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The BTFR and MOND with Redshifts of Graviton Energy
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作者 Firmin J. Oliveira 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第4期1903-1917,共15页
This report is about the graviton redshift theory (GRST) which hypothesises the redshift of the energy of gravitons traveling in fields. A new source of energy loss in galaxy dynamics is introduced. Due to the hypothe... This report is about the graviton redshift theory (GRST) which hypothesises the redshift of the energy of gravitons traveling in fields. A new source of energy loss in galaxy dynamics is introduced. Due to the hypothetical interactions of gravitons with the expansion of the universe, which causes an energy loss of the gravitons due to cosmological redshift, the rotation equation for galaxies, which previously had the Newtonian potential energy and the graviton gravitational redshift energy loss, is now updated with the graviton cosmological redshift energy loss. From the galaxy rotation equation, the baryonic Tully-Fisher relation (BTFR) and the modified Newtonian dynamics (MOND) are defined in radial distribution form. Fits to galaxy rotation motion are detailed. A cosmic connection for the BTFR is defined. The result is that galaxy rotation curves are fully accounted for with the GRST rotation equation and the BTFR and MOND theories are incorporated into a unified framework. 展开更多
关键词 GRAVITONS Gravitational Redshift Cosmological Redshift Graviton Coupling Coefficients Spiral Galaxies
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Modelling and Analysis of the Hubble Diagram of 280 Type SNIa Supernovae and Gamma Ray Bursts Redshifts with Analytical and Empirical Redshift/Magnitude Functions 被引量:2
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作者 Laszlo A. Marosi 《International Journal of Astronomy and Astrophysics》 2016年第3期272-275,共5页
Based on an analysis of 280 Type SNIa supernovae and gamma-ray bursts redshifts in the range of z = 0.0104 - 8.1 the Hubble diagram is shown to follow a strictly exponential slope predicting an exponentially expanding... Based on an analysis of 280 Type SNIa supernovae and gamma-ray bursts redshifts in the range of z = 0.0104 - 8.1 the Hubble diagram is shown to follow a strictly exponential slope predicting an exponentially expanding or static universe. At redshifts > 2 - 3 ΛCDM models show a poor agreement with the observed data. Based on the results presented in this paper, the Hubble diagram test does not necessarily support the idea of expansion according to the big-bang concordance model. 展开更多
关键词 MAGNITUDE Redshift Data Fitting SUPERNOVAE Gamma Ray Bursts Hubble Diagram ΛCDM Cosmological Model
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Structural regulation and optical behavior of zero-dimensional Cu(Ⅰ)-based organometallic halides under pressure
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作者 Runnan Ye Jingtian Wang +6 位作者 Jiayi Yang Xuchen Wang Junce Lei Wenya Zhao Yufan Meng Guanjun Xiao Bo Zou 《Chinese Physics B》 2025年第6期54-58,共5页
Low-dimensional hybrid metal halides exhibit broadband emission and high photoluminescence quantum yield(PLQY), making them promising candidates for the next-generation luminescent materials in lighting applications. ... Low-dimensional hybrid metal halides exhibit broadband emission and high photoluminescence quantum yield(PLQY), making them promising candidates for the next-generation luminescent materials in lighting applications. Here,the emission intensity of(C_(12)H_(24)O_(6))_(2)Na_(2)(H_(2)O)_(3)Cu_(4)I_(6) was strengthened between 9.3 GPa and 17.2 GPa, accompanied by the redshift of emission wavelength. The photoluminescence(PL) of Cu(Ⅰ)-based organometallic halides originates from multiple emission states, which are a metal-to-ligand charge transfer or a halide-to-ligand charge transfer(MLCT/HLCT)excited state and a cluster-centered(CC) excited state. MLCT/HLCT-related emission wavelength redshifts while CCrelated emission wavelength remains unchanged, indicating that the rearrangement of different emission states plays a critical role in the changes of luminescence wavelength. This study not only deepens the understanding of the influence of high pressure on(C_(12)H_(24)O_(6))_(2)Na_(2)(H_(2)O)_(3)Cu_(4)I_(6), but also provides valuable insights into the structure–property relationship of zero-dimensional Cu(Ⅰ)-based organometallic halides. 展开更多
关键词 low-dimensional Cu-based halides high pressure REDSHIFT REARRANGEMENT
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Erratum to “Data from Twenty-Three FRB’s Confirm the Universe Is Static and Not Expanding”, [Journal of High Energy Physics, Gravitation and Cosmology 2024, 10, 1152-1177]
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作者 Lyndon Errol Ashmore 《Journal of High Energy Physics, Gravitation and Cosmology》 2025年第1期165-167,共3页
