Large Phase Difference Research Articles

Initial wavefunction dependence on atom interferometry phases

In this paper we present a mathematical procedure to analytically calculate the output signal of a pulsed atom interferometer in an inertial field. Using the well-known ABCDξ method we take into account the full wave dynamics of the atoms with a first order treatment of the wavefront distortion by the laser pulses. Using a numerical example we study the effect of both the length of the beam splitting laser pulses and of the width of the initial spatial distribution of the atoms. First, we find that in a general inertial field the interferometer only has a limited window in terms of the initial width (centered around 100 μm in the example calculation) in which interference fringes are visible at all. This effect is caused by the inevitable statistical spread in atomic parameters, such as initial position and momentum, and the dependence of the interferometer phase on these. In the optimum case, the useful range of the initial width is formed by the range in which both the spatial distribution and the diffraction limited momentum spread are small enough to avoid large phase differences over the atomic wavefunction. As a second result we find that the interferometer phase depends strongly on the length of the laser pulses and, to a smaller extent, on the initial width of the atomic cloud. This spatial dependency is relatively small (∼10−5 rad) and justifies semiclassical approximations, as used in other calculations, for most experiments. New high-accuracy experiments, however, will come in the range where this effect is no longer negligible.

A binaural advantage in the subjective modulation transfer function with simple impulse responses

The speech transmission index (STI) has been a popular method for predicting speech intelligibility in rooms. It is based on the magnitude of the modulation transfer function, which can be derived from the impulse response of the room and the background noise levels. However, it does not take into account that humans listen with two ears. There can be large interaural phase differences in the modulation transfer functions, which can create detectable interaural level difference fluctuations. Measurements were made to determine whether these interaural modulation phase differences can be used to enhance the detectability of sinusoidal intensity modulations imposed on a broadband noise carrier and then convolved with simple, dichotic impulse responses. The results show that there can be a significant advantage to listening with two ears over listening with just one. Some further investigations were made to determine whether this advantage in signal detection can also be used as an advantage for speech intelligibility.

Synchronization and firing death in the dynamics of two interacting excitable units with heterogeneous signals

We study the response of two coupled FitzHugh-Nagumo systems to heterogeneous external inputs. The latter, modeled by periodic parametric stimuli, force the uncoupled excitable systems into a regime of chaotic firing. Due to parameter dispersion involved in randomly distributed amplitudes and/or phases of the external forces the units are nonidentical and their firing events will be asynchronous. Interest is focused on mutually synchronized spikings arising through the coupling. It is demonstrated that the phase difference of the two external forces crucially affects the onset of spike synchronization as well as the resulting degree of synchrony. For large phase differences the degree of spike synchrony is constricted to a maximal possible value and cannot be enhanced upon increasing the coupling strength. We even found that overcritically strong couplings lead to suppression of firing so that the units perform synchronous subthreshold oscillations. This effect, which we call "firing death," is due to a coupling-induced modification of the excitation threshold impeding spiking of the units. In clear contrast, when only the amplitudes of the forces are distributed perfect spike synchrony is achieved for sufficiently strong coupling.

DirectCPviolation inB¯0→ρ0(ω)ρ0(ω)→π+π−π+π−

We study the direct CP violation in $\bar{B}^0 \to \rho^0(\omega)\rho^0(\omega) \to \pi^+\pi^-\pi^+\pi^-$ (with unpolarized $\rho^0(\omega)$) via the $\rho-\omega$ mixing mechanism which causes a large strong phase difference and consequently a large CP violating asymmetry when the masses of the $\pi^+\pi^-$ pairs are in the vicinity of the $\omega$ resonance. Since there are two $\rho (\omega)$ mesons in the intermediate state $\rho-\omega$ mixing contributes twice to the first order of isospin violation, leading to an even larger CP violating asymmetry (could be 30% -- 50% larger) than in the case where only one $\rho (\omega)$ meson is involved. The CP violating asymmetry depends on the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements and the hadronic matrix elements. The factorization approach is applied in the calculation of the hadronic matrix elements with the nonfactorizable effects being included effectively in an effective parameter, $N_c$. We give the constraint on the range of $N_c$ from the latest experimental data for the branching ratios for $\bar{B}^0 \to\rho^0\rho^0$ and $\bar{B}^0 \to\rho^+\rho^-$. We find that the CP violating asymmetry could be very large (even more than 90% for some values of $N_c$). It is shown that the sensitivity of the CP violating asymmetry to $N_c$ is large compared with its smaller sensitivity to the CKM matrix elements. We also discuss the possibility to remove the mod $(\pi)$ ambiguity in the determination of the CP violating phase angle $\alpha$ through the measurement of the CP violating asymmetry in the decay $\bar{B}^0\to \rho^0(\omega)\rho^0(\omega) \to \pi^+\pi^-\pi^+\pi^-$.

