arXiv subjects

B. S. Xie

Publications and source records attributed to B. S. Xie.

At least 19 recordsLinked to original sources

arXiv2023

Stability range of parameters at fixed points for a class of complex dynamics

We study the parameters range for the fixed point of a class of complex dynamics with the rational fractional function as $R_{n,a,c}(z)=z^n+\frac{a}{z^n}+c$, where $n=1,2,3,4$ is specified, $a$ and $c$ are two complex parameters. The relationship between two parameters, $a$ and $c$, is obtained at the fixed point. Moreover the explicit expression of the parameter $a$ and $c$ in terms of $λ$ is derived, where $λ$ is the derivative function at fixed point. The parameter regimes for the stability of the fixed point are presented numerically for some typical different cases.

math.DS↗

arXiv2023

Momentum spirals in multiphoton pair production revisited

Spirals in multiphoton pair production are revisited by two counter-rotating fields with time delay for different cycles in pulse. Novel findings include that for subcycle fields, the remarkable spiral structure in the momentum spectrum can be still caused by a large time delay compared to the previous study for supercycle case where it is easier to be generated by a small time delay. And also there exist a range of critical polarization values for the spirals appearance corresponding to the different cycle number. The relative phase difference between two fields causes not only severe symmetry breaking of the momentum spectra pattern and spiral, but also a significant change for the shape and the number of spiral arm. Upon the number density, it is found a more sensitive to the cycle number, in particularly, it is enhanced by more than one order of magnitude for small cycle pulse, while it is increased about few times when the time delay is small. These results provide an abundant theoretical testbed for the possible experimental observation on the multiphoton pair production in future. Meanwhile, it is applicable to regard the particles momentum signatures as a new probing to the laser field information with it from the vacuum.

hep-ph↗

arXiv2023

Effect of spatially oscillating field on Schwinger pair production

Effect of spatially oscillating fields on the electron-positron pair production is studied numerically and analytically when the work done by the electric field over its spatial extent is smaller than twice the electron mass. Under large spatial scale, we further explain the characteristics of the position and momentum distribution via tunneling time, tunneling distance and energy gap between the positive and negative energy bands in the Dirac vacuum. Our results show that the maximum reduced particle number is about five times by comparing to maximum number for non-oscillating field. Moreover, the pair production results via Dirac-Heisenberg-Wigner formalism can be also calculated by using local density approximation and analytical approximation method when spatial oscillating cycle number is large. Moreover, in case of large spatial scale field, the position distribution of created particles could be interpreted by the tunneling time.

hep-ph↗

arXiv2022

Phase effect and symmetry on pair production in spatially inhomogeneous frequency chirping electric fields

Effect of the carrier envelop phase on the electron-positron pair production is studied in spatially inhomogeneous electric field with symmetrical frequency chirping. In high or low original frequency field without chirping as well as one with chirping, we find that the strength of interference effect of the momentum spectrum and the reduced particle number are all changeable periodically with phase, in particular, these periodical changes are more sensitive to the applied parameters in case of low frequency field. At the small spatial scale, the reduced particle number change is over one order magnitude by phase in small chirping. For the reduced particle number, the different optimal phases are obtained at different spatial scales, however, the larger the chirping is applied, the higher the created pair number is got. Interestingly, some different types of symmetries, i.e., the mutual symmetry of mirror/coincidence for two correlated phases and the individual self symmetry for single phase, are unfolded on the momentum spectrum. The physical reason of the mutual symmetry between two correlated phases and also the individual symmetry for two fixed specific phases are examined and discussed analytically in detail. The combined roles by phase and chirping on the periodic and symmetrical behaviors of the momentum spectrum and the reduced particle number are expected to have the potential extension to more fields such as that with multidimensional spatial coordinate.

hep-ph↗

arXiv2022

Pair production in inhomogeneous electric fields with phase modulation

Electron-positron pair production is investigated in spatial inhomogeneous electric fields with high or/and low central frequency as well as sinusoidal phase modulation. It is found that the momentum spectrum (the reduced particle number) is more sensitive to the modulated amplitude (modulated frequency) of the phase. The stronger the modulation parameters are applied, the more remarkable the interference effect in momentum spectrum occur. In particular, for high central frequency field, an extremely good symmetry in momentum spectrum is found while it is destroyed severely when the modulated amplitude becomes large. The reduced particle number can be also enhanced greatly at about a few times or/and one order by the modulation parameters. Moreover, the effect of spatial scales on the reduced particle number are examined carefully and found that it increases rapidly at small spatial scales, while it tends to be a constant at large spatial scales. Two interesting features are revealed for the reduced particle number, i.e., the optimal modulation parameters are found and the same particle number can be got through different set of modulation parameters. The latter findings is important because one can choose different ways of phase modulation to realize the required pair number even if for the optimal pair production.

