Neutron experiments to search for new spin-dependent interactions

The consideration is presented of possible neutron experiments to search for new short-range spin-dependent forces. The spin-dependent nucleon-nucleon interaction between neutron and nuclei may cause different effects: phase shift of a neutron wave in neutron interferometers of different kind, in particular of the Lloyd mirror configuration, neutron spin rotation in the pseudo-magnetic field, and transverse deflection of polarized neutron beam by a slab of substance. Estimates of sensitivity of these experiments are performed.     

Neutron interferometry in gravitational field with torsion

We consider the possibility of finding experimental evidence of the fifth force with the measurement of a phase shift of neutron beams via an interferometric apparatus and also a possible rotation of the polarization plane of polarized neutron beams when torsion is introduced in a gravitational field.     

Rotating Fermi gases in an anharmonic trap

Motivated by recent experiments on rotating Bose-Einstein condensates, we investigate a rotating, polarized Fermi gas trapped in an anharmonic potential. We apply a semiclassical expansion of the density of states in order to determine how the thermodynamic properties depend on the rotation frequency. The accuracy of the semiclassical approximation is tested and shown to be sufficient for describing typical experiments. At zero temperature, rotating the gas above a given frequency Ω_DO leads to a ‘donut’-shaped cloud which is analogous to the hole found in two-dimensional Bose-Einstein condensates. The free expansion of the gas after suddenly turning off the trap is considered and characterized by the time and rotation frequency dependence of the aspect ratio. Temperature effects are also taken into account and both low- and high-temperature expansions are presented for the relevant thermodynamical quantities. In the high-temperature regime a virial theorem approach is used to study the delicate interplay between rotation and anharmonicity.     

Should There Be a Spin-Rotation Coupling for a Dirac Particle?

It was argued by Mashhoon that a spin-rotation coupling term should add to the Hamiltonian operator in a rotating frame, as compared with the one in an inertial frame. For a Dirac particle, the Hamiltonian and energy operators H and E in a given reference frame were recently proved to depend on the tetrad field. We argue that this non-uniqueness of H and E really is a physical problem. We show that a tetrad field contains two informations about local rotation, which usually do not coincide. We compute the energy operator in the inertial and the rotating frame, using three different tetrad fields. We find that Mashhoon’s term is there if the spatial triad rotates as does the reference frame—but then it is also there in the energy operator for the inertial frame. In fact, if one uses the same given tetrad field, the Dirac Hamiltonian operators in two reference frames in relative rotation differ only by the angular momentum term. If the Mashhoon effect is to exist for a Dirac particle, the tetrad field must be selected in a specific way for each reference frame.     

The gravity-induced phase shift detected by high-T c Josephson junctions

We derive from the Kaluza-Klein theory a formula for the gravity-induced phase shift around a circuit loop, which amounts to the order of 10^?6 We propose experiments to detect this phase shift by using the high-T _c d-wave Josephson junction, which is included in a cuprate superconductor circuit loop. By rotating the loop around the horizontal axis, the gravity-induced phase shift can be detected as a frequency shift. These settings can also be used in turn to determine the gravitational constant. This method will be sensitive and accurate.     

Spin-rotation coupling and Fermi–Walker transport

It is demonstrated that a spin-rotation coupling term only appears in the Hamiltonian of a Dirac particle if the rotating frame obeys the rules of Fermi–Walker transport. This is illustrated by examples in Minkowski space and the paper concludes with some speculations about spin-rotation coupling in Kerr space-time.     

The gravity-induced phase shift detected by high-Tc Josephson junctions

We derive from the Kaluza-Klein theory a formula for the gravity-induced phase shift around a circuit loop, which amounts to the order of 10⁻⁶ We propose experiments to detect this phase shift by using the high-T _c d-wave Josephson junction, which is included in a cuprate superconductor circuit loop. By rotating the loop around the horizontal axis, the gravity-induced phase shift can be detected as a frequency shift. These settings can also be used in turn to determine the gravitational constant. This method will be sensitive and accurate.      

Bose–Einstein condensates in concentrically coupled annular traps with spin–orbit coupling and rotation

We investigate Bose–Einstein condensates in concentrically coupled annular traps with spin–orbit coupling and rotation. The ground state wave functions are computed by minimizing the Gross–Pitaevskii energy functional, and the combined effects of system?s parameters, especially the spin–orbit coupling and rotating, are investigated. The results show that for a finite fixed spin–orbit coupling, with increasing the angular frequency of rotation, the system is always in phase coexistence. Moreover, phase transitions between different ground state phases can be induced not only by spin–orbit coupling, but also rotation, which resembles very much the one where the s-wave interactions are varied.     

