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1.
Recently, a tachyonic field was presented as a dark energy model to represent the present acceleration of the Universe. In this paper, we consider a mixture of tachyonic fluid with a perfect fluid. For this purpose we consider barotropic fluid and Generalized Chaplygin gas (GCG). We present a particular form of the scale factor. We solve the equations of motion to get exact solutions of the density, tachyonic potential and the tachyonic field. We introduce a coupling term to show that the interaction decays with time. We also show that the nature of the potentials vary, so the interaction term reduces the potential in both cases. 相似文献
2.
Surajit Chattopadhyay Ujjal Debnath Goutami Chattopadhyay 《Astrophysics and Space Science》2008,314(1-3):41-44
In this letter, we have assumed that the Universe is filled in tachyonic field with potential, which gives the acceleration
of the Universe. For certain choice of potential, we have found the exact solutions of the field equations. We have shown
the decaying nature of potential. From recently developed statefinder parameters, we have investigated the role of tachyonic
field in different stages of the evolution of the Universe. 相似文献
3.
Tachyonic scalar field-driven late universe with dust matter content is considered. The cosmic expansion is modeled with power-law and phantom power-law expansion at late time, i.e. z?0.45. WMAP7 and its combined data are used to constraint the model. The forms of potential and the field solution are different for quintessence and tachyonic cases. Power-law cosmology model (driven by either quintessence or tachyonic field) predicts unmatched equation of state parameter to the observational value, hence the power-law model is excluded for both quintessence and tachyonic field. In the opposite, the phantom power-law model predicts agreeing valued of equation of state parameter with the observational data for both quintessence and tachyonic cases, i.e. $w_{\phi, 0} = -1.49^{+11.64}_{-4.08}$ (WMAP7+BAO+H 0) and $w_{\phi, 0} = -1.51^{+3.89}_{-6.72} $ (WMAP7). The phantom-power law exponent β must be less than about ?6, so that the ?2<w ?,0<?1. The phantom power-law tachyonic potential is reconstructed. We found that dimensionless potential slope variable Γ at present is about 1.5. The tachyonic potential reduced to V=V 0 ? ?2 in the limit Ω m,0→0. 相似文献
4.
We consider a spatially homogeneous and isotropic flat Robertson-Walker model filled with a scalar (or tachyonic) field minimally
coupled to gravity in the framework of higher derivative theory. We discuss the possibility of the emergent universe with
normal and phantom scalar fields (or normal and phantom tachynoic fields) in higher derivative theory. We find the exact solution
of field equations in normal and phantom scalar fields and observe that the emergent universe is not possible in normal scalar
field as the kinetic term is negative. However, the emergent universe exists in phantom scalar field in which the model has
no time-like singularity at infinite past. The model evolves into an inflationary stage and finally admits an accelerating
phase at late time. The equation of state parameter is found to be less than −1 in early time and tends to −1 in late time
of the evolution. The scalar potential increases from zero at infinite past to a flat potential in late time. More precisely,
we discuss the particular case for phantom field in detail. We also carry out a similar analysis in case of normal and phantom
tachyonic field and observe that only phantom tachyonic field solution represents an emergent universe. We find that the coupling
parameter of higher order correction affects the evolution of the emergent universe. The stability of solutions and their
physical behaviors are discussed in detail. 相似文献
5.
We discuss the expansion of the universe in the FRLW model assuming that the source of dark energy is either tachyonic scalar field or quintessence. The tachyonic scalar field with exponential and power-law potential (function of homogeneous scalar field ?) both gives exponential expansion of the universe. It is found that this behaviour is not distinguishable from the quintessence with respect to these potentials. 相似文献
6.
《天文和天体物理学研究(英文版)》2016,(10)
Type Ia supernovae(SNe Ia) play an important role in studies of cosmology and galactic chemical evolution.They are believed to be thermonuclear explosions of carbon-oxygen white dwarfs(CO WDs)when their masses approach the Chandrasekar(Ch) mass limit.However,it is still not completely understood how a CO WD increases its mass to the Ch-mass limit in the classical single-degenerate(SD) model.In this paper,we studied the mass accretion process in the SD model to examine whether the WD can explode as an SN Ia.Employing the stellar evolution code called modules for experiments in stellar astrophysics(MESA),we simulated the He accretion process onto CO WDs.We found that the WD can increase its mass to the Ch-mass limit through the SD model and explosive carbon ignition finally occurs in its center,which will lead to an SN Ia explosion.Our results imply that SNe Ia can be produced from the SD model through steady helium accretion.Moreover,this work can provide initial input parameters for explosion models of SNe Ia. 相似文献
7.
