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Scalar dark energy models and scalar–tensor gravity:theoretical explanations for the accelerated expansion of the present Universe

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Communications in Theoretical physics 2024年第10期 160-189页

作者： Peixiang Ji Lijing Shao department of astronomy School of Physics Peking University Kavli Institute for astronomy and Astrophysics Peking University National Astronomical Observatories Chinese Academy of Sciences

The reason for the present accelerated expansion of the Universe stands as one of the most profound questions in the realm of science, with deep connections to both cosmology and fundamental physics. From a cosmological point of view, physical models aimed at elucidating the observed expansion can be categorized into two major classes: dark energy and modified gravity. We review various major approaches that employ a single scalar field to account for the accelerating phase of our present Universe. Dynamic system analysis was employed in several important models to find cosmological solutions that exhibit an accelerating phase as an *** scalar field models of dark energy, we consistently focused on addressing challenges related to the fine-tuning and coincidence problems in cosmology, as well as exploring potential solutions to them. For scalar–tensor theories and their generalizations, we emphasize the importance of constraints on theoretical parameters to ensure overall consistency with experimental tests. Models or theories that could potentially explain the Hubble tension are also emphasized throughout this review.

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Adaptive State-Dependent Diffusion for Derivative-Free Optimization

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Communications on applied Mathematics and Computation 2024年第2期6卷 1241-1269页

作者： Bjorn Engquist Kui Ren Yunan Yang department of Mathematics and the Oden Institute The University of TexasAustinTX 78712USA department of applied physics and applied Mathematics Columbia UniversityNew YorkNY10027USA department of Mathematics Cornell UniversityIthacaNY 14853USA

This paper develops and analyzes a stochastic derivative-free optimization strategy.A key feature is the state-dependent adaptive *** prove global convergence in probability with algebraic rate and give the quantitative results in numerical examples.A striking fact is that convergence is achieved without explicit information of the gradient and even without comparing different objective function values as in established methods such as the simplex method and simulated *** can otherwise be compared to annealing with state-dependent temperature.

关键词： Derivative-free optimization Global optimization Adaptive diffusion Stationary distribution Fokker-Planck theory

Rapidly growing primordial black holes as seeds of the massive high-redshift JWST Galaxies

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Science China(physics,Mechanics & astronomy) 2024年第10期Mechanics & Astronomy) .卷 143-150页

作者： Guan-Wen Yuan Lei Lei Yuan-Zhu Wang Bo Wang Yi-Ying Wang Chao Chen Zhao-Qiang Shen Yi-Fu Cai Yi-Zhong Fan Key Laboratory of Dark Matter and Space astronomy Purple Mountain ObservatoryChinese Academy of Sciences School of astronomy and Space Science University of Science and Technology of China Institute of High Energy physics Chinese Academy of Sciences Deep Space Exploration Laboratory/department of astronomy School of Physical SciencesUniversity of Science and Technology of China Jockey Club Institute for Advanced Study The Hong Kong University of Science and Technology

A group of massive galaxies at redshifts of z■7 have been recently detected by the James Webb Space Telescope（JWST）, which were unexpected to form at such an early time within the standard Big Bang cosmology. In this work, we propose that this puzzle can be explained by the presence of some primordial black holes（PBHs） with a mass of ～1000M⊙. These PBHs act as seeds for early galaxy formation with masses of ～10～8-1010M⊙at high redshift, hence accounting for the JWST observations. We use a hierarchical Bayesian inference framework to constrain the PBH mass distribution models, and find that the Lognormal model with the Mc～750M⊙is preferred over other hypotheses. These rapidly growing BHs are expected to have strong radiation and may appear as high-redshift compact objects, similar to those recently discovered by JWST. Although we focused on PBHs in this work, the bound on the initial mass of the seed black holes remains robust even if they were formed through astrophysical channels.