Observing build up of geometric phase in an adiabatic RF flipper with the amplitude of its rotating field

To demonstrate that adiabatic RF flippers impose an inherent geometric phase on the neutron polarization vector, we built a NSE setup consisting of two pairs of such flippers in a pulsed neutron beam. As is well known, the combined gradient and RF fields in each flipper—in the rotating frame—behave as a rotating field. The amplitude of this field in the first three flippers was kept maximum. For various amplitudes of the rotating field in the remaining flipper we measured the NSE pattern. Besides the shift of the NSE-point due to the variation of the dynamic phase, the NSE patterns show the development of the geometric phase.     

A phase sensitive optical rotation measurement in a scattered chiral medium using a Zeeman laser

A novel circular polarized optical heterodyne interferometer using a Zeeman laser to measure optical rotation both in nonscattered and scattered chiral medium is proposed. A pair of correlated orthogonal circular polarized light waves of different temporal frequency propagating in the chiral medium at different speed is studied. This results in phase retardation between circular polarized light waves of which the phase difference is proportional to the optical rotation angle of a linear polarized light in a chiral medium. In the mean time, two orthogonal circular polarized light waves can be treated as a circular polarized photon pair that is able to reduce the scattering effect in a scattered chiral medium. Then the optical rotation angle can be measured in the scattering medium. In addition, a common-path configuration with respect to circular polarized light waves immune the background noise. This further improves the sensitivity on optical rotation measurement based on phase difference detection.     

Berry phase in Tavis-Cummings model

In this paper we investigate the Berry phase in Tavis-Cummings model in the rotating wave approximation. The dipole-dipole interaction between the atoms is considered. The eigenfunctions of the system are obtained and thus the Berry phase is evaluated explicitly in terms of the introduction of the phase shift. It is shown that the Berry phase can be easily controlled by the atom-cavity coupling strength, the cavity frequency detuning, which can be important in applications in geometric quantum computing.     

左手材料中圆偏振光束的反常旋转特性研究

根据Whittaker标量势理论,建立了圆偏振光束的矢量传输模型.基于这一模型研究了圆偏振光束在左手材料中的反常旋转特性.通过分析光束偏振态、衍射对强度质心旋转特性的影响,发现圆偏振光束在左手材料中旋转方向反转并揭示其旋转角等于古伊相.采用分析横向能流的方法,揭示左手材料中反向的横向能流是导致反常旋转特性的主要原因.对圆偏振光束在左手材料中反常旋转特性的研究,有利于增强对左手材料中光束传输特性的认识. 关键词： 左手材料 圆偏振光束 旋转特性     

Neutrino wave packet propagation in gravitational fields

We discuss the propagation of neutrino wave packets in a Lense–Thirring metric using a gravitational phase approach. We show that the neutrino oscillation length is altered by gravitational corrections and that neutrinos are subject to helicity flip induced by stellar rotation. For the case of a rapidly rotating neutron star, we show that absolute neutrino masses can be derived, in principle, from rotational contributions to the mass-induced energy shift, without recourse to mass generation models presently discussed in the literature.     

Error analysis and Stokes parameter measurement of rotating quarter-wave plate polarimeter

In this paper, we present a simple Stokes parameter measurement method for a rotating quarter-wave plate polarimeter.This method is used to construct a model to describe the principle of how the magnitudes of errors influence the deviation of the output light Stokes parameter, on the basis of accuracy analysis of the retardance error of the quarter-wave plate,the misalignment of the analyzing polarizer, and the phase shift of the measured signals, which will help us to determine the magnitudes of these errors and then to acquire the correct results of Stokes parameters. The method is validated by the experiments on left-handed circularly polarized and linear horizontal polarization beams. With the improved method, the maximum measurement deviations of Stokes parameters for these two different polarized states are reduced from 2.72%to 2.68%, and from 3.83% to 1.06% respectively. Our results demonstrate that the proposed method can be used as a promising approach to Stokes parameter measurement for a rotating quarter-wave plate polarimeter.     

A proposed investigation of parity non-conserving effects using a polarized target and an unpolarized epithermal neutron beam

Parity non-conserving (PNC) effects can be studied with unpolarized neutron beams and polarized targets. TheI·k term in the forward scattering amplitude (I=target spin, k=neutron momentum) is enhanced at a p-wave resonance in the same way as thes·k term which has been studied in previous experiments (s=neutron spin). A large number of resonances can be studied in a polarized target experiment because level densities are high in odd-odd nuclei (typically 25 s and p levels per 100 eV in¹⁶⁶Ho). The goal of the experiments is to extract an average PNC matrix element from a statistically distributed set of PNC matrix elements. A rotating cryostat for use in longitudinal analyzing power measurements is described. Suitable rare earth targets are holmium, thulium, terbium and hyperfine enhanced targets such as praesodymium compounds.     

