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Using the coupled-wave method, we consider anharmonic Bloch oscillations of light in an array of waveguides, taking into account the coupling between waveguides up to the third order. It is shown that the beam trajectory is periodic, with the trajectory oscillating within a single period. (paper)
Self-modulation oscillations of the intensity of a solid-state coupled-cavity ring laser are theoretically investigated. The results obtained analytically show that external optical coupling allows the frequency of self-modulation oscillations to be varied in a wide range (from a few kilohertz to hundreds of megahertz). Using coupled cavities, it is possible to significantly weaken the influence of the coupling of counterpropagating waves through backscattering on the self-modulation frequency and to increase the scale factor that determines the dependence of the self-modulation frequency on the rotation velocity. (paper)
We have observed damped longitudinal cosmological-scale oscillations in a unique model-independent plot of scale factor against lookback time for Type Ia supernovae data. We found several first-derivative relative maxima/minima spanning the range of reported transition redshifts. These extrema comprise two full cycles with a period of approximately 0.15 Hubble times (H{sub 0}=68 km s{sup −1} Mpc{sup −1}). This period corresponds to a fundamental frequency of approximately seven cycles over the Hubble time. Transition-z values quoted in the literature generally fall near these minima and may explain the reported wide spread up to the predicted ΛCDM value of approximately z = 0.77. We also observe second and third harmonics of the fundamental. The scale factor data is analyzed several different ways, including smoothing, Fourier transform, and autocorrelation. We propose a cosmological scalar field harmonic oscillator model for the observation. On this timescale, for a quantum scalar field, the scalar field mass is extraordinarily small at 3 × 10{sup −32} eV. Our scalar field density parameter precisely replaces the ΛCDM dark matter density parameter in the Friedmann equations, resulting in essentially identical data fits, and its present value matches the Planck value. Thus the wave is fundamentally a dark matter wave. We therefore posit that this scalar field manifests itself as the dark matter.
Neutrons play an important role in the dynamics of gamma-ray bursts. The presence of neutrons in the baryon-loaded fireball is expected. If the neutron abundance is comparable to that of protons, important features may be observed, such as quasi-thermal multi-GeV neutrinos in coincidence with a subphotospheric γ-ray emission, nucleosynthesis at later times, and rebrightening of the afterglow emission. Additionally, thermal MeV neutrinos are created by electron-positron annihilation, electron (positron) capture on protons (neutrons), and nucleonic bremsstrahlung. Although MeV neutrinos are difficult to detect, quasi-thermal GeV neutrinos are expected in cubic kilometer detectors and/or DeepCore and IceCube. In this paper, we show that neutrino oscillations have outstanding implications for the dynamics of the fireball evolution and also that they can be detected through their flavor ratio on Earth. For that, we derive the resonance and charged-neutrality conditions as well as the neutrino self-energy and effective potential up to the order of m{sub W}{sup −4} at strong, moderate, and weak magnetic field approximations to constrain the dynamics of the fireball. We found important implications: (1) resonant oscillations are suppressed for high baryon densities as well as neutron abundance larger than that of protons, and (2) the effect of magnetic field is to decrease the proton-to-neutron ratio aside from the number of multi-GeV neutrinos expected in the DeepCore detector. Also, we estimate the GeV neutrino flavor ratios along the jet and on Earth.
RE J1034+396, a narrow-line Seyfert 1 active galactic nucleus (AGN), is the first example of AGNs that exhibited a nearly coherent quasi-periodic oscillation (QPO) for the data collected by XMM-Newton in 2007. The spectral behaviors and timing properties of the QPO have been studied since its discovery. We present an analysis of the QPO in RE J1034+396 based on the Hilbert-Huang transform. Comparing with other time-frequency analysis methods, the Hilbert spectrum reveals the variation of the QPO period in great detail. Furthermore, the empirical mode decomposition provides bandpass-filtered data that can be used in the O – C and correlation analysis. We suggest that it is better to divide the evolution of the QPO in this observation into three epochs according to their different periodicities. In addition to the periodicities, the correlations between the QPO periods and corresponding mean count rates are also different in these three epochs. Further examining the phase lags in these epochs, we found no significant phase lags between the soft and hard X-ray bands, which is also confirmed in the QPO phase-resolved spectral analysis. Finally, we discuss the indications of current models including a spotted accretion disk, diskoseismology, and oscillation of shock according to the observed time-frequency and spectral behaviors.
