Self-organized criticality in multi-pulse gamma-ray bursts

The variability in multi-pulse gamma-ray bursts(GRBs)may help to reveal the mechanism of underlying processes from the central engine.To investigate whether the self-organized criticality(SOC)phenomena exist in the prompt phase of GRBs,we statistically study the proper ties of GRBs with more than 3 pulses in each burst by fitting the distributions of several observed physical variables with a Markov Chain Monte Carlo approach,including the isotropic energy E_iso,the duration time T,and the peak count rate P of each pulse.Our sample consists of 454 pulses in 93 GRBs observed by the CGRO/BATSE satellite.The best-fitting values and uncertainties for these power-law indices of the differential frequency distributions are:α_E^d=1.54±0.09,α_T^d=1.82_-0.15^+0.14andα_P^d=2.09_-0.19^0.18,while the power-law indices in the cumulative frequency distributions are:α_E^c=1.44_-0.10^+0.08,α_T^c=1.75_-0.13^0.11andα_P^c=1.99_-0.19^+0.16.We find that these distributions are roughly consistent with the physical framework of a Fractal-Diffusive,Self^Organized Criticality(FD-SOC)system with the spatial dimension S=3 and the classical diffusionβ=1.Our results support that the jet responsible for the GRBs should be magnetically dominated and magnetic instabilities(e.g.,kink model,or tearing-model instability)lead the GRB emission region into the SOC state.     

Relation between gravitational mass and baryonic mass for non-rotating and rapidly rotating neutron stars

With a selected sample of neutron star(NS)equations of state(EOSs)that are consistent with the current observations and have a range of maximum masses,we investigate the relations between NS gravitational mass Mg and baryonic mass and the relations between the maximum NS mass supported through uniform rotation(Mmax)and that of nonrotating NSs(Mtov).We find that for an EOS-independent quadratic,universal transformation formula(Mb=Mg+A×M^2/g),the best-fit A value is 0.080 for non-rotating NSs,0.064 for maximally rotating NSs,and 0.073 when NSs with arbitrary rotation are considered.The residual error of the transformation is?0.1M⊙ for non-spin or maximum-spin,but is as large as?0.2M⊙ for all spins.For different EOSs,we find that the parameter A for non-rotating NSs is proportional to R^-1/1.4(where R1.4 is NS radius for 1.4M⊙ in units of km).For a particular EOS,if one adopts the best-fit parameters for different spin periods,the residual error of the transformation is smaller,which is of the order of O.O1M⊙ for the quadratic form and less than O.O1M⊙ for the cubic form(Mb=Mg+A1×M^2/g+A2×M^3/g).We also find a very tight and general correlation between the normalized mass gain due to spin △m≡(Mmax-MTOV)MTOV and the spin period normalized to the Keplerian period P,i.e.,log10 △m=(-2.74±0.05)log10 P+log10(0.20±0.01),which is independent of EOS models.These empirical relations are helpful to study NS-NS mergers with a long-lived NS merger product using multi-messenger data.The application of our results to GW170817 is discussed.     

Spatial modulation of unitary impurity-induced resonances in superconducting CeCoIn5

Motivated by recent experimental progress in high-resolution scanning tunneling microscopy (STM) techniques, we investigate the local quasiparticle density of states around a unitary impurity in the heavy-fermion superconductor CeCoIn₅. Based on the T -matrix approach we obtain a sharp nearly zero-energy resonance state in the strong impurity potential scattering localized around the impurity and find qualitative differences in the spatial pattern of the tunneling conductance modulated by the nodal structure of the superconducting gap. These unique features may be used as a probe of the superconducting gap symmetry and, in combination with further STM measurements, may help to confirm the dx2−y2 pairing in CeCoIn₅ at ambient pressure.     

Kinetic modeling of multiphase flow based on simplified Enskog equation

A new kinetic model for multiphase flow was presented under the framework of the discrete Boltzmann method (DBM). Significantly different from the previous DBM, a bottom-up approach was adopted in this model. The effects of molecular size and repulsion potential were described by the Enskog collision model; the attraction potential was obtained through the mean-field approximation method. The molecular interactions, which result in the non-ideal equation of state and surface tension, were directly introduced as an external force term. Several typical benchmark problems, including Couette flow, two-phase coexistence curve, the Laplace law, phase separation, and the collision of two droplets, were simulated to verify the model. Especially, for two types of droplet collisions, the strengths of two non-equilibrium effects, {\overline{D}}_2^{*} and {\overline{D}}_3^{*} , defined through the second and third order non-conserved kinetic moments of (f-f^{eq}), are comparatively investigated, where f\left(f^{eq}\right)is the (equilibrium) distribution function. It is interesting to find that during the collision process, {\overline{D}}_2^{*} is always significantly larger than {\overline{D}}_3^{*}, {\overline{D}}_2^{*} can be used to identify the different stages of the collision process and to distinguish different types of collisions. The modeling method can be directly extended to a higher-order model for the case where the non-equilibrium effect is strong, and the linear constitutive law of viscous stress is no longer valid.     

