arXiv subjects

Xiao-Li Huang

Publications and source records attributed to Xiao-Li Huang.

At least 37 records · Page 2Linked to original sources

arXiv2024

Cascade Radiations of $e^\pm$ from $γγ$-annihilation process as an extra component of the Early Optical/X-Ray Afterglows of Gamma-Ray Bursts

Chromatic break and/or plateau observed in the early optical and X-ray afterglow lightcurves challenge the conventional external shock models of gamma-ray bursts (GRBs). Detection of TeV gamma-ray afterglows indicates strong gamma-ray production within the afterglow jets. We investigate the cascade radiations of the $e^\pm$ production via the $γγ$ interaction in the jets. Our numerical calculations show that the cascade synchrotron emission can make a significant contribution to the early optical/X-ray afterglows. The combination of the primary and cascade emission fluxes can shape a chromatic break and/or plateau in the early optical/X-ray lightcurves, depending on the jet properties. Applying our model to GRBs 050801 and 080310, we found that their optical plateaus and the late X-ray/optical lightcurves can be explained with our model in reasonable parameter values. We suggest that such a chromatic optical plateau could be a signature of strong $e^\pm$ production in GRB afterglow jets. The TeV gamma-ray flux of such kind GRBs should be significantly reduced, hence tends to be detectable for those GRBs that have a single power-law decaying optical afterglow lightcurve.

astro-ph.HE↗

arXiv2024

Gaussian quantum steering in multi-event horizon spacetime

We study Gaussian quantum steering in the Schwarzschild-de Sitter (SdS) spacetime that is endowed with both a black hole event horizon (BEH) and a cosmological event horizon (CEH), giving rise to two different Hawking temperatures. It is shown that the Hawking effect of the black hole always reduces the quantum steering, but the Hawking effect of the expanding universe does not always play the same role. For the first time, we find that the Hawking effect can improve quantum steering. We also find that the observer who locates in the BEH has stronger steerability than the observer who locates in CEH. Further, we study the steering asymmetry, and the conditions for two-way, one-way and no-way steering in the SdS spacetime. Finally, we study the Gaussian quantum steering in the scenario of effective equilibrium temperature. We show that quantum steering reduces monotonically with the effective temperature but now increases monotonically with the Hawking temperature of the black hole, which banishes the belief that the Hawking effect can only destroy quantum steering.

quant-ph↗

arXiv2024

Fermionic steering is not nonlocal in the background of dilaton black hole

We study the redistribution of the fermionic steering and the relation among fermionic Bell nonlocality, steering, and entanglement in the background of the Garfinkle-Horowitz-Strominger dilaton black hole. We analyze the meaning of the fermionic steering in terms of the Bell inequality in curved spacetime. We find that the fermionic steering, which is previously found to survive in the extreme dilaton black hole, cannot be considered to be nonlocal. We also find that the dilaton gravity can redistribute the fermionic steering, but cannot redistribute Bell nonlocality, which means that the physically inaccessible steering is also not nonlocal. Unlike the inaccessible entanglement, the inaccessible steering may increase non-monotonically with the dilaton. Furthermore, we obtain some monogamy relations between the fermionic steering and entanglement in dilaton spacetime. In addition, we show the difference between the fermionic and bosonic steering in curved spacetime.

quant-ph↗

arXiv2023

Does Hawking effect always degrade fidelity of quantum teleportation in Schwarzschild spacetime?

Previous studies have shown that the Hawking effect always destroys quantum correlations and the fidelity of quantum teleportation in the Schwarzschild black hole. Here, we investigate the fidelity of quantum teleportation of Dirac fields between users in Schwarzschild spacetime. We find that, with the increase of the Hawking temperature, the fidelity of quantum teleportation can monotonically increase, monotonically decrease, or non-monotonically increase, depending on the choice of the initial state, which means that the Hawking effect can create net fidelity of quantum teleportation. This striking result banishes the extended belief that the Hawking effect of the black hole can only destroy the fidelity of quantum teleportation. We also find that quantum steering cannot fully guarantee the fidelity of quantum teleportation in Schwarzschild spacetime. This new unexpected source may provide a new idea for the experimental evidence of the Hawking effect.

gr-qc↗

arXiv2023

Hard TeV Gamma-Ray Afterglows of Nearby GRB 190829A as a Tentative Signature of Ultra-High-Energy Cosmic Rays Accelerated in Gamma-Ray Burst Jets