We report oscillator strengths for six strong vibrational bands between 105.0 and 115.2 nm, associated with transitions from the v = 0 level of the X {sup 1}Σ{sup +} ground state to the v = 0 and 1 levels of the B {sup 1}Σ{sup +}, C {sup 1}Σ{sup +}, and E {sup 1}Π states, in {sup 12}C{sup 16}O, {sup 12}C{sup 17}O, {sup 12}C{sup 18}O, {sup 13}C{sup 16}O, and {sup 13}C{sup 18}O. These measurements extend the development of a comprehensive database of line positions, oscillator strengths, and linewidths of photodissociating transitions for all astrophysically relevant CO isotopologues. The E-X bands, in particular, play central roles in CO photodissociation and fractionation models of interstellar clouds and circumstellar disks including the early solar nebula. The resolving powers of the room-temperature measurements, R = 300,000-400,000, allow for the analysis of individual line strengths within bands; the measurements reveal J-dependences in the branch intensities of the C(v = 0,1)-X(0) and E(v = 0,1)-X(0) bands in all isotopologues. Minimal or no isotopologue dependence was found in the f-values of the C(v = 0,1)-X(0) and E(v = 0,1)-X(0) bands at a ∼5% uncertainty level. Revised dissociation branching ratios for the C(v = 0,1) and E(v = 0,1) levels are computed based on these f-values. The weak isotopologue dependence of the f-values presented here eliminates this mechanism as an explanation for the large {sup 17}O enrichments seen in recent laboratory photolysis experiments on CO at wavelengths from 105 to 108 nm.
This study investigates the dynamical response of dark matter (DM) halos to recurrent starbursts in forming less-massive galaxies to solve the core-cusp problem. The gas, which is heated by supernova feedback after a starburst, expands and the star formation then terminates. This expanding gas loses energy by radiative cooling and then falls back toward the galactic center. Subsequently, the starburst is enhanced again. This cycle of expansion and contraction of the interstellar gas leads to a repetitive change in the gravitational potential of the gas. The resonance between DM particles and the density wave excited by the oscillating potential plays a key role in understanding the physical mechanism of the cusp-core transition of DM halos. DM halos effectively gain kinetic energy from the baryon potential through the energy transfer driven by the resonance between the particles and density waves. We determine that the critical condition for the cusp-core transition is such that the oscillation period of the gas potential is approximately the same as the local dynamical time of DM halos. We present the resultant core radius of a DM halo after the cusp-core transition induced by the resonance by using the conventional mass density profile predicted by the cold dark matter models. Moreover, we verify the analytical model by using N-body simulations, and the results validate the resonance model.
Quasi-periodic oscillations (QPOs) observed in the giant flares of magnetars are of particular interest due to their potential to open up a window into the neutron star interior via neutron star asteroseismology. However, only three giant flares have been observed. We therefore make use of the much larger data set of shorter, less energetic recurrent bursts. Here, we report on a search for QPOs in a large data set of bursts from the two most burst-active magnetars, SGR 1806-20 and SGR 1900+14, observed with Rossi X-ray Timing Explorer. We find a single detection in an averaged periodogram comprising 30 bursts from SGR 1806–20, with a frequency of 57 Hz and a width of 5 Hz, remarkably similar to a giant flare QPO observed from SGR 1900+14. This QPO fits naturally within the framework of global magneto-elastic torsional oscillations employed to explain giant flare QPOs. Additionally, we uncover a limit on the applicability of Fourier analysis for light curves with low background count rates and strong variability on short timescales. In this regime, standard Fourier methodology and more sophisticated Fourier analyses fail in equal parts by yielding an unacceptably large number of false-positive detections. This problem is not straightforward to solve in the Fourier domain. Instead, we show how simulations of light curves can offer a viable solution for QPO searches in these light curves.
