Relativistic nucleon–nucleon potentials in a spin-dependent three-dimensional approach

The matrix elements of relativistic nucleon–nucleon (NN) potentials are calculated directly from the nonrelativistic potentials as a function of relative NN momentum vectors, without a partial wave decomposition. To this aim, the quadratic operator relation between the relativistic and nonrelativistic NN potentials is formulated in momentum-helicity basis states. It leads to a single integral equation for the two-nucleon (2N) spin-singlet state, and four coupled integral equations for two-nucleon spin-triplet states, which are solved by an iterative method. Our numerical analysis indicates that the relativistic NN potential obtained using CD-Bonn potential reproduces the deuteron binding energy and neutron-proton elastic scattering differential and total cross-sections with high accuracy.

Comparison of Estimation Methods of Room Impulse Responses in Local Region Using Small Number of Microphones

Measurements of Room Impulse Responses (RIRs) at multiple points have been used in various acoustic techniques using the room acoustic characteristics. To obtain multi-point RIRs more efficiently, spatial interpolation of RIRs using plane wave decomposition method (PWDM) and equivalent source method (ESM) has been proposed. Recently, the estimation of RIRs from a small number of microphones using spatial and temporal sparsity has been studied. In this study, by using the measured RIRs, we compare the estimation accuracies of RIRs interpolation methods with a small number of fixed microphones. In particular, we consider the early and late reflections separately. The direct sound and early reflection components are represented using sparse ESM, and the late reflection component is represented using ESM or PWDM. And then, we solve the two types of optimization problems: individual optimization problems for early and late reflections decomposed by the arrival time and a single optimization problem for direct sound and all reflections. In the evaluation experiment, we measured the multiple RIRs by moving the linear microphone array and compare the measured and estimated RIRs.

Optimization of secondary source configuration in enclosure using plane wave decomposition

The optimization of secondary source configuration for an active noise control (ANC) system in its enclosed space generally focuses on noise reduction requirements at discrete points only. This may lead to the poor noise reduction performance in the whole spatial region, and it is necessary to know the information on error sensor positions in advance. To address this problem, a cost function for spatial-region-oriented noise reduction is proposed. The plane wave decomposition of the enclosed sound field is used to obtain the primary field plane waves and the unit secondary field plane wave of each candidate secondary source as the prior knowledge for configuration optimization, so as to formulate a wave-domain ANC cost function. The optimization method adopts the simulated annealing search. Taking a rigid-walled rectangular cavity as an example, the optimization method is firstly compared with two space-domain methods by using analytic values of the wave-domain prior knowledge. The comparison results show that the better reduction of spatial acoustic potential energy can be achieved independent of the error sensor configuration information. Then the estimated values of the wave-domain prior knowledge through measuring randomly distributed microphones are used to optimize the configuration of the ANC system. The optimization results suggest that the noise reduction of spatial acoustic potential energy of the optimized configuration can be better than that of the space-domain method, but the microphone positions have a great influence on the noise reduction performance.

Scattering amplitudes for monopoles: pairwise little group and pairwise helicity

On-shell methods are particularly suited for exploring the scattering of electrically and magnetically charged objects, for which there is no local and Lorentz invariant Lagrangian description. In this paper we show how to construct a Lorentz-invariant S-matrix for the scattering of electrically and magnetically charged particles, without ever having to refer to a Dirac string. A key ingredient is a revision of our fundamental understanding of multi-particle representations of the Poincaré group. Surprisingly, the asymptotic states for electric-magnetic scattering transform with an additional little group phase, associated with pairs of electrically and magnetically charged particles. The corresponding “pairwise helicity” is identified with the quantized “cross product” of charges, e1g2− e2g1, for every charge-monopole pair, and represents the extra angular momentum stored in the asymptotic electromagnetic field. We define a new kind of pairwise spinor-helicity variable, which serves as an additional building block for electric-magnetic scattering amplitudes. We then construct the most general 3-point S-matrix elements, as well as the full partial wave decomposition for the 2 → 2 fermion-monopole S-matrix. In particular, we derive the famous helicity flip in the lowest partial wave as a simple consequence of a generalized spin-helicity selection rule, as well as the full angular dependence for the higher partial waves. Our construction provides a significant new achievement for the on-shell program, succeeding where the Lagrangian description has so far failed.

