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In this paper, we present a detailed study of both nonrotating and rotating black hole solutions in f (R) = R − 2 α R model. The complicated expression of Ricci scalar, which appears in the vacuum field equations, brings the main difficulty of searching analytic solutions. In the case of searching nonrotating black hole solution, we use the 00 component minus 11 component of field equations to constrain the Ricci scalar. In order to obtain analytic solutions of rotating black hole, two strategies are used. One is the simplification of the line element using Carter's consideration that the Klein–Gordon equation is separable. The other is that we give the general solutions of the simultaneous equations of 00 minus 11 component equation and 01 component of the field equations. These strategies greatly simplify the process and difficulty of solving the axisymmetric solutions. The calculation process is more friendly to generalize to other modified gravities. [ABSTRACT FROM AUTHOR]

In order to realize the agility, collaboration and visualization of alloy material development process, a product development platform based on simulation and modeling technologies is established in this study. In this platform, the whole-process simulation module builds multi-level simulation models based on metallurgical mechanisms from the production line level, the thermo-mechanical coupling field level and the microstructure evolution level. The design knowledge management module represents the multi-source heterogeneous material design knowledge through ontology model, including customers' requirement knowledge, material component knowledge, process design knowledge and quality inspection knowledge, and utilizes the case-based reasoning approach to reuse the knowledge. The data-driven modeling module applies machine learning algorithms to mine the relationships between product mechanical properties, material components, and process parameters from historical samples, and utilizes multi-objective optimization algorithms to find the optimal combination of process parameters. Application of the developed platform in actual steel mills shows that the proposed method helps to improve the efficiency of product design process. [ABSTRACT FROM AUTHOR]

The spectral energy distribution (SED) sequence for type Ia supernovae (SN Ia) is modeled by an artificial neural network. The SN Ia luminosity is characterized as a function of phase, wavelength, a color parameter and a decline rate parameter. After training and testing the neural network, the SED sequence could give both the spectrum with wavelength range from 3000 Åto 8000 Åand the light curve with phase from 20 days before to 50 days after the maximum luminosity for the supernovae with different colors and decline rates. Therefore, we call this the Artificial Neural Network Spectral Light Curve Template (ANNSLCT) model. We retrain the Joint Light-curve Analysis (JLA) supernova sample by using the ANNSLCT model and obtain the parameters for each supernova to make a constraint on the cosmological Λ CDM model. We find that the best fitting values of these parameters are very close to those from the JLA sample trained with the Spectral Adaptive Lightcurve Template 2 (SALT2) model. It is expectable that the ANNSLCT model has potential to analyze more SN Ia multi-color light curves measured in future observation projects. [ABSTRACT FROM AUTHOR]

In the framework of the new version of the gedanken experiments proposed by Sorce and Wald, we investigate the weak cosmic censorship conjecture (WCCC) for an Einstein–Maxwell–Dilaton–Axion (EMDA) black hole. Our result shows that no violations of WCCC can occur with the increase of the background solution parameters for this near-extremal EMDA black hole when the second-order correction of the perturbations is taken into account. Namely, the near-extremal EMDA black hole cannot be over-charged or over-spun. [ABSTRACT FROM AUTHOR]

Recently, a new kind of f (z) theory is proposed to provide a different perspective for the development of reliable alternative models of gravity in which the f (R) Lagrangian terms are reformulated as polynomial parametrizations f (z). In the previous study, the parameters in the f (z) models have been constrained by using cosmological data. In this paper, these models will be tested by the observations in the solar system. After solving the Ricci scalar as a function of the redshift, one could obtain f (R) that could be used to calculate the standard Parametrized-Post-Newtonian (PPN) parameters. First, we fit the parametric models with the latest cosmological observational data. Then, the tests are performed by solar system observations. And last we combine the constraints of solar system and cosmology together and reconstruct the f (R) actions of the f (z) parametric models. [ABSTRACT FROM AUTHOR]

Recently, it was found that after imposing a helix boundary condition on a scalar field, the Casimir force coming from the quantum effect is linearly proportional to r, which is the ratio of the pitch to the circumference of the helix. This linear behavior of the Casimir force is just like that of the force obeying Hooke's law on a spring. In this paper, inspired by some complex structures that live in the cells of human body like DNA, protein, collagen, etc., we generalize the helix boundary condition to a more general one, in which the helix consists of a tiny helix structure, and makes up a hierarchy of helix. After imposing this kind of boundary condition on a massless and a massive scalar, we calculate the Casimir energy and force by using the so-called zeta function regularization method. We find that Hooke's law with the generalized helix boundary condition is not exactly the same as the usual one. In this case, the force is proportional to the cube of r instead. So, we regard it as a generalized Hooke's law, which is complied by a generalized quantum spring. [ABSTRACT FROM AUTHOR]