Dispersion measure in an FRB’s signal is produced by the photons of the radio waves interacting with the free electrons in the IGM. In New Tired Light (NTL), redshifts are produced by the photons of light interacting... Dispersion measure in an FRB’s signal is produced by the photons of the radio waves interacting with the free electrons in the IGM. In New Tired Light (NTL), redshifts are produced by the photons of light interacting with these self-same electrons and so, one would expect a direct relationship between the DM of an FRB and the redshift of the host galaxy. However, workers in this field assume expansion and weight the DM by dividing it by the scale factor (1 + z) to allow for expansion. Once this weighting is removed, it was predicted back in 2016 (when the first FRB was localized) and later presented at a conference and published in the proceedings that, as more FRB’s were localized, a graph of DM versus ln(1 + z) would be a straight line of gradient (mec/2hre) or 7.32 × 1025 m−2 in SI units. The original paper had twenty-four data points but this has risen significantly to sixty-four useable FRB’s and so this corrigendum updates that paper so that all sixty-four are used. The data give a straight-line graph of gradient 7.12 × 1025 m−2, a difference of 3% from (mec/2hre) predicted nine years earlier. 展开更多
关键词 REDSHIFT Dispersion Measure Fast Radio Bursts FRB’s Tired Light Static Universe IGM
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Dark energy effects on surface gravitational redshift and Keplerian frequency of neutron stars
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作者 Jia-Jing He Yan Xu +3 位作者 Yi-Bo Wang Xiu-Lin Huang Xing-Xing Hu Yu-Fu Shen 《Communications in Theoretical Physics》 2025年第1期122-129,共8页
Research on the properties of neutron stars with dark energy is a particularly interesting yet unresolved problem in astrophysics.We analyze the influence of dark energy on the equation of state,the maximum mass,the s... Research on the properties of neutron stars with dark energy is a particularly interesting yet unresolved problem in astrophysics.We analyze the influence of dark energy on the equation of state,the maximum mass,the surface gravitational redshift and the Keplerian frequency for the traditional neutron star and the hyperon star matter within the relativistic mean field theory,using the GM1 and TM1 parameter sets by considering the two flavor symmetries of SU(6)and SU(3)combined with the observations of PSR J1614-2230,PSR J0348+0432,PSR J0030+0451,RX J0720.4-3125,and 1E 1207.4-5209.It is found that the existence of dark energy leads to the softened equations of the state of the traditional neutron star and the hyperon star.The radius of a fixed-mass traditional neutron star(or hyperon star)with dark energy becomes smaller,which leads to increased compactness.The existence of dark energy can also enhance the surface gravitational redshift and the Keplerian frequency of traditional neutron stars and hyperon stars.The growth of the Keplerian frequency may cause the spin rate to speed up,which may provide a possible way to understand and explain the pulsar glitch phenomenon.Specifically,we infer that the mass and the surface gravitational redshift of PSR J1748-2446ad without dark energy for the GM1(TM1)parameter set are 1.141 M_(☉)(1.309 M_(☉))and 0.095(0.105),respectively.The corresponding values for the GM1(TM1)parameter set are 0.901 M_(☉)(1.072M_(☉))and 0.079(0.091)if PSR J1748-2446ad contains dark energy withα=0.05.PSR J1748-2446ad may be a low-mass pulsar with a lower surface gravitational redshift under our selected models. 展开更多
关键词 dark energy neutron stars gravitational redshift Keplerian frequency
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Messenger from the Early Universe-Einstein Probe Fuels New Hope for High-redshift GRB Observations
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作者 SONG Jianlan 《Bulletin of the Chinese Academy of Sciences》 2025年第1期51-54,共4页
A team of researchers from the Beijing Normal University,the Institute of High Energy Physics(IHEP)under the Chinese Academy of Sciences(CAS),and the National Astronomical Observatories,CAS(NAOC),reported in Nature As... A team of researchers from the Beijing Normal University,the Institute of High Energy Physics(IHEP)under the Chinese Academy of Sciences(CAS),and the National Astronomical Observatories,CAS(NAOC),reported in Nature Astronomy on January 23,2025 their discovery of an X-ray flash about 12.5 billion lightyears away.The signals burst out only 1.2 billion years after the Big Bang,when our 13.8-billion-year-old universe was still in its infancy,and a science satellite swiftly recorded them. 展开更多
关键词 science satellite big bangwhen early universe high energy physics ihep MESSENGER einstein probe high redshift grb big bang
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Resolving gravitational redshift with sub-millimeter height differences using spin-squeezed optical clocks
