JournalTOCs

Journal of Physics A : Mathematical and Theoretical
Journal Prestige (SJR): 0.843

Citation Impact (citeScore): 2
Number of Followers: 22

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1751-8113 - ISSN (Online) 1751-8121
Published by IOP

[40 journals]

Preface: characterisation of physical processes from anomalous diffusion
data
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  Authors: Carlo Manzo; Gorka Muñoz-Gil, Giovanni Volpe, Miguel Angel Garcia-March, Maciej Lewenstein Ralf Metzler
  First page: 010401
  Citation: Journal of Physics A: Mathematical and Theoretical
  PubDate: 2023-01-19T00:00:00Z
  DOI: 10.1088/1751-8121/acb1e1
  Issue No: Vol. 56, No. 1 (2023)
Magnetic excitations in the one-dimensional Heisenberg–Ising model with
external fields and their experimental realizations
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  Authors: Jiahao Yang; Xiao Wang Jianda Wu
  First page: 013001
  Abstract: The one dimensional (1D) spin-1/2 Heisenberg–Ising model, a prototype quantum many-body system, has been intensively studied for many years. In this review, after a short introduction on some basic concepts of group theory for the octahedral group, a detailed pedagogical framework is laid down to derive the low-energy effective Hamiltonian for the Co-based materials. The 1D spin-1/2 Heisenberg–Ising model is obtained when applying the analysis to quasi-1D antiferromagnetic materials and . After the preparation, we review the theoretical progresses of a variety of novel magnetic excitations and emergent physics in the 1D spin-1/2 Heisenberg–Ising model, and further summarize their recent experimental realizations.
  Citation: Journal of Physics A: Mathematical and Theoretical
  PubDate: 2023-01-13T00:00:00Z
  DOI: 10.1088/1751-8121/acad48
  Issue No: Vol. 56, No. 1 (2023)
Characterization of anomalous diffusion through convolutional transformers
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  Authors: Nicolas Firbas; Òscar Garibo-i-Orts, Miguel Ángel Garcia-March J Alberto Conejero
  First page: 014001
  Abstract: The results of the Anomalous Diffusion Challenge (AnDi Challenge) (Muñoz-Gil G et al 2021 Nat. Commun. 12 6253) have shown that machine learning methods can outperform classical statistical methodology at the characterization of anomalous diffusion in both the inference of the anomalous diffusion exponent α associated with each trajectory (Task 1), and the determination of the underlying diffusive regime which produced such trajectories (Task 2). Furthermore, of the five teams that finished in the top three across both tasks of the AnDi Challenge, three of those teams used recurrent neural networks (RNNs). While RNNs, like the long short-term memory network, are effective at learning long-term dependencies in sequential data, their key disadvantage is that they must be trained sequentially. In order to facilitate training with larger data sets, by training in parallel, we propose a new transformer based neural network architecture for the characterization of anomalous diffusion. Our new architecture, the Convolutional Transformer (ConvTransformer) uses a bi-layered convolutional neural network to extract features from our diffusive trajectories that can be thought of as being words in a sentence. These features are then fed to two transformer encoding blocks that perform either regression (Task 1 1D) or classification (Task 2 1D). To our knowledge, this is the first time transformers have been used for characterizing anomalous diffusion. Moreover, this may be the first time that a transformer encoding block has been used with a convolutional neural network and without the need for a transformer decoding block or positional encoding. Apart from being able to train in parallel, we show that the ConvTransformer is able to outperform the previous state of the art at determining the underlying diffusive regime (Task 2 1D) in short trajectories (length 10–50 steps), which are the most important for experimental researchers.
  Citation: Journal of Physics A: Mathematical and Theoretical
  PubDate: 2023-01-13T00:00:00Z
  DOI: 10.1088/1751-8121/acafb3
  Issue No: Vol. 56, No. 1 (2023)
Weyl conjecture and thermal radiation of finite systems
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  Authors: M C Baldiotti; M A Jaraba, L F Santos C Molina
