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The Tension Cosmology, Largest Cosmic Structures and Explosions of Supernovae from SST
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作者 Sylwester Kornowski 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第3期1029-1044,共16页
Here, using the Scale-Symmetric Theory (SST) we explain the cosmological tension and the origin of the largest cosmic structures. We show that a change in value of strong coupling constant for cold baryonic matter lea... Here, using the Scale-Symmetric Theory (SST) we explain the cosmological tension and the origin of the largest cosmic structures. We show that a change in value of strong coupling constant for cold baryonic matter leads to the disagreement in the galaxy clustering amplitude, quantified by the parameter S8. Within the same model we described the Hubble tension. We described also the mechanism that transforms the gravitational collapse into an explosion—it concerns the dynamics of virtual fields that lead to dark energy. Our calculations concern the Type Ia supernovae and the core-collapse supernovae. We calculated the quantized masses of the progenitors of supernovae, emitted total energy during explosion, and we calculated how much of the released energy was transferred to neutrinos. Value of the speed of sound in the strongly interacting matter measured at the LHC confirms that presented here model is correct. Our calculations show that the Universe is cyclic. 展开更多
关键词 Scale-Symmetric theory Tension cosmology Coupling Constants Parameters σ8 and S8 Largest Cosmic Structures Dark Energy Supernova Explosion Cyclic universe
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The “Dead Universe” Theory: Natural Separation of Galaxies Driven by the Remnants of a Supermassive Dead Universe
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作者 Joel Almeida 《Natural Science》 2024年第6期65-101,共37页
This article explores the dead universe theory as a novel interpretation for the origin and evolution of the universe, suggesting that our cosmos may have originated from the remnants of a preceding universe. This per... This article explores the dead universe theory as a novel interpretation for the origin and evolution of the universe, suggesting that our cosmos may have originated from the remnants of a preceding universe. This perspective challenges the conventional Big Bang theory, particularly concerning dark matter, the expansion of the universe, and the interpretation of phenomena such as gravitational waves. 展开更多
关键词 Dead universe theory Heat Death of the universe Big Bang theory universe’s Ultimate Fate universe Expansion Big Freeze universe cosmological Models End of universe Theories Natural Galaxy Drift Future of the universe universe Cooling Down cosmology and Entropy
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New Cosmology: The Global Dynamics of the Higgs Quantum Space and the Accelerated Expansion of the Universe
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作者 Jacob Schaf 《Journal of Modern Physics》 2019年第3期281-293,共13页
This work investigates the nature of the empty space and of the energy accelerating expansion of the universe, within the context of the Higgs theory. It is consensus among the cosmologists that dark energy, accelerat... This work investigates the nature of the empty space and of the energy accelerating expansion of the universe, within the context of the Higgs theory. It is consensus among the cosmologists that dark energy, accelerating the expansion of the universe, is energy of the empty space (vacuum) itself. According to the Higgs theory, empty space (vacuum) is filled up by a real quantum fluid medium, closely analogous to the superconducting condensate, giving mass to the elementary particles by the Higgs mechanism. This spatial medium is the holder of the vacuum energy. Current theories describe the empty space (vacuum) in terms of the stress-energy tensor of a perfect fluid and estimate the vacuum energy density in terms of zero-point energies of the various force fields. They come to the scandalous conclusion that the vacuum energy density is 120 decimal orders of magnitude larger than shown by the observations. In the context of the Higgs theory, empty space, far from a perfect fluid, is a very strongly correlated boson condensate, a perfect quantum fluid ruled by the principles of quantum physics and governed by a powerful order parameter. This order parameter is stabilized by a huge energy gap that, according to the Glashow-Weinberg-Salam electroweak model, achieves more than 200 GeV. This huge energy gap very strongly suppresses the quantum fluctuations and the zero-point energies. This lets clear that estimating the vacuum energy density in terms of the zero-point energies cannot be correct. The expanding universe does not create more and more vacuum energy and does not expand against a negative pressure. The universe is an adiabatic system that conserves the total mass-energy and expansion only reduces the vacuum energy density. Calculations within this context show that the vacuum energy density converges closely to the observed value. 展开更多