In outburst sources, quasi-periodic oscillation (QPO) frequency is known to evolve in a certain way: in the rising phase, it monotonically goes up until a soft intermediate state is achieved. In the propagating oscillatory shock model, oscillation of the Compton cloud is thought to cause QPOs. Thus, in order to increase QPO frequency, the Compton cloud must collapse steadily in the rising phase. In decline phases, the exact opposite should be true. We investigate cause of this evolution of the Compton cloud. The same viscosity parameter that increases the Keplerian disk rate also moves the inner edge of the Keplerian component, thereby reducing the size of the Compton cloud and reducing the cooling timescale. We show that cooling of the Compton cloud by inverse Comptonization is enough for it to collapse sufficiently so as to explain the QPO evolution. In the two-component advective flow configuration of Chakrabarti-Titarchuk, centrifugal force-induced shock represents the boundary of the Compton cloud. We take the rising phase of 2010 outburst of Galactic black hole candidate H 1743-322 and find an estimation of variation of the α parameter of the sub-Keplerian flow to be monotonically rising from 0.0001 to 0.02, well within the range suggested by magnetorotational instability. We also estimate the inward velocity of the Compton cloud to be a few meters per second, which is comparable to what is found in several earlier studies of our group by empirically fitting the shock locations with the time of observations.
We studied the horizontal branch oscillations (HBO) and the band-limited components observed in the power spectra of the transient neutron star low-mass X-ray binary XTE J1701-462 and the persistent ''Sco-like'' Z source GX 17+2. These two components were studied based on the state-resolved spectra. We found that the frequencies of XTE J1701-462 lie on the known correlations (WK and PBK), showing consistency with other types of X-ray binaries (black holes, atoll sources, and millisecond X-ray pulsars). However, GX 17+2 is shifted from the WK correlation like other typical Z sources. We suggest that the WK/PBK main track forms a boundary that separates persistent sources from transient sources. The characteristic frequencies of break and HBO are independent of accretion rate in both sources, though it depends on spectral models. We also report the energy dependence of the HBO and break frequencies in XTE J1701-462 and how the temporal properties change with spectral state in XTE J1701-462 and GX 17+2. We studied the correlation between rms at the break and the HBO frequency. We suggest that HBO and break components for both sources probably arise from a similar physical mechanism: Comptonization emission from the corona. These two components could be caused by the same kind of oscillation in a corona with uneven density, and they could be generated from different areas of the corona. We further suggest that different proportions of the Comptonization component in the total flux cause the different distribution between GX 17+2 and XTE J1701-462 in the rms{sub break}-rms{sub HBO} diagram.
Radiative emission lines from nitrogen and its ions are often observed in nebula spectra, where the N{sup 2+} abundance can be inferred from lines of the 2p4f configuration. In addition, intensity ratios between lines of the 2p3p-2p3s and 2p4f-2p3d transition arrays can serve as temperature diagnostics. To aid abundance determinations and plasma diagnostics, wavelengths and oscillator strengths were calculated with high precision for electric dipole (E1) transitions from levels in the 2p4f configuration of N{sup +}. Electron correlation and relativistic effects, including the Breit interaction, were systematically taken into account within the framework of the multiconfiguration Dirac-Hartree-Fock method. Except for the 2p4f-2p4d transitions with quite large wavelengths and the two-electron-one-photon 2p4f-2s2p {sup 3} transitions, the uncertainties of the present calculations were controlled to within 3% and 5% for wavelengths and oscillator strengths, respectively. We also compared our results with other theoretical and experimental values when available. Discrepancies were found between our calculations and previous calculations due to the neglect of relativistic effects in the latter.
