高能物理-Lattice学术速递[1.10]
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hep-lat高能物理-Lattice，共计7篇
【1】 Twisted mass gauge ensembles at physical values of the light, strange and charm quark masses
标题：轻夸克质量、奇异夸克质量和魅力夸克质量的物理价值下的扭曲质量规系综
链接：https://arxiv.org/abs/2201.02551
备注：12 pages, 12 figures, The 38th International Symposium on Lattice Field Theory (LATTICE2021), 26th-30th July, 2021, Zoom/Gather@Massachusetts Institute of Technology
摘要：Lattice QCD simulations directly at physical masses of dynamical light,
strange and charm quarks are highly desirable especially to remove systematic
errors due to chiral extrapolations. However such simulations are still
challenging. We discuss the adaption of efficient algorithms, like multi-grid
methods or higher order integrators, within the molecular dynamic steps of the
Hybrid Monte Carlo algorithm, that are enabling simulations of a new set of
gauge ensembles by the Extended Twisted Mass collaboration (ETMC). We present
the status of the on-going ETMC simulation effort that aims to enabling studies
of finite size and discretization effects. We work within the twisted mass
discretization which is free of odd-discretization effects at maximal twist and
present our tuning procedure.
【2】 Chiral condensates and screening masses of neutral pseudoscalar mesons in thermomagnetic QCD medium
标题：热磁QCD介质中中性赝标介子的手征凝聚和屏蔽质量
链接：https://arxiv.org/abs/2201.02349
备注：11 pages, 9 figures
摘要：We point out that chiral condensates at nonzero temperature and magnetic
fields are in strict connection to the space-time integral of corresponding
two-point neutral meson correlation functions in the pseudoscalar channel via
the Ward-Takahashi identity. Screening masses of neutral pseudoscalar mesons,
which are defined as the exponential decay of the corresponding spatial
correlation functions in the long distance, thus are intrinsically connected to
(inverse) magnetic catalysis of chiral condensates. To study this we performed
lattice simulations of $(2+1)$-flavor QCD on $32^3\times N_t$ lattices with
pion mass $M_\pi\simeq 220$ MeV in a fixed scale approach having temperature
$T\in[17, 281]$ MeV and magnetic field strength $eB\in[0, 2.5]$ GeV$^2$. We
find that screening lengths, i.e. inverses of screening masses of $\pi^0$,
$K^0$ and $\eta^0_{s\bar{s}}$, turn out to have the similar complex $eB$ and
$T$ dependences of the corresponding chiral condensates. Although the
transition temperature is found to always decrease as $eB$ grows, we show that
the suppression due to magnetic fields becomes less significant for hadron
screening length and chiral condensates with heavier quarks involved, and
ceases to occur for $\eta^0_{s\bar{s}}$ and strange quark chiral condensate.
The complex $eB$ and $T$ dependences of both screening masses and chiral
condensates, reflecting the crossover nature of the QCD transition, are
attributed to the competition between sea and valence quark effects. These
findings could be useful to guide low-energy models and effective theories of
QCD.
【3】 $K\toππ$ decay matrix elements at the physical point with periodic boundary conditions
标题：$K oππ$周期边界条件下物理点的衰减矩阵元
链接：https://arxiv.org/abs/2201.02320
备注：Proceedings of the 38th International Symposium on Lattice Field Theory (Lattice 2021), July 26-30, 2021, Zoom/Gather@MIT
摘要：We calculate $K\to\pi\pi$ matrix elements using periodic boundary conditions
as an independent calculation from our previous study with G-parity boundary
conditions. We present our preliminary results for $K\to\pi\pi$ three-point
functions and matrix elements on a $24^3, a^{-1} = 1$~GeV, $2+1$-flavor
M\"obius DWF ensemble at physical pion and kaon masses generated by the RBC and
UKQCD collaborations and discuss the prospect for high-precision computation of
$\varepsilon'$ with periodic boundary conditions.