hep-ph↗

arXiv2022

Schwinger pair production rate and time for some space-dependent electromagnetic fields via worldline instantons formalism

Schwinger pair production in some of space-dependent electromagnetic fields is studied analytically by using worldline instantons formalism for scalar quantum electrodynamics. With the increase of the modified Keldysh parameter $γ_{keb}$, the pair production rate decreases, the region of instanton paths expands regardless of the electromagnetic field form. We also find that all of the paths of the instantons for various electromagnetic fields are exactly in the same plane while with the different elliptical shapes. Moreover, the magnitudes of the normalized instantons action with different external electromagnetic fields are all bounded within the region from $π$ to $2π$ in spatial inhomogeneity fields. We further analytically identify and obtain two kinds of the pair-production time associated to the worldline instantons action.

hep-ph↗

arXiv2021

Schwinger pair production in inhomogeneous electric fields with symmetrical frequency chirp

Pair production in inhomogeneous electric fields with symmetrical frequency chirp is studied numerically using the Dirac-Heisenberg-Wigner formalism. We investigate high- and low-frequency modes and consider two carrier envelope phases. Momentum spectrum is sensitive to chirp causing different interference effect for different spatial scales as well as the carrier phase of the external field. The reduced particle number is in general enhanced with increasing chirp. The effect of spatial scale of the field on the reduced particle number is also examined. It is found that it is enhanced at small spatial scale but is almost unchangeable at large spatial scales for the considered field parameters. On the other hand, at small spatial scale, the reduced particle number is enhanced by one or two orders when chirp is applied with the exception of cosine low-frequency field which is only a few times larger. Moreover it is found that the reduced particle number is further increased by symmetrical chirp at about two times by comparing to the usual asymmetrical chirp in high frequency field.

hep-ph↗

arXiv2021

Effect of symmetrical frequency chirp on pair production

By using Dirac-Heisenberg-Wigner formalism we study electron-positron pair production for linear, elliptic, nearly circular and circular polarizations of electric fields with symmetrical frequency chirp, and we obtain Momentum spectra and pair yield. The difference of results among polarized fields is obvious for the small chirp. When the chirp parameter increases, the momentum spectra tend to exhibit the multiphoton pair generation that is characterized by the multi-concentric ring structure. The increase of number density is also remarkable compared to the case of asymmetrical frequency chirp. Note that the dynamically assisted Schwinger Mechanism plays an important role for the enhanced pair production in the symmetrical frequency chirp.

hep-ph↗

arXiv2021

Pair production in asymmetric Sauter potential well

Electron-positron pair production in asymmetric Sauter potential well is studied, where the potential well has been built as the width of the right edge fixed but the left side of the well is changeable at different values. We study the momentum spectrum, the location distribution and the total pair numbers in this case of asymmetric potential well and compare them with the symmetric case. The relationship between created electron energy, the level energy in the bound states and the photon energy in the symmetric potential well is used to the studied problem for the created electrons in the asymmetric potential well and its validity is confirmed by this approximation. By the location distribution of the electrons we have also shown the reason why the momentum spectrum has an optimization in the asymmetric well compared with the symmetric one.

quant-ph↗

arXiv2020

Chirp effects on pair production in oscillating electric fields with spatial inhomogeneity

Dirac-Heisenberg-Wigner formalism is used to study chirp effects on the vacuum pair creation under inhomogeneous electric fields. For rapidly oscillating electric fields, the particle momentum spectrum is sensitive to both of the spatial scale and the chirp parameter, and the external field width has less significant effect for the maximally large chirp. For slowly oscillating electric fields, chirp effects could be identified at large spatial extents and the carrier phase plays a significant role reflecting chirp effects even at small spatial scales. We also notice that, the local density approximation holds for all external field profiles considered in this work at the quasihomogeneous limit allowing one to use arguments from homogeneous scenarios to analyze inhomogeneous results.

quant-ph↗

arXiv2020

Enhanced pair production in frequency modulated Sauter potential wells

Electron-positron pair production in frequency modulated Sauter potential wells is investigated in the framework of the computational quantum field theory. In combined potential wells with a static Sauter potential well and a frequency modulated oscillating one, the modulated amplitude has a large effect on the number of created pairs. The optimal modulation amplitude of frequency at different center frequencies is obtained, which increases the number of electrons at about two times. However, for a single oscillating potential well with frequency modulation, chirp effect is sensitive to the center frequency, and the number of electrons can be enhanced even to four orders of magnitude at a regime of low center frequency. It implies that for a slowly oscillating Sauter potential well, the chirp effect through the frequency modulation is better than adding a static potential well to improve the pair production.