There is evidence that long-duration gamma-ray bursts (GRBs) originate from the core collapse of massive stars. When a jet punctures through the progenitor envelope, high-energy neutrinos can be produced by the reverse shock formed at the jet head. It is suggested that low-luminosity GRBs are possible candidates of this high-energy neutrino precursor up to ∼PeV scales. Before leaving the progenitor, these high-energy neutrinos must oscillate from one flavor to another with the matter effect in the envelope. Under the assumption of a power-law stellar envelope density profile ρ∝r{sup −α} with an index α, we study the properties of TeV–PeV neutrino oscillation. We find that adiabatic conversion is violated for these neutrinos so we calibrate the level crossing effect. The resonance condition is reached for different energies at different radii. We note that the effective mixing angles in matter for PeV neutrinos are close to zero, so the transition probabilities from one flavor to another are almost invariant for PeV neutrinos. We plot all the transition probabilities versus the energy of TeV–PeV neutrinos from the birth place to the surface of the progenitor. With an initial flavor ratio ϕ{sub ν{sub e}{sup 0}}:ϕ{sub ν{sub μ}{sup 0}}:ϕ{sub ν{sub τ}{sup 0}}=1:2:0, we plot how the flavor ratio evolves with energy and distance when neutrinos are still in the envelope, and we find the ratio when they reach the Earth. For PeV neutrinos, the ratio is always ϕ{sub ν{sub e}}:ϕ{sub ν{sub μ}}:ϕ{sub ν{sub τ}}≃0.30:0.37:0.33 on Earth. In addition, we discuss the dependence of the flavor ratio on energy and α and find a good result. This dependence may provide a promising probe of the progenitor structure.
We describe sophisticated new Bayesian analysis methods that make it possible to estimate quickly the masses and radii of rapidly rotating, oblate neutron stars by fitting oblate-star waveform models to energy-resolved observations of the waveforms of X-ray burst oscillations produced by such stars. We find that a 25% variation of the temperature of the hot spot in the north-south direction does not significantly bias estimates of the mass M and equatorial radius R{sub eq} derived by fitting a model that assumes a uniform-temperature spot. Our results show that fits of oblate-star waveform models to waveform data can simultaneously determine M and R{sub eq} with 1σ uncertainties ≲7% if (1) the star's rotation rate is ≳ 600 Hz; (2) the spot center and observer's sightline are both within 30{sup ∘} of the star's rotational equator; and (3) ∼10{sup 7} counts are collected during burst oscillations that have a fractional rms amplitude ≳10%. A fractional amplitude of ∼10% is realistic, and the accepted NICER and proposed LOFT and AXTAR space missions could collect 10{sup 7} counts from a single star by combining data from many X-ray bursts from the star. Uncertainties ≲7% are small enough to improve substantially our understanding of cold, ultradense matter.
We describe mock data-sets generated to simulate the high-redshift quasar sample in Data Release 11 (DR11) of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). The mock spectra contain Lyα forest correlations useful for studying the 3D correlation function including Baryon Acoustic Oscillations (BAO). They also include astrophysical effects such as quasar continuum diversity and high-density absorbers, instrumental effects such as noise and spectral resolution, as well as imperfections introduced by the SDSS pipeline treatment of the raw data. The Lyα forest BAO analysis of the BOSS collaboration, described in Delubac et al. 2014, has used these mock data-sets to develop and cross-check analysis procedures prior to performing the BAO analysis on real data, and for continued systematic cross checks. Tests presented here show that the simulations reproduce sufficiently well important characteristics of real spectra. These mock data-sets will be made available together with the data at the time of the Data Release 11.
We present a systematical study on single crystalline FeSb 2 using electrical transport and magnetic torque measurements at low temperatures. Nonlinear magnetic field dependence of Hall resistivity demonstrates a multi-carrier transport instinct of the electronic transport. Current-controlled negative differential resistance (CC-NDR) observed in current–voltage characteristics below ~ 7 K is closely associated with the intrinsic transition ~ 5 K of FeSb 2 , which is, however, mediated by extrinsic current-induced Joule heating effect. The antimony crystallized in a preferred orientation within the FeSb 2 lattice in the high-temperature synthesis process leaves its fingerprint in the de Haas-Van Alphen (dHvA) oscillations, and results in the regular angular dependence of the oscillating frequencies. Nevertheless, possible existence of intrinsic non-trivial states cannot be completely ruled out. Our findings call for further theoretical and experimental studies to explore novel physics on flux-free grown FeSb 2 crystals.