Band Edge Effects and Normal Mode Propagation in Waveguide Magnetophotonic Crystals

A study of band edge phenomena in ridge waveguide magnetophotonic crystals is presented. Normal mode analysis is used to examine the near-band edge and Bragg center-wavelength group velocities and their relation to the polarization. Large polarization departures from the input are observed in Bragg gratings patterned by focused-ion-beam milling on liquid-phase-epitaxial (LPE) (Bi,Lu)(2.8±0.1)Fe(4.6±0.2)O(12.4±0.3) films on (111) gadolinium gallium garnet (GGG) substrates. Transfer matrix analysis of the spectral response in the photonic crystals allows the determination of the phase of the elliptically polarized normal modes from measured transmittances and polarization rotation. Unlike non-birefringent Faraday rotators a non-linear-relation exists between polarization rotation and the normal mode phase difference. Large phase differences between right- and left-elliptically polarized normal modes and optical slow-down are found near the band edges and at the resonant cavity center-wavelength. Standing-wave photon trapping and optical slow-down are analyzed and compared for these systems.

On low-frequency modulations and three-dimensionality in vortex shedding behind a normal plate

In this study spanwise correlation measurements and smoke flow visualization were performed on vortex shedding behind a normal plate. For Reynolds numbers in a range between 1800 and 27000, the hot-wire signals measured were analysed by a wavelet transformation, from which the instantaneous properties of vortex shedding were obtained and examined. Results show that the phase difference of vortex shedding detected at two spanwise locations, separated by twice the characteristic length, can be as high as 35. A correlation analysis further shows that large spanwise phase differences occur when small fluctuating amplitudes in the vortex shedding signals are measured. Smoke-wire visualization performed at Reynolds number 1800 indicates that the formation of shedding vortex can be divided into two distinct situations, namely, one featuring a long formation region, called Mode L; and the other featuring a short formation region, called Mode S. In Mode S, the three-dimensionality of vortex formation appears to be very pronounced, and the secondary vortices are clearly present in the separated shear layer. The events of Mode S occupy less than 5% of the total time measured, and are called the burst events in this study.

Large electroweak penguin contribution inB→Kπandππdecay modes

We discuss about a possibility of large electroweak penguin contribution in B -> K pi and pi pi from recent experimental data. The experimental data may be suggesting that there are some discrepancies between the data and theoretical estimation in the branching ratios of them. In B -> K pi decays, to explain it, a large electroweak penguin contribution and large strong phase differences seem to be needed. The contributions should appear also in B -> pi pi. We show, as an example, a solution to solve the discrepancies in both B -> K pi and B -> pi pi. However the magnitude of the parameters and the strong phase estimated from experimental data are quite large compared with the theoretical estimations. It may be suggesting some new physics effects are including in these processes. We will have to discuss about the dependence of the new physics. To explain both modes at once, we may need large electroweak penguin contribution with new weak phases and some SU(3) breaking effects by new physics in both QCD and electroweak penguin type processes.

Response of planktonic foraminifera to glacial cycles: Mid-Pleistocene change in the southern South China Sea