关键词 Dark ENERGY Vacuum ENERGY cosmologICAL Constant HIGGS theory EXPANDING universe
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The bulk viscous string cosmology in an anisotropic universe with late time acceleration
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作者 Hassan Amirhashchi 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2013年第4期387-398,共12页
A model of a cloud formed by massive strings is used as a source of Bianchi type II cases. We assume that the expansion (θ) in the model is proportional to the shear (σ). To get an exact solution, we consider th... A model of a cloud formed by massive strings is used as a source of Bianchi type II cases. We assume that the expansion (θ) in the model is proportional to the shear (σ). To get an exact solution, we consider the equation of state of the fluid to be in the stiff form. It is found that the bulk viscosity played a very important role in the history of the universe. In the presence of bulk viscosity the particles dominate over strings whereas in the absence of it, strings dominate over the particles, which is not consistent with recent observations. Also we observe that the viscosity causes the expansion of the universe to be accelerating. Our models are evolving from an early decelerating phase to a late time accelerating phase. The physical and geometrical behaviors of these models are discussed. 展开更多
关键词 cosmology theory -- viscous fluid -- massive string
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A new interpretation of zero Lyapunov exponents in BKL time for Mixmaster cosmology 被引量:1
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作者 Xin Wu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2010年第3期211-219,共9页
A global relationship between cosmological time and Belinskii-Khalatnikov -Lifshitz (BKL) time during the entire evolution of the Mixmaster Bianchi IX universe is used to explain why all the Lyapunov exponents are z... A global relationship between cosmological time and Belinskii-Khalatnikov -Lifshitz (BKL) time during the entire evolution of the Mixmaster Bianchi IX universe is used to explain why all the Lyapunov exponents are zero at the BKL time. The actual reason is that the domain of the cosmological time is finite as the BKL time runs from minus infinity to infinity. 展开更多
关键词 cosmology early universe -- relativity
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Split Membrane 11D Spacetime = 1D Eleventh Dimension Interval Space + 6D Rishon Space + 3D Higgs Space + 1D Einstein Time: Cosmology
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作者 Ding-Yu Chung 《Journal of Modern Physics》 2019年第11期1310-1341,共32页
The paper posits that the cyclic universe cosmology involves the split of the membrane 11D (11 dimensional) spacetime into the 1D eleventh dimension orbifold interval space to form gravity, the 6D discrete interior ri... The paper posits that the cyclic universe cosmology involves the split of the membrane 11D (11 dimensional) spacetime into the 1D eleventh dimension orbifold interval space to form gravity, the 6D discrete interior rishon space (TTT-VVV for positron-neutrino or TTV-TVV for?quarks) to form the Standard Model, the 3D Higgs space (attachment space to attach matter or detachment space to detach matter) to form the Higgs or reverse Higgs field, and 1D Einstein time to be shared by all spaces. To establish particle masses, spacetime dimension number decreases with decreasing speed of light, decreasing vacuum energy, and increasing rest mass. The 4D and the 10D have zero and the highest vacuum energies, respectively. The cyclic universe cosmology starts with the zero-energy 4D inter-universal void and the positive-energy membrane and negative-energy antimembrane 11D dual universe which is split into four equal 10D string branes, including the 10D positive-energy weak-gravity brane with matter, negative-energy strong-gravity brane, negative-energy weak-gravity brane with antimatter, and positive-energy strong-gravity brane in the 11D bulk with the 1D eleventh dimension interval space in between the strong and the weak-gravity branes. To form the home universe where we inhabit, the 10D positive-energy weak-gravity brane with attachment space absorbed the zero-energy 4D inter-universal void with detachment space, resulting in the combination of rest mass from attachment space and kinetic energy from detachment space, the formation of the 4D spacetime universe by transforming 6D connected exterior space into 6D discrete interior rishon space, and cosmic inflation. The other three branes did not absorb the inter-universal void, resulting in the oscillating dimension branes between 10D and 4D stepwise without kinetic energy. The three branes are hidden when D > 4, and they are dark energy when D = 4. The split 11D spacetime and cosmology provide the matter-antimatter imbalance and the accurately calculated masses for leptons, quarks, hadrons, gauge bosons, the Higgs boson, gravity, dark matter, and dark energy. 展开更多
