A possible resolution of tension between Planck and Type Ia supernova observations

There is an apparent tension between cosmological parameters obtained from Planck cosmic microwave background radiation observations and that derived from the observed magnitude-redshift relation for the type Ia supernova(SNe Ia).Here,we show that the tension can be alleviated,if we first calibrate,with the help of the distance-duality relation,the light-curve fitting parameters in the distance estimation in SNe Ia observations with the angular diameter distance data of the galaxy clusters and then re-estimate the distances for the SNe Ia with the corrected fitting parameters.This was used to explore their cosmological implications in the context of the spatially flat cosmology.We find a higher value for the matter density parameter,m,as compared to that from the original SNLS3,which is in agreement with Planck observations at 68.3%confidence.Therefore,the tension between Planck measurements and SNe Ia observations regarding m can be efectively alleviated without invoking new physics or resorting to extensions for the standard concordance model.Moreover,with the absolute magnitude of a fiducial SNe Ia,M,determined first,we obtained a constraint on the Hubble constant with SNLS3 alone,which is also consistent with Planck.     

The initial and final state of SNe Ia from the single degenerate model

Although type Ia supernovae(SNe Ia) show their importance in many astrophysical fields,the nature of the progenitors of SNe Ia is still unclear.At present,the single degenerate(SD) model is presented to be a very likely progenitor model.Following the comprehensive SD model developed by Meng Yang(2010),we show the initial and final state of the progenitor systems of SNe Ia in an orbital period—the secondary mass(log Pi,M2i) plane.Our results may explain the location of some supersoft X-ray sources and recurrent novae in the(log Pi,M2i) plane,and be helpful to judge whether an SD system is the potential progenitor system of SNe Ia,as well as to simulate the interaction between SN ejecta and its companion.     

Progenitor-age dependence of type Ia supernova luminosity and its cosmological implication

<正>Empirically standardised peak luminosity of Type Ia supernovae(SNe Ia) as a standard candle has become one of the most powerful probes of the expansion history of the late universe. Although the existence of such a consistent peak luminosity could be interpreted as a consequence of the fixed critical Chandrasekhar mass at which a carbon-oxygen white dwarf explodes, there is growing evidence for a more complex environmental dependence to the SN Ia luminosity beyond the current understand...     

Testing the distance-duality relation with the baryon acoustic oscillations data and type Ia supernovae data

In this letter,the cosmic distance-duality relation has been constrained with a model-independent method by combining the baryon acoustic oscillation(BAO)data and the type Ia supernova(SNe Ia)data.The results show that this relation is consistent with the observational data in the 68.27%error range,except for the instance of Union 2.1 plus BAO with the statistic errors only,where the relation is consistent with the observations in the 95.45%error range.To study the result of the uncertainty of the Hubble constant on the investigation of this relation,we treat the dimensionless Hubble constant h as a free parameter and get that the observational data favors the relation in the 68.27%error range.And then h has been marginalized and the results support that this relation is favored by the observations in the 68.27%error range too.     

Toy Model for Eternal Expanding Universe Driven by Quintessence

Recent observations of microwave background and type Ia supernovae (SNe Ia) suggest a space-fiat and accelerated expansion Universe. On the other hand, observations of supernovae 1997ff reveal that the Universe has undergone a decelerating-acceleratingprocess. Combining these two classes of observations, wepresent an eternal expanding Universe toy model driven by quintessence. In this picture, the Universe undergoes an endless sequence of accelerating-decelerating cycles.     

T2K indication of relatively large θ13 and a natural perturbation to the democratic neutrino mixing pattern

The T2K Collaboration has recently reported a remarkable indication of the ν→ν oscillation which is consistent with a relatively large value of θ₁₃ in the three-flavor neutrino mixing scheme. We show that it is possible to account for such a result of θ₁₃ by introducing a natural perturbation to the democratic neutrino mixing pattern, without or with CP violation. A testable correlation between θ₁₃ and θ₂₃ is predicted in this ansatz. We also discuss the Wolfenstein-like parametrization of neutrino mixing, and comment on other possibilities of generating sufficiently large θ₁₃ at the electroweak scale.     

Quintessence Cosmology with a Coupled Real Scalar Field

In the light of the recent observations of type Ia supernovae (SNe Ia) suggesting an accelerating Universe,we show the possibility of a coupled real scalar field to be quintessence for the source of the accelerating Universe.We derive the main equations which govern the evolution of the Universe and rewrite them with the observable quantities.Finally we point out very briefly how future observations may determine the equation of state of quintessence.     

