arXiv subjects

Xiao-Long Liu

Publications and source records attributed to Xiao-Long Liu.

6 recordsLinked to original sources

arXiv2026

Quantum Corrections to $η/s$ from JT Gravity

We revisit the computation of the shear viscosity to entropy ratio $η/s$ at finite chemical potential in a holographic model that takes into account the quantum fluctuations in the IR region of near-extremal black branes. Such quantum corrections can be computed from JT gravity and generate non-trivial temperature dependence for $η/s$, which deviates from the universal $1/4π$ result. In the semi-classical regime, $η/s$ attains a minimum which is below the KSS bound, generated by the presence of the quantum effects. In the quantum regime at lower temperatures, $η/s$ increases and is well above the KSS bound. We also compare the shear viscosity to the quantum-corrected absorption cross-section of near-extremal black holes, and find agreement.

hep-th↗

arXiv2025

Quantum-Corrected Holographic Wilson Loop Expectation Values and Super-Yang-Mills Confinement

Confinement is a well-known phenomenon in the infrared regime of (supersymmetric) Yang-Mills theory. While both experimental observations and numerical simulations have robustly confirmed its existence, the underlying physical mechanism remains elusive. Unraveling the theoretical origin of confinement continues to be a profound and longstanding challenge in both physics and mathematics. Motivated by recent advances in quantum Jackiw-Teitelboim gravity, we investigate the Wilson loop expectation values in the large-$N$ limit of $\mathscr{N}=4$ super-Yang-Mills theory at finite chemical potential, employing a holographic approach within the background of an extremal AdS$_5$ Reissner-Nordström black brane. Our results reveal that quantum gravitational fluctuations in the near-horizon region significantly modify the holographic Wilson loop expectation values. These values exhibit an area-law behavior, indicative of a confining quark-antiquark potential. Within this framework, our findings suggest that confinement in the super-Yang-Mills theory arises as a consequence of near-horizon quantum gravity fluctuations in the bulk extremal AdS$_5$ black brane geometry.

hep-th↗

arXiv2024

Quantum Corrections to Holographic Strange Metal at Low Temperature

The holographic approach to the strange metal phase relies on near-extremal asymptotically AdS$_4$ electrically charged black branes with important input from their AdS$_2$ near-horizon throat geometry. Motivated by the current understanding of the role of quantum fluctuations in the throat of near-extremal black holes, we revisit some transport properties. We model quantum gravitational and gauge fluctuations in the throat region by adopting results in Jackiw-Teitelboim gravity, effectively leading to quantum corrections for the dual CFT$_1$ Green's function in the near-horizon infrared region. We use the quantum-corrected Green's function to compute the conductivity for (2+1)-dimensional holographic strange metals and obtain corrections for the DC resistivity and the optical conductivity. We also compare the quantum-corrected holographic approach with results from the complex Sachdev-Ye-Kitaev model and point out qualitative differences. Although experimental detection for the quantum-corrected holographic approach to the DC resistivity requires higher precision than current experimental accuracy, future experiments with improved technologies could detect these quantum corrections. Interestingly, including quantum corrections to the optical conductivity does provide a plausible explanation for the experimental anomalous power-law behavior detected in various strange metals.

hep-th↗

arXiv2021

The UV/optical peak and X-ray brightening in TDE candidate AT2019azh: A case of stream-stream collision and delayed accretion

We present and analyze the optical/UV and X-ray observations of a nearby tidal disruption event (TDE) candidate AT2019azh, spanning from $\sim$ 30 d before to $\sim$ 400 d after its early optical peak. The X-rays show a late brightening by a factor of $\sim$ 30-100 around 200 days after discovery, while the UV/opticals continuously decayed. The early X-rays show two flaring episodes of variation, temporally uncorrelated with the early UV/opticals. We found a clear sign of X-ray hardness evolution, i.e., the source is harder at early times, and becomes softer as it brightens later. The drastically different temporal behaviors in X-rays and UV/opticals suggest that the two bands are physically distinct emission components, and probably arise from different locations. These properties argue against the reprocessing of X-rays by any outflow as the origin of the UV/optical peak. The full data are best explained by a two-process scenario, in which the UV/optical peak is produced by the debris stream-stream collisions during the circularization phase; some shocked gas with low angular momentum forms an early, low-mass 'precursor' accretion disk which emits the early X-rays. The major body of the disk is formed after the circularization finishes, whose enhanced accretion rate produces the late X-ray brightening. AT2019azh is a strong case of TDE whose emission signatures of stream-stream collision and delayed accretion are both identified.

astro-ph.HE↗

arXiv2021

Photovoltaic Self-Powered Gas Sensing: A Review

The self-powered sensing system could harness ambient energy to power the sensor without the need for external electrical energy. Recently, the concept of photovoltaic (PV) self-powered gas sensing has aroused wider attentions due to room-temperature operation, low power consumption, small size and potential applications. The PV self-powered gas sensors integrate the photovoltaic effects and the gas sensing function into a single chip, which could truly achieve the goal of zero power consumption for an independent gas sensing device. As an emerging concept, the PV self-powered gas sensing has been achieved by using different strategies, including integrated gas sensor and solar cell, integrated light filter and solar cell, gas-sensitive heterojunction photovoltaics, and gas-sensitive lateral photovoltaics, respectively. The purpose of this review is to summarize recent advances of PV self-powered gas sensing and also remark on the directions for future research in this topic.

physics.app-ph↗

arXiv2016

Universal threshold for femtosecond laser ablation with oblique illumination

We quantify the dependence of the single-shot ablation threshold on the angle of incidence and polarization of a femtosecond laser beam, for three dissimilar solid-state materials: a metal, a dielectric and a semiconductor. Using the constant, linear value of the index of refraction, we calculate the laser fluence transmitted through the air-material interface at the point of ablation threshold. We show that, in spite of the highly nonlinear ionization dynamics involved in the ablation process, the so defined transmitted threshold fluence is universally independent of the angle of incidence and polarization of the laser beam for all three material types. We suggest that angular dependence of ablation threshold can be utilized for profiling fluence distributions in ultra-intense femtosecond laser beams.

physics.optics↗