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作者 Deshui Yu Jia Zhang +2 位作者 Shougang Zhang Tiantian Shi Jingbiao Chen 《Chinese Physics B》 2025年第5期147-155,共9页
The phenomenon that a clock at a higher gravitational potential ticks faster than one at a lower potential,also known as gravitational redshift,is one of the classical tests of Einstein’s theory of general relativity... The phenomenon that a clock at a higher gravitational potential ticks faster than one at a lower potential,also known as gravitational redshift,is one of the classical tests of Einstein’s theory of general relativity.Owing to their ultra-high accuracy and stability,state-of-the-art optical lattice clocks have enabled resolving the gravitational redshift with a millimeter-scale height difference.Further reducing the vertical inter-clock separation down to the sub-millimeter level and especially shortening the required measurement time may be achieved by employing spin squeezing.Here,we theoretically investigate the spin-squeezing-enhanced differential frequency comparison between two optical clocks within a lattice-trapped cloud of^(171)Yb atoms.The numerical results illustrate that for a sample of 10^(4)atoms,the atomic-collision-limited resolution of the vertical separation between two clocks can reach 0.48 mm,corresponding to a fractional gravitational redshift at the 10^(-20)level.In addition,the required averaging time may be reduced to less than one hundredth of that of conventional clocks with independent atoms.Our work opens a door to the future spin-squeezing-enhanced test of general relativity. 展开更多
关键词 optical lattice clock quantum projection noise spin squeezing gravitational redshift
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CERENKOV REDSHIFTS OF BALMER LINES IN QUASARS
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作者 程富华 尤峻汉 晏明 《Science China Mathematics》 SCIE 1989年第4期453-458,共6页
Based on the Cerenkov line-emission theory, this paper estimates the Cerenkov red-shifts of Balmer lines and gives a better explanation of the observations, that is, the high-ionization broad emission lines of quasars... Based on the Cerenkov line-emission theory, this paper estimates the Cerenkov red-shifts of Balmer lines and gives a better explanation of the observations, that is, the high-ionization broad emission lines of quasars are blueshifted with respect to the neutral hy-drogen and the low-ionization broad lines. 展开更多
关键词 CERENKOV REDSHIFT redshiff difference.
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On the Relation Between Symmetry of Radio Galaxies and Their Physical Parameters
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作者 Mohsen Javaherian Halime Miraghaei Hooman Moradpour 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第9期37-59,共23页
Gravity as a fundamental force plays a dominant role in the formation and evolution of cosmic objects and leaves its effect in the emergence of symmetric and asymmetric structures.Thus,analyzing the symmetry criteria ... Gravity as a fundamental force plays a dominant role in the formation and evolution of cosmic objects and leaves its effect in the emergence of symmetric and asymmetric structures.Thus,analyzing the symmetry criteria allows us to uncover mechanisms behind the gravity interaction and understand the underlying physical processes that contribute to the formation of large-scale structures such as galaxies.We use a segmentation process using intensity thresholding and the k-means clustering algorithm to analyze radio galaxy images.We employ a symmetry criterion and explore the relation between morphological symmetry in radio maps and host galaxy properties.Optical properties(stellar mass,black hole mass,optical size(R_(50)),concentration,stellar mass surface density(μ_(50)),and stellar age)and radio properties(radio flux density,radio luminosity,and radio size)are considered.We found that there is a correlation between symmetry and radio size,indicating larger radio sources have smaller symmetry indices.Therefore,size of radio sources should be considered in any investigation of symmetry.Weak correlations are also observed with other properties,such as R_(50)for FRI galaxies and stellar age.We compare the symmetry differences between FRI and FRII radio galaxies.FRII galaxies show higher symmetry in 1.4 GHz and 150 MHz maps.Investigating the influence of radio source sizes,we discovered that this result is independent of the sizes of radio sources.These findings contribute to our understanding of the morphological properties and analyses of radio galaxies. 展开更多
关键词 methods:data analysis techniques:image processing catalogs galaxies:nuclei galaxies:distances and redshifts
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Quantized Redshift and its Significance for Recent Observation
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作者 Arindam Mal Sarbani Palit +1 位作者 Christopher C.Fulton Sisir Roy 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第9期156-166,共11页