关键词 String theory Rishon Cyclic universe cosmology DARK Energy DARK Matter Particle Masses
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How a Realistic Linear <i>R<sub>h</sub>= ct </i>Model of Cosmology Could Present the Illusion of Late Cosmic Acceleration
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作者 Eugene Terry Tatum U. V. S. Seshavatharam 《Journal of Modern Physics》 2018年第7期1397-1403,共7页
Realistic FLRW cosmic coasting models which contain matter now appear to be a reasonable alternative in explaining the accumulated Supernova Cosmology Project data since 1998. In sharp contrast to the unrealistic orig... Realistic FLRW cosmic coasting models which contain matter now appear to be a reasonable alternative in explaining the accumulated Supernova Cosmology Project data since 1998. In sharp contrast to the unrealistic original classic Milne universe, which was entirely devoid of matter, these modified Milne-type models containing matter, often referred to as realistic linear Rh = ct models, have rapidly become the primary competition with standard cosmology. This paper compares the expected relative luminosity distances and relative angular diameter distances for given magnitudes of redshift within these two competing models. A simple ratio formula is derived, which explains how expected luminosity distances and angular diameter distances for given magnitudes of redshift within a realistic Milne-type cosmic expansion could create the illusion (for standard model proponents) of cosmic acceleration where none exists. 展开更多
关键词 Dark Energy Survey cosmology theory COSMIC COASTING COSMIC Flatness Type Ia Supernovae CMBR Flat Space cosmology MILNE universe Theories
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Flat Space Cosmology as a Model of Light Speed Cosmic Expansion—Implications for the Vacuum Energy Density
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作者 Eugene Terry Tatum U. V. S. Seshavatharam 《Journal of Modern Physics》 2018年第10期2008-2020,共13页
Cosmologists have long ignored a stipulation by quantum field theorists that the vacuum pressure p corresponding to the zero-state vacuum energy must always be equal in magnitude to the vacuum energy density &rho;... Cosmologists have long ignored a stipulation by quantum field theorists that the vacuum pressure p corresponding to the zero-state vacuum energy must always be equal in magnitude to the vacuum energy density &rho;(i.e., p=&rho;). Although general relativity stipulates the additional condition of proportionality between the vacuum gravitational field and (&rho;+3p), the equation of state for the cosmic vacuum must fulfill both relativistic and quantum stipulations. This paper fully integrates Flat Space Cosmology (FSC) into the Friedmann equations containing a cosmological term, with interesting implications for the nature of dark energy, cosmic entropy and the entropic arrow of time. The FSC vacuum energy density is shown to be equal to the cosmic fluid bulk modulus at all times, thus meeting the quantum theory stipulation of (p=&rho;). To date, FSC is the only viable dark energy cosmological model which has fully-integrated general relativity and quantum features. 展开更多
关键词 cosmology theory General RELATIVITY Dark Energy COSMIC Flatness COSMIC Entropy Entropic ARROW of Time COSMIC Inflation MILNE universe Black Holes cosmologICAL Constant Problem
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Temperature Scaling in Flat Space Cosmology in Comparison to Standard Cosmology
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作者 Eugene Terry Tatum U. V. S. Seshavatharam 《Journal of Modern Physics》 2018年第7期1404-1414,共11页
Flat Space Cosmology (FSC) is a mathematical model of universal expansion which has proven to be remarkably accurate in comparison to observations. Temperature scaling is redefined in this paper in terms of a new “Un... Flat Space Cosmology (FSC) is a mathematical model of universal expansion which has proven to be remarkably accurate in comparison to observations. Temperature scaling is redefined in this paper in terms of a new “Universal Temperature” Tu scale according to Tu = T 2, where T 2 is in K2. This rescaling puts FSC cosmic temperature, time, total matter mass, and Hubble radius on the same scale, covering roughly 60.63 logs of 10 from the Planck scale to the present scale. This paper focuses on the relatively subtle temperature curve differences between the FSC model and standard cosmology. These changes become more pronounced in the early universe. Recent observational studies of the early universe, particularly with respect to the “cosmic dawn” epoch, the first stars and first galaxies, have surprised standard model proponents as to how soon these events have occurred following the Big Bang. This paper suggests that, because the FSC model temperature/time curve is lower at each stage of cosmic time, FSC may actually be a better fit for the timing of these events. 展开更多
关键词 cosmology theory General RELATIVITY CMB TEMPERATURE COSMIC FLATNESS Black Holes universal TEMPERATURE
