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Nuclear Theory·nucl-th

Wednesday·June 16, 2021

5 papers—2 primary·3 cross-listed

All5Primary2Cross-lists3
  1. 03

    [Submitted on 15 Jun 2021] (cross-list from hep-ph)

    Electric conductivity with the magnetic field and the chiral anomaly in a holographic QCD model

    Kenji Fukushima🇯🇵 · Akitoshi Okutsu🇯🇵

    We calculate the electric conductivity in deconfined QCD matter using a holographic QCD model, i.e., the Sakai-Sugimoto Model with varying magnetic field and chiral anomaly strength. After confirming that our estimated for is consistent with the lattice-QCD results, we study the case with in which the coefficient in the Chern-Simons term controls the chiral anomaly strength. Our results imply that the transverse conductivity, , is suppressed to be at as compared to the case when the temperature is fixed as . Since the Sakai-Sugimoto Model has massless fermions, the longitudinal conductivity, , with should diverge due to production of the matter chirality. Yet, it is possible to extract a regulated part out from with an extra condition to neutralize the matter chirality. This regulated quantity is interpreted as an Ohmic part of . We show that the longitudinal Ohmic conductivity increases with increasing for small , while it is suppressed with larger for physical due to anomaly induced interactions.

    Comments:
    9 pages, 2 figures; references added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2106.07968 [pdf]
    PRD(2022)·21 citations
  2. 04

    [Submitted on 15 Jun 2021] (cross-list from hep-ph)

    Application of radial basis functions neutral networks in spectral functions

    Meng Zhou🇨🇳 · Fei Gao🇩🇪 · Jingyi Chao🇨🇳 · Yu-Xin Liu🇨🇳 · Huichao Song🇨🇳

    The reconstruction of spectral function from correlation function in Euclidean space is a challenging task. In this paper, we employ the Machine Learning techniques in terms of the radial basis functions networks to reconstruct the spectral function from a finite number of correlation data. To test our method, we first generate one type of correlation data using a mock spectral function by mixing several Breit-Wigner propagators. We found that compared with other traditional methods, TSVD, Tikhonov, and MEM, our approach gives a continuous and unified reconstruction for both positive definite and negative spectral function, which is especially useful for studying the QCD phase transition. Moreover, our approach has considerably better performance in the low frequency region. This has advantages for the extraction of transport coefficients which are related to the zero frequency limit of the spectral function. With the mock data generated through a model spectral function of stress energy tensor, we find our method gives a precise and stable extraction of the transport coefficients.

    Comments:
    10 pages, 7 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2106.08168 [pdf]
    PRD(2021)·21 citations
  3. 05

    [Submitted on 15 Jun 2021] (cross-list from hep-ph)

    Constraining baryon annihilation in the hadronic phase of heavy-ion collisions via event-by-event fluctuations

    Oleh Savchuk🇩🇪 · Volodymyr Vovchenko🇺🇸 · Volker Koch🇺🇸 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪

    We point out that the variance of net-baryon distribution normalized by the Skellam distribution baseline, , is sensitive to the possible modification of (anti)baryon yields due to annihilation in the hadronic phase. The corresponding measurements can thus place stringent limits on the magnitude of the annihilation and its inverse reaction. We perform Monte Carlo simulations of the hadronic phase in Pb-Pb collisions at the LHC via the recently developed subensemble sampler + UrQMD afterburner and show that the effect survives in net-proton fluctuations, which are directly accessible experimentally. The available experimental data of the ALICE Collaboration on net-proton fluctuations disfavors a notable suppression of (anti)baryon yields in annihilations predicted by the present version of UrQMD if only global baryon conservation is incorporated. On the other hand, the annihilations improve the data description when local baryon conservation is imposed. The two effects can be disentangled by measuring , which at the LHC is notably suppressed by annihilations but virtually unaffected by baryon number conservation.

    Comments:
    6 pages, 4 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2106.08239 [pdf]
    PLB(2022)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE