurate KSL Ansatz with the bond dimension $D=8$ in a compact form, where the energy is about 0.007% higher than the exact one.

We present a first-principles method for the calculation of the temperature-dependent relaxation of symmetry-breaking atomic driving forces in photoexcited systems. We calculate the phonon-assisted decay of the photoexcited force on the low-symmetry $E_g$ mode following absorption of an ultrafast pulse in Bi, Sb, and As. The force decay lifetimes for Bi and Sb are of the order of 10 fs and in agreement with recent experiments, demonstrating that electron-phonon scattering is the primary mechanism relaxing the symmetry-breaking forces. Calculations for a range of absorbed photon energies suggest that larger amplitude, symmetry-breaking atomic motion may be induced by choosing a pump photon energy which maximizes the product of the initial $E_g$ force and its lifetime. The high-symmetry $A_{1g}$ force undergoes a partial decay to a nonzero constant on similar timescales, which has not yet been measured in experiments. The average imaginary part of the electron self-energy over the photoexcited carrier distribution provides a crude indication of the decay rate of symmetry-breaking forces.

Inspired by the recent discovery of correlated insulating states in twisted bilayer graphene, we study a two-orbital Hubbard model on the honeycomb lattice with two electrons per unit cell. Based on the real-space density matrix renormalization group simulation, we identify a metal-insulator transition around $U_c/t=2.5–3$. In the vicinity of $U_c$, we find strong spin-orbital density wave fluctuations at commensurate wave vectors, accompanied by weaker incommensurate charge density wave fluctuations. The spin-orbital density wave fluctuations are enhanced with increasing system sizes, suggesting the possible emergence of long-range order in the two-dimensional limit. At larger $U$, our calculations indicate a possible nonmagnetic Mott insulator phase without spin or orbital polarization. Our findings offer new insight into correlated electron phenomena in twisted bilayer graphene and other multiorbital honeycomb materials.

We report on the quantum storage of a heralded frequency-multiplexed single photon in an integrated laser-written rare-earth doped waveguide. The single photon contains 15 discrete frequency modes separated by 261 MHz and spanning across 4 GHz. It is obtained from a nondegenerate photon pair created via cavity-enhanced spontaneous down-conversion, where the heralding photon is at telecom wavelength and the heralded photon is at 606 nm. The frequency-multimode photon is stored in a praseodymium-doped waveguide using the atomic frequency comb (AFC) scheme, by creating multiple combs within the inhomogeneous broadening of the crystal. Thanks to the intrinsic temporal multimodality of the AFC scheme, each spectral bin includes 9 temporal modes, such that the total number of stored modes is about 130. We demonstrate that the storage preserves the nonclassical properties of the single photon, and its normalized frequency spectrum.

Nearly all theoretical analyses of Maxwell’s demon focus on its energetic and entropic costs of operation. Here, we focus on its rate of operation. In our model, a demon’s rate limitation stems from its finite response time and gate area. We determine the rate limits of mass and energy transfer, as well as entropic reduction for four such demons: those that select particles according to (1) direction, (2) energy, (3) number, and (4) entropy. Last, we determine the optimal gate size for a demon with small, finite response time, and compare our predictions with molecular dynamics simulations with both ideal and nonideal gasses. Also, we study the conditions under which the demons are able to move both energy and particles in the chosen direction when attempting to only move one.

We investigate the impact of prior models on the upper bound of the sum of neutrino masses, $\sum m_{\nu }$. Using data from the large scale structure of galaxies, cosmic microwave background, type Ia supernovae, and big bang nucleosynthesis, we argue that cosmological neutrino mass and hierarchy determination should be pursued using exact models, since approximations might lead to incorrect and nonphysical bounds. We compare constraints from physically motivated neutrino mass models (i.e., ones respecting oscillation experiments) to those from models using standard cosmological approximations. The former give a consistent upper bound of $\sum m_{\nu }\lesssim 0.26\mathrm{eV}$ (95% CI) and yield the first approximation-independent upper bound for the lightest neutrino mass species, $m_0^{\nu }<0.086\mathrm{eV}$ (95% CI). By contrast, one of the approximations, which is inconsistent with the known lower bounds from oscillation experiments, yields an upper bound of $\sum m_{\nu }\lesssim 0.15\mathrm{eV}$ (95% CI); this differs substantially from the physically motivated upper bound.

We investigate the variation of holographic complexity for two nearby target states. Based on Nielsen’s geometric approach, we find the variation only depends on the end point of the optimal trajectory, a result which we designate the first law of complexity. As an example, we examine the $\text{complexity}=\text{action}$ conjecture when the anti–de Sitter vacuum is perturbed by a scalar field excitation, which corresponds to a coherent state. Remarkably, the gravitational contributions completely cancel and the final variation reduces to a boundary term coming entirely from the scalar field action. Hence, the null boundary of Wheeler-DeWitt patch appears to act like the “end of the quantum circuit”.

We find and analyze the exact time-dependent potential energy surface driving the proton motion for a model of cavity-induced suppression of proton-coupled electron transfer. We show how, in contrast to the polaritonic surfaces, its features directly correlate to the proton dynamics and we discuss cavity modifications of its structure responsible for the suppression. The results highlight the interplay between nonadiabatic effects from coupling to photons and coupling to electrons and suggest caution is needed when applying traditional dynamics methods based on polaritonic surfaces.

Coupled parametric oscillators were recently employed as simulators of artificial Ising networks, with the potential to solve computationally hard minimization problems. We demonstrate a new dynamical regime within the simplest network—two coupled parametric oscillators, where the oscillators never reach a steady state, but show persistent, full-scale, coherent beats, whose frequency reflects the coupling properties and strength. We present a detailed theoretical and experimental study and show that this new dynamical regime appears over a wide range of parameters near the oscillation threshold and depends on the nature of the coupling (dissipative or energy preserving). Thus, a system of coupled parametric oscillators transcends the Ising description and manifests unique coherent dynamics, which may have important implications for coherent computation machines.

We present a controlled cascade of self-assemblings of colloidal droplets at a nematic liquid crystal–air interface into large-scale ordered structures. Changing the tilt of the droplet-induced elastic dipoles via its dependence on the nematic film thickness, we are able to control the dipole-dipole interaction and thus the self-assembling regime. For a progressively large tilt, droplets form anisotropic lattices, which then transform into arrays of repulsive chains, then to bands of half-period-shifted densely bound chains. These structures with chain order at the inner scale aggregate into different large-scale clusters that have a pronounced circular pattern and are stabilized by the many-body elastocapillary attraction.