Influences of the bag constant on properties of hybrid stars

Influences of the bag constant on the properties of hybrid stars are investigated by using relativistic mean field theory and the MIT bag model to describe the hadron phase and quark phase in the interior of neutron stars, respectively. Our results indicate that the onset of hadron-quark phase transition is put off and the appearance of hyperon species is increased with the increase in bag constant. As a result, the hybrid star equation of state for a mixed phase range stiffens whereas that of the quark phase range softens, and the gravitational mass as well as the corresponding radius of hybrid stars are increased obviously. The gravitational mass of a hybrid star is increased from 1.42 M_⊙ (M_⊙ is solar mass) to 1.63 M_⊙ and the corresponding radius is changed from 9.1 km to 12.2 km when the bag constant (B^1/4) is increased from 170 MeV to 200 MeV. It is interesting to find that hybrid star equations of state become non-smooth when the TM2 parameter sets in the framework of relativistic mean field theory used to describe the hadronic matter, and consequently, the third family of compact stars appear in the mass-radius relations of hybrid stars in the narrow scope of the bag constant from 175 MeV to 180 MeV. These show that the choice of the bag constant in the MIT bag model has significant influence on the properties of hybrid stars.     

One-loop QCD contribution to the potential of QQ

Without the non-relativistic approximation in one-loop function, the dominating one-loop contribution to the quark-antiquark potential is studied numerically in terms of perturbative Quantum Chromo Dynamics (QCD). For Coulomb-like potential, the ratio of the one-loop correction to the tree diagram contribution is presented, whose absolute value is about 20%. Our result is consistent with the analysis that the one-loop contribution should be suppressed by a factor α_s/π to the leading order contribution. This work can deepen the comprehension of α_s in Cornel potential.     

A new parametric equation of state and quark stars

It is still a matter of debate to understand the equation of state of cold matter with supra-nuclear density in compact stars because of unknown non-perturbative strong interaction between quarks. Nevertheless, it is speculated from an astrophysical view point that quark clusters could form in cold quark matter due to strong coupling at realistic baryon densities. Although it is hard to calculate this conjectured matter from first principles, one can expect that the inter-cluster interaction will share some general features with the nucleon-nucleon interaction successfully depicted by various models. We adopt a two-Gaussian component soft-core potential with these general features and show that quark clusters can form stable simple cubic crystal structure if we assume that the wave function of quark clusters have a Gaussian form. With this parametrization, the Tolman-Oppenheimer-Volkoff equation is solved with reasonably constrained parameter space to give mass-radius relations of crystalline solid quark stars. With baryon number densities truncated at 2_n0 at surface and the range of the interaction fixed at 2 fm we can reproduce similar mass-radius relations to that obtained with bag model equations of state. The maximum mass ranges from 0.5M_⊙ to 3M_⊙. The recently measured high pulsar mass ( 2M_⊙) is then used to constrain the parameters of this simple interaction potential.     

Cosmological constraints from the joint analysis of clustering and lensing with the DESI Legacy Imaging Surveys

<正>The comparison between the amplitude of density fluctuations in matter today as inferred from the observations of the Cosmic Microwave background by the Planck collaboration [1] to that from the observations of the late Universe,is a stringent test of the concordance cosmological model. A joint analysis of the clustering of galaxies and their galaxygalaxy lensing signal is a unique way to constrain cosmological parameters. The tentative indication of a discrepancy,     

Spin Splitting in In0.53Ga0.47As/InP Heterostructures

Spin-orbit coupling in a gate-controlled In_0.53Ga_0.47As/InP quantum well isinvestigated in the presence of a large Zeeman effect. We develop a Fourier-transform fitting procedure to extract the zero-field spin-splitting Rashba parameter α. The bare g factor value is found to be of the order of 3 from magnetotransport measurements in tilted magnetic fields. It is found that both Zeeman splitting and Rashba splitting play important roles in determining the total spin splitting in In_0.53Ga_0.47As.     

Some Magnetized Bulk Viscous String Cosmological Models in Cylindrically Symmetric Inhomogeneous Universe with Variable ∧-Term

Some cylindrically symmetric inhomogeneous viscous fluid string cosmological models with magnetic field and cosmological term A varying with time are investigated. To get the deterministic solution, it has been assumed that the expansion （θ） in the model is proportional to the eigen value σ^11 of the shear tensor σ^ij. The value of cosmological constant for the model is found to be small and positive, which is supported by the results from recent supernovae Ia observations. The effect of bulk viscosity is to produce a change in perfect fluid and hence exhibits essential influence on the character of the solution. The physical and geometric properties of the models are also discussed in presence and absence of magnetic field.     

