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Xiaosong Liu

Publications and source records attributed to Xiaosong Liu.

10 recordsLinked to original sources
arXiv2026

Detector-level simulation closure of radio air-shower reconstruction with native RF-chain inversion and out-of-fold endpoint interpolation

Autonomous radio arrays reconstruct air showers from trigger-selected digitized voltage traces rather than ideal electric-field footprints. We present a detector-level simulation-closure test linking RF-chain-triggered ZHAireS event packages to reconstructed direction, energy and quality diagnostics. Voltage amplitudes and station timing determine geometry through a robust joint timing--amplitude axis fit. Native-grid RF-chain inversion recovers 50--200 MHz electric-field peaks along the shower-plane v cross B axis. Symmetric four-arm iron and proton templates generated with 2 ns time bins provide endpoint estimates that are combined by a nested five-fold out-of-fold interpolation estimator. One estimator is used over the full angular range without a fitted multiplicative energy scale. Of 972 triggered event packages, 725 pass common quality selection in raw-noisy weighted, hard-gated denoised equal-weight and clean equal-weight branches. In the primary reconstructed-zenith range 60--85 degrees, 693 common events have mean energy residuals of -0.05, -0.30 and -0.66 percent with standard deviations of 11.04, 10.90 and 10.75 percent. The hard-gated denoised branch has a median angular separation of 0.052 degrees. Boundary zenith ranges are reported separately; the upper boundary has a mean energy residual of +14.2 percent and a 19.9 percent standard deviation. These results describe cross-fitted closure within a matched simulation framework, not deployed-array resolution or independent energy calibration.

astro-ph.IM↗
arXiv2025

Embedding derivatives and derivative Area operators of Hardy spaces into Lebesgue spaces

We characterize the compactness of embedding derivatives from Hardy space $H^p$ into Lebesgue space $L^q(μ)$. We also completely characterize the boundedness and compactness of derivative area operators from $H^p$ into $L^q(\mathbb{S}_n)$, $0<p, q<\infty$. Some of the tools used in the proof of the one-dimensional case are not available in higher dimensions, such as the strong factorization of Hardy spaces. Therefore, we need the theory of tent spaces which was established by Coifman, Mayer and Stein in 1985.

cs.IR↗
arXiv2020

Low temperature specific heat of 12442-type KCa_2Fe_4As_4F_2 single crystals

Low-temperature specific heat (SH) is measured for the 12442-type KCa$_2$Fe$_4$As$_4$F$_2$ single crystal under different magnetic fields. A clear SH jump with the height of $ΔC/T|_{T_c}$ = 130 mJ/mol K$^2$ is observed at the superconducting transition temperature $T_c$. It is found that the electronic SH coefficient $Δγ(H)$ quickly increases when the field is in the low-field region below 3 T and then considerably slows down the increase with a further increase in the field, which indicates a rather strong anisotropy or multi-gap feature with a small minimum in the superconducting gap(s). The temperature-dependent SH data indicates the presence of the $T^2$ term, which supplies further information and supports the picture with a line-nodal gap structure. Moreover, the onset point of the SH transition remains almost unchanged under the field as high as 9 T, which is similar to that observed in cuprates, and placed this system in the middle between the BCS limit and the Bose-Einstein condensation.

cond-mat.supr-con↗
arXiv2019

Strong Pauli paramagnetic effect in the upper critical field of KCa$_2$Fe$_4$As$_4$F$_2$

