Crossing w=1 in Gauss-Bonnet Brane World with Induced Gravity

Recent type Ia supernovas data seemingly favor a dark energy model whose equation of state w（z） crosses -1 very recently, which is a much more amazing problem than the acceleration of the universe. In this paper we show that it is possible to realize such a crossing without introducing any phantom component in a Gauss-Bonnet brane worm with induced gravity, where a four-dimensional curvature scalar on the brahe and a five-dimensional Gauss-Bonnet term in the bu/k are present. In this realization, the Gauss-Bonnet term and the mass parameter in the bulk play a crucial role.     

Abundance of Asymmetric Dark Matter in Brane World Cosmology

Relic abundance of asymmetric Dark Matter particles in brane world cosmological scenario is investigated in this article. Hubble expansion rate is enhanced in brane world cosmology and it affects the relic abundance of asymmetric Dark Matter particles. We analyze how the relic abundance of asymmetric Dark Matter is changed in this model. We show that in such kind of nonstandard cosmological scenario, indirect detection of asymmetric Dark Matter is possible if the cross section is small enough which let the anti-particle abundance kept in the same amount with the particle. We show the indirect detection signal constraints can be used to such model only when the cross section and the 5-dimensional Planck mass scale are in appropriate values.     

Coleman–de Luccia Instanton of the Second Order in a Brane World

The second order Coleman–de Luccia instanton and its action in the Randall–Sundrum type II model are investigated and the comparison with the results in Einstein’s general relativity is done in the present paper. PACS Numbers: 98.80.Cq.     

Holographic Dark Energy in Induced Gravity

Many astrophysics data show that our universe has a critical energy density, and 73% of it is dark energy, which drives the accelerating expansion of the universe. We consider the holographic dark energy in induced gravity by taking the Hubble scale, particle horizon and event horizon as the infrared cutoff. We find that only the event horizon can give accelerating expansion of our universe.     

Fluctuation with dust of de Sitter ground state of scalar-tensor gravity

An exact de Sitter solution of scalar-tensor gravity is found in our recent work, in which the non-minimal coupling scalar is rolling along a non-constant potential. Based on this solution, a dust-filled FRW universe is explored in frame of scalar-tensor gravity in this article. The effective dark energy induced by the sole non-minimal scalar can be quintessence-like, phantom-like, and more significantly, can cross the phantom divide. The rich and varied properties of scalar-tensor gravity even with only one scalar is shown.     

Spherical Gravitational Collapse in f(R) Gravity with Linear Equation of State

In a paper[Gen. Relativ. Gravit. 48 (2016) 57] Chakrabarti and Banerjee investigated perfect fluid collapse in f(R) gravity model and claimed that such a collapse is possible. In this paper we show that without the assumption of dark energy it is not possible that perfect fluid spherical gravitational collapse will occur. We have solved the field equations by assuming linear equation of state (p=ωμ) in metric f(R) gravity with ω=-1. It is shown that Chakrabarti and Banerjee reached to false conclusion as they derived wrong field equations. We have also discussed formation of apparent horizon and singularity.     

Dark Energy Models and Cosmic Acceleration with Anisotropic Universe in f（T） Gravity

This paper is devoted to studing the accelerated expansion of the universe in context of f（T） theory of gravity. For this purpose, we construct different f（T） models and investigate their cosmological behavior through equation of state parameter by using holographic, new agegraphic and their power-law entropy corrected dark energy models. We discuss the graphical behavior of this parameter versus redshif~ for particular values of constant parameters in Bianchi type I universe model. It is shown that the universe lies in different forms of dark energy, namely quintessence, phantom, and quintom corresponding to the chosen scale factors, which depend upon the constant parameters of the models.     