A high-resolution study (∼2 ka) of planktonic foraminifers in 997 samples from ODP Site 1143 (9°21.72′N, 113°17.11′E, water depth 2772 m) in the southern South China Sea (SCS) reveals faunal response to glacial cycles in the last 2.1 Ma. Most distinctive is the contrasting variations in the abundance of two tropical–subtropical species that exhibit similar resistance to dissolution in modern oceans. The relative and absolute abundances of Globorotalia menardii are high in interglacials and low in glacials and covary with δ 18O fluctuations over the studied interval. Pulleniatina obliquiloculata, however, follow oxygen isotopes only before the Mid-Pleistocene Revolution (MPR), showing high abundances during glacials and low during interglacials after ∼850 ka. Three abundance maxima of P. obliquiloculata are observed, corresponding to three major glacial episodes, Marine Isotope Stages (MIS) 2, 12, and 16, respectively. This change in abundance patterns of P. obliquiloculata appears to be unique to the southern SCS, as in late Pleistocene records from other western Pacific regions, including the Okinawa Trough and the northern SCS, all show co-varying patterns with δ 18O as G. menardii does. Cross-spectral analyses performed between percentages of Globorotalia menardii and δ 18O records show high coherency at 41 ka obliquity and then at 100 ka eccentricity bands. We suggest that the high abundances of G. menardii during interglacials in the past 2.1 Ma reflect warmer temperatures. Percentages of Pulleniatina obliquiloculata vs. oxygen isotope records show quite large phase difference at 41 ka obliquity band before the MPR. As a contrast, there are negligible phase differences in the vicinity of 100 and 41 ka after the MPR, which means reverse trend between percentages of P. obliquiloculata and δ 18O fluctuations. The differences of P. obliquiloculata from G. menardii in abundance and orbital forcings are interpreted as resulting from a profound change in the regional upper ocean structure during the MPR time, probably relating to a final glacial cut-off of the southern SCS from the Indian water at ∼850 ka and to higher salinity during glacial times after 850 ka. We speculate that this change is related to the decreased connection between the Pacific and Indian Ocean.

Phase contrast and attraction–repulsion transition in tapping mode atomic force microscopy

The origin of phase contrast in tapping mode (TM) atomic force microscopy (AFM) images has been a persistent issue of concern to many TM-AFM users. In the present study, it is revealed experimentally that phase contrast relates principally to large phase differences between regions of attractive and repulsive dominated probe–sample interactions at the attraction–repulsion transition point rather than variations in energy dissipation due to shifting probe–sample interactions. To provide a rational basis for characterizing phase contrast we demonstrate that the length of the attractive-dominated region in amplitude–phase-distance (apd) data can not only help to determine whether a reliable phase image can be obtained on a particular sample surface, but also provide a quantitative “fingerprint” for a sample surface. We term this quantity the attraction-dominated region length.

Transequatorial propagation of the Pc1 emission on 23 October 1997

A Pc1 emission event with uncommon propagation characteristics was revealed in the study of the search‐coil magnetometer data from two Russian midlatitude observatories separated by 4000 km. Dynamic spectra of the emission showed pronounced structure with a repetition period of about 130 s. By comparing the wave form plots for the two locations we found an unusually large phase difference as much as nearly 180 between the plotted envelopes. We discuss a most probable model assuming that the signal received at one of the two observatories must propagate from the source region in the opposite hemisphere.

Models for double proton and electron transfer reactions: analyses by means of quantum dynamics

We here explore a physical mechanism of coupled proton and electron transfer (PET) reactions in multiple hydrogen transfer systems. A one-dimensional model for the PET systems is defined, in which relevant internal modes are interpreted as time-dependent charge fluctuations on proton donor and acceptor atoms. We elucidate the role of phase difference of the two internal modes by extending the single transfer site model to the double proton transfer reaction in the carboxylic acid dimer. It is found in the case of large phase difference, a strong coupling between electronic and protonic motions, thereby affecting the DPT, is observed.

Photometric modelling of slowly pulsating B stars

The photometric characteristics of slowly pulsating B stars are investigated using a numerical approach. Stability calculations are performed for a set of stellar models representative of the mid-B type, using a non-radial non-adiabatic pulsation code. The results from these calculations are used to synthesize photometry, in several common systems, for unstable modes of harmonic degrees l = 1...4. Focusing on the Geneva system for illustrative purposes, a variety of techniques are employed to analyse and visualize the synthetic data, including the use of multicolour-amplitudes and amplitude-phase diagnostic diagrams. One outstanding aspect of the analysis is the discovery, for the l = 2...4 modes, of 'inter-term cancellation' (ITC) - the process of destructive interference between the flux variations originating from surface temperature perturbations and those arising from radius perturbations. The ITC can be severe enough that a mode may be excited to a significant amplitude, and yet exhibit levels of photometric variability that fall below typical observational detection thresholds. Furthermore, it can affect not only the light variations in a given photometric passband, but also the variations of the bolometric flux. However, the cancellation is dependent on wavelength, and will not occur to the same degree in more than one passband. Therefore, simultaneous observation in a multitude of passbands represents the best approach to ensuring that no modes are overlooked during searches for variability in B-type stars. A consequence of ITC is that ratios between the variability amplitude, in differing passbands, become very sensitive towards mode-to-mode changes in the pulsation. This increased sensitivity will tend to complicate any attempts at identifying the harmonic degrees of the modes responsible for observed variability. However, the cancellation also introduces significant phase differences between the light variations in each passband, especially for the l = 3 and l = 4 modes. On the grounds that correspondingly large phase differences are not seen in observational data, it is argued that the variability seen in slowly pulsating B stars can tentatively be attributed to l = 1 and l = 2 modes.