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A class of transient acceleration models consistent with Big Bang cosmology
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作者 Tian-Long Zu Jie-Wen Chen Yang Zhang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2014年第2期129-138,共10页
Is it possible that the current cosmic accelerating expansion will turn into a decelerating one? Can this transition be realized by some viable theoretical model that is consistent with the standard Big Bang cosmolog... Is it possible that the current cosmic accelerating expansion will turn into a decelerating one? Can this transition be realized by some viable theoretical model that is consistent with the standard Big Bang cosmology? We study a class of phenomeno- logical models with a transient acceleration, based on a dynamical dark energy with a very general form of equation of state Pde = αPde -- βpdem. It mimics the cosmolog- ical constant αde → const for a small scale factor a, and behaves as a barotropic gas with pde → α-3(α+1) with α 〉 0 for large a. The cosmic evolution of four models in the class has been examined in detail, and all yield a smooth transient acceleration. Depending on the specific model, the future universe may be dominated by either dark energy or by matter. In two models, the dynamical dark energy can be explicitly real- ized by a scalar field with an analytical potential V(O). Moreover, a statistical analysis shows that the models can be as robust as ACDM in confronting the observational data of Type Ia supernovae, cosmic microwave background (CMB) and baryon acoustic os- cillation. As improvements over previous studies, our models overcome the problem of over-abundance of dark energy during early eras, and satisfy the constraints on dark energy from WMAP observations of CMB. 展开更多
关键词 cosmology theory -- methods: analytical
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Predicting Dark Energy Survey Results Using the Flat Space Cosmology Model
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作者 Eugene Terry Tatum U.V.S.Seshavatharam 《Journal of Modern Physics》 2019年第9期1083-1089,共7页
The Flat Space Cosmology (FSC) model is utilized to show how this model predicts the value of the Hubble parameter at each epoch of cosmic expansion. Specific attention in this paper is given to correlating the observ... The Flat Space Cosmology (FSC) model is utilized to show how this model predicts the value of the Hubble parameter at each epoch of cosmic expansion. Specific attention in this paper is given to correlating the observable galactic redshifts since the beginning of the “cosmic dawn” reionization epoch. A graph of the log of the Hubble parameter as a function of redshift z is presented as the FSC prediction of the pending Dark Energy Survey results. In the process, it is discovered that the obvious tension between the SHOES local Hubble constant value and the 2018 Planck Survey and the 2018 Dark Energy Survey global Hubble constant values may be explained by a time-variable, scalar, Hubble parameter acting in accordance with the FSC model. 展开更多
关键词 Flat Space cosmology Dark Energy Hubble Parameter SHOES Hubble Constant ΛCDM Concordance Model cosmology theory early universe
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Alternative kind of hydrogen atoms as a possible explanation for the latest puzzling observation of the 21 cm radio line from the early Universe 被引量:1
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作者 Eugene Oks 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2020年第7期172-176,共5页
There is a puzzling astrophysical result concerning the latest observation of the absorption profile of the redshifted radio line 21 cm from the early Universe(as described in Bowman et al.). The amplitude of the prof... There is a puzzling astrophysical result concerning the latest observation of the absorption profile of the redshifted radio line 21 cm from the early Universe(as described in Bowman et al.). The amplitude of the profile was more than a factor of two greater than the largest predictions. This could mean that the primordial hydrogen gas was much cooler than expected. Some explanations in the literature suggested a possible cooling of baryons either by unspecified dark matter particles or by some exotic dark matter particles with a charge a million times smaller than the electron charge. Other explanations required an additional radio background. In the present paper, we entertain a possible different explanation for the above puzzling observational result: the explanation is based on the alternative kind of hydrogen atoms(AKHA),whose existence was previously demonstrated theoretically, as well as by the analysis of atomic experiments. Namely, the AKHA are expected to decouple from the cosmic microwave background(CMB) much earlier(in the course of the Universe expansion) than usual hydrogen atoms, so that the AKHA temperature is significantly lower than that of usual hydrogen atoms. This seems to lower the excitation(spin) temperature of the hyperfine doublet(responsible for the 21 cm line) sufficiently enough for explaining the above puzzling observational result. This possible explanation appears to be more specific and natural than the previous possible explanations. Further observational studies of the redshifted 21 cm radio line from the early Universe could help to verify which explanation is the most relevant. 展开更多
