Axion emission from a hot plasma

We give the technics for the calculation of production and energy loss rates for axion-like particles (scalar or pseudo-scalar coupling to the gauge boson) from a hot QED (or QCD) heat bath. We compute the contribution coming from, the decay mode of a transverse to a longitudinal photon (or gluon). The energy loss rate for this process behaves asT ⁷. Considering the supernova SN1987A event, this behaviour could improve the upper bound on the coupling constant between asions and photons.     

Axion flux from nascent neutron stars

The emission rate of the invisible axion due to electron-related processes is evaluated in detail at high temperatures (T∼20 MeV) and at high densities (ρ∼10¹⁴g cm⁻³), relevant to the supernova explosion. If one properly treats relativistic kinematics, no useful bound on the Peccei-Quinn symmetry breaking scale (f_A) is obtained from SN1987A, contrary to the recent argument by others. A brief comment on the bound from the neutron-neutron axion bremsstrahlung process is also made.     

Polarized x-ray emission from magnetized neutron stars: signature of strong-field vacuum polarization

In the atmospheric plasma of a strongly magnetized neutron star, vacuum polarization can induce a Mikheyev-Smirnov-Wolfenstein type resonance across which an x-ray photon may (depending on its energy) convert from one mode into the other, with significant changes in opacities and polarizations. We show that this vacuum resonance effect gives rise to a unique energy-dependent polarization signature in the surface emission from neutron stars. The detection of polarized x rays from neutron stars can provide a direct probe of strong-field quantum electrodynamics and constrain the neutron star magnetic field and geometry.     

Electromagnetic emission in a magnetized plasma

We present a theory of emission of electromagnetic waves, in the ordinary and extraordinary modes, in the presence of Langmuir turbulence in a magnetized plasma due to a high frequency nonlinear force. The mechanism of emission considered is the plasma-maser interaction which is essentially an energy up-conversion process. The growth rates of the ordinary and extra-ordinary mode emissions are calculated and the results are compared with those obtained from the direct formulation. The scope of application of the results to radio spectra from solar flares is then stressed.M.C. College, India. College of General Education, Kyushu University, Ropponmatsu, Japan. Gauhati University, India. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 5, pp. 548–562, May, 1994.     

Dilepton emission from a resonance gas

We consider the dilepton emission from a dense and hot hadron gas near a critical point. The hadron gas is described as a resonance one. The dilepton spectrum generated by vector resonances is shown to be equivalent to the one generated by quarks.     

Systematics of neutron emission probabilities from delayed neutron precursors

A simple correlation based on the gross theory ofβ-decay is derived between the neutron emission probabilitiesP _n of delayed neutron precursors, theirβ-decay energies and the neutron binding energies of the daughter nuclei. The correlation is shown to be valid for delayed neutron precursors among the fission products. TheP _n-values of several expected but still unidentified neutron precursors are estimated together with their contributions to the delayed neutron groups in thermal-neutron induced fission of²³⁵U. Some aspects of theβ-strength function for transitions into highly excited states are discussed.     

On neutron depolarization in magnetized media

The neutron depolarization in magnetized samples is considered as a result of scattering in the case of arbitrary orientations between the incident polariztion, the sample field and the direction of polarization analysis. It is shown that the depolarization is determined by the small-angle magnetic scattering within the angular beam width and by an additional contribution arising from the spin-dependent scattering outside the passing beam. The latter follows from the consideration of the interference between the scattered and the transmitted beams. Special attention is paid to the analysis of several measuring regimes for the depolarization and its dependence on neutron wavelength. The depolarization in multidomain ferromagnets is considered.     

High-multiplicity neutron emission from muon capture

The nuclear excitation function resulting from muon captures on pairs of nucleons which is induced by meson-exchange currents, is used to calculate the probabilities of high-multiplicity (X⩾6) neutron emission. For muon capture in ²⁰⁹Bi these are found to be 8 × 10⁻³ for X = 6, 3.5 × 10⁻³ for X = 7 and 0.7 × 10⁻³ for X = 8. Results are presented also for Pb, Ho and Ag. The agreement with existing experiments is very good.     