Recently, 12442 system of Fe-based superconductors has attracted considerable attention owing to its unique double-FeAs-layer structure. A steep increase in the in-plane upper critical field with cooling has been observed near the superconducting transition temperature, $T_c$, in KCa$_2$Fe$_4$As$_4$F$_2$ single crystals. Herein, we report a high-field investigation on upper critical field of this material over a wide temperature range, and both out-of-plane ($H\|c$, $H_{c2}^{c}$) and in-plane ($H\|ab$, $H_{c2}^{ab}$) directions have been measured. A sublinear temperature-dependent behavior is observed for the out-of-plane $H_{c2}^{c}$, whereas strong convex curvature with cooling is observed for the in-plane $H_{c2}^{ab}$. Such behaviors could not be described by the conventional Werthamer--Helfand--Hohenberg (WHH) model. The data analysis based on the WHH model by considering the spin aspects reveals a large Maki parameter $α=9$, indicating that the in-plane upper critical field is affected by a very strong Pauli paramagnetic effect.

cond-mat.supr-con↗
arXiv2019

Two-Gap Superconductivity in CaFe_{0.88}Co_{0.12}AsF Revealed by Temperature Dependence of the Lower Critical Field H_{c1}^c(T)

Gap symmetry and structure are crucial issues in understanding the superconducting mechanism of unconventional superconductors. Here we report an in-depth investigation on the out-of-plane lower critical field $H_{c1}^{c}$ of fluorine-based 1111 system superconductor CaFe$_{0.88}$Co$_{0.12}$AsF with $T_c$ = 21 K. A pronounced two-gap feature is revealed by the kink in the temperature dependent $H_{c1}^c(T)$ curve. The magnitudes of the two gaps are determined to be $Δ_1$ = 0.86 meV and $Δ_2$ = 4.48 meV, which account for 74% and 26% of the total superfluid density respectively. Our results suggest that the local antiferromagnetic exchange pairing picture is favored compared to the Fermi surface nesting scenario.

cond-mat.supr-con↗
arXiv2019

Weighted Bergman spaces induced by doubling weights in the unit ball of $\mathbb{C}^n$

This paper is devoted to the study of the weighted Bergman space $A_ω^p $ in the unit ball $\mathbb{B}$ of $\mathbb{C}^n$ with doubling weight $ω$ satisfying $$\int_r^1ω(t)dt <C \int_{\frac{1+r}{2}}^1ω(t)dt ,\,\, 0\leq r<1.$$ The $q-$Carleson measures for $A_ω^p$ are characterized in terms of a neat geometric condition involving Carleson block. Some equivalent characterizations for $A_ω^p$ are obtained by using the radial derivative and admissible approach regions. The boundedness and compactness of Volterra integral operator $T_g:A_ω^p\to A_ω^q$ are also investigated in this paper with $0<p\leq q<\infty$, where $$T_gf(z)=\int_0^1 f(tz)\Re g(tz)\frac{dt}{t}, ~~\qquad~~~~f\in H(\mathbb{B}), ~~z\in \mathbb{B}. $$

math.FA↗
arXiv2019

Single-crystal growth and extremely high H_c2 of 12442-type Fe-based superconductor KCa_2Fe_4As_4F_2

Millimeter sized single crystals of KCa_2Fe_4As_4F_2 were grown using a self-flux method. The chemical compositions and crystal structure were characterized carefully. Superconductivity with the critical transition T_c = 33.5 K was confirmed by both the resistivity and magnetic susceptibility measurements. Moreover, the upper critical field H_c2 was studied by the resistivity measurements under different magnetic fields. A rather steep increase for the in-plane H_c2^ab with cooling, dμ_0H_c2^a/dT|T_c = -50.9 T/K, was observed, indicating an extremely high upper critical field. Possible origins for this behavior were discussed. The findings in our work is a great promotion both for understanding the physical properties and applications of 12442-type Fe-based superconductors.

cond-mat.supr-con↗
arXiv2013

Characterizations of Dirichlet-type Spaces

We give three characterizations of the Dirichlet-type spaces $D(μ)$. First we characterize $D(μ)$ in terms of a double integral and in terms of the mean oscillation in the Bergman metric, none of them involve the use of derivatives. Next, we obtain another characterization for $D(μ)$ in terms of higher order derivatives. Also, a decomposition theorem for $D(μ)$ is established.

math.CV↗