A possible relation between flare activity in superluminous supernovae and gamma-ray bursts

Significant undulations appear in the light curve of a recently discovered super-luminous supernova (SLSN) SN 2015bn after the first peak, while the underlying profile of the light curve can be well explained by a continuous energy supply from a central engine, possibly the spin-down of a millisecond magnetar. We propose that these undulations are caused by an intermittent pulsed energy supply, indicating an energetic flare activity of the central engine of the SLSN. Many post-burst flares were discovered during X-ray afterglow observations of Gamma-Ray Bursts (GRBs). We find that the SLSN flares described here approximately obey the empirical correlation between the luminosity and time scale of GRB flares, extrapolated to the relevant longer time scales of SLSN flares. This confirms the possible connection between these two different phenomena as previously suggested.Comment: 6 pages, 4 figures, accepted for publication in MNRA

Statistics of Chaotic Resonances in an Optical Microcavity

Distributions of eigenmodes are widely concerned in both bounded and open systems. In the realm of chaos, counting resonances can characterize the underlying dynamics (regular vs. chaotic), and is often instrumental to identify classical-to-quantum correspondence. Here, we study, both theoretically and experimentally, the statistics of chaotic resonances in an optical microcavity with a mixed phase space of both regular and chaotic dynamics. Information on the number of chaotic modes is extracted by counting regular modes, which couple to the former via dynamical tunneling. The experimental data are in agreement with a known semiclassical prediction for the dependence of the number of chaotic resonances on the number of open channels, while they deviate significantly from a purely random-matrix-theory-based treatment, in general. We ascribe this result to the ballistic decay of the rays, which occurs within Ehrenfest time, and importantly, within the timescale of transient chaos. The present approach may provide a general tool for the statistical analysis of chaotic resonances in open systems.Comment: 5 pages, 5 figures, and a supplemental informatio

What Powered the Optical Transient AT2017gfo Associated with GW170817?

The groundbreaking discovery of the optical transient AT2017gfo associated with GW170817 opens a unique opportunity to study the physics of double neutron star (NS) mergers. We argue that the standard interpretation of AT2017gfo as being powered by radioactive decay of r-process elements faces the challenge of simultaneously accounting for the peak luminosity and peak time of the event, as it is not easy to achieve the required high mass, and especially the low opacity of the ejecta required to fit the data. A plausible solution would be to invoke an additional energy source, which is probably provided by the merger product. We consider energy injection from two types of the merger products: (1) a post-merger black hole powered by fallback accretion; and (2) a long-lived NS remnant. The former case can only account for the early emission of AT2017gfo, with the late emission still powered by radioactive decay. In the latter case, both early- and late-emission components can be well interpreted as due to energy injection from a spinning-down NS, with the required mass and opacity of the ejecta components well consistent with known numerical simulation results. We suggest that there is a strong indication that the merger product of GW170817 is a long-lived (supramassive or even permanently stable), low magnetic field NS. The result provides a stringent constraint on the equations of state of NSs

Studying newborn neutron stars by the transient emission after stellar collapses and compact binary mergers

The formation of neutron stars (NSs), both from collapses of massive stars and mergers of compact objects, can be usually indicated by bright transients emitted from explosively-ejected material. In particular, if the newborn NSs can rotate at a millisecond period and have a sufficiently high magnetic field, then the spin-down of the NSs would provide a remarkable amount of energy to the emitting material. As a result, super-luminous supernovae could be produced in the massive stellar collapse cases, while some unusual fast evolving and luminous optical transients could arise from the cases of NS mergers and accretion-induced collapses of white dwarfs. In all cases, if the dipolar magnetic fields of the newborn NSs can be amplified to be as high as $10^{15}$ G, a relativistic jet could be launched and then a gamma-ray burst can be produced as the jet successfully breaks out from the surrounding nearly-isotropic ejected material.Comment: 10 pages, 9 pictures, to appear in the AIP Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy, Jan. 3-7, Xiamen, Chin

Hybrid quantum device based on NV centers in diamond nanomechanical resonators plus superconducting waveguide cavities

We propose and analyze a hybrid device by integrating a microscale diamond beam with a single built-in nitrogen-vacancy (NV) center spin to a superconducting coplanar waveguide (CPW) cavity. We find that under an ac electric field the quantized motion of the diamond beam can strongly couple to the single cavity photons via dielectric interaction. Together with the strong spin-motion interaction via a large magnetic field gradient, it provides a hybrid quantum device where the dia- mond resonator can strongly couple both to the single microwave cavity photons and to the single NV center spin. This enables coherent information transfer and effective coupling between the NV spin and the CPW cavity via mechanically dark polaritons. This hybrid spin-electromechanical de- vice, with tunable couplings by external fields, offers a realistic platform for implementing quantum information with single NV spins, diamond mechanical resonators, and single microwave photons.Comment: Accepted by Phys. Rev. Applie

Decoupled advection-dispersion method for determining wall thickness of slurry trench cutoff walls

Low-permeability slurry trench cutoff walls are commonly constructed as barriers for containment of subsurface point-source pollution or as part of seepage-control systems on contaminated sites. A method to estimate wall thickness in slurry wall design is proposed based on decoupling the advective and dispersive components of contaminant fluxes through the wall. The relative error of the result obtained by the proposed method compared with that by an analytical solution was found to increase as the ratio of the specified breakthrough exit concentration (c*) to the source concentration (c0) increased. For c*/c0 of less than 0.1, which covers common practical situations, the relative error was not greater than 4% and was always conservative, indicating that the proposed method provides sufficient accuracy for design. For a given breakthrough criterion (i.e., c*/c0), the relative error was low for the scenarios having either a low or high column Peclet number, where either dispersion or advection dominates the contaminant migration, respectively, and the relative error was high for the scenario having an intermediate column Peclet number, in which case the coupling effect of advective and dispersive migrations is relatively high