  First page: 015002
  Abstract: In this work, corrections for the Weyl law and Weyl conjecture in d dimensions are obtained and effects related to the polarization and area term are analyzed. The derived formalism is applied on the quasithermodynamics of the electromagnetic field in a finite d-dimensional box within a semi-classical treatment. In this context, corrections to the Stefan–Boltzmann law are obtained. Special attention is given to the two-dimensional scenario, since it can be used in the characterization of experimental setups. Another application concerns acoustic perturbations in a quasithermodynamic generalization of Debye model for a finite solid in d dimensions. Extensions and corrections for known results and usual formulas, such as the Debye frequency and Dulong–Petit law, are calculated.
  Citation: Journal of Physics A: Mathematical and Theoretical
  PubDate: 2023-01-19T00:00:00Z
  DOI: 10.1088/1751-8121/acb09b
  Issue No: Vol. 56, No. 1 (2023)
Interaction of a tubular charged-particle beam with eigenwaves of a plasma
solid-state cylinder located in strong longitudinal magnetic field
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  Authors: Yu O Averkov; Yu V Prokopenko V M Yakovenko
  First page: 015202
  Abstract: An electrodynamic system in which a magnetized tubular electron beam blows around a cylindrical solid-state plasma waveguide located coaxially in a longitudinal magnetic field is theoretically studied. It has been established, when quasi-stationary conditions are satisfied, hybrid bulk-surface or surface electromagnetic waves of helicon origin are excited in the waveguide. The waveguide eigenwaves are excited by the space-charge field of beam with matching of the longitudinal spectral components of electric field. It is noted that helicons and waves of their nature are formed in a conducting plasma medium in the assistance of an external magnetic field. It is shown the instability of coupled waves of the electrodynamic system is due to the Vavilov–Cherenkov effect.
  Citation: Journal of Physics A: Mathematical and Theoretical
  PubDate: 2023-01-20T00:00:00Z
  DOI: 10.1088/1751-8121/acb024
  Issue No: Vol. 56, No. 1 (2023)
Nonequilibrium spectral moment sum rules of the Holstein–Hubbard
model
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  Authors: Khadijeh Najafi; J Alexander Jacoby, R D Nesselrodt J K Freericks
  First page: 015301
  Abstract: We derive a general procedure for evaluating the nth derivative of a time-dependent operator in the Heisenberg representation and employ this approach to calculate the zeroth to third spectral moment sum rules of the retarded electronic Green’s function and self-energy for a system described by the Holstein–Hubbard model allowing for arbitrary spatial and time variation of all parameters (including spatially homogeneous electric fields and parameter quenches). For a translationally invariant (but time-dependent) Hamiltonian, we also provide sum rules in momentum space. The sum rules can be applied to various different phenomena like time-resolved angle-resolved photoemission spectroscopy and benchmarking the accuracy of numerical many-body calculations. This work also corrects some errors found in earlier work on simpler models.
  Citation: Journal of Physics A: Mathematical and Theoretical
  PubDate: 2023-01-20T00:00:00Z
  DOI: 10.1088/1751-8121/acafb1
  Issue No: Vol. 56, No. 1 (2023)
Average capacity of quantum entanglement
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  Authors: Lu Wei
  First page: 015302
  Abstract: As an alternative to entanglement entropies, the capacity of entanglement becomes a promising candidate to probe and estimate the degree of entanglement of quantum bipartite systems. In this work, we study the statistical behavior of entanglement capacity over major models of random states. In particular, the exact and asymptotic formulas of average capacity have been derived under the Hilbert–Schmidt and Bures-Hall ensembles. The obtained formulas generalize some partial results of average capacity computed recently in the literature. As a key ingredient in deriving the results, we make use of techniques in random matrix theory and our previous results pertaining to the underlying orthogonal polynomials and special functions. Simulations have been performed to numerically verify the derived formulas.