Diverse magnetism in stable and metastable structures of CrTe

In this paper, we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations. By considering the electronic correlation effect, we predicted the ground-state structure of CrTe to be NiAs-type (space group P6₃/mmc) structure at ambient pressure, consistent with the experimental observation. Moreover, we found two extra meta-stable Cmcaand R\overline{3}m structures which have negative formation enthalpy and stable phonon dispersion at ambient pressure. The Cmcastructure is a layered antiferromagnetic metal. The cleaved energy of a single layer is 0.464 J/m² , indicating the possible synthesis of CrTe monolayer. The R\overline{3}m structure is a ferromagnetic half-metal. When external pressure is applied, the ground-state structure of CrTe transitions from P63/mmc structure to R\overline{3}m structure at a pressure of 34 GPa, then to R\overline{3}m structure at 42 GPa. We thought these results help to motivate experimental studies of the CrTe compounds in the application of spintronics.     

A comparison between repeating bursts of FRB 121102 and giant pulses from Crab pulsar and its applications

There are some similarities between bursts of repeating fast radio bursts (FRBs) and giant pulses (GPs) of pulsars. To explore possible relations between them, we study the cumulative energy distributions of these two phenomena using the observations of repeating FRB 121102 and the GPs of Crab pulsar. We find that the power-law slope of GPs (with fluence≥130 Jy·ms) is 2.85±0.10. The energy distribution of FRB 121102 can be well fitted by a smooth broken power-law function. For the bursts of FRB 121102 above the break energy (1.22 ×10³⁷ erg), the best-fitting slope is {2.90}_{-0.44}^{+0.55}, similar to the index of GPs at the same observing frequency (∼1.4 GHz). We further discuss the physical origin of the repeating FRB 121102 in the framework of the super GPs model. And we find that the super GPs model involving a millisecond pulsar is workable and favored for explaining FRB 121102 despite that the magnetar burst model is more popular.     

Gluon number fluctuations and diffusive scaling effect

The diffusive scaling is studied based on pomeron loop equations in the fixed coupling case. At Y?YDS, the gluon number fluctuations become important, the geometric scaling is replaced by the diffusive scaling. In the diffusive scaling regime, the deep inelastic scattering (DIS) total scattering cross-section is a function of single variable ln?[1/(r2Qs2(X))]/DY. We show that the deep inelastic scattering experimental data lie on a single curve, which seems to indicate the existence of the diffusive scaling phenomenology in the deep inelastic scattering.     

On the entangled fractional squeezing transformation

We propose an entangled fractional squeezing transformation (EFrST) generated by using two mutually conjugate entangled state representations with the following operator: e-iα(a1?a2?+a1a2)eiπa2?a2; this transformation sharply contrasts the complex fractional Fourier transformation produced by using e-iα(a1?a2?+a2?a2)eiπa2?a2 (see Front. Phys. DOI 10.1007/s11467-014-0445-x). The EFrST is obtained by converting the triangular functions in the integration kernel of the usual fractional Fourier transformation into hyperbolic functions, i.e., tanα → tanhα and sinα → sinhα. The fractional property of the EFrST can be well described by virtue of the properties of the entangled state representations.     

Conditions for ponderomotive resonances in the Kapitza–Dirac effect

By applying a nonperturbative quantum electrodynamic theory, we study ponderomotive resonances when an electron beam is scattered by a standing photon wave. Our study shows that the ponderomotive parameter u_p, the ponderomotive energy per laser-photon energy, for each of the two traveling laser modes possesses a minimum value ℏω/(mec2). Ponderomotive resonances occur only when the ratio of the laser photon energy to the electron rest-mass energy is a fraction, where the denominator is twice the square of a positive integer and the numerator is the total ponderomotive number, which is also a positive integer.     