The observed hard TeV gamma-ray spectrum of the nearby gamma-ray burst (GRB) 190829A may challenge the conventional leptonic GRB afterglow model. It has been proposed that an ultra-high-energy (UHE; $\varepsilon^{'}_{\rm p}\sim 10^{20}$ eV) proton population can be pre-accelerated by internal shocks in GRB jets. We study possible signatures of the UHE protons embedded in the TeV afterglows when they escape the afterglow fireball. We show that the leptonic model can represent the observed multiwavelength lightcurves and spectral energy distributions of GRB 190829A by considering the uncertainties of the model parameters. Attributing the TeV gamma-ray afterglows to the emission of both the electron self-Compton scattering process and the UHE proton synchrotron radiations in the afterglow fireball, we obtain tentative upper limits of $\log_{10} \varepsilon_{\rm p}^{\prime}/{\rm eV}\sim 20.46$ and $\log_{10}E_{\rm p, total}/{\rm erg}\leq 50.75$, where $E_{\rm p, total}$ is the total energy of the proton population. The synchrotron radiations of the UHE protons should dominate the early TeV gamma-ray afterglows, implying that early observations are critical for revealing the UHE proton population.

astro-ph.HE↗

arXiv2023

Quantum entanglement for continuous variables sharing in an expanding spacetime

Detecting the structure of spacetime with quantum technologies has always been one of the frontier topics of relativistic quantum information. Here, we analytically study the generation and redistribution of Gaussian entanglement of the scalar fields in an expanding spacetime. We consider a two-mode squeezed state via a Gaussian amplification channel that corresponds to the time-evolution of the state from the asymptotic past to the asymptotic future. Therefore, the dynamical entanglement of the Gaussian state in an expanding universe encodes historical information about the underlying spacetime structure, suggesting a promising application in observational cosmology. We find that quantum entanglement is more sensitive to the expansion rate than the expansion volume. According to the analysis of quantum entanglement, choosing the particles with the smaller momentum and the optimal mass is a better way to extract information about the expanding universe. These results can guide the simulation of the expanding universe in quantum systems.

quant-ph↗

arXiv2023

Would quantum coherence be increased by curvature effect in de Sitter space?

We study the quantum coherence in de Sitter space for the bipartite system of Alice and Bob who initially share an entangled state between the two modes of a free massive scalar field. It is shown that the space-curvature effect can produce both local coherence and correlated coherence, leading to the increase of the total coherence of the bipartite system. These results are sharp different from the Unruh effect or Hawking effect, which, in the single mode approximation, cannot produce local coherence and at the same time destroy correlated coherence, leading to the decrease of the total coherence of the bipartite systems. Interestingly, we find that quantum coherence has the opposite behavior compared with the quantum correlation in de Sitter space. We also find that quantum coherence is most severely affected by the curvature effect of de Sitter space for the cases of conformal invariance and masslessness. Our result reveals the difference between the curvature effect in the de Sitter space and the Unruh effect in Rindler spacetime or the Hawking effect in black hole spacetime on quantum coherence.

gr-qc↗

arXiv2023

Genuine tripartite entanglement of W state subject to Hawking effect of a Schwarzschild black hole

We study the genuine tripartite entanglement (GTE), one-tangle and two-tangle of W state of fermionic fields in the background of a Schwarzschild black hole. We find that, with the increase of the Hawking temperature, the GTE of W state first decreases and then tends to zero, while the GTE of GHZ state first decreases and then freezes. We also find that the Hawking effect can completely destroy the two-tangle of W state, whilie one-tangle first decreases and then appears freezing phenomenon with the growth of the Hawking temperature. These results are helpful to guide us to select appropriate quantum states and quantum resources to deal with relativistic quantum information tasks.