The underlying mechanism of inter-site discrepancies in ejection time measurements from arterial waveforms and its validation in the Framingham Heart Study

Radial applanation tonometry is a well-established method for clinical hemodynamic assessment and is also becoming popular in wrist-worn fitness trackers. The time difference between the foot and the dicrotic notch of the arterial pressure waveform is a well-accepted approximation for the left ventricular ejection time (ET). However, several clinical studies have shown that ET measured from the radial pressure waveform deviates from that measured centrally. In this work, we consider the systolic wave and the dicrotic wave as two independent traveling waves and hypothesize that their wave speed difference leads to the inter-site differences of measured ET (ΔET). Accordingly, we derived a mathematical dicrotic wave decomposition model and identified the most influential factors on ΔET via global sensitivity analysis. In our clinical validation on a heterogeneous cohort (N = 5742) from the Framingham Heart Study (FHS), the local sensitivity analysis results resembled the sensitivity variations patterns of ΔET from model simulations. A regression analysis on FHS data, using morphological features of radial pressure waveforms to estimate the Carotid ET, produced a root mean square error of 3.76 ms and R2 of 0.91. The proposed dicrotic wave decomposition model can explain the inter-site ET measurement discrepancies observed in the clinical data of FHS and can facilitate the precise identification of ET with radial pressure waveforms. Therefore, the proposed model will improve various physics-based pulse wave analysis methods as well as prospective artificial intelligence methods for tackling the subsequent big data produced­ from widespread wearable radial pressure monitoring.

Conformal partial waves in momentum space

The decomposition of 4-point correlation functions into conformal partial waves is a central tool in the study of conformal field theory. We compute these partial waves for scalar operators in Minkowski momentum space, and find a closed-form result valid in arbitrary space-time dimension d \geq 3d≥3 (including non-integer dd). Each conformal partial wave is expressed as a sum over ordinary spin partial waves, and the coefficients of this sum factorize into a product of vertex functions that only depend on the conformal data of the incoming, respectively outgoing operators. As a simple example, we apply this conformal partial wave decomposition to the scalar box integral in d = 4d=4 dimensions.

Wave decomposition applied to LA phasic longitudinal strain evaluated from MRI feature tracking to estimate a true LA booster strain index

Funding Acknowledgements Type of funding sources: None. Background. Feature tracking (FT) is an emerging approach for the evaluation of both left atrium (LA) and left ventricular (LV) myocardial strain from the same cine MRI dataset. We hypothesized that the LA active contraction longitudinal strain, is a merge of an intrinsic LA booster contraction with the early diastolic LA emptying, especially when this latter is extended because of a poor LV relaxation (Figure 1, bottom). Such index can be estimated through LA phasic strain wave-decomposition as conventionally done for pressure curves to estimate forward and reflected components. Purpose. To compare the newly proposed LA intrinsic or "true" booster index (Sla_fit) against the conventional index (Sla) in terms of associations with LV remodeling (LV mass/ LV volume), LV systolic longitudinal strain (LV_GLS), and transmitral LV filling indices in healthy controls and aortic valve stenosis (AVS) patients with preserved LV ejection fraction. Methods. We studied 55 patients (34 AVS:71 ± 11years, 21 controls:66 ± 9years) who had an MRI exam with cine SSFP and phase contrast (PC) images. FT was applied to cine images to extract LV and LA phasic longitudinal strain and strain rates. Transmitral flow early (E, cm/s) and late (A, cm/s) filling peak velocities were calculated from PC data. To estimate intrinsic LA booster index, the LA longitudinal strain curve corresponding to the reservoir and conduit phases was fitted using two half cosine waves, to account for an eventual LA filling to LA early emptying asymmetry, while fitting the LA contraction with a full cosine wave (Figure 1). The peak of this latter wave was defined as the intrinsic LA booster strain index (Sla_fit), while the second peak of the measured LA strain was defined as the conventional LA booster strain (Sla). Results. While conventional Sla was significantly higher than intrinsic LA booster Sla_fit in AVS patients (13.55 ± 4.26 vs. 8.09 ± 6.07, p = 0.0002), it was nearly equivalent in controls (14.34 ± 4.30 vs.13.43 ± 4.23, p =.49). But the newly proposed LA booster strain index was significantly related to LV_GLS (r=-48,p=.0004); to LV remodeling (r=-.44,p = 0.0012) as well as to transmitral flow A wave ( r=-.49, p=.0005) none of these associations were significant when considering conventional LA booster strain. Interestingly our intrinsic LA booster index Sla_fit was significantly associated with LV longitudinal strain in both controls (r=-.55,p = 0.009) and asymptomatic AVS (N = 10) (r=-.77,p = 0.0081) but not in symptomatic AVS (N = 24) (p>.70). This may reveal a maintained LA-LV coupling in the asymptomatic phase and an uncoupling in the symptomatic phase, caused by elevated LV filling pressures. Conclusions. A promising index for the quantitative evaluation of intrinsic LA booster function was proposed and its consistency was demonstrated through its significant associations with LV remodeling, LV longitudinal strain and transmitral late filling peak. Abstract Figure.