Final-state phases in doubly Cabibbo-suppressed charmed meson nonleptonic decays

Cabibbo-favored nonleptonic charmed particle decays exhibit large final-state phase differences in $\bar K \pi$ and $\bar K^* \pi$ but not $\bar K \rho$ channels. It is of interest to know the corresponding pattern of final-state phases in doubly-Cabibbo-suppressed decays, governed by the $c \to d u \bar s$ subprocess. An experimental program is outlined for determining such phases via measurements of rates for $D \to K^* \pi$ and $K (\rho, \omega,\phi)$ channels, and determination of interference between bands in Dalitz plots. Such a program is feasible at planned high-intensity sources of charmed particles.

Reflection of a long‐period gravity wave observed in the nightglow over Arecibo on May 8–9, 1989?

During the Arecibo Initiative for Dynamics of the Atmosphere (AIDA) campaign in 1989 a characteristic of gravity wave perturbations observed in mesopause region airglow emissions was that airglow brightness fluctuations and airglow‐derived temperature fluctuations often occurred either in phase or in antiphase. This stimulated the development of a theory suggesting that such in‐phase fluctuations were most probably the result of strong reflections occurring in the mesosphere and lower thermosphere region. Recent examination of a particular wave event and application of simple WKB‐type theory has appeared to support this hypothesis. Here we use a full‐wave model and a WKB‐type model, each coupled with a chemical‐airglow fluctuation model describing O2 atmospheric and OH Meinel airglow fluctuations, to assess the strength of wave reflection and also to explicitly calculate the phase difference between the airglow brightness and the temperature fluctuations. Our results suggest that reflection is not strong for the particular wave event, and the model produces fairly large phase differences between the airglow brightness and the temperature fluctuations (∼35° and ∼134°–165° for the O2 atmospheric and OH airglow emissions, respectively). These results are not particularly sensitive to the nominal mean winds used in the simulations. There is an instance when a region of minimum refractive index occurs directly above a region in which reflection is strongest, suggesting that the two are related. However, the reflection does not appear to be strong. Our results suggest that chemical effects can account for the inferred phases of the observed airglow fluctuations and that effects associated with wave reflection appear to play a relatively minor role in the airglow fluctuations.

Final-state phases in charmed meson two-body nonleptonic decays

Observed decay rates indicate large phase differences among the amplitudes for the charge states in $\stackrel{\ensuremath{\rightarrow}}{D}\overline{K}\ensuremath{\pi}$ and $\stackrel{\ensuremath{\rightarrow}}{D}{K}^{*}\ensuremath{\pi}$ but relatively real amplitudes in the charge states for $\stackrel{\ensuremath{\rightarrow}}{D}\overline{K}\ensuremath{\rho}.$ This feature is traced using an SU(3) flavor analysis to a sign flip in the contribution of one of the amplitudes contributing to the latter processes in comparison with its contribution to the other two sets. This amplitude may be regarded as an effect of rescattering and is found to be of magnitude comparable to others contributing to charmed particle two-body nonleptonic decays.

The light quark sector, CP violation, and the unitarity triangle

In view of the observed strong hierarchy of quark masses, we propose a new description of flavor mixing which is particularly suited for models of quark mass matrices based on flavor symmetries. The necessary and sufficient conditions for CP violation are clarified. The emergence of CP violation is primarily linked to a large phase difference (near 90°) in the light quark sector. The unitarity triangle is determined by the mass ratios of the light quarks. We conclude that the unitarity triangle should be close or identical to a rectangular triangle, and CP violation is maximal in this sense. Instructive predictions for flavor mixing angles and CP-violating parameters, which can directly be confronted with the forthcoming data from B-meson factories, are obtained from a specific texture of quark mass matrices.