关键词： primordial black hole dark matter halo black hole accretion primordial galaxies

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Predicted Critical State Based on Invariance of the Lyapunov Exponent in Dual Spaces

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Chinese physics Letters 2024年第1期41卷 68-76页

作者：刘通夏旭 department of applied physics School of ScienceNanjing University of Posts and TelecommunicationsNanjing 210003China Academy of Mathematics and System Sciences Chinese Academy of SciencesBeijing 100190China

Critical states in disordered systems,fascinating and subtle eigenstates,have attracted a lot of research ***,the nature of critical states is difficult to describe quantitatively,and in general,it cannot predict a system that hosts the critical *** propose an explicit criterion whereby the Lyapunov exponent of the critical state should be 0 simultaneously in dual spaces,namely the Lyapunov exponent remains invariant under the Fourier *** this criterion,we can exactly predict a one-dimensional quasiperiodic model which is not of self-duality,but hosts a large number of critical ***,we perform numerical verification of the theoretical prediction and display the self-similarity of the critical *** to computational complexity,calculations are not performed for higher dimensional ***,since the description of extended and localized states by the Lyapunov exponent is universal and dimensionless,utilizing the Lyapunov exponent of dual spaces to describe critical states should also be ***,we conjecture that some kind of connection exists between the invariance of the Lyapunov exponent and conformal invariance,which can promote the research of critical phenomena.

关键词： state exponent critical

Observational appearance and extra photon rings of an asymmetric thin-shell wormhole with a Bardeen profile

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Chinese physics C 2024年第6期48卷 211-221页

作者：何柯腱罗智郭森李国平 department of physics Chongqing UniversityChongqing 401331China Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and TechnologyGuangxi UniversityNanning 530004China School of physics and astronomy China West Normal UniversityNanchong 637000China

In this work,the optical appearance of an asymmetric thin-shell wormhole with a Bardeen profile is *** initiate the process,we need to construct an asymmetric thin-shell wormhole utilizing the cut-and-paste technique proposed by Visser and subsequently ascertain its pertinent physical quantities such as the radius of the photon sphere and critical impact parameters for different values of magnetic charge ***,the effective potential and motion behavior of photons are also investigated within the framework of asymmetric thin-shell wormholes with a Bardeen *** can be found that the effective potential,ray trajectory,and azimuthal angle of the thin-shell wormhole exhibit a strong correlation with the mass ratio of black *** considering the accretion disk as the sole background light source,we observe additional photon rings and lensing bands in the optical appearance of the asymmetric thin-shell wormhole with a Bardeen profile compared to those exhibited by the Bardeen black *** can find that there is an increase in the size of the specific additional light bands with increasing magnetic charge g,which is different from the black hole *** exceptionally luminous rings can serve as a robust criterion for the identification and characterization of the thin-shell wormhole spacetime.

关键词： shadow asymmetric thin-shell wormhole Bardeen black hole

Generation of millijoule-level sub-5 fs violet laser pulses

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High Power Laser Science and Engineering 2024年第2期12卷 33-40页

作者： Xinhua Xie Yi Hung Yunpei Deng Adrian L.Cavalieri Andrius Baltuška Steven L.Johnson SwissFEL Paul Scherrer InstituteVilligen PSISwitzerland Photonics Institute Technische Universität WienViennaAustria Institute of applied physics University of BernBernSwitzerland Institute for Quantum Electronics Physics DepartmentETH ZurichZurichSwitzerland

We demonstrate the generation,spectral broadening and post-compression of second harmonic pulses using a thin beta barium borate(BBO)crystal on a fused-silica substrate as the nonlinear interaction *** combining second harmonic generation in the BBO crystal with self-phase modulation in the fused-silica substrate,we efficiently generate millijoule-level broadband violet pulses from a single optical *** second harmonic spectrum covers a range from long wave ultraviolet(down to 310 nm)to visible(up to 550 nm)with a bandwidth of 65 ***,we compress the second harmonic beam to a duration of 4.8 fs with a pulse energy of 0.64 mJ(5 fs with a pulse energy of 1.05 mJ)using chirped *** all-solid free-space apparatus is compact,robust and pulse energy scalable,making it highly advantageous for generating intense second harmonic pulses from near-infrared femtosecond lasers in the sub-5 fs regime.