With the recent observational evidence in extragalactic astronomy,the interpretation of the nature of quasar redshift continues to be a research interest.Very high redshifts are being detected for extragalactic object... With the recent observational evidence in extragalactic astronomy,the interpretation of the nature of quasar redshift continues to be a research interest.Very high redshifts are being detected for extragalactic objects that are presumably very distant and young while also exhibiting properties that are characteristic of a more mature galaxy such as ours.According to Halton Arp and Geoffrey Burbidge,redshift disparities consist of an intrinsic component and are related to an evolutionary process.Karlsson observed redshift periodicity at integer multiples of0.089 in log scale and Burbidge observed redshift periodicity at integer multiples of 0.061 in linear scale.Since Singular Value Decomposition based periodicity estimation is known to be superior for noisy data sets,especially when the data contain multiple harmonics and overtones,mainly irregular in nature,we have chosen it to be our primary tool for analysis of the quasar-galaxy pair redshift data.We have observed a fundamental periodicity of0.051 with a confidence interval of 95%in linear scale with the site-available Sloan Digital Sky Survey Data Release 7(SDSS DR7)quasar-galaxy pair data set.We have independently generated quasar-galaxy pair data sets from both 2d F and SDSS and found fundamental periodicities of 0.077 and 0.089,respectively,in log scale with a confidence interval of 95%. 展开更多
关键词 galaxies:distances and redshifts (galaxies:)quasars:absorption lines cosmology:observations
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The Jiao Tong University Spectroscopic Telescope Project 被引量:1
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作者 JUST Team Chengze Liu +28 位作者 Ying Zu Fabo Feng Zhaoyu Li Yu Yu Hua Bai Xiangqun Cui Bozhong Gu Yizhou Gu Jiaxin Han Yonghui Hou Zhongwen Hu Hangxin Ji Yipeng Jing Wei Li Zhaoxiang Qi Xianyu Tan Cairang Tian Dehua Yang Xiangyan Yuan Chao Zhai Congcong Zhang Jun Zhang Haotong Zhang Pengjie Zhang Yong Zhang Yi Zhao Xianzhong Zheng Qingfeng Zhu Xiaohu Yang 《Astronomical Techniques and Instruments》 CSCD 2024年第1期16-30,共15页
The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a di... The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets. 展开更多
关键词 Astronomical instrumentation Optical telescopes Large-scale structure of the universe Redshift surveys Time domain astronomy Exoplanet astronomy
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Cosmological Redshift Caused by Head-On Collisions with CMB Photons, Not by Expansion of Space
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作者 Gurcharn S. Sandhu Ishaan S. Dhindsa 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第4期1675-1698,共24页
The Big Bang model was first proposed in 1931 by Georges Lemaitre. Lemaitre and Hubble discovered a linear correlation between distances to galaxies and their redshifts. The correlation between redshifts and distances... The Big Bang model was first proposed in 1931 by Georges Lemaitre. Lemaitre and Hubble discovered a linear correlation between distances to galaxies and their redshifts. The correlation between redshifts and distances arises in all expanding models of universe as the cosmological redshift is commonly attributed to stretching of wavelengths of photons propagating through the expanding space. Fritz Zwicky suggested that the cosmological redshift could be caused by the interaction of propagating light photons with certain inherent features of the cosmos to lose a fraction of their energy. However, Zwicky did not provide any physical mechanism to support his tired light hypothesis. In this paper, we have developed the mechanism of producing cosmological redshift through head-on collision between light and CMB photons. The process of repeated energy loss of visual photons through n head-on collisions with CMB photons, constitutes a primary mechanism for producing the Cosmological redshift z. While this process results in steady reduction in the energy of visual photons, it also results in continuous increase in the number of photons in the CMB. After a head-on collision with a CMB photon, the incoming light photon, with reduced energy, keeps moving on its original path without any deflection or scattering in any way. After propagation through very large distances in the intergalactic space, all light photons will tend to lose bulk of their energy and fall into the invisible region of the spectrum. Thus, this mechanism of producing cosmological redshift through gradual energy depletion, also explains the Olbers’s paradox. 展开更多
关键词 REDSHIFT CMBR Big Bang COSMOLOGY Elastic Collisions Tired Light
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Evaluating the Effects of Graviton Redshift upon Spiral Galaxy Rotation Curves, Surface Brightness Magnitudes and Gravitational Lensing