Type Ia supernovae (SNe Ia) play an important role in astrophysics and are crucial for the studies of stellar evolution, galaxy evolution and cosmology. They are generally thought to be thermonuclear explosions of accreting carbon–oxygen white dwarfs (CO WDs) in close binaries, however, the nature of the mass donor star is still unclear. In this article, we review various progenitor models proposed in the past years and summarize many observational results that can be used to put constraints on the nature of their progenitors. We also discuss the origin of SN Ia diversity and the impacts of SN Ia progenitors on some fields. The currently favourable progenitor model is the single-degenerate (SD) model, in which the WD accretes material from a non-degenerate companion star. This model may explain the similarities of most SNe Ia. It has long been argued that the double-degenerate (DD) model, which involves the merger of two CO WDs, may lead to an accretion-induced collapse rather than a thermonuclear explosion. However, recent observations of a few SNe Ia seem to support the DD model, and this model can produce normal SN Ia explosion under certain conditions. Additionally, the sub-luminous SNe Ia may be explained by the sub-Chandrasekhar mass model. At present, it seems likely that more than one progenitor model, including some variants of the SD and DD models, may be required to explain the observed diversity of SNe Ia. 相似文献
8.
Surajit Chattopadhyay 《Astrophysics and Space Science》2011,331(2):651-655
In this letter we considered an interaction between Ricci dark energy and tachyonic field. We investigated the equation of
state parameters in presence of the interaction and revealed a quintessence like behavior. Also, we investigated the validity
of the generalized second law of thermodynamics in presence of this interaction and observed that it is broken down under
this interaction. 相似文献
9.
Supernova rates (hypernova, type II, type Ib/c and type Ia) in a particular galaxy depend on the metallicity (i.e. on the galaxy age), on the physics of star formation and on the binary population. In order to study the time evolution of the galactic supernova rates, we use our chemical evolutionary model that accounts in detail for the evolution of single stars and binaries. In particular, supernovae of type Ia are considered to arise from exploding white dwarfs in interacting binaries and we adopt the two most plausible physical models: the single degenerate model and the double degenerate model. Comparison between theoretical prediction and observations of supernova rates in different types of galaxies allows to put constraints on the population of intermediate mass and massive close binaries.
The temporal evolution of the absolute galactic rates of different types of supernovae (including the type Ia rate) is presented in such a way that the results can be directly implemented into a galactic chemical evolutionary model. Particularly for type Ia’s the inclusion of binary evolution leads to results considerably different from those in earlier population synthesis approaches, in which binary evolution was not included in detail. 相似文献
10.
Bo Wang 《天文和天体物理学研究(英文版)》2018,(5)
Type Ia supernovae(SNe Ia) play a prominent role in understanding the evolution of the Universe. They are thought to be thermonuclear explosions of mass-accreting carbon-oxygen white dwarfs(CO WDs) in binaries, although the mass donors of the accreting WDs are still not well determined. In this article, I review recent studies on mass-accreting WDs, including H-and He-accreting WDs. I also review currently most studied progenitor models of SNe Ia, i.e., the single-degenerate model(including the WD+MS channel, the WD+RG channel and the WD+He star channel), the doubledegenerate model(including the violent merger scenario) and the sub-Chandrasekhar mass model.Recent progress on these progenitor models is discussed, including the initial parameter space for producing SNe Ia, the binary evolutionary paths to SNe Ia, the progenitor candidates for SNe Ia, the possible surviving companion stars of SNe Ia, some observational constraints, etc. Some other potential progenitor models of SNe Ia are also summarized, including the hybrid CONe WD model, the core-degenerate model, the double WD collision model, the spin-up/spin-down model and the model of WDs near black holes. To date, it seems that two or more progenitor models are needed to explain the observed diversity among SNe Ia. 相似文献
11.