On the existence of N*(890) resonance in S11 channel of πN scatterings

Low-energy partial-wave πN scattering data is reexamined with the help of the production representation of partial-wave S matrix, where branch cuts and poles are thoroughly under consideration. The left-hand cut contribution to the phase shift is determined, with controlled systematic error estimates, by using the results of O(p³) chiral perturbative amplitudes obtained in the extended-onmass- shell scheme. In S₁₁ and P₁₁ channels, severe discrepancies are observed between the phase shift data and the sum of all known contributions. Statistically satisfactory fits to the data can only be achieved by adding extra poles in the two channels. We find that a S₁₁ resonance pole locates at \sqrt{z_r} = (0.895±0.081)−(0.164±0.023)i GeV, on the complex s-plane. On the other hand, a P₁₁ virtual pole, as an accompanying partner of the nucleon bound-state pole, locates at \sqrt{z_v} = (0.966±0.018) GeV, slightly above the nucleon pole on the real axis below threshold. Physical origin of the two newly established poles is explored to the best of our knowledge. It is emphasized that the O(p³) calculation greatly improves the fit quality comparing with the previous O(p²) one.     

Finite temperature physics of 1D topological Kondo insulator: Stable Haldane phase,emergent energy scale and beyond

In recent years, interacting topological insulators have emerged as new frontiers in condensed matter physics, and the hotly studied topological Kondo insulator (TKI) is one of such prototypes. Although its zero-temperature ground-state has been widely investigated, the finite temperature physics on TKI is largely unknown. Here, we explore the finite temperature properties in a simplified model for TKI, namely the one-dimensional p-wave periodic Anderson model, with numerically exact determinant quantum Monte Carlo simulation. It is found that the topological Haldane phase established for groundstate is still stable against small thermal fluctuation and its characteristic edge magnetization develops at low temperature. Such facts emphasize the robustness of (symmetry-protected) topological order against temperature effect, which always exists at real physical world. Moreover, we use the saturated low-T spin structure factor and the \frac{1}{T}-law of susceptibility to detect the free edge spin moment, interestingly the low-temperature upturn behavior of the latter one is similar to experimental finding in SmB₆ at T<50 K. It implies that similar physical mechanism may work both for idealized models and realistic correlated electron materials. We have also identified an emergent energy scale T_cr, which signals a crossover into interesting low-T regime and seems to be the expected Ruderman–Kittel–Kasuya–Yosida coupling. Finally, the collective Kondo screening effect has been examined and it is heavily reduced at boundary, which may give a fruitful playground for novel physics beyond the wellestablished Haldane phase and topological band insulators.     

Evolution law of Wigner function in laser process

Based on the density operator’s o perator-sum representation r ecently obtained by Fan and Hu for a laser process (Opt. Commun., 2008, 281: 5571; Opt. Commun., 2009, 282: 932; Phys. Lett. B, 2008, 22: 2435), we derive the evolution law of Wigner operator, the law is concisely expressed in the normally ordered formΔ(α,α*,t)=Tπ:exp?[-2T(a?e-(κ-g)t-α*)-(ae-(k-g)t-α)] :, where g and κ are the cavity gain and the loss, respectively, and T≡ (κ-g )(κ+g-2ge^{-2(κ-g) t})^-1. When t=0,Δ(α,α,t)→1π : exp?[-2(a?-α*)-(a-α)] :, which is the initial Wigner operator. Using this formalism the evolution law of Wigner functions in laser process can be directly obtained.     

Experimental review of the ϒ(1S, 2S, 3S) physics at e+e− colliders and the LHC

The three lowest-lying \mathrm{\Upsilon } states, i.e., \mathrm{\Upsilon }(1S), \mathrm{\Upsilon }(2S), and \mathrm{\Upsilon }(3S), composed of bb¯ pairs and below the BB ¯ threshold, provide a good platform for the researches of hadronic physics and physics beyond the Standard Model. They can be produced directly in e⁺e⁻ colliding experiments, such as CLEO, Babar, and Belle, with low continuum backgrounds. In these experiments, many measurements of the exclusive \mathrm{\Upsilon }(1S) and \mathrm{\Upsilon }(2S) decays into light hadrons, which shed light on the “80% rule” for the Okubo–Zweig–Iizuka suppressed decays in the bottomonium sector, were carried out. Meanwhile, many studies of the charmonium and bottomonium productions in \mathrm{\Upsilon }(1S, 2S, 3S) decays were performed, to distinguish different Quantum Chromodynamics (QCD) models. Besides, exotic states and new physics were also extensively explored in \mathrm{\Upsilon }(1S, 2S, 3S) decays at CLEO, BaBar, and Belle. The \mathrm{\Upsilon }(1S, 2S, 3S) states can also be produced in pp collisions and in collisions involving heavy ions. The precision measurements of their cross sections and polarizations at the large hadron collider (LHC), especially in the CMS, ATLAS, and LHCb experiments, help to understandΥproduction mechanisms in pp collisions. The observation of the sequentialΥsuppression in heavy ion collisions at CMS, LHCb, and ALICE is of great importance for verifying the quark–gluon plasma predicted by QCD. In this article, we review the experimental results on \mathrm{\Upsilon }(1S, 2S, 3S) at e⁺e⁻ colliders and the LHC, and summarize their prospects at Belle II and the LHC.     