quant-ph↗

arXiv2022

TeV and keV-MeV Excesses as Probes for Hadronic Process in BL Lacertaes

A hard TeV $γ$-ray component excess over the single-zone leptonic model prediction (TeV excess) is observed in the spectral energy distributions (SEDs) of some BL Lacs. Its origin is uncertain. We revisit this issue with four BL Lacs (1ES 0229+200, 1ES 0347--121, 1ES 1101--232, and H2356--309), in which the TeV excess is detected in their intrinsic SEDs. We represent their SEDs with a single-zone leptohadronic model, where radiations of the electrons and protons as well as the cascade electrons produced by the $γγ$ and p$γ$ interactions within their jets are considered. We show that the observed SEDs below the GeV gamma-ray band are attributed to the synchrotron radiations and self-Compton process of the primary electrons, and the TeV excess is explained with the $γ$-ray emission from the p$γ$ process via the $π^{0}$ decay. The cascade emission of the electrons produced via the $γγ$ and p$γ$ interactions results in a keV-MeV excess in the SEDs, illustrated as a bump or plateau. This extra photon field enhances the production of TeV photons from the $pγ$ process, resulting in a reduction of the proton power by about one order of magnitude. However, the derived powers are still 3--4 orders of magnitude larger than the Eddington limit, being challenged by the current black hole accretion physics. Applying our model to Mrk 421, we propose that synergic observations with current and upcoming TeV and keV-MeV telescopes for its tentative TeV and MeV excesses can give insights to the hadronic process in its jet.

astro-ph.HE↗

arXiv2020

Very High Energy Emission and Cascade Radiation of Gamma-Ray Burst Afterglows: Homogeneous Versus Wind External Media

Recent detection of sub-TeV emission from gamma-ray bursts (GRBs) represents a breakthrough in the GRB study. The multi-wavelength data of the afterglows of GRB 190114C support the synchrotron self-Compton (SSC) origin for its sub-TeV emission. We present a comparative analysis on the SSC emission of GRB afterglows in the homogeneous and wind environment in the framework of the forward shock model. The $γγ$ absorption of very high-energy photons due to pair production within the source and the Klein-Nishina effect on the inverse-Compton scattering are considered. Generally a higher SSC flux is expected for a larger circum-burst density due to a larger Compton parameter, but meanwhile the internal $γγ$ absorption is more severer for sub-TeV emission. The flux ratio between the SSC component and the synchrotron component decreases more quickly with time in the wind medium case than that in the homogenous-density medium case. The light curves of the SSC emission are also different for the two types of media. We also calculate the cascade emission resulted from the absorbed high-energy photons. In the ISM environment with $n> 1\,\rm cm^{-3}$, the cascade synchrotron emission could be comparable to the synchrotron emission of the primary electrons in the optical band, which may flatten the optical afterglow light curve at early time ($t<1$ h). In the wind medium with $A_{\ast}> 0.1$, the cascade emission in the eV-GeV band is comparable or even larger than the emission of the primary electrons at early time.

astro-ph.HE↗

arXiv2020

$L_{\rm syn}-E_{\rm syn, p}-δ$ relation in Active Galactic Nucleus Jets and Implication for the physical origin of the $L_{\rm p}-E_{\rm p,z}-Γ_0$ relation of Gamma-Ray Bursts

High energy photon radiations of gamma-ray bursts (GRBs) and active galactic nuclei (AGNs) are dominated by their jet radiations. We examine wether the synchrotron radiations of jets in BL Lacs, flat spectrum radio quasars (FSRQs), and Narrow Line Seyfert 1 galaxies (NLS1s) follow the relation between the prompt gamma-ray emission and the initial Lorentz factor ($Γ_0$) of GRBs. It is showed that the AGNs sample does not agree with the $L_{\rm p}-E_{\rm p,z}-Γ_{0}$ of GRBs. In addition, we obtain a tight relation of $L_{\rm syn}\propto E^{0.45\pm0.15}_{\rm syn,p}δ^{3.50\pm0.25}$ for FSRQs and NLS1 galaxies, where $L_{\rm syn}$ is the luminosity at peak photon energy $E_{\rm syn, p}$ of the synchrotron radiations. This relation is different from the $L_{\rm p}-E_{\rm p,z}-Γ_{0}$ relation of GRBs. The dependence of $L_{\rm syn}$ to $δ$ is consistent with the expectation of the Doppler boosting effect for the FSRQs and NLS1 galaxies, but it is not for GBRs. We argue that $Γ_0$ may be a representative of the kinetic power of the radiating region and the tight $L_{\rm p}-E_{\rm p, z}-Γ_0$ relation is shaped by the radiation physics and the jet power together.

astro-ph.HE↗

arXiv2020

Afterglow Synchrotron Radiations follow the $L_{\rm p, iso}-E_{\rm p,z}-Γ_0$ relation of Gamma-Ray Bursts? Cases of GRBs 190114C, 130427A, and 180720B