The currently accelerated expansion of our universe is unarguably one of the most intriguing problems in today's physics research. Two realistic nonminimal torsion–matter coupling f (T) models have been established and studied in our previous papers [C. J. Feng, F. F. Ge, X. Z. Li, R. H. Lin and X. H. Zhai, Phys. Rev. D92 (2015) 104038; R. H. Lin, X. H. Zhai and X. Z. Li, Eur. Phys. J. C77 (2017) 504] aiming to explain this "dark energy" problem. In this paper, we study the generalized power-law torsion–matter coupling f (T) model. Dynamical system analysis shows that the three expansion phases of the universe, i.e. the radiation-dominated era, the matter-dominated era and the dark energy-dominated era, can all be reproduced in this generalized model. By using the statefinder and O m diagnostics, we find that the different cases of the model can be distinguished from each other and from other dark energy models such as the two models in our previous papers, Λ CDM, quintessence and Chaplygin gas. Furthermore, the analyses also show that all kinds of generalized power-law torsion–matter coupling model are able to cross the w = − 1 divide from below to above, which is a realization of quintom scenario. The decrease of the energy density resulting from the crossing of w will make the catastrophic fate of the universe avoided and a de Sitter expansion fate in the future will be approached. [ABSTRACT FROM AUTHOR]

In this paper, we apply the statefinder diagnostic on the cosmology in the framework of the generalized Proca theories with derivative self-interactions possessing three propagating physical degrees of freedom. We discuss the evolving trajectories of the statefinder parameters with the parameter n of this model recently fitted as n = 0.254 and n = 0.16 by use of the current observational data and find that some typical characteristic of the evolution of statefinder parameters makes the model distinguishable between n = 0.254 case and n = 0.16 case and also from other dark energy models. [ABSTRACT FROM AUTHOR]

The Casimir effect for rectangular boxes has been studied for several decades. But there are still some unclear points. Recently, there are new developments related to this topic, including the demonstration of the equivalence of the regularization methods and the clarification of the ambiguity in the regularization of the temperature-dependent free energy. Also, the interesting quantum spring was raised stemming from the topological Casimir effect of the helix boundary conditions. We review these developments together with the general derivation of the Casimir energy of the p-dimensional cavity in (D + 1)-dimensional space-time, paying special attention to the sign of the Casimir force in a cavity with unequal edges. In addition, we also review the Casimir piston, which is a configuration related to rectangular cavity. [ABSTRACT FROM AUTHOR]

Zeta function regularization is an effective method to extract physical significant quantities from infinite ones. It is regarded as mathematically simple and elegant but the isolation of the physical divergency is hidden in its analytic continuation. By contrast, Abel-Plana formula method permits explicit separation of divergent terms. In regularizing the Casimir energy for a massless scalar field in a D-dimensional rectangular box, we give the rigorous proof of the equivalence of the two methods by deriving the reflection formula of Epstein zeta function from repeatedly application of Abel-Plana formula and giving the physical interpretation of the infinite integrals. Our study may help with the confidence of choosing any regularization method at convenience among the frequently used ones, especially the zeta function method, without the doubts of physical meanings or mathematical consistency. [ABSTRACT FROM AUTHOR]

We reconsider the thermal scalar Casimir effect for p-dimensional rectangular cavity inside (D+1)-dimensional Minkowski space-time and clarify the ambiguity in the regularization of the temperature-dependent part of the free energy. We derive rigorously the regularization of the temperature-dependent part of the free energy by making use of the Abel-Plana formula repeatedly and get the explicit expression of the terms to be subtracted. In the cases of D = 3, p = 1 and D = 3, p = 3, we precisely recover the results of parallel plates and three-dimensional box in the literature. Furthermore, for D>p and D = p cases with periodic, Dirichlet and Neumann boundary conditions, we give the explicit expressions of the Casimir free energy in both low temperature (small separations) and high temperature (large separations) regimes, through which the asymptotic behavior of the free energy changing with temperature and the side length is easy to see. We find that for D>p, with the side length going to infinity, the Casimir free energy tends to positive or negative constants or zero, depending on the boundary conditions. But for D = p, the leading term of the Casimir free energy for all three boundary conditions is a logarithmic function of the side length. We also discuss the thermal Casimir force changing with temperature and the side length in different cases and find that when the side length goes to infinity, the force always tends to be zero for different boundary conditions regardless of D>p or D = p. The Casimir free energy and force at high temperature limit behave asymptotically alike that they are proportional to the temperature, be they positive (repulsive) or negative (attractive) in different cases. Our study may be helpful in providing a comprehensive and complete understanding of this old problem. [ABSTRACT FROM AUTHOR]