On the cutoff law of laser induced high harmonic spectra

The currently well accepted cutoff law for laser induced high harmonic spectra predicts the cutoff energy as a linear combination of two interaction energies, the ponderomotive energy U_p and the atomic biding energy I_p, with coefficients 3.17 and 1.32, respectively. Even though, this law has been there for twenty years or so, the background information for these two constants, such as how they relate to fundamental physics and mathematics constants, is still unknown. This simple fact, keeps this cutoff law remaining as an empirical one. Based on the cutoff property of Bessel functions and the Einstein photoelectric law in the multiphoton case, we show these two coefficients are algebraic constants, 9 - 42≈ 3.34 and 22- 1 ≈ 1.83, respectively. A recent spectra calculation and an experimental measurement support the new cutoff law.     

Optimal phase sensitivity of atomic Ramsey interferometers with coherent spin states

We present a detailed analysis of phase sensitivity for a nonlinear Ramsey interferometer, which utilize effective mean-field interaction of a two-component Bose–Einstein condensate in phase accumulation. For large enough particle number N and small phase shift ?, analytical results of the Ramsey signal and the phase sensitivity are derived for a product coherent state |θ,0?. When collisional dephasing is absent, we confirm that the optimal sensitivity scales as 2/N^3/2 for polar angle of the initial state θ = π/4 or 3π/4. The best-sensitivity phase satisfies different transcendental equations, depending upon the initial state and the observable being measured after the phase accumulation. In the presence of the collisional dephasing, we show that the N^-3/2-scaling rule of the sensitivity maintains with spin operators J^x and J^y measurements. A slightly better sensitivity is attainable for optimal coherent state with θ = π/6 or 5π/6.     

K±p elastic scattering in the QCD inspired eikonalized model

Based on our previous study of the QCD inspired eikonalized model for describing vector meson photoproduction, pp, and p ˉp elastic scattering at high energies, we apply the mode to high energy K^±p elastic scattering. The total cross section σ_tot(s), differential cross section dσ/dt, the ratio of the real part to imaginary part of the forward scattering amplitude ρ(s), and nuclear slope parameter function β(s) are calculated in the model. Our results show that the theoretical prediction for σ_tot(s) is in a good agreement with the experimental data within error bars of the data. For the other theoretical predictions there are no data to test the predictive power of the model. We need the corresponding experimental data to examinate the validity of our QCD inspired eikonalized model. However, our calculations clearly show that the Odderon exchange in the process makes a significant contribution to the observable of ρ(s) and β(s). Therefore, we may conclude that there is a good opportunity to find the QCD Odderon in the K^±p elastic scattering at high energies.     

Equivariant PT-symmetric real Chern insulators

It was understood that Chern insulators cannot be realized in the presence of PT symmetry.In this paper,we reveal a new class of PT-symmetric Chern insulators,which has internal degrees of freedom forming real representations of a symmetry group with a complex endomorphism field.As a generalization to the conventional 2n-dimensional Chern insulators with integer n≥1,these PT-symmetric Chern insulators have the n-th complex Chern number as their topological invariant,and have a Z classification given by the equivariant orthogonal K theory.Thus,in a fairly different sense,there exist ubiquitously Chern insulators with PT.symmetry.By generalizing the Thouless charge pump argument,we find that,for a PT-symmetric Chern insulator with Chern number v.there are equally many v flavors of coexisting left-and right-handed chiral modes.Chiral modes with opposite chirality are complex conjugates to each other as complex representations of the internal symmetry group,but are not isomorphic.For the physical dimensionality d=2,the PT-symmetric Chern insulators may be realized in artificial systems including photonic crystals and periodic mechanical systems.     

Redshift drift constraints on f(T) gravity

We explore the impact of the Sandage−Loeb (SL) test on the precision of cosmological constraints for f(T) gravity theories. The SL test is an important supplement to current cosmological observations because it measures the redshift drift in the Lyman-α forest in the spectra of distant quasars, covering the “redshift desert” of 2≲z≲5. To avoid data inconsistency, we use the best-fit models based on current combined observational data as fiducial models to simulate 30 mock SL test data. We quantify the impact of these SL test data on parameter estimation for f(T) gravity theories. Two typical f(T) models are considered, the power-law model f(T)_PL and the exponential-form model f(T)_EXP. The results show that the SL test can effectively break the existing strong degeneracy between the present-day matter density Ω_m and the Hubble constant H₀ in other cosmological observations. For the considered f(T) models, a 30-year observation of the SL test can improve the constraint precision of Ω_m and H₀ enormously but cannot effectively improve the constraint precision of the model parameters.