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作者 Firmin J. Oliveira 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第3期967-985,共19页
The effects of the gravitational redshift of gravitons upon spiral galaxy rotation energy are compared to the standard mass to light analyses in obtaining rotation curves. The derivation of the total baryonic matter c... The effects of the gravitational redshift of gravitons upon spiral galaxy rotation energy are compared to the standard mass to light analyses in obtaining rotation curves. The derivation of the total baryonic matter compares well with the standard theory and the rotation velocity is matched to a high precision. The stellar mass distributions obtained from the fit with graviton energy loss are used to derive the surface brightness magnitudes for the galaxies, which agree well with the observed measurements. In a new field of investigation, the graviton theory is applied to the observations of gravitational lenses. The results of these applications of the theory suggest that it can augment the standard methods and may eliminate the need for dark matter. 展开更多
关键词 GRAVITONS Gravitational Redshift Surface Brightness Gravitational Lens Lens Mass
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Data from Twenty-Three FRB’s Confirm the Universe Is Static and Not Expanding
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作者 Lyndon Errol Ashmore 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第3期1152-1177,共26页
Fast Radio Bursts from far away galaxies have travelled through the IGM and provide a tool to study its composition. Presently there are 23 FRB’s whose host galaxies have been identified and the redshift found. This ... Fast Radio Bursts from far away galaxies have travelled through the IGM and provide a tool to study its composition. Presently there are 23 FRB’s whose host galaxies have been identified and the redshift found. This gives us the opportunity to test Dispersion Measure versus redshift predictions made by two models. The Macquart relation for an expanding Universe and the New Tired Light relationship in a static universe. In New Tired Light, redshifts are produced when a photon is absorbed and re-emitted by the electrons in the IGM which recoil on both occasions. Some of the energy of the photon has been transferred to the kinetic energy of the recoiling electron. The photon has less energy, a lower frequency and a longer wavelength. It has been redshifted. Since dispersion is due to an interaction between radio signals and these same electrons one would expect a direct relationship between DM and redshift in the New Tired light model. The relation is DM=(mec/2hre)ln(1+z)and contains no adjustable parameters—just a combination of universal constants related to the electron and photon. Notice that the relation is independent of the electron number density ne since a change in ne affects both the DM and redshift equally. A graph of DM versus ln(1 + z) will be a straight line of gradient (mec/2hre)and, using SI units, substituting for the constants gives 7.318 × 1025 m−2. Using the data from the 23 well localized FRB’s, with the weighting of the DM’s for expansion removed (so that the data corresponds to a static universe), a graph of DM versus ln(1 + z) has a gradient of 6.7 × 1025 m−2—9% below the predicted (mec/2hre). The Macquart relation involves highly processed data and adjustable parameters to allow for “dark energy” and “dark matter” (neither of which has yet been found) and can be reduced to DM = 850z (in units of pc∙cm−3). Using the data from this set of localized FRB’s gives a trendline with gradient 1.10 × 103 pc∙cm−3—almost 30% higher than that predicted in an expanding universe model. The FRB data clearly comes down in favour of a static universe rather than an expanding one. Combining the DM-z relationship for the 23 well localized FRB’s, with the Hubble diagram, drawn using the NED-D compilation of redshift independent extragalactic distances, produces a value of “ne” the mean electron number density of the IGM, of ne=0.48 m−3close to the value ne=0.5 m−3, long since predicted by NTL. 展开更多
关键词 REDSHIFT Dispersion Measure Fast Radio Bursts FRB’s Tired Light Static Universe IGM
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Dynamic Spacetime: Key to the Mysteries of Dark Matter and Dark Energy
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作者 Tianxi Zhang 《Journal of Modern Physics》 2024年第4期416-434,共19页