When one studies the Casimir effect, the periodic (anti-periodic) boundary condition is usually taken to mimic a periodic (anti-periodic) structure for a scalar field living in a flat space with a non-Euclidean topology. However, there could be an arbitrary phase difference between the value of the scalar field on one endpoint of the unit structure and that on the other endpoint, such as the structure of nanotubes. Then, in this paper, a periodic condition on the ends of the system with an additional phase factor, which is called the "quasi-periodic" condition, is imposed to investigate the corresponding Casimir effect. And an attractive or repulsive Casimir force is found, whose properties depend on the phase angle value. Especially, the Casimir effect disappears when the phase angle takes a particular value. High dimensional spacetime case is also investigated. [ABSTRACT FROM AUTHOR]

We use the generalized Chowla-Selberg formula to consider the Casimir effect of a scalar field with a helix torus boundary condition in the flat (D + 1)-dimensional spacetime. We obtain the exact results of the Casimir energy density and pressure for any D for both massless and massive scalar fields. The numerical calculation indicates that once the topology of spacetime is fixed, the ratio of the sizes of the helix will be a decisive factor. There is a critical value rc of the ratio r of the lengths at which the pressure vanishes. The pressure changes from negative to positive as the ratio r passes through rc increasingly. In the massive case, we find the pressure tends to the result of massless field when the mass approaches zero. Furthermore, there is another critical ratio of the lengths $r_{\rm c}^{\prime}$ and the pressure is independent of the mass at $r = r_{\rm c}^{\prime}$ in the D = 3 case. [ABSTRACT FROM AUTHOR]

The Casimir effect for a massless scalar field on the helix boundary condition which is named as quantum spring is studied in our recent paper.27 Here, the Casimir effect of the quantum spring is investigated in (D+1)-dimensional spacetime for the massless and massive scalar fields by using the zeta function techniques. We obtain the exact results of the Casimir energy and Casimir force for any D, which indicate a Z2 symmetry of the two space dimensions. The Casimir energy and Casimir force have different expressions for odd and even dimensional space in the massless case but in both cases the force is attractive. In the case of odd-dimensional space, the Casimir energy density can be expressed by the Bernoulli numbers, while in the even case it can be expressed by the ζ-function. And we also show that the Casimir force has a maximum value which depends on the spacetime dimensions. In particular, for a massive scalar field, we found that the Casimir force varies as the mass of the field changes. [ABSTRACT FROM AUTHOR]

The Casimir force on two-dimensional pistons for massive scalar fields with both Dirichlet and hybrid boundary conditions is computed. The physical result is obtained by making use of generalized ζ-function regularization technique. The influence of the mass and the position of the piston in the force is studied graphically. The Casimir force for massive scalar field is compared to that for massless scalar field. [ABSTRACT FROM AUTHOR]

The Chinese herbal medicine Huang Qin (Radix Scutellariae) had been used for restless fetus for hundreds of years in China, however, little attention had been given to the components of the herb, specifically its ability to exert abortion-preventing effects at the maternal fatal interface. The present study was carried out to investigate the protective effects of baicalin and the possible mechanisms on pregnancies. Baicalin (at 10, 20, and 50 mg/kg BW respectively) was gavaged to bromocriptine-treated mice from gestation day (GD) 1 through GD 7. Abortion rates were calculated and the changes of interferon-γ (IFN-γ), interleukin-10 (IL-10) and progesterone were assayed on different gestation days. Results showed that the embryonic death rates were significantly decreased in groups supplemented with 20 or 50 mg/kg BW of baicalin, accompanied with reduced IFN-γ and enhanced progesterone contents. Moreover, the highest levels of IFN-γ appeared on GD 5 both in the control and in baicalin treated groups. It is concluded that baicalin can exert an anti-abortive effect by cutting down the production of IFN-γ and elevating the levels of progesterone in a dose dependent manner and IFN-γ is involved in an inflammatory reaction which is beneficial for a successful implantation. [ABSTRACT FROM AUTHOR]