Bimodal spectral energy distributions (SEDs) of gamma-ray burst (GRB) afterglow of GRBs 190114C, 130427A and 180720B confirm that they are originated from the synchrotron emission (Syn) and synchrotron self-Compton Scattering process (SSC) of electrons accelerated in the jets. The radiation mechanism and the physics of the observed spectrum-luminosity/energy relations of GRBs remain as open questions. By extracting the Syn component through fitting their early afterglow SEDs with the Syn+SSC model, we find that their luminosity ($L_{\rm syn}$), peak energy ($E_{\rm p,syn,z}$), and the Lorentz factor of the afterglow fireball ($Γ_t$) follow the $L_{\rm p, iso}-E_{\rm p,z}-Γ_{0}$ relation of prompt gamma-rays, where $L_{\rm p, iso}$ is the isotropic luminosity, $E_{\rm p, z}$ is the peak energy of the $νf_ν$ spectrum in the burst frame, and $Γ_0$ is the initial Lorentz factor of the fireball. To examine whether late afterglows is consistent with this relation, we calculate the synchrotron component at late afterglows. It is found that they also follow the same $L_{\rm p, iso}-E_{\rm p,z}-Γ_{0}$ relation, albeit they are not consistent with the $L_{\rm p, iso}-E_{\rm p,z}$ relation. Our results may imply that the $L_{\rm p, iso}-E_{\rm p,z}-Γ_{0}$ would be an universal feature of synchrotron radiations of electrons accelerated in GRB jets throughout the prompt and afterglow phases among GRBs. Its origin is not fully understood and possible explanations are briefly discussed.

astro-ph.HE↗

arXiv2018

Interaction-induced supercurrent in quantum Hall setups

Recently we have proposed an unusual mechanism of superconducting current that is specific for Quantum Hall Edge channels connected to superconducting electrodes. We have shown that the supercurrent can be mediated by a nonlocal electon-electon interaction that provide an opportunity for a long-distance information transfer in the direction opposite to the electron flow. A convenient model for such interaction is that of an external circuit. The consideration has been done for the case of a single channel. In this work, we extend these results to more sophisticated setups that include the scattering between Quantum Hall channels of opposite direction and multiple superconducting contacts. For a single Quantum Hall constriction, we derive a general and comprehensive relation for the interaction- induced supercurrent in terms of scattering amplitudes and demonstrate the non-local nature of the current by considering its sensitivity to scattering. We understand the phase dependences of the supercurrents in multi-terminal setups in terms of interference of Andreev reflection processes. For more complex setups encompassing at least two constrictions we find an interplay between non-interacting and interaction-induced currents and contibutions of complex interference processes.

cond-mat.mes-hall↗

arXiv2018

Photometric and Spectroscopic Observations of GRB 140629A

We present our optical photometric and spectroscopical observations of GRB 140629A. A redshift of $z=2.275\pm0.043$ is measured through the metal absorption lines in our spectroscopic data. Using our photometric data and multiple observational data observed with other telescopes, we show that its optical light curve is well interpreted with the standard forward shock models in the thin shell case. Its optical-X-ray afterglow spectrum is jointly fitted with a single power-law function, yielding a photon index of $-1.90\pm 0.05$. The optical extinction and neutral hydrogen absorption of the GRB host galaxy are negligible. The fit to the light curve with the standard models shows that the ambient density is $60\pm 9$ cm$^{-3}$ and the GRB radiating efficiency is as low as $\sim 0.24\%$, likely indicating a baryonic-dominated ejecta of this GRB. This burst agrees well with the $L_{\rm p, iso}-E_p^{'}-Γ_0$ relation, but confidently violates those empirical relations involving geometric corrections (or jet break time). This gives rise to an issue of possible selection effect on these relations since the jet opening angle of this GRB is extremely narrow (0.04 rad).

astro-ph.HE↗

arXiv2018

GRB120729A: external shock origin for both the prompt gamma-ray emission and afterglow