Physics is a branch of science to study matter and its motion in space and time. Development of physics usually upgrades human perspective and understanding of the space and time. Einstein successfully developed speci... Physics is a branch of science to study matter and its motion in space and time. Development of physics usually upgrades human perspective and understanding of the space and time. Einstein successfully developed special and general theories of relativity and creatively promoted our perspective of spacetime from Newton’s absolute space and time to his relative spacetime. Based on redshift and distance measurements of galaxies and distant type Ia supernovae, cosmologists have suggested that our universe is expanding at an ever-increasing rate driven by a mysterious dark energy. Recently, the author has proposed that spacetime is dynamic. Spacetime is said to be absolute if it is independent of matter and motion, relative if it is affected by matter and motion, and dynamic if it mutually interacts with matter and motion. In dynamic spacetime, not only do matter and motion distort spacetime, but they are also affected by the distorted spacetime. Spacetime to be dynamic is a consequence of a deep insight to Mach’s principle, which tells us that the inertia of an object results from the gravitational interaction by the rest of the universe. Reaction of dynamic spacetime on a traveling light causes light redshift. Reaction of dynamic spacetime on a fast moving neutrino slows down the neutrino. The derived redshift-distance relation perfectly explained the measurements of distant type Ia supernovae and gamma ray bursts (GRBs) and also naturally obtained Hubble’s law as an approximate relation at small redshift. This explanation of cosmological redshift as the opposition of dynamic spacetime does not mandate the universe to be expanding and accelerating, so that it does not need the universe to be initiated from a Big Bang and driven out mainly by a mysterious dark energy. Extremely slowed down neutrinos in dynamic spacetime, when they are gravitationally trapped around clusters, galaxies, and any celestial objects, would play the role of dark matter in explaining the velocity-radius relations of galaxy’s or cluster’s rotations. 展开更多
关键词 SPACETIME Cosmology REDSHIFT NEUTRINO GRAVITATION Dark Matter Dark Energy
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Does the Redshift Distribution of Swift Long GRBs Trace the Star-Formation Rate?
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作者 Ali M. Hasan Walid J. Azzam 《International Journal of Astronomy and Astrophysics》 2024年第1期20-44,共25页
Gamma-ray bursts (GRBs) are extremely powerful explosions that have been traditionally classified into two categories: long bursts (LGRBs) with an observed duration T<sub>90 </sub>> 2 s, and short burst... Gamma-ray bursts (GRBs) are extremely powerful explosions that have been traditionally classified into two categories: long bursts (LGRBs) with an observed duration T<sub>90 </sub>> 2 s, and short bursts (SGRBs) with an observed duration T<sub>90</sub> T<sub>90</sub> is the time interval during which 90% of the fluence is detected. LGRBs are believed to emanate from the core-collapse of massive stars, while SGRBs are believed to result from the merging of two compact objects, like two neutron stars. Because LGRBs are produced by the violent death of massive stars, we expect that their redshift distribution should trace the star-formation rate (SFR). The purpose of our study is to investigate the extent to which the redshift distribution of LGRBs follows and reflects the SFR. We use a sample of 370 LGRBs taken from the Swift catalog, and we investigate different models for the LGRB redshift distribution. We also carry out Monte Carlo simulations to check the consistency of our results. Our results indicate that the SFR can describe the LGRB redshift distribution well for high redshift bursts, but it needs an evolution term to fit the distribution well at low redshift. 展开更多
关键词 Gamma-Ray Bursts Redshift Distribution Star-Formation Rate
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Predicting Dark Energy Survey Results within the Haug-Tatum Cosmology Model
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作者 Eugene Terry Tatum Espen Gaarder Haug 《Journal of Modern Physics》 2024年第12期2220-2227,共8页
Given the pending completion and publication of the final Dark Energy Survey (DESI) results, this letter presents the corresponding predictions of the Haug-Tatum cosmology (HTC) model. In particular, we show in tabula... Given the pending completion and publication of the final Dark Energy Survey (DESI) results, this letter presents the corresponding predictions of the Haug-Tatum cosmology (HTC) model. In particular, we show in tabular and graphic form the “dark energy decay” curve which the HTC model predicts for cosmological redshifts covering the range of 0 - 2.0 z. Furthermore, we present the HTC model distance-vs-redshift curve in comparison to the three very different curves (for luminosity distance, angular diameter distance, and co-moving distance) calculated within the Lambda-CDM model. Whether the expansion of our universe is actually undergoing slight acceleration or the finely-tuned cosmic coasting at constant velocity of Rh = ct models, including HTC, will hopefully soon be answered by the many pending observational studies. 展开更多
关键词 Haug-Tatum Cosmology Dark Energy Lambda-CDM Cosmology Cosmological Redshift Hubble Parameter Upsilon Constant DESI Rh = ct Cosmology