Large final-state interaction in the0−0−decays ofJ/ψ

In view of important implications in the B decay, the 0-0- decay modes of J/psi are analyzed with broken flavor SU(3) symmetry in search for long-distance final-state interactions. If we impose one mild theoretical constraint on the electromagnetic form factors, we find that a large phase difference of final-state interactions is strongly favored between the one-photon and the gluon decay amplitudes. Measurement of the \pi+\pi- and K+K- cross sections off the J/psi peak in e+e- annihilation can settle the issue without recourse to theory.

Scattering of Tidal Frequency Waves around a Cylindrical Island

Abstract The scattering solution around a small cylindrical island in a shelf sea of uniform depth is derived for Sverdrup, right-bounded Poincare, and Kelvin waves, which includes linear bottom friction, and the solution is extended to the subinertial frequency range. Effects of scattering on the amplitude and phase vary, depending on the type of incident waves. A Sverdrup wave scattering near the inertial frequency produces large amplitude and phase differences around the island due to singularity effect. However, the singularity effect does not happen for Poincare and Kelvin waves, even though the amplitude and phase variation depends on bottom friction and wave frequency. For an observer looking down the direction of wave propagation around the island, the maximum amplitude due to Sverdrup wave scattering occurs on the left-hand side, and the phase difference increases more than twice that by incident wave propagation. Scattering of Poincare waves at a superinertial frequency for an island located at ...

Long-range connections synchronize rather than spread intrathalamic oscillations: computational modeling and in vitro electrophysiology.

A thalamic network model was developed based on recent data regarding heterogeneous thalamic reticular (RE) cell axonal arborizations that indicate at least two projection patterns, short-range cluster projections and long-range diffuse projections. The model was constrained based on expected convergence and the biophysical properties of RE and thalamocortical (TC) cells and their synapses. The model reproduced in vitro synchronous slow (3-Hz) oscillatory activity and the known effects of T-channel blockade and cholecystokinin (CCK) application on this activity. Whereas previous models used the speed at which approximately 3-Hz oscillations propagate in vitro to infer the spatial extent of intrathalamic projections, we found that, so long as the gamma-aminobutyric acid-B synaptic conductance was adjusted appropriately, a network with only short-range projections and another network with both short- and long-range projections could both produce physiologically realistic propagation speeds. Although the approximately 3-Hz oscillations propagated at similar speeds in both networks, phase differences between oscillatory activity at different locations in the network were much smaller in the network containing both short- and long-range projections. We measured phase differences in vitro and found that they were similar to those that arise in the network containing both short- and long-range projections but are inconsistent with the much larger phase differences that occur in the network containing only short-range projections. These results suggest that, although they extend much further than do short-range cluster projections, long-range diffuse projections do not spread activity over greater distances or increase the speed at which intrathalamic oscillations propagate. Instead, diffuse projections may function to synchronize activity and minimize phase shifts across thalamic networks. One prediction of this hypothesis is that, immediately after a collision between propagating oscillations, phase gradients should vary smoothly across the thalamic slice. The model also predicts that phase shifts between oscillatory activity at different points along a thalamic slice should be unaffected by T-channel blockers and decreased by suppression of synaptic transmission or application of CCK.

Quantum effects in two-level atom/squeezed vacuum interactions for large phase differences

Many unusual features in the interaction between driven two-level atom atoms and the squeezed vacuum have been reported recently. These effects are usually most pronounced when the phase difference Φ between the driving field phase and the squeezed vacuum phase is small, and tend to disappear as Φ→ π. In this paper, we show that a range of unusual features arise when Φ is close to π. In the present treatment, it is essential not to make the secular approximation. The effects described include population trapping of a dressed state, disappearance of peaks in the resonance fluorescence spectrum, amplification of a probe beam and a large peak in the coherently scattered amplitude. These features disappear when the two-photon correlations in the squeezed vacuum are reduced to the classical level, and their existence must be attributed to the quantum nature of the squeezed vacuum.