关键词 cosmology:early universe explanation of the puzzle of 21cm radio line Galaxies:intergalactic medium cosmology:observations cosmology:theory
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A Theory of Our Universe 被引量:2
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作者 Robert M. L. Baker Jr. 《Journal of High Energy Physics, Gravitation and Cosmology》 2020年第4期609-622,共14页
Contemporary theories of our Universe, such as the Friedmann-Lema<span style="white-space:nowrap;">&icirc;</span>tre-Robertson-Walker (FLRW) model of the cosmos, assume that time marches on a... Contemporary theories of our Universe, such as the Friedmann-Lema<span style="white-space:nowrap;">&icirc;</span>tre-Robertson-Walker (FLRW) model of the cosmos, assume that time marches on at a uniform, constant pace from its very beginning. But what if that is not the case? It is proposed that our Universe is not a “Big Bang”, but rather a “Big Rollout” in space and time, spacetime, from the shortest meaningful length, Planck Length, and the shortest meaningful measure of time, Planck Time. It is speculated that time and dimensions, spacetime, grow in concert very rapidly at first. The fundamental equation, which relates the change in the space dimensions to the change in the speed of time at the beginning of time for the new Theory, is derived. Spacetime rolls out initially at light speed. As time increases, the rate of change of the speed of time could be erratic, that is although in general, it slows (rate of time slows approaching zero at the end of time), its rate of change could decelerate, pause or perhaps accelerate for a while, no need however, for dark matter or dark energy. 展开更多
关键词 cosmology theory early universe Dark Matter High-Frequency Relic Gravitational Waves
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An Alternative to Dark Matter? Part 1: The Early Universe (<i>t<sub>p</sub></i>to 10<sup>-9</sup>s), Energy Creation the Alphaton, Baryogenesis 被引量:2
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作者 Jean Perron 《Journal of High Energy Physics, Gravitation and Cosmology》 2021年第3期784-807,共24页
A cosmological model was developed using the equation of state of photon gas, as well as cosmic time. The primary objective of this model is to see if determining the observed rotation speed of galactic matter is poss... A cosmological model was developed using the equation of state of photon gas, as well as cosmic time. The primary objective of this model is to see if determining the observed rotation speed of galactic matter is possible, without using dark matter (halo) as a parameter. To do so, a numerical application of the evolution of variables in accordance with cosmic time and a new state equation was developed to determine precise, realistic values for a number of cosmological parameters, such as the energy of the universe <i>U</i>, cosmological constant Λ, the curvature of space <i>k</i>, energy density <i>ρ</i><sub>Λe</sub>, age of the universe <i>t</i><sub>Ω</sub> etc. The development of the state equation highlights the importance of not neglecting any of the differential terms given the very large amounts in play that can counterbalance the infinitesimals. Some assumptions were put forth in order to solve these equations. The current version of the model partially explains several of the observed phenomena that raise questions. Numerical application of the model has yielded the following results, among others: Initially, during the Planck era, at the very beginning of Planck time, <i>t<sub>p</sub></i>, the universe contained a single photon at Planck temperature <i>T<sub>P</sub></i>, almost Planck energy <i>E<sub>P</sub></i> in the Planck volume. During the photon inflation phase (before characteristic time ~10<sup>-9</sup> [s]), the number of original photons (alphatons) increased at each unit of Planck time <i>t<sub>p</sub></i> and geometrical progression~<i>n</i><sup>3</sup>, where n is the quotient of cosmic time over Planck time <i>t</i>/<i>t<sub>p</sub></i>. Then, the primordial number of photons reached a maximum of <i>N</i>~10<sup>89</sup>, where it remained constant. These primordial photons (alphatons) are still present today and represent the essential of the energy contained in the universe via the cosmological constant expressed in the form of energy <i>E</i><sub>Λ</sub>. Such geometric growth in the number of photons can bring a solution to the horizon problem through <i>γγ</i> exchange and a photon energy volume that is in phase with that of the volume energy of the universe. The predicted total mass (p, n, e, and <i>ν</i>), based on the Maxwell-Juttner relativistic statistical distribution, is ~7 × 10<sup>50</sup> [kg]. The predicted cosmic neutrino mass is ≤8.69 × 10<sup>-32</sup> [kg] (≤48.7 [keV·<i>c</i><sup>-2</sup>]) if based on observations of SN1987A. The temperature variation of the cosmic microwave background (CMB), as measured by Planck, can be said to be partially due to energy variations in the universe (Δ<i>U</i>/<i>U</i>) during the primordial baryon synthesis (energy jump from the creation of protons and neutrons). 展开更多