关键词： post-compression second harmonic generation self-phase modulation supercontinuum generation

Testing the first law of black hole mechanics with gravitational waves

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Science China(physics,Mechanics & astronomy) 2024年第10期Mechanics & Astronomy) .卷 80-86页

作者： Chao-Wan-Zhen Wang Jin-Bao Zhu Guo-Qing Huang Fu-Wen Shu department of physics Nanchang University Center for Relativistic Astrophysics and High Energy physics Nanchang University GCAP-CASPER Physics DepartmentBaylor University

The successful observation of gravitational waves has provided humanity with an additional method to explore the universe, particularly black holes. In this study, we utilize data from LIGO and Virgo gravitational wave observations to test the first law of black hole mechanics, employing two different approaches. We consider the secondary compact object as a perturbation to the primary black hole before the merger, and the remnant black hole as a stationary black hole after the merger. In the pre-merger and post-merger analysis, our results demonstrate consistency with the first law, with an error level of approximate 25% at a68% credibility level for GW190403 051519. In the full inspiral-merger-ringdown analysis, our results show consistency with the first law of black hole mechanics, with an error level of about 6% at a 68% credibility level and 10% at a 95% credibility level for GW191219 163120. Additionally, we observe that the higher the mass ratio of the gravitational wave source, the more consistent our results are with the first law of black hole mechanics. Overall, our study sheds light on the nature of compact binary coalescence and their implications for black hole mechanics.

关键词： gravitational waves black hole mechanics data analysis ringdown

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Long Term X-Ray Spectral Variations of the Seyfert-1 Galaxy Mrk 279

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Research in astronomy and Astrophysics 2024年第6期24卷 307-314页

作者： K.Akhila Ranjeev Misra Savithri H.Ezhikode K.Jeena department of physics Providence Women’s CollegeUniversity of CalicutKerala 673009India Inter-University Centre for astronomy and Astrophysics(IUCAA) PB No.4GaneshkhindPune 411007India department of physics and Electronics CHRIST(Deemed to be University)Hosur Main RoadBangalore 560029India

We present the results from a long term X-ray analysis of Mrk 279 during the period 2018–*** use data from multiple missions–AstroSat,NuSTAR and XMM-Newton,for the *** X-ray spectrum can be modeled as a double Comptonization along with the presence of neutral Fe Kαline emission,at all *** determined the source’s X-ray flux and luminosity at these different *** find significant variations in the source’s flux *** also investigate the variations in the source’s spectral components during the observation *** find that the photon index and hence the spectral shape follow the variations only over longer time *** probe the correlations between fluxes of different bands and their photon indices,and found no significant correlations between the parameters.

关键词： galaxies:Seyfert galaxies:individual(Mrk 335) X-rays:galaxies

Life under tension: the relevance of force on biological polymers

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Biophysics Reports 2024年第1期10卷 48-56页

作者： Matthew T.J.Halma Longfu Xu department of physics and astronomy and Laser Lab Vrije Universiteit Amsterdam LUMICKS B.V.

Optical tweezers have elucidated numerous biological processes, particularly by enabling the precise manipulation and measurement of tension. One question concerns the biological relevance of these experiments and the generalizability of these experiments to wider biological systems. Here, we categorize the applicability of the information garnered from optical tweezers in two distinct categories: the direct relevance of tension in biological systems, and what experiments under tension can tell us about biological systems, while these systems do not reach the same tension as the experiment, still, these artificial experimental systems reveal insights into the operations of biological machines and life processes.

关键词： Tension Optical tweezers Molecular force