quant-ph↗

arXiv2019

Electron-positron pair production in combined Sauter potential wells

Electron-positron pair production, in combined Sauter potential wells and an oscillating one is imposed on a static Sauter potential, is investigated by using the computational quantum field theory. We find that the gain number (the difference of pair number under combined potentials to the simple addition of pair number for each potential) of the created pairs depends strongly on the depth of static potential and the frequency of oscillating potential. In particular, it is more sensitive to the frequency compared with the depth. For the low-frequency multiphoton regime, the gaining is almost positive and exhibits interesting nonlinear characteristics on both depth and frequency. For the single-photon regime, however, the gaining is almost negative and decreases near linearly with depth while it exhibits an oscillation characteristic with frequency. Furthermore, the optimal frequency and depth of gain number are found and discussed.

quant-ph↗

arXiv2019

Boson pair production in arbitrarily polarized electric fields

The momentum spectrum and number density of created bosons for two types of arbitrarily polarized electric fields are calculated and compared with those of created fermions, employing the equal-time Feshbach-Villars-Heisenberg-Wigner formalism which is confirmed that for an uniform and time-varying electric field it is completely equivalent to the quantum Vlasov equation in scalar QED. For an elliptically polarized field, it is found that the number density of created bosons is a square root of the number density of spin-up electrons times that of spin-down ones for a circularly polarized multicycle field. Moreover, the degree of spin polarization roughly grows as the Keldysh adiabaticity parameter increases for arbitrarily polarized multicycle fields. For a field constituted of two circularly polarized fields with a time delay, it is shown that momentum vortices also exist in boson pair creation and are induced only by the orbital angular momentum of particles. However, the vortices can reproduce the quantum statistic effect due to the effect of spin of particles. These results further deepen the understanding of some significant signatures in pair production.

quant-ph↗

arXiv2019

Schwinger pair production correction in thermal system

In this paper, we give formal results of Schwinger pair production correction in thermal systems with external background field by using the evolution operator method of thermo field dynamics, where especially tree level correction of thermal photons is considered with linear response approaches by an effective mass shift. We consider initial systems in two types of vacuums as zero temperature and thermal vacuum, respectively, with correction of thermal photons is or not included. As an example we give results of these corrections to pair production for a constant external background electric field.

hep-ph↗

arXiv2019

Electron-positron pair production in frequency modulated laser fields

The momentum spectrum and the number density of created electron-positron pairs in a frequency modulated laser field are investigated using quantum kinetic equation. It is found that the momentum spectrum presents obvious interference pattern. This is an imprint of the frequency modulated field on the momentum spectrum, because the momentum peaks correspond to the pair production process by absorbing different frequency component photons. Moreover, the interference effect can also be understood qualitatively by analyzing turning point structures. The study of the pair number density shows that the number density is very sensitive to modulation parameters and can be enhanced by over two orders of magnitude for certain modulation parameters, which may provide a new way to increase the number of created electron-positron pairs in future experiments.

quant-ph↗

arXiv2017

Momentum vortices on pairs production by two counter-rotating fields

Multiphoton pair production is investigated by focusing on the momentum structures of produced pairs in the polarization plane for the two circularly polarized fields. Upon the momentum spectra, different from the concentric rings with the familiar Ramsey interference fringes for the same handedness, however, the obvious vortex structures are found constituted by the Archimedean spirals for two opposite handedness fields. The underlying physical reasons are analyzed and discussed. It is also found that the vortex patterns are sensitive to the relative carrier envelope phase, the time delay, and the handedness of two fields, which can be used to detect the applied laser field characteristics as a probe way.

quant-ph↗

arXiv2017

Massless quark production in chromoelectric field with back reaction

We study the massless quark production in $SU(2)$ gauge chromoelectric field by single-time Wigner function covariantly with back reaction. The evolution of field and current are investigated. For a phenomenological distribution function, both the time and momentum dependence have been studied. Interesting phenomena are found, which are: when considering the back reaction, the yield of quark production is higher than the Bjorken expanding field, and momentum 'gap' with confinement phenomenon exists in the phenomenological distribution function. To have a better understanding on the phenomena, components of the Wigner function are qualitatively analyzed.

hep-ph↗

arXiv2016

Effect of ion mass on pair production in the interaction of an ultraintense laser with overdense plasmas

The effect of ion mass on pair production in the interaction of an ultraintense laser with overdense plasmas has been explored by particle-in-cell (PIC) simulation. It is found that the heavier ion mass excites the higher and broader electrostatic field, which is responsible for the enhancement of backward photon number. The pair yields are also reinforced due to the increase of head-on collision of backwards photon with incoming laser. By examining the density evolution and angle distribution of each particle species the origin of pair yields enhancement has been clarified further.

physics.plasm-ph↗