Journal of Physics Communications最新文献_第7页

Sublattice imbalance of states in graphene nanoflakes 石墨烯纳米片中亚晶格状态的不平衡

Journal of Physics Communications Pub Date : 2023-09-01 DOI: 10.1088/2399-6528/ad0022

H Yorikawa

引用次数: 0

Neoclassical models of charged particles 带电粒子的新古典模型

IF 1.2

Journal of Physics Communications Pub Date : 2023-08-11 DOI: 10.1088/2399-6528/acefa6

F. De Zela

{"title":"Neoclassical models of charged particles","authors":"F. De Zela","doi":"10.1088/2399-6528/acefa6","DOIUrl":"https://doi.org/10.1088/2399-6528/acefa6","url":null,"abstract":"Classical electrodynamics (CED) has achieved great success in its domain of application, but despite this success, it has remained a theory that lacks complete self-consistency. It is worthwhile trying to make CED a self-consistent theory, because many important phenomena lie within its scope, and because modern field theories have been modelled on it. Alternative approaches to CED might help finding a definite formulation, and they might also lead to the prediction of new phenomena. Here we report two main results. The first one derives from standard CED. It is shown that the motion of a charged particle is ruled not only by the Lorentz equation, but also by equations that are formally identical to Maxwell equations. The latter hold for a velocity field and follow as a strict logical consequence of Hamilton’s action principle for a single particle. We construct a tensor with the velocity field in the same way as the electromagnetic tensor is constructed with the four potential. The two tensors are shown to be proportional to one another. As a consequence, and without leaving the realm of standard CED, one can envision new phenomena for a charged particle, which parallel those involving electromagnetic fields. The second result refers to a field-free approach to CED. This approach confirms the simultaneous validity of Maxwell-like and Lorentz equations as rulers of charged particle motion.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42220003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

On the comparison of diversity of parts of a distribution 关于分布各部分多样性的比较

IF 1.2

Journal of Physics Communications Pub Date : 2023-07-20 DOI: 10.1088/2399-6528/ace952

R. Rajaram, N. Ritchey, B. Castellani

{"title":"On the comparison of diversity of parts of a distribution","authors":"R. Rajaram, N. Ritchey, B. Castellani","doi":"10.1088/2399-6528/ace952","DOIUrl":"https://doi.org/10.1088/2399-6528/ace952","url":null,"abstract":"The literature on diversity measures, regardless of the metric used (e.g., Gini-Simpson index, Shannon entropy) has a notable gap: not much has been done to connect these measures back to the shape of the original distribution, or to use them to compare the diversity of parts of a given distribution and their relationship to the diversity of the whole distribution. As such, the precise quantification of the relationship between the probability of each type p i and the diversity D in non-uniform distributions, both among parts of a distribution as well as the whole, remains unresolved. This is particularly true for Hill numbers, despite their usefulness as ‘effective numbers’. This gap is problematic as most real-world systems (e.g., income distributions, economic complexity indices, rankings, ecological systems) have unequal distributions, varying frequencies, and comprise multiple diversity types with unknown frequencies that can change. To address this issue, we connect case-based entropy, an approach to diversity we developed, to the shape of a probability distribution; allowing us to show that the original probability distribution g 1, the case-based entropy curve g 2 and the c {1,k} versus the c{1,k}*lnA{1,k} curve g 3, which we call the slope of diversity, are one-to-one (or injective), i.e., a different probability distribution g 1 gives a different curve for g 2 and g 3. Hence, a different permutation of the original probability distribution g 1(that leads to a different shape) will uniquely determine the graphs g 2 and g 3. By proving the injective nature of our approach, we will have established a unique way to measure the degree of uniformity of parts as measured by D P /c P for a given part P of the original probability distribution, and also have shown a unique way to compute the D P /c P for various shapes of the original distribution and (in terms of comparison) for different curves.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44657990","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Dynamic & norm-based weights to normalize imbalance in back-propagated gradients of physics-informed neural networks 基于动态和范数的权重来归一化物理信息神经网络反向传播梯度中的不平衡

IF 1.2

Journal of Physics Communications Pub Date : 2023-07-04 DOI: 10.1088/2399-6528/ace416

S. Deguchi, M. Asai

{"title":"Dynamic & norm-based weights to normalize imbalance in back-propagated gradients of physics-informed neural networks","authors":"S. Deguchi, M. Asai","doi":"10.1088/2399-6528/ace416","DOIUrl":"https://doi.org/10.1088/2399-6528/ace416","url":null,"abstract":"Physics-Informed Neural Networks (PINNs) have been a promising machine learning model for evaluating various physical problems. Despite their success in solving many types of partial differential equations (PDEs), some problems have been found to be difficult to learn, implying that the baseline PINNs is biased towards learning the governing PDEs while relatively neglecting given initial or boundary conditions. In this work, we propose Dynamically Normalized Physics-Informed Neural Networks (DN-PINNs), a method to train PINNs while evenly distributing multiple back-propagated gradient components. DN-PINNs determine the relative weights assigned to initial or boundary condition losses based on gradient norms, and the weights are updated dynamically during training. Through several numerical experiments, we demonstrate that DN-PINNs effectively avoids the imbalance in multiple gradients and improves the inference accuracy while keeping the additional computational cost within a reasonable range. Furthermore, we compare DN-PINNs with other PINNs variants and empirically show that DN-PINNs is competitive with or outperforms them. In addition, since DN-PINN uses exponential decay to update the relative weight, the weights obtained are biased toward the initial values. We study this initialization bias and show that a simple bias correction technique can alleviate this problem.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44954100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Current-density functional theory for bosonic superfluids 玻色子超流体的电流密度泛函理论