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Active Optics in LAMOST 被引量:4
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作者 Ding-QiangSu Xiang-QunCui 《Chinese Journal of Astronomy and Astrophysics》 CSCD 北大核心 2004年第1期1-9,共9页
Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is one of the major national projects under construction in China. Active optics is one of the most important technologies for new large telescopes. I... Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is one of the major national projects under construction in China. Active optics is one of the most important technologies for new large telescopes. It is used for correcting telescope errors generated by gravitational and thermal changes. Here, however, we use this technology to realize the configuration of LAMOST,—a task that cannot be done in the traditional way. A comprehensive and intensive research on the active optics used in LAMOST is also reported, including an open-loop control method and an auxiliary closed-loop control method. Another important development is in our pre-calibration method of open-loop control, which is with some new features: simultaneous calculation of the forces and displacements of force actuators and displacement actuators; the profile of mirror can be arbitrary; the mirror surface shape is not expressed by a fitting polynomial, but is derived from the mirror surface shape formula which is highly accurate; a proof is given that the solution of the pre-calibration method is the same as the least squares solution. 展开更多
关键词 galaxies: distances and redshifts techniques: active optics telescopes instrumentation: adaptive optics
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The Multiple Images of the Plasma Lensing FRB 被引量:1
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作者 Yu-Bin Wang Zhi-Gang Wen +3 位作者 Rai Yuen Na Wang Jian-Ping Yuan Xia Zhou 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2022年第6期190-203,共14页
We investigate the formation of multiple images as the radio signals from fast radio bursts(FRBs)pass through the plane of a plasma clump.The exponential model for the plasma clump is adopted to analyze the properties... We investigate the formation of multiple images as the radio signals from fast radio bursts(FRBs)pass through the plane of a plasma clump.The exponential model for the plasma clump is adopted to analyze the properties of the multiple images.By comparing with the classical dispersion relations,we find that one image has exhibited specific inverse properties to others,such as their delay times at high frequency is higher than that at low frequency,owing to the lensing effects of the plasma clump.We demonstrate that these inverse effects should be observable in some repeating FRBs.Our results predict deviation in the estimated dispersion measure(DM)across multiple images,consistent with the observations of FRB 121102 and FRB 180916.J0158+65.If other plasma lenses have effects similar to an exponential lens,we find that they should also give rise to a similar dispersion relation in the multiple images.For some repeating FRBs,analysis of the differences in time delay and in DM between multiple images at different frequencies can serve as a method to reveal the plasma distribution. 展开更多
关键词 GALAXIES distances and redshifts GALAXIES ISM gravitational lensing:strong-ISM structure-scattering
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Two Novel Approaches for Photometric Redshift Estimation based on SDSS and 2MASS 被引量:1
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作者 Dan Wang Yan-Xia Zhang +1 位作者 Chao Liu Yong-Heng Zhao 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2008年第1期119-126,共8页
We investigate two training-set methods; support vector machines (SVMs) and Kernel Regression (KR) for photometric redshift estimation with the data from the databases of Sloan Digital Sky Survey Data Release 5 an... We investigate two training-set methods; support vector machines (SVMs) and Kernel Regression (KR) for photometric redshift estimation with the data from the databases of Sloan Digital Sky Survey Data Release 5 and Two Micron All Sky Survey. We probe the performances of SVMs and KR for different input patterns. Our experiments show that with more parameters considered, the accuracy does not always increase, and only when appropriate parameters are chosen, the accuracy can improve. For different approaches, the best input pattern is different. With different parameters as input, the optimal bandwidth is dissimilar for KR. The rms errors of photometric redshifts based on SVM and KR methods are less than 0.03 and 0.02, respectively. Strengths and weaknesses of the two approaches are summarized. Compared to other methods of estimating photometric redshifts, they show their superiorities, especially KR, in terms of accuracy. 展开更多
关键词 GALAXIES distances and redshifts - galaxies general - methods data analysis - techniques PHOTOMETRIC
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