Gamma-ray burst (GRB) 120729A was detected by Swift/BAT and Fermi/GBM, and then rapidly observed by Swift/XRT, Swift/UVOT, and ground-based telescopes. It had a single long and smooth γ-ray emission pulse, which extends continuously to the X-rays. We report Lick/KAIT observations of the source, and make temporal and spectral joint fits of the multiwavelength light curves of GRB 120729A. It exhibits achromatic light-curve behavior, consistent with the predictions of the external shock model. The light curves are decomposed into four typical phases: onset bump (Phase I), normal decay (Phase II), shallow decay (Phase III), and post-jet break (Phase IV). The spectral energy distribution (SED) evolves from prompt γ-ray emission to the afterglow with photon index from $Γ_{\rm γ}=1.36$ to $Γ\approx 1.75$. There is no obvious evolution of the SED during the afterglow. The multiwavelength light curves from γ-ray to optical can be well modeled with an external shock by considering energy injection, and a time-dependent microphysics model with $ε_B\propto t^{α_B}$ for the emission at early times, $T < T_{\rm 0} + 157$~s. Therefore, we conclude that both the prompt γ-ray emission and afterglow of GRB 120729A have the same external shock physical origin. Our model indicates that the $ε_B$ evolution can be described as a broken power-law function with $α_{\rm B,1} = 0.18 \pm 0.04$ and $α_{\rm B,2} = 0.84 \pm 0.04$. We also systematically investigate single-pulse GRBs in the Swift era, finding that only a small fraction of GRBs (GRBs 120729A, 051111, and 070318) are likely to originate from an external shock for both the prompt γ-ray emission and afterglow.

astro-ph.HE↗

arXiv2017

Flux and Spectral Variation Characteristics of 3C 454.3 at the GeV Band

We analyze the long-term lightcurve of 3C 454.3 observed with Fermi/LAT and investigate its relation to the flux in the radio, optical, and X-ray bands. By fitting the 1-day binned GeV lightcurve with multiple Gaussian function (MGF), we propose that the typical variability timescale in the GeV band is 1--10 days. The GeV flux variation is accompanied by the spectral variation characterized as flux-tracking, i.e., "harder when brighter". The GeV flux is correlated with the optical and X-ray fluxes, and a weak correlation between gamma-ray flux and radio flux is also observed. The gamma-ray flux is not correlated with the optical linear polarization degree for the global lightcurves, but they show a correlation for the lightcurves before MJD 56000. The power density spectrum of the global lightcurve shows an obvious turnover at ~7.7 days, which may indicate a typical variability timescale of 3C 454.3 in the gamma-ray band. This is also consistent with the derived timescales by fitting the global lightcurve with MGF. The spectral evolution and an increase of the optical linear polarization degree along with the increase of the gamma-ray flux may indicate that the radiation particles are accelerated and the magnetic field is ordered by the shock processes during the outbursts. In addition, the nature of 3C 454.3 may be consistent with the self-organized criticality system, similar to Sagittarius A, and thus the outbursts are from plasmoid ejections driven by magnetic reconnection. This may further support the idea that the jet radiation regions are magnetized.

astro-ph.HE↗

arXiv2017

Extremely bright GRB 160625B with multi-episodes emission: Evidences for long-term ejecta evolution

GRB 160625B is an extremely bright GRB with three distinct emission episodes. By analyzing its data observed with the GBM and LAT on board the {\em Fermi} mission, we find that a multi-color black body (mBB) model can be used to fit the spectra of initial short episode (Episode I) very well within the hypothesis of photosphere emission of a fireball model. The time-resolved spectra of its main episode (Episode II), which was detected with both GBM and LAT after a long quiet stage ($\sim 180$ seconds) of the initial episode, can be fitted with a model composing of an mBB component plus a cutoff power-law (CPL) component. This GRB was detected again in the GBM and LAT bands with a long extended emission (Episode III) after a quiet period of $\sim 300$ seconds. The spectrum of Episode III is adequately fitted with a CPL plus a single power-law models, and no mBB component is required. These features may imply that the emission of three episodes are dominated by distinct physics process, i.e., Episode I is possible from cocoon emission surrounding the relativistic jet, Episode II may be from photosphere emission and internal shock of relativistic jet, and Episode III is contributed by internal and external shocks of relativistic jet. On the other hand, both X-ray and optical afterglows are consistent with standard external shocks model.

astro-ph.HE↗

arXiv2017

Topology protection-unprotection transition: an example from multi-terminal superconducting nanostructures

We show theoretically that in the superconducting nanostructures the gapped states of different topology are not always protected by separating gapped states. Depending on the structure design parameters, they can be either protected or not, with a protection-unprotection transition separating these two distinct situations. We build up a general theoretical description of the transition vicinity in the spirit of Landau theory. We speculate that similar protection-unprotection transitions may also occur for other realizations of topological protection in condensed matter systems.

cond-mat.mes-hall↗