IF 1.2

Journal of Physics Communications Pub Date : 2023-07-01 DOI: 10.1088/2399-6528/ace236

Tomoya Aizawa, M. Higuchi, K. Higuchi

引用次数: 0

A generalized scattering theory in quantum mechanics 量子力学中的广义散射理论

IF 1.2

Journal of Physics Communications Pub Date : 2023-07-01 DOI: 10.1088/2399-6528/acde44

Huai-Yu Wang

{"title":"A generalized scattering theory in quantum mechanics","authors":"Huai-Yu Wang","doi":"10.1088/2399-6528/acde44","DOIUrl":"https://doi.org/10.1088/2399-6528/acde44","url":null,"abstract":"In quantum mechanics textbooks, a single-particle scattering theory is introduced. In the present work, a generalized scattering theory is presented, which can be in principle applied to the scattering problems of arbitrary number of particle. In laboratory frame, a generalized Lippmann-Schwinger scattering equation is derived. We emphasized that the derivation is rigorous, even for treating infinitesimals. No manual operation such as analytical continuation is allowed. In the case that before scattering N particles are plane waves and after the scattering they are new plane waves, the transition amplitude and transition probability are given and the generalized S matrix is presented. It is proved that the transition probability from a set of plane waves to a new set of plane waves of the N particles equal to that of the reciprocal process. The generalized theory is applied to the cases of one- and two-particle scattering as two examples. When applied to single-particle scattering problems, our generalized formalism degrades to that usually seen in the literature. When our generalized theory is applied to two-particle scattering problems, the formula of the transition probability of two-particle collision is given. It is shown that the transition probability of the scattering of two free particles is identical to that of the reciprocal process. This transition probability and the identity are needed in deriving Boltzmann transport equation in statistical mechanics. The case of identical particles is also discussed.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48284314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Retraction notice – ‘Entropy optimization in MHD nanofluid flow over a curved exponentially stretching surface with binary chemical reaction and Arrhenius activation energy’ Saeed Islam et al 2020 J. Phys. Commun. 4 075021 撤回通知-“具有二元化学反应和阿伦尼乌斯活化能的MHD纳米流体在弯曲指数拉伸表面上流动的熵优化”Saeed Islam et al . 2020 J. physics。4 075021

IF 1.2

Journal of Physics Communications Pub Date : 2023-06-01 DOI: 10.1088/2399-6528/accdcc

S. Islam

引用次数: 0

Non-reciprocal transmission of coupled LC resonators through parity-time symmetry breaking 偶偶时间对称性破缺耦合LC谐振腔的非互易传输

IF 1.2

Journal of Physics Communications Pub Date : 2023-06-01 DOI: 10.1088/2399-6528/acdbbb

Yi Zhou, Hao Wang, Lifeng Wang, Lei Dong, Qing-An Huang

引用次数: 0

Bending of electric field lines and light-ray trajectories in a static gravitational field 静电引力场中电场线和光线轨迹的弯曲

IF 1.2

Journal of Physics Communications Pub Date : 2023-06-01 DOI: 10.1088/2399-6528/acdc83

A. Singal

{"title":"Bending of electric field lines and light-ray trajectories in a static gravitational field","authors":"A. Singal","doi":"10.1088/2399-6528/acdc83","DOIUrl":"https://doi.org/10.1088/2399-6528/acdc83","url":null,"abstract":"It is well known that the light-ray trajectories follow a curved path in a gravitational field. This has been confirmed observationally where light rays coming from distant astronomical objects are seen to get bent in Sun’s gravitational field. We explore here the bending of electric field lines due to gravity. We determine, from a theoretical perspective, not only the exact shapes of the bent trajectories of light rays, emitted isotropically by a source supported in a gravitational field, but also demonstrate that the electric field lines of a charge, supported in a gravitational field, follow exactly the trajectories of light rays emitted isotropically from a source at the charge location. From a detailed examination of the electrostatic field of a charge accelerated uniformly in the instantaneous rest frame, exploiting the strong principle of equivalence, we determine the bending of the electric field lines of a charge in a gravitational field. The fraction of electric field lines crossing a surface, stationary above or below the charge in the gravitational field, are shown to be exactly similar to the fraction of light-ray trajectories intersecting that surface, emanating from a source lying at the charge location. On the other hand, for a freely falling charge in the gravitational field there is no such bending of electric field lines. The field lines continue to extend in radial straight lines from the instantaneous ‘present’ position of the charge, as do the trajectories of light rays spreading away from the instantaneous position of a freely falling source in the gravitational field. The electric field configuration of a freely falling charge in the gravitational field is shown to be exactly the same as that of a charge moving uniformly in an inertial frame with velocity equal to the instantaneous ‘present’ velocity of the freely falling charge.","PeriodicalId":47089,"journal":{"name":"Journal of Physics Communications","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46644782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Temperature-induced hysteresis in amplification and attenuation of surface-plasmon-polariton waves 表面等离子体激元波放大和衰减过程中的温度滞后现象

IF 1.2

Journal of Physics Communications Pub Date : 2023-05-31 DOI: 10.1088/2399-6528/acda7a

T. Mackay, T. Son, A. Haché, A. Lakhtakia

引用次数: 0