Current analytical and numerical modeling suggest the existence of ubiquitous thin current sheets in the corona that could explain the observed heating requirements. On the other hand, new high resolution observations of the corona indicate that its magnetic field may tend to organize itself in fine strand-like structures of few hundred kilometers widths. The link between small structure in models and the observed widths of strand-like structure several orders of magnitude larger is still not clear. A popular theoretical scenario is the nanoflare model, in which each strand is the product of an ensemble of heating events. Here, we suggest an alternative mechanism for strand generation. Through forward modeling of three-dimensional MHD simulations we show that small amplitude transverse MHD waves can lead in a few periods time to strand-like structure in loops in EUV intensity images. Our model is based on previous numerical work showing that transverse MHD oscillations can lead to Kelvin-Helmholtz instabilities that deform the cross-sectional area of loops. While previous work has focused on large amplitude oscillations, here we show that the instability can occur even for low wave amplitudes for long and thin loops, matching those presently observed in the corona. We show that the vortices generated from the instability are velocity sheared regions with enhanced emissivity hosting current sheets. Strands result as a complex combination of the vortices and the line-of-sight angle, last for timescales of a period, and can be observed for spatial resolutions of a tenth of loop radius.
This tutorial offers a pedagogical guide to hybrid quantum processors that integrate discrete-variable (DV) qubits and continuous-variable (CV) oscillators. Aimed at computer scientists, engineers, and physicists, it provides an overview of the experimental, algorithmic, and architectural aspects of this novel and rapidly developing hardware model. Experimental realizations of this model include superconducting, trapped-ion, and neutral-atom platforms. By combining DV and CV components, hybrid oscillator-qubit processors enable a powerful new paradigm that offers complementary strengths for quantum control, error correction, computation, and simulation. Working toward the goal of a full-stack system connecting applications to CV-DV hardware, we define and formulate abstract machine models and instruction set architectures. These essential abstractions enable codesign of hardware and software, and resource estimation for exploring the potential of current and future hardware for computational and simulation tasks. Using these abstractions, we present both new and existing examples that illustrate the benefits of hybrid CV-DV processors relative to traditional DV-only hardware in computation as well as quantum simulation of physical models. Examples include algorithms for transferring states between DV and CV systems, performing the quantum Fourier transform, and simulation of lattice gauge theories. Relative to qubit-only hardware, the bosonic degrees of freedom natively available in hybrid architectures can substantially reduce the circuit complexity of simulations for physical models containing bosons. A key technique is the extension of quantum signal processing ideas to CV-DV systems. This work is intended to serve as a timely and comprehensive guide to this relatively unexplored yet promising approach to quantum computation and to provide a road map to guide future development.
The recent detection of the solar neutrino background at dark matter direct detection experiments paves the way to fully explore an important degeneracy in neutrino oscillations in the presence of new interactions, named the LMA-Dark degeneracy. This degeneracy makes it impossible to determine the neutrino mass ordering in oscillation experiments if neutrinos have new vectorial interactions with matter. As the composition of solar neutrinos at the Earth consists of all three neutrino flavors, testing the presence of new neutrino interactions in the muon and tau neutrino sector in scatterings can fully probe the LMA-Dark region for the first time. In this paper we show that current data from XENONnT and PandaX-4T do not yet exclude the LMA-Dark region with equal couplings of a new mediator to muon and tau neutrinos and quarks, and we identify the possible experimental scenarios to do so in the future. We also show that dark matter experiments can distinguish new interactions in the muon or tau sector only from new interactions affecting both sectors.