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SIMPLE ANALYTIC FORMULA RELATING THE MASS AND SPIN OF ACCRETING COMPACT OBJECTS TO THEIR RAPID X-RAY VARIABILITY

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arXiv 2022年

作者： Török, Gabriel Kotrlová, Andrea Matuszková, Monika Klimovičová, Kateřina Lančová, Debora Urbancová, Gabriela Šrámková, Eva Goluchová, Kateřina Research Centre for Computational Physics and Data Processing Institute of Physics Silesian University in Opava Bezručovo nám. 13 OpavaCZ-746 01 Czech Republic

Following the previous research on epicyclic oscillations of accretion disks around black holes (BHs) and neutron stars (NSs), a new model of high-frequency quasi-periodic oscillations (QPOs) has been proposed (CT model), which deals with oscillations of fluid in marginally overflowing accretion tori (i.e., tori terminated by cusps). According to preliminary investigations, the model provides better fits of the NS QPO data compared to the relativistic precession (RP) model. It also implies a significantly higher upper limit on the Galactic microquasars BH spin. A short analytic formula has been noticed to well reproduce the model’s predictions on the QPO frequencies in Schwarzschild spacetimes. Here we derive an extended version of this formula that applies to rotating compact objects. We start with the consideration of Kerr spacetimes and derive a formula that is not restricted to a particular specific angular momentum distribution of the inner accretion flow, such as Keplerian or constant. Finally, we consider Hartle-Thorne spacetimes and include corrections implied by the NS oblateness. For a particular choice of a single parameter, our relation provides frequencies predicted by the CT model. For another value, it provides frequencies predicted by the RP model. We conclude that the formula is well applicable for rotating oblateness NSs and both models. We briefly illustrate application of our simple formula on several NS sources and confirm the expectation that the CT model is compatible with realistic values of the NS mass and provides better fits of data than the RP model. © 2022, CC BY.

关键词： Stars

A Survey of Classical and Quantum Sequence Models 16

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A Survey of Classical and Quantum Sequence Models

16th International Conference on COMmunication Systems and NETworkS, COMSNETS 2024

作者： Chen, I.-Chi Singh, Harshdeep Anukruti, V.L. Quanz, Brian Yogaraj, Kavitha Iowa State University Department of Physics and Astronomy AmesIA United States Iit Kharagpur Centre for Computational and Data Sciences India Iiit Hyderabad Cqst India Ibm Quantum Ibm Research United States Ibm Quantum Ibm Research India

ISBN: (纸本)9798350383119

Our primary objective is to conduct a brief survey of various classical and quantum neural net sequence models, which includes self-attention and recurrent neural networks, with a focus on recent quantum approaches proposed to work with near-term quantum devices, while exploring some basic enhancements for these quantum models. We re-implement a key representative set of these existing methods, adapting an image classification approach using quantum self-attention to create a quantum hybrid transformer that works for text and image classification, and applying quantum self-attention and quantum recurrent neural networks to natural language processing tasks. We also explore different encoding techniques and introduce positional encoding into quantum self-attention neural networks leading to improved accuracy and faster convergence in text and image classification experiments. This paper also performs a comparative analysis of classical self-attention models and their quantum counterparts, helping shed light on the differences in these models and their performance. © 2024 IEEE.

关键词： quantum-computing quantum-machine-learning self-attention transformers

New approaches to the general relativistic Poynting-Robertson effect

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arXiv 2020年

作者： de Falco, Vittorio Research Centre for Computational Physics and Data Processing Faculty of Philosophy & Science Silesian University in Opava Bezručovo nám. 13 OpavaCZ-74601 Czech Republic

Objectives: A systematic study on the general relativistic Poynting-Robertson effect has been developed so far by introducing different complementary approaches, which can be mainly divided in two kinds: (1) improving the theoretical assessments and model in its simple aspects, and (2) extracting mathematical and physical information from such system with the aim to extend methods or results to other similar physical systems of analogue structure. Methods/Analysis: We use these theoretical approaches: relativity of observer splitting formalism;Lagrangian formalism and Rayleigh potential with a new integration method;Lyapunov theory os stability. Findings: We determined the three-dimensional formulation of the general relativistic Poynting-Robertson effect model. We determine the analytical form of the Rayleigh potential and discuss its implications. We prove that the critical hypersurfaces (regions where there is a balance between gravitational and radiation forces) are stable configurations. Novelty /Improvement: Our new contributions are: to have introduced the three-dimensional description;to have determined the general relativistic Rayleigh potential for the first time in the General Relativity literature;to have provided an alternative, general and more elegant proof of the stability of the critical hypersurfaces. Copyright © 2020, The Authors. All rights reserved.