Orbital responses to methyl sites in CnH2n+2 (n=1-6)

Orbital responses to methyl sites in C_nH_2n+2 (n=1-6) are studied by B3LYP/TZVP based on the most stable geometries using the B3LYP/aug-cc-pVTZ method. Vertical ionization energies are produced using the SAOP/et-pVQZ model for the complete valence space. The highest occupied molecular orbital (HOMO) investigations indicate the p-electron profiles in methane, ethane, propane, and n-butane. By increasing the number of carbon-carbon bonds in lower momentum regions, the s, p-hybridized orbitals are built and display strong exchange and correlation interactions in lower momentum space (P≤0.50 a.u.). Meanwhile, the relative intensities of the isomers in lower momentum space show the strong bonding number dependence of the carbon-carbon bonds, meaning that more electrons have contributed to orbital construction. The study of representative valence orbital momentum distribution further confirms that the structural changes lead to evident electronic rearrangement over the whole valence space. An analysis based on the isomers reveals that the valence orbitals are isomer-dependent and the valence ionization energy experiences an apparent shift in the inner valence space. However, such shifts are greatly reduced in the outer valence space. Meanwhile, the opposite energy shift trend is found in the intermediate valence space.     

Alloy formation in the Au{1 1 1}/Ni system - An investigation with scanning tunnelling microscopy and medium energy ion scattering

Using the techniques of scanning tunnelling microscopy (STM) and medium energy ion scattering (MEIS), we examine the growth and annealing behaviour of ultrathin Ni films on Au{1 1 1} at 300 K. As has been shown previously, submonolayer growth of Ni on Au{1 1 1} is strongly influenced by the presence of the herringbone reconstruction with two-dimensional clusters nucleating at herringbone elbows. Second layer growth commences prior to the completion of the monolayer. After multiple layers have been deposited, the surface morphology retains a similar cluster-like appearance. Annealing produces surfaces exhibiting long range Moiré structures and, at higher temperature, triangular misfit dislocations. We use MEIS to examine the composition and structure of these surface alloy phases and conclude that in each case, they consist of an essentially pure Au surface layer on a bimetallic second layer.     

Double Electron Processes in Collisions of Partially Stripped Ions C^q＋ （q = 1-4） with Helium

The multi-electron processes are investigated for 17.9-120 keV/u C^1＋, 30-323 keV/u C^2＋, 120-438 keV/u ^C3＋, 287-480 keV/u C^4＋ incident on a helium target. The cross-section ratios of double electron （DE） process to the total of the single electron （SE） and the double electron process （i.e. SE＋DE）, the direct double electron （DDI） to the direct single ionization （DSI） as well as the contributions of DDI to DE and of TI to DE are measured using coincidence techniques. The energy and charge state dependences of the measured cross-section ratios are studied and discussed.     

Transfer Ionization of Helium in Collisions with C^q＋ and O^q＋ （q =1 - 3）

Cross-section ratios σTI/σSC of transfer ionization （TI） to single capture （SC） of C^q＋- and O^q＋-He （q = 1 - 3） collisions in the energy range of 15-440 keV/u （0.8-4.2 vBohr） are experimentally determined. It is shown that σTI/σSC strongly depends on the projectile velocity, and there is a maximum for E（keV/u）/q1/2 ≈, 150. Combining the Bohr-Lindhard model and the statistical model, a theoretical estimate is presented, in reasonable agreement with the experimental data when E（keV//u）/q^1/2 〉 35.     

Cross sections of Oq+（q=1-4） electron loss in collisions with He,Ne and Ar

Electron-loss cross sections of O q+(q = 1 4) colliding with He,Ne and Ar atoms are measured in the intermediate velocity regime.The ratios of the cross sections of two-electron loss to that of one-electron loss R 21 are presented.It is shown that single-channel analysis is not sufficient to explain the results,but that projectile electron loss,electron capture by the projectile and target ionization must be considered together to interpret the experimental data.The screening and antiscreening effects can account for the threshold velocity results,but cannot explain the dependence of the ratio R 21 on velocity quantitatively.In general,the effective charge of the target atom increases with velocity increasing because the high-speed projectile ion can penetrate into the inner electronic shell of target atom.Ne and Ar atoms have similar effective charges in this velocity regime,but He atoms have smaller ones at the same velocities due to its smaller nuclear charge.