Nuclear Theory·nucl-th

Monday·January 10, 2022

8 papers—4 primary·4 cross-listed

05
[Submitted on 1 Jan 2022] (cross-list from hep-th)
Topological confinement in Skyrme holography
Casey Cartwright🇺🇸 · Benjamin Harms🇺🇸 · Matthias Kaminski🇺🇸 · Ronny Thomale🇩🇪
We study phase transitions in five-dimensional Einstein Gravity with a negative cosmological constant, coupled to a Skyrme matter field. These transitions are topological generalizations of the Hawking-Page transition between thermal Anti de Sitter (AdS) spacetime and an AdS black hole. Phases are characterized by a topological number associated with the Skyrme field configuration. Depending on that topological number and on the Skyrme coupling strength, there occur transitions between those phases at two, one, or no value(s) of the temperature. Through the holographic (AdS/CFT) correspondence, these solutions are dual to topologically non-trivial states in a conformal field theory (CFT) with an SU(2)-symmetry, which support either confined or deconfined (quasi-)particles at strong coupling. We compare to similar known phase transitions, and discuss potential applications to confinement in topological phases of condensed matter and the quark-gluon plasma.
Comments:
21 pages, 8 figures, new title, additional author
Subjects:
High Energy Physics — Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2201.00105 [pdf]
Class.Quant.Grav.(2022)·3 citations
06
[Submitted on 7 Jan 2022] (cross-list from hep-lat)
Chiral condensates and screening masses of neutral pseudoscalar mesons in thermomagnetic QCD medium
H.-T. Ding🇨🇳 · S.-T. Li🇨🇳 · J.-H. Liu🇨🇳 · X.-D. Wang🇨🇳
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 $3 2^{3} \times N_{t}$ lattices with pion mass $M_{π} ≃ 220$ MeV in a fixed scale approach having temperature $T \in [17, 281]$ MeV and magnetic field strength $e B \in [0, 2.5]$ GeV $^{2}$ . We find that screening lengths, i.e. inverses of screening masses of $π^{0}$ , $K^{0}$ and $η_{s s ˉ}^{0}$ , turn out to have the similar complex $e B$ and $T$ dependences of the corresponding chiral condensates. Although the transition temperature is found to always decrease as $e B$ 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 $η_{s s ˉ}^{0}$ and strange quark chiral condensate. The complex $e B$ 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.
Comments:
12 pages, 10 figures, typos corrected, version to appear in PRD
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2201.02349 [pdf]
PRD(2022)·54 citations
07
[Submitted on 7 Jan 2022] (cross-list from hep-ph)
Rethinking the ill-posedness of the spectral function reconstruction -- why is it fundamentally hard and how Artificial Neural Networks can help
Shuzhe Shi🇨🇦 · Lingxiao Wang🇩🇪 · Kai Zhou🇩🇪
Reconstructing hadron spectral functions through Euclidean correlation functions are of the important missions in lattice QCD calculations. However, in a Källen--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~[Phys. Rev. D 106 (2022) L051502]. 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.
Comments:
29 pages, 6 figures; final version. source code and data are available at: https://github.com/ShuzheShi/SpectralFunction}{https://github.com/ShuzheShi/SpectralFunction
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th)
arXiv:
2201.02564 [pdf]
Comput.Phys.Commun.(2023)·37 citations
08
[Submitted on 7 Jan 2022] (cross-list from hep-ph)
On the definition of local spatial densities in hadrons
E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · N. Lange🇩🇪 · U.-G. Meißner🇩🇪 · M. V. Polyakov🇩🇪
We show that the matrix element of a local operator between hadronic states gives rise to an unambiguous definition of the associated spatial density. As an explicit example, we consider the charge density of a spinless particle in the rest and moving frames and clarify its relationship to the electric form factor. Our results suggest that the interpretation of the spatial densities of local operators and their moments such as the mean square charge radius needs to be revised.
Comments:
5 pages, 1 figure
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2201.02565 [pdf]
PRL(2022)·67 citations

Affiliations

first authorsco-authorsvia INSPIRE

Topological confinement in Skyrme holography

Chiral condensates and screening masses of neutral pseudoscalar mesons in thermomagnetic QCD medium

Rethinking the ill-posedness of the spectral function reconstruction -- why is it fundamentally hard and how Artificial Neural Networks can help

On the definition of local spatial densities in hadrons

Affiliations