关键词： Relativity

Manifestation of kaonium in the e+e− → K+K− process

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arXiv 2020年

作者： Lichard, Peter Institute of Physics Research Centre for Computational Physics and Data Processing Silesian University in Opava Opava746 01 Czech Republic Institute of Experimental and Applied Physics Czech Technical University in Prague Prague128 00 Czech Republic

We analyze the precise data obtained by the CMD-3 experiment on the e+e− annihilation into two charged kaons in the vicinity of the φ peak. A perfect fit is obtained only if a pole on the real axis below the reaction threshold is assumed. This can be interpreted as proof of the existence of the 2p-state of kaonium, a compound of K+ and K−. To determine the binding energy, more data points with the same, or better, precision would be needed. The possibility of discovering 2p kaonium in the e+e− → π+π− process is discussed. The indication of the 2p-state of K0-onium on the basis of the (formula presented) data is inconclusive. Copyright © 2020, The Authors. All rights reserved.

关键词： Binding energy

New narrow resonance in the e+e− → φ η data by Belle collaboration

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arXiv 2023年

Fitting the recent e+e− → φ η data by the Belle collaboration with a theoretical formula reveals, besides the dominant φ(1680) resonance, two narrow resonances: expected φ(2170) resonance and an unexpected resonance with the mass of about 1851 MeV. Close proximity to the X(1835) resonance suggests that the new resonance may be interpreted as the pp¯ baryonium in an excited state. Followup analysis found the same resonance also in e+e− → ω η data by CMD-3 experiment. © 2023, CC BY.

关键词： Excited states

Possible manifestation of the 2p pionium in particle physics processes

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arXiv 2020年

We suggest a few particle physics processes in which excited 2p pionium A′2π may be observed. They include the e+e− → π+π− annihilation, the V 0 → π0+− and K± → π±+− ( = e, µ) decays, and the photoproduction of two neutral pions from nucleons. We analyze available experimental data and find that they, in some cases, indicate the presence of 2p pionium, but do not provide definite proof. Copyright © 2020, The Authors. All rights reserved.

关键词： Hadrons

Pionium as a source of false events in the K → π ν ν¯ decays

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arXiv 2020年

作者： Lichard, Peter Institute of Physics and Research Centre for Computational Physics and Data Processing Silesian University in Opava Opava746 01 Czech Republic Institute of Experimental and Applied Physics Czech Technical University in Prague Prague128 00 Czech Republic

We suggest that the unexpected rare KL decay events that appeared in the KOTO experiment can be explained by accounting for pionia (A2π) that were produced in the KL → π0 A2π decays and escaped (a very small portion of them) the decay volume before decaying into two π0s. Agreement with the observation is reached when one assumes that the participating pionia are those in a 2p state. However, this explanation of the KOTO anomaly has to be abandoned because of the disagreement with the NA62 upper limit. The false events rate caused by the 1s pionia is also calculated and shown to constitute only a small ( Copyright © 2020, The Authors. All rights reserved.

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Analytical Rayleigh potential for the general relativistic Poynting-Robertson effect

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arXiv 2019年

作者： de Falco, Vittorio Battista, Emmanuele Research Centre for Computational Physics and Data Processing Faculty of Philosophy & Science Silesian University in Opava Bezručovo nám. 13 OpavaCZ-746 01 Czech Republic

–We determine the analytic expression of the Rayleigh potential associated to the general relativistic Poynting-Robertson effect. This constitutes the first example of a physical dissipative system treated analytically in General Relativity. The employed approach and further implications are discussed. Copyright © 2019, The Authors. All rights reserved.

关键词： Relativity

New trends in the general relativistic Poynting-Robertson effect modeling

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arXiv 2023年

作者： De Falco, Vittorio Research Centre for Computational Physics and Data Processing Faculty of Philosophy & Science Silesian University in Opava Bezručovo nám. 13 OpavaCZ-746 01 Czech Republic

The general relativistic Poynting-Robertson (PR) effect is a very important dissipative phenomenon occurring in high-energy astrophysics. Recently, it has been proposed a new model, which upgrades the two-dimensional (2D) description in the three-dimensional (3D) case in Kerr spacetime. The radiation field is considered as constituted by photons emitted from a rigidly rotating spherical source around the compact object. Such dynamical system admits the existence of a critical hypersurface, region where the gravitational and radiation forces balance and the matter reaches it at the end of its motion. Selected test particle orbits are displayed. We show how to prove the stability of these critical hypersurfaces within the Lyapunov theory. Then, we present how to study such effect under the Lagrangian formalism, explaining how to analytically derive the Rayleigh potential for the radiation force. In conclusion, further developments and future projects are discussed. © 2023, CC BY.

关键词： Dynamical systems