【4】 Tackling critical slowing down using global correction steps with equivariant flows: the case of the Schwinger model
标题：使用具有等变流的全局校正步骤解决临界减速问题：Schwinger模型的情况
链接：https://arxiv.org/abs/2201.02216
备注：9 pages, 8 figures
摘要：We propose a new method for simulating lattice gauge theories in the presence
of fermions. The method combines flow-based generative models for local gauge
field updates and hierarchical updates of the factorized fermion determinant.
The flow-based generative models are restricted to proposing updates to
gauge-fields within subdomains, thus keeping training times moderate while
increasing the global volume. We apply our method performs to the 2-dimensional
(2D) Schwinger model with $N_f=2$ Wilson Dirac fermions and show that no
critical slowing down is observed in the sampling of topological sectors up to
$\beta=8.45$. Furthermore, we show that fluctuations can be suppressed
exponentially with the distance between active subdomains, allowing us to
achieve acceptance rates of up to $99\%$ for the outer-most accept/reject step
on lattices volumes of up to $V=128\times128$.
【5】 Rethinking the ill-posedness of the spectral function reconstruction -- why is it fundamentally hard and how Artificial Neural Networks can help
标题：关于谱函数重构不适定性的再思考--为什么从根本上说是困难的以及人工神经网络是如何提供帮助的
链接：https://arxiv.org/abs/2201.02564
备注：29 pages, 6 figures
摘要：Reconstructing hadron spectral functions through Euclidean correlation
functions are of the important missions in lattice QCD calculations. However,
in a K\"allen--Lehmann(KL) spectral representation, the reconstruction is
observed to be ill-posed in practice. It is usually ascribed to the fewer
observation points compared to the number of points in the spectral function.
In this paper, by solving the eigenvalue problem of continuous KL convolution,
we show analytically that the ill-posedness of the inversion is fundamental and
it exists even for continuous correlation functions. We discussed how to
introduce regulators to alleviate the predicament, in which include the
Artificial Neural Networks(ANNs) representations recently proposed by the
Authors in [arXiv:2111.14760]. The uniqueness of solutions using ANNs
representations is manifested analytically and validated numerically.
Reconstructed spectral functions using different regularization schemes are
also demonstrated, together with their eigen-mode decomposition. We observe
that components with large eigenvalues can be reliably reconstructed by all
methods, whereas those with low eigenvalues need to be constrained by
regulators.
【6】 U(1) Fields from Qubits: an Approach via D-theory Algebra
标题：量子比特的U(1)场：一种基于D-理论代数的方法
链接：https://arxiv.org/abs/2201.02412
备注：42 pages, 8 figures
摘要：A new quantum link microstructure was proposed for the lattice QCD
Hamiltonian, replacing the Wilson gauge links by a bilinear of fermionic
qubits, later generalized to D-theory. This formalism provides a general
framework for building lattice field theory algorithms for quantum computing.
We focus mostly on the simplest case of a quantum rotor for a single compact
U(1) field. We also make some progress for non-abelian setups, making it clear
that the ideas developed in the U(1) case extend to other groups. These in turn
are building blocks for 1+0 matrix models, 1+1 sigma models and non-Abelian
gauge theories in 2+1 and 3+1 dimensions. By introducing multiple flavors for
the U(1) field, where the flavor symmetry is gauged, we can efficiently
approach the infinite-dimensional Hilbert space of the quantum O(2) rotor with
increasing flavors. The emphasis of the method is on preserving the symplectic
algebra exchanging fermionic qubits by sigma matrices (or hard bosons) and
developing a formal strategy capable of generalization to SU(3) field for
lattice QCD and other non-Abelian 1+1 sigma models or 1+3 gauge theories. For
U(1) we discuss briefly the qubit algorithms for the study of the discrete 1+1
Sine-Gordon equation.
【7】 Precision Bootstrap for the $\mathcal{N}=1$ Super-Ising Model
链接：https://arxiv.org/abs/2201.02206
备注：32 pages, 6 figures
摘要：In this note we report an improved determination of the scaling dimensions
and OPE coefficients of the minimal supersymmetric extension of the 3d Ising
model using the conformal bootstrap. We also show how this data can be used as
input to the Lorentzian inversion formula, finding good agreement between
analytic calculations and numerical extremal spectra once mixing effects are
resolved.
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