Mon·Sep 20, 2021Monday·September 20, 2021

1. 01*

   Interpreting machine learning functions as physical observables

   Gert Aarts🇬🇧 · Dimitrios Bachtis🇬🇧 · Biagio Lucini🇬🇧

   We propose to interpret machine learning functions as physical observables, opening up the possibility to apply "standard" statistical-mechanical methods to outputs from neural networks. This includes histogram reweighting and finite-size scaling, to analyse phase transitions quantitatively. In addition we incorporate predictive functions as conjugate variables coupled to an external field within the Hamiltonian of a system, allowing to induce order-disorder phase transitions in a novel manner. A noteworthy feature of this approach is that no knowledge of the symmetries in the Hamiltonian is required.

   hep-latPoS(2022)·4 citations
2. 02*

   Tetraquark systems $\bar{b}b\bar{d}u$ in the static limit and lattice QCD

   Mitja Sadl🇸🇮 · Sasa Prelovsek🇸🇮

   Two hadrons with exotic quark content $Z_b^{+}\simeq \bar{b}b\bar{d}u$ were discovered by Belle. We present a lattice study of the $\bar{b}b\bar{d}u$ systems with various quantum numbers using static bottom quarks. Only one set of quantum numbers that couples to $Z_b$ and ${\rm Y}\pi$ was explored on the lattice before; these studies found an attractive potential between $B$ and ${\bar{B}}^{\ast }$ resulting in a bound state below the threshold. The present study considers the other three sets of quantum numbers. Eigenenergies of the $\bar{b}b\bar{d}u$ system are extracted as a function of separation between $b$ and $\bar{b}$. The resulting eigenenergies do not show any sizable deviation from noninteracting energies of the systems $\bar{b}b+\bar{d}u$ and $\bar{b}u+\bar{d}b$, so no significant attraction or repulsion is found. A slight exception is a small attraction between $B$ and ${\bar{B}}^{\ast }$ at small distance for the quantum number that couples to $Z_b$ and ${\eta }_b\rho$.

   hep-lathep-phPRD(2021)·32 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.