双中子星并合的中微子信号

2017年8月17日,LIGO/Virgo首次探测到了双中子星并合事件的引力波信号,随后多波段的跟进观测获得了GW170817事件的多波段“全息”图像并确认源头在40 Mpc外的NGC4993星系,但颇为遗憾的是(尽管与理论预期符合)当时全球运行中的中微子探测器都没有探测到与GW170817相关联的中微子。普遍认为,热中微子在双星引力潮汐撕裂绕行阶段就会产生,在并合事件后的十几毫秒内达到峰值;若并合中心产物为伽马射线暴或者稳定的磁星,还会在并合的即刻至数天内产生超高能中微子。因此,中微子信号不仅可以辅助研究并合后的产物环境,还可以在天文尺度上研究中微子的基本性质和寻找粒子物理标准模型之外的新物理。即使只探测到一个热中微子事件,也可以获得热中微子的能谱标度信息和诊断并合后十几毫秒内星体本身和周围环境的物理参数。另外,因为引力波以光速传播,通过热中微子信号相对引力波信号的时延,可限制中微子的绝对质量。若探测到延迟的高能中微子信号,除了可以清楚地证明双中子星并合的中心产物是磁星,还可以研究并合产物附近的磁场环境和宇宙射线加速机制。     

On polarized neutron scattering from magnetized samples and the spin echo effect

The scattering of polarized neutrons from magnetized samples is considered in the general case of arbitrary orientation between the incident polarization, the magnetic field of the sample and the polarization of the scattered neutrons. Including both nuclear and magnetic scattering the general expressions for the cross section and the polarization of the scattered beam are derived in the case of small-angle scattering. It is shown that under certain experimental conditions an effect analogous to the Neutron Spin Echo should be observed, which could be used to measure small energy transfers. The contribution arising from the scattering by spin waves is examined in detail.     

Current diversion in the accretion disk of a magnetized neutron star

Summary We revisited the magnetized accretion disk problem and studied the currents flowing in the magnetosphere. We noted the importance of the radial currents in the disk and examined how these radial currents can be diverted to flow along the magnetic-field lines. One fluid magneto-hydrodynamic analysis was applied to the model neutron star and the self-consistent current system was obtained. This work was supported by Korea Institute of Technology and Korea Science and Engineering Foundation.     

Axion electrodynamics in a waveguide

The interaction of axion and electromagnetic waves is studied in the presence of a magnetic field threading a waveguide. This interaction, which vanishes in free space, is found to induce transverse magnetic waves with frequency spectra associated with transverse electric waves in the absence of the axion.     

Temperatures determined from neutron emission in nucleus-nucleus collisions

Most neutron spectra from ¹⁴N+¹⁶⁵Ho collisions at 35 MeV/nucleon are described by two moving thermal sources, one at a temperature of ≈2.5 MeV and the other of ≈8 MeV. Resonances in gragment-neutron relative velocity spectra are used to determine a temperature from the relative populations of excited states of ¹³C nuclei. There is a discrepancy with the equilibrium assumption in that the fitted value, ≈1 MeV, does not match that of either thermal source.     

Dielectric properties of a magnetized electron gas in a nanotube

A quantum expression is derived for the longitudinal permittivity of a magnetized electron gas in a quantum cylinder. The asymptotics of the dispersion law are calculated for longitudinal plasma waves in a degenerate electron gas. The approximations of the weak and strong spatial dispersions are considered. It is shown that the longitudinal permittivity is an oscillating function of the magnetic flux through the cross section of the nanotube.     

Isotopic dependence of neutron emission from dinuclear system

Using the statistical approach, we study the isotopic dependence of the de-excitation of dinuclear systems formed in the entrance channel of heavy-ion reactions. The probabilities of neutron emission from the dinuclear systems ^62-73Ni + ²⁰⁸Pb are estimated and a possible experiment for the observation of this emission is discussed.     

Axion constraints from white dwarf cooling times

Hypothetical, pseudoscalar particles would be abundantly emitted from the interior of white dwarfs through bremsstrahlung processes. These stars would then rapidly cool. From the observed number of hot degenerates we find a new bound on the Yukawa coupling to electrons of g < 4 × 10⁻¹³. For “invisible axions” this translates into a new bound on the Peccei-Quinn scale of v > 1 × 10⁹ GeV, corresponding to m_a < 3 × 10⁻² eV.     

Energy and momentum losses of a magnetized plasma via familon emission

Familon emission from a dense magnetized plasma in the processes e^? → e^?φ and e^? → μ^?φ is investigated. The contribution of these processes to the energy losses of a supernova remnant is calculated. It is shown that, at a late stage of the cooling of a supernova remnant, the energy loss of a plasma via familon emission may become commensurate with the loss via neutrino emission. It is found that, because of asymmetry of familon emission in the process e^? → gm^?φ, there arises a force acting on the plasma.