关键词 cosmological Parameters Numerical Values cosmology early universe
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String cosmological models in the Brans-Dicke theory for five-dimensional space-time
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作者 Koijam Manihar Singh Kangujam Priyokumar Singh 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第1期39-45,共7页
Five-dimensional space-time string cosmological models generated by a cloud of strings with particles attached to them are studied in the Brans-Dicke theory. We obtain two types of interesting models by taking up the ... Five-dimensional space-time string cosmological models generated by a cloud of strings with particles attached to them are studied in the Brans-Dicke theory. We obtain two types of interesting models by taking up the cases of geometric strings (or Nambu strings) and p-strings (Takabayasi strings), and study their different physi- cal and dynamical properties. The roles of the scalar field in getting different phases, such as the inflationary phase and the string-dominated phase, are discussed. An in- teresting feature obtained here is that in one of the models there is a "bounce" at a particular instant of its evolution. 展开更多
关键词 cosmology theory -- string universes -- Brans-Dicke theory
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The Reversible Cyclic Universe in the Reversible Multiverse and the Reversible String Theory
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作者 Ding-Yu Chung 《Journal of Modern Physics》 2015年第9期1249-1260,共12页
The paper posits that the multiverse is reversible, so all universes in the multiverse are reversible cyclic universes which have the inexhaustible resources of space-time to expand. The collision of expanding univers... The paper posits that the multiverse is reversible, so all universes in the multiverse are reversible cyclic universes which have the inexhaustible resources of space-time to expand. The collision of expanding universes is permanently irreversible, forbidden in the reversible multiverse, so every universe is surrounded by the zero-energy interuniversal void as the permanent gap among universes to keep universes apart. A zero-sum energy dual universe of positive energy universe and negative energy universe can be created in the interuniversal void, and the new dual universe is again surrounded by the interuniversal void. This paper also posits the reversible string theory with oscillating space-time dimension number oscillating between 11D (space-time dimension) and 4D without the conventional compactization of string. Dimension number decreases with decreasing speed of light, decreasing vacuum energy, and increasing rest mass. The 4D and the 11D have zero and the highest vacuum energies, respectively. The universes in the reversible multiverse oscillate reversibly between high and low dimension numbers. Under symmetry breaking as in our universe, the positive energy universe as our observed universe absorbed the interuniversal void, while the negative energy universe did not. The interuniversal void has zero vacuum energy, so the absorption of the interuniversal void by the positive energy universe forced the positive energy 10D universe with high vacuum energy to be transformed into the positive energy 4D universe with zero vacuum energy, resulting in the inflation followed by the Big Bang. The negative energy universe undergoes dimension number oscillation between 4D and 10D dimension by dimension. The negative energy >4D universe is hidden, and the negative energy 4D universe appears as dark energy. The calculated percentages of dark energy, dark matter, and baryonic matter and the calculated time for dark energy to start are in good agreements with the observed values. 展开更多
关键词 CYCLIC universe MULTIVERSE Interuniversal Void String theory cosmology Big Bang INFLATION DARK Energy DARK Matter
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Cosmological perturbations in a noncommutative braneworld inflation
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作者 Kourosh Nozari Siamak Akhshabi 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第6期625-635,共11页
We use the smeared, coherent state picture of noncommutativity to study evolution of perturbations in a noncommutative braneworld scenario. Within the stan- dard procedure of studying braneworld cosmological perturbat... We use the smeared, coherent state picture of noncommutativity to study evolution of perturbations in a noncommutative braneworld scenario. Within the stan- dard procedure of studying braneworld cosmological perturbations, we study the evo- lution of the Bardeen metric potential and curvature perturbations in this model. We show that in this setup, the early stage of the universe's evolution has a transient phan- tom evolution with imaginary effective sound speed. 展开更多