In this work, we have considered different candidates of dark energy such as tachyonic field, DBI-essence, hessence, k-essence and dilaton dark energy in the framework of f-essence cosmology and investigated the consequences for their co-existence. Also we have reconstructed the potential functions and the scalar fields in this scenario. The potential function can be directly obtained in terms of fermionic kinetic term and fermionic Lagrangian density. 相似文献
12.
《天文和天体物理学研究(英文版)》2020,(1)
Type Ia supernovae(SNe Ia) are thermonuclear explosions of carbon-oxygen white dwarfs(CO WDs), and are believed to be excellent cosmological distance indicators due to their high luminosity and remarkable uniformity. However, there exists a diversity among SNe Ia, and a poor understanding of the diversity hampers the improvement of the accuracy of cosmological distance measurements. The variations of the ratios of carbon to oxygen(C/O) of WDs at explosion are suggested to contribute to the diversity. In the canonical model of SNe Ia, a CO WD accretes matter from its companion and increases its mass till the Chandrasekhar mass limit when the WD explodes. In this work, we studied the C/O ratio for accreting CO WDs. Employing the stellar evolution code MESA, we simulated the accretion of He-rich material onto CO WDs with different initial WD masses and different mass accretion rates. We found that the C/O ratio varies for different cases. The C/O ratio of He-accreting CO WDs at explosion increases with a decreasing initial WD mass or a decreasing accretion rate. The various C/O ratios may, therefore, contribute to the diversity of SNe Ia. 相似文献
13.
Ia型超新星爆发理论（I）：主要观测特征及其爆发机理 总被引：2，自引：2，他引：0
从光谱特性、光变曲线、爆发能量、在星系内分布特征等诸方面,简要介绍了I_a型超新星（SNI_a）的主要观测特征．并根据近年来人们提出的改进标准模型阐述了SNI_a爆发的物理原因和物理过程以及核合成特征． 相似文献
14.
Guoliang Lü Chunhua Zhu Zhaojun Wang Na Wang 《Monthly notices of the Royal Astronomical Society》2009,396(2):1086-1095
By assuming an aspherical stellar wind with an equatorial disc from a red giant, we investigate the production of Type Ia supernovae (SNe Ia) via a symbiotic channel. We estimate that the Galactic birthrate of SNe Ia via the symbiotic channel is between 1.03 × 10−3 and 2.27 × 10−5 yr−1 , while the delay time of SNe Ia has a wide range from ∼0.07 to 5 Gyr. The results are greatly affected by the outflow velocity and mass-loss rate of the equatorial disc. Using our model, we discuss the progenitors of SN 2002ic and SN 2006X. 相似文献
15.
The universe with adiabatic matter creation is considered. It is thought that the negative pressure caused by matter creation
can play the role of a dark energy component, and drive the accelerating expansion of the universe. Using the Type Ia supernovae
(SNe Ia) data, the observational Hubble parameter data, the Cosmic Microwave Background (CMB) data and the Baryonic Acoustic
Oscillation (BAO) data, we make constraints on the cosmological parameters, assuming a spatially flat universe. Our results
show that the model with matter creation is consistent with the SNe Ia data, while the joint constraints of all these observational
data disfavor this model. If the cosmological constant is taken into account, a traditional model without matter creation
is favored by the joint observations. 相似文献
16.
Roman Tomaschitz 《Celestial Mechanics and Dynamical Astronomy》2000,77(2):107-126
The causality of superluminal signal transfer in the galaxy background is scrutinized. The cosmic time of the comoving galaxy
frame determines a distinguished time order for events connected by superluminal signals. Every observer can relate his rest
frame to the galaxy frame, and compare so the time order of events in his proper time to the cosmic time order. In this way
all observers arrive at identical conclusions on the causality of events connected by superluminal signals. The energy of
tachyons (superluminal particles) is defined in the comoving galaxy frame analogous to the energy of subluminal particles.