  Citation: Journal of Physics A: Mathematical and Theoretical
  PubDate: 2023-01-20T00:00:00Z
  DOI: 10.1088/1751-8121/acb114
  Issue No: Vol. 56, No. 1 (2023)
Unextendible product bases from tile structures in bipartite systems
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  Authors: Siwen You; Chen Wang, Fei Shi, Sihuang Hu Yiwei Zhang
  First page: 015303
  Abstract: Unextendible product basis (UPB) is one of the most fundamental concepts in the field of quantum information theory, and its constructions attract much attention. Recently, Shi et al (2020 Phy. Rev. A 101 062329) constructed UPBs via a tile structure approach. They showed that a tile structure in an m × n grid with certain properties leads to explicit constructions of UPBs in . The size of the UPB is if the tile structure contains exactly s tiles. In this paper, we deeply analyze the extent of the tile structure approach, by showing that a desired tile structure in an m × m grid contains at most tiles, and thus the smallest size of a UPB in constructed by this approach is . Such tile structures and UPBs are referred to as extremal tile structures and extremal UPBs. We provide algorithms both for constructing possible candidates of extremal tile structures and checking their validity. For applications, we connect the extremal UPBs to local irreducibility and bound entangled states with large ranks.
  Citation: Journal of Physics A: Mathematical and Theoretical
  PubDate: 2023-01-20T00:00:00Z
  DOI: 10.1088/1751-8121/acb099
  Issue No: Vol. 56, No. 1 (2023)
Topological Dirac sigma models and the classical master equation
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  Authors: Athanasios Chatzistavrakidis; Larisa Jonke, Thomas Strobl Grgur Šimunić
  First page: 015402
  Abstract: We present the construction of the classical Batalin–Vilkovisky (BV) action for topological Dirac sigma models. The latter are two-dimensional topological field theories that simultaneously generalise the completely gauged Wess–Zumino–Novikov–Witten model and the Poisson sigma model. Their underlying structure is that of Dirac manifolds associated to maximal isotropic and integrable subbundles of an exact Courant algebroid twisted by a 3-form. In contrast to the Poisson sigma model, the AKSZ construction is not applicable for the general Dirac sigma model. We therefore follow a direct approach for determining a suitable BV extension of the classical action functional with ghosts and antifields satisfying the classical master equation. Special attention is paid to target space covariance, which requires the introduction of two connections with torsion on the Dirac structure.
  Citation: Journal of Physics A: Mathematical and Theoretical
  PubDate: 2023-01-19T00:00:00Z
  DOI: 10.1088/1751-8121/acb09a
  Issue No: Vol. 56, No. 1 (2023)
Analytical results for the entanglement dynamics of disjoint blocks in the
XY spin chain
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  Authors: Gilles Parez; Riccarda Bonsignori
  First page: 505005
  Abstract: The study of the dynamics of entanglement measures after a quench has become a very active area of research in the last two decades, motivated by the development of experimental techniques. However, exact results in this context are available in only very few cases. In this work, we present the proof of the quasiparticle picture for the dynamics of entanglement entropies for two disjoint blocks in the XY chain after a quantum quench. As a byproduct, we also prove the quasiparticle conjecture for the mutual information in that model. Our calculations generalize those presented in Fagotti and Calabrese (2008 Phys. Rev. A 78 010306) to the case where the correlation matrix is a block-Toeplitz matrix, and rely on the multidimensional stationary phase approximation in the scaling limit. We also test the quasiparticle predictions against exact numerical calculations, and find excellent agreement. In the case of three blocks, we show that the tripartite information vanishes when at least two blocks are adjacent.
  Citation: Journal of Physics A: Mathematical and Theoretical
  PubDate: 2023-01-19T00:00:00Z
  DOI: 10.1088/1751-8121/acb097
  Issue No: Vol. 55, No. 50 (2023)