Berry phase magnification in optical microcoil resonators

We have studied the effects of the Berry phase on the linear transmission properties of optical microcoil resonators and analyzed the resonant behavior for different input polarizations and coil geometries. Contrary to previous expectations, we find that on resonance the size of the Berry phase shift can be magnified significantly, leading to a measurable polarization rotation for some geometries. Our model also considers other polarization effects including elasto-optic bend birefringence and the polarization dependent coupling coefficients, which were also previously neglected, and we still find that observable Berry phase effects persist. For example, in a three turn microcoil with a diameter of 0.2 mm, close to 100% of an initially x polarized light will be coupled into the orthogonal y polarization, due to the optical activity arising from the cumulative effects of Berry phase on resonance. More generally, the cross-polarization coupling also significantly influences the resonance extinction ratio and quality factor.     

一种可用于极化~3He实验的新型磁场系统

原子核自旋极化的~3He气体已被深入研究并广泛用于各种科学实验.在过去的极化~3He实验中,为了减小磁场梯度对纵向弛豫时间的影响,通常会建造大尺寸的亥姆霍兹线圈来提供所需均匀度的主磁场环境.本文通过计算得到了新的六正方形线圈系统,可以为极化~3He实验提供小型高均匀性的磁场装置.其中线圈系√统内部超过30%的区域磁场梯度满足(|▽B_x|~2+|▽B_y|~2)/B_0 10~(-4)cm~(-1),这一均匀区域比例超过了现在所有用于极化~3He实验的线圈装置.对于其他需要大均匀区域磁场环境的研究实验,新的六线圈系统也具有很好的应用价值.     

Spontaneous Formation of Antiferromagnetic Vortex Lattice in a Fast Rotating BEC with Dipole Interactions

When a Bose-Einstein condensate is set to rotate,superfluid vortices will be formed,which finally condense into a vortex lattice as the rotation frequency further increases.We show that the dipole-dipole interactions renormalize the short-range interaction strength and result in a distinction between interactions of parallel-polarized atoms and interactions of antiparallel-polarized atoms.This effect may lead to a spontaneous breakdown of the rapidly rotating Bose condensate into a novel anti-ferromagnetic-like vortex lattice.The upward-polarized Bose condensate forms a vortex lattice,which is staggered against a downward-polarized vortex lattice.A phase diagram related to the coupling strength is obtained.     

Two-dimensional wave propagation in a rotating elastic solid with voids

Two-dimensional wave propagation is studied in an isothermal linear isotropic elastic material with voids rotating with constant angular velocity based on a theory of elastic material with voids developed by Ie?an (1986) in the thermoelastic context. It is found that there exist three coupled plane waves propagating with distinct phase speeds. The presence of voids and the rotation of the medium are responsible for this coupling. In the absence of voids, the classical longitudinal and transverse waves are found to be coupled through the rotation of the medium. At very large frequency or when the angular rotation is very small relative to the wave frequency the waves are decoupled and propagate with distinct phase speeds. These are (i) a longitudinal wave, (ii) a transverse wave and (iii) a longitudinal wave corresponding to the change in void volume fraction. The first two correspond to the waves of classical elasticity, while the third is new and arises from the presence of the voids. The results are illustrated graphically.     

Spin-rotating magnet for the ΔσL(np) experiment at LHEP JINR

The spin rotating magnet (SRM) is purposed for the orientation rotation of the nucleon spins in the polarized beam from the transverse (T) direction with respect to the nucleon beam momentum to the longitudinal (L) one. The longitudinally polarized neutron beam was used in the experiment for measuring the total cross section difference Δσ_L(np) with parallel and antiparallel orientation of the participant L polarization. To perform the nucleon spin rotation in the polarized nucleon beam through the angle of 90° over the beam momentum region of ～1.8–5.5 GeV/c, a proper spin rotation device had to be prepared. For this purpose, the necessary calculations of corresponding values of the magnetic induction integral were carried out. Using the calculations the dipole magnet SP 57 type was chosen for the Δσ_L(np) experiment and the required reconstruction of its pole tips was also accomplished. After the SRM installation at the neutron beam line the appropriate apparatus set for the magnetic measurements was prepared and the precise measurements of the whole set of the SRM characteristics were performed. The obtained results for the SRM magnetic field parameters were successfully used during the Δσ_L(np) experimental runs to specify the current at this magnet coil corresponding to the calculated magnetic induction integral for the given neutron beam momentum.