关键词 early universe cosmology -- cosmology theory
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PhotoNs-GPU:A GPU accelerated cosmological simulation code 被引量:2
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作者 Qiao Wang Chen Meng 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第11期98-104,共7页
We present a GPU-accelerated cosmological simulation code,PhotoNs-GPU,based on an algorithm of Particle Mesh Fast Multipole Method(PM-FMM),and focus on the GPU utilization and optimization.A proper interpolated method... We present a GPU-accelerated cosmological simulation code,PhotoNs-GPU,based on an algorithm of Particle Mesh Fast Multipole Method(PM-FMM),and focus on the GPU utilization and optimization.A proper interpolated method for truncated gravity is introduced to speed up the special functions in kernels.We verify the GPU code in mixed precision and different levels of the interpolated method on GPU.A run with single precision is roughly two times faster than double precision for current practical cosmological simulations.But it could induce an unbiased small noise in power spectrum.Compared with the CPU version of PhotoNs and Gadget-2,the efficiency of the new code is significantly improved.Activated all the optimizations on the memory access,kernel functions and concurrency management,the peak performance of our test runs achieves 48%of the theoretical speed and the average performance approaches to~35%on GPU. 展开更多
关键词 methods:numerical cosmology:theory large-scale structure of universe
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A hybrid Fast Multipole Method for cosmological N-body simulations 被引量:2
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作者 Qiao Wang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第1期25-32,共8页
We investigate a hybrid numerical algorithm aimed at large-scale cosmological N-body simulation for on-going and future high precision sky surveys.It makes use of a truncated Fast Multiple Method(FMM)for short-range g... We investigate a hybrid numerical algorithm aimed at large-scale cosmological N-body simulation for on-going and future high precision sky surveys.It makes use of a truncated Fast Multiple Method(FMM)for short-range gravity,incorporating a Particle Mesh(PM)method for long-range potential,which is applied to deal with extremely large particle number.In this work,we present a specific strategy to modify a conventional FMM by a Gaussian shaped factor and provide quantitative expressions for the interaction kernels between multipole expansions.Moreover,a proper Multipole Acceptance Criterion for the hybrid method is introduced to solve potential precision loss induced by the truncation.Such procedures reduce the amount of computation compared to an original FMM and decouple the global communication.A simplified version of code is introduced to verify the hybrid algorithm,accuracy and parallel implementation. 展开更多
关键词 methods:numerical cosmology:theory large-scale structure of universe
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Cosmological neutrino simulations at extreme scale
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作者 J.D.Emberson Hao-Ran Yu +8 位作者 Derek Inman Tong-Jie Zhang Ue-Li Pen Joachim Harnois-Deraps Shuo Yuan Huan-Yu Teng Hong-Ming Zhu Xuelei Chen Zhi-Zhong Xing 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2017年第8期89-100,共12页
Constraining neutrino mass remains an elusive challenge in modern physics.Precision measurements are expected from several upcoming cosmological probes of large-scale structure.Achieving this goal relies on an equal l... Constraining neutrino mass remains an elusive challenge in modern physics.Precision measurements are expected from several upcoming cosmological probes of large-scale structure.Achieving this goal relies on an equal level of precision from theoretical predictions of neutrino clustering.Numerical simulations of the non-linear evolution of cold dark matter and neutrinos play a pivotal role in this process.We incorporate neutrinos into the cosmological N-body code CUBEP3M and discuss the challenges associated with pushing to the extreme scales demanded by the neutrino problem.We highlight code optimizations made to exploit modern high performance computing architectures and present a novel method of data compression that reduces the phase-space particle footprint from 24 bytes in single precision to roughly 9 bytes.We scale the neutrino problem to the Tianhe-2 supercomputer and provide details of our production run,named Tian Nu,which uses 86%of the machine(13 824 compute nodes).With a total of 2.97 trillion particles,Tian Nu is currently the world’s largest cosmological N-body simulation and improves upon previous neutrino simulations by two orders of magnitude in scale.We finish with a discussion of the unanticipated computational challenges that were encountered during the Tian Nu runtime. 展开更多
关键词 cosmology theory—large-scale structure of universe—methods NUMERICAL
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