It is positive in the galaxy frame and bounded from below in the rest frames of geodesically moving observers, so that particle-tachyon
interactions can be based on energy-momentum conservation. We study tachyons in a Robertson-Walker cosmology with linear expansion
factor and open, negatively curved 3-space (Milne universe). This cosmology admits globally geodesic rest frames for uniformly
moving observers, synchronized by Lorentz boosts. In this context we show that no signals can be sent into the past of observers.
If an observer emits a tachyonic signal, then the response of a second observer can never reach him prior to the emission,
i.e., no predetermination can occur. The proof is based on the positivity of tachyonic energy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
We consider the BSBM(Bekenstein, Sandvik, Barrow and Magueijo) cosmological model in the presence of tachyon potential with the aim of studying the stability of the model and test it against observations. The phase space analysis shows that from fourteen critical points that represent the state of the universe, only one is stable.With a small perturbation, the universe transits from a state of unstable deceleration to stable acceleration. The stability analysis combined with the best fitting process imposes constraints on the cosmological parameters that are in agreement with observation. In the BSBM theory, the variation of fundamental constants is driven from variation of a scalar field. The tachyonic scalar field, responsible for both variation of fundamental constants and universal acceleration, is reconstructed. 相似文献
18.
Supernova 2002ic was an atypical Type Ia supernova (SN Ia) with evidence for substantial amounts of hydrogen associated with the system. Contrary to previous claims, we show that its unusual properties can be understood within the framework of one of the most favoured progenitor models, the so-called supersoft channel. This requires that the donor star was initially relatively massive (∼3 M⊙ ) and that the system experienced a delayed dynamical instability, leading to a large amount of mass-loss from the system in the last few 104 yr before the explosion. This can produce the inferred hydrogen-rich circumstellar environment, most likely with a disc-like geometry. However, in order for this model to be feasible, it requires a larger accretion efficiency on to the white dwarf than is assumed in present parametrizations. If this is confirmed, it would most likely increase estimates for the frequency of the single-degenerate channel. Based on population synthesis simulations we estimate that not more than 1 in 100 SNe Ia should belong to this subgroup of SNe Ia. 相似文献
19.
The single-degenerate (SD) channel for the progenitors of type Ia supernovae (SNe Ia) is one of the most popular channels, in which a carbon–oxygen white dwarf (CO WD) accretes hydrogen-rich material from its companion, increases its mass to the Chandrasekhar mass limit, and then explodes as a SN Ia. We show the initial and final parameter space for SNe Ia in a ( $\log P^{\mathrm{i}},M_{2}^{\mathrm{i}}$ ) plane and find that the positions of some famous recurrent novae, as well as a supersoft X-ray source (SSS), RX J0513.9-6951, are well explained by our model. The model can also explain the space velocity and mass of Tycho G, which is now suggested to be the companion star of Tycho’s supernova. Our study indicates that the SSS, V Sge, might be the potential progenitor of supernovae like SN 2002ic if the delayed dynamical-instability model due to Han and Podsiadlowski (Mon. Not. R. Astron. Soc. 368:1095, 2006) is appropriate. Following the work of Meng et al. (Mon. Not. R. Astron. Soc. 395:2103, 2009a), we found that the SD model (WD+MS) with an optically thick wind can explain the birth rate of supernovae like SN 2006X and reproduce the distribution of the color excess of SNe Ia. The model also predicts that at least 75% of all SNe Ia may show a polarization signal in their spectra. 相似文献
20.
Teleparallel gravity is an equivalent formulation of general relativity in which instead of the Ricci scalar R, one uses the torsion scalar T for the Lagrangian density. Recently teleparallel dark energy has been proposed by Geng et al. (in Phys. Lett. B 704, 384, 2011). They have added quintessence scalar field, allowing also a non-minimal coupling with gravity in the Lagrangian of teleparallel gravity and found that such a non-minimally coupled quintessence theory has a richer structure than the same one in the frame work of general relativity. In the present work we are interested in tachyonic teleparallel dark energy in which scalar field is responsible for dark energy in the frame work of torsion gravity. We find that such a non-minimally coupled tachyon gravity can realize the crossing of the phantom divide line for the effective equation of state. Using the numerical calculations we display such a behavior of the model explicitly. 相似文献