Rotational properties in even-even superheavy 254-258Rf nuclei based on total-Routhian-surface calculations

High-spin yrast structures of even-even superheavy nuclei ^254-258Rf are investigated by means of total-Routhian-surface approach in three-dimensional (β₂, γ, β₄) space. The behavior in the moments of inertia of ²⁵⁶Rf is well reproduced by our calculations, which is attributed to the j_15/2 neutron rotation-alignment. The competition between the rotationally aligned i_13/2 proton and j_15/2 neutron may occur to a large extent in ²⁵⁶Rf. High-spin predictions are also made for its neighboring isotopes ^254,258Rf, showing that the alignment of the j_15/2 neutron pair is more favored than that of the i_13/2 proton pair.     

Strange magnetic moments of octet baryons under SU (3) breaking

Magnetic moments of octet baryons are parameterized to all orders of the flavor SU(3) breaking with the irreducible tensor technique in order to extract the contribution of each flavor quark to the magnetic moments of the octet baryons. The not-yet measured magnetic moment of ∑⁰ is predicted to be 0.649μ_N. Our parameterized forms for the magnetic moments are explicitly flavor-dependent, and hence each flavor component of the magnetic moments can be evaluated directly via the flavor projection operator. It is found that the strange magnetic moment of the nucleon is suppressed due to the small isoscalar anomalous magnetic moment of the nucleon. In particular, the strange magnetic form factor of the nucleon turns out to be positive, G_N^s(0)=0.428μ_N, which is consistent with recent data.     

Remarks on Two-Dimensional Power Correction in Soft Wall Model

We present a direct derivation of the two-point correlation function of the vector current in the soft wall model by using the AdS/CFT dictionary. The resulting correlator is exactly the same as the one previously obtained from dispersion relation with the same spectral function as in this model. The coefficient C₂ of the two-dimensional power correction is found to be C₂=-c/2 with c the slope of the Regge trajectory, rather than C₂=-c/3 derived from the strategy of the first quantized string theory. Taking the slope of the ρ trajectory c≈0.9GeV² as input, we then obtain C₂≈-0.45GeV². The gluon condensate is found to be <α_sG²>≈pprox0.064GeV⁴, which is almost identical to the QCD sum rule estimation. By comparing these two equivalent derivation of the correlator of scalar glueball operator, we demonstrate that the two-dimensional correction cannot be eliminated by including the non-leading solution in the bulk-to-boundary propagator, as carried out by Colangelo et al.[arXiv:0711.4747]. In other words, the two-dimensional correction does exist in the scalar glueball case. Also it is manifest by using the dispersion relation that the minus sign of gluon condensate and violation of the low energy theorem are related to the subtraction scheme.     

Phase Transition in CCl4 under Pressure: a Raman Spectroscopic Study

High-pressure Raman studies at room temperature are performed on CCl₄ up to 13GPa. The Raman bands of the internal modes (v₂, v₄ and v₁) show entirely positive pressure dependence. The slopes dω/dP of the internal modes exhibit two sudden changes at 0.73GPa and 7.13GPa, respectively. A new lower frequency mode (225cm^-1) appears at 3.03GPa, and the splitting of v₂, ν₃ and v₄ occurs at about 7.13GPa. Moreover, Raman spectra of Fermiresonance show that the relative position of the v₁ + v₄ combination and the ν₃ fundamental firstly interchanges corresponding to that at ambient pressure, then the v₁ +v₄ combination disappears in the gradual process of compression. It is indicated that the pressure-induced phase transition from CCl₄ II to CCl₄ III occurs at 0.73GPa, and CCl₄ III undergoes a transition to CCl₄ IV below 3.03GPa. Further CCl₄ IV transforms in a new high-pressure phase at about 7.13GPa, and the symmetry of the new high-pressure phase is lower than that of CCl₄ IV. All the transitions are reversible during decompression.     

A new probe of neutron skin thickness

The correlation between neutron-to-proton yield ratio (R_np) and neutron skin thickness (δ_np) in neutron-rich projectile induced reactions is investigated within the framework of the Isospin-Dependent Quantum Molecular Dynamics (IQMD) model. The density distribution of the Droplet model is embedded in the initialization of the neutron and proton densities in the present IQMD model. By adjusting the diffuseness parameter of neutron density in the Droplet model for the projectile, the relationship between the neutron skin thickness and the corresponding R_np is obtained. The results show strong linear correlation between R_np and δ_np for neutron-rich Ca and Ni isotopes. It is suggested that R_np may be used as an experimental observable to extract δ_np for neutron-rich nuclei, which is very interesting in the study of the nuclear structure of exotic nuclei, the equation of state (EOS) of asymmetric nuclear matter and neutron-rich matter in astrophysics, etc.