The null-surface formulation (NSF) of general relativity has three coupled and highly nonlinear eld equations whose solution determines (a family of) null surfaces indicated by the variable u. This variable is one of a set of intrinsic coordinates that are defined in terms of the surfaces. The first of the three field equations is called the main metricity condition, and it is by far the most complicated. This work considers the NSF in 2+1 dimensions and presents a solution that is founded on the following strategy: Simplify the main metricity condition by requiring the uu-component of the metric tensor to be zero and then search for an additively separable solution formed from a sum of separate terms, each term being linked with a term in a certain differential operator ∂ so as to cause a convenient cancellation. The main motivation for this approach is that it may suggest how to find a solution in higher dimensions, where the role of ∂ is played by the eth operator of Newman and Penrose.
广义相对论的空面公式（NSF）有三个高度非线性的耦合长方程，其解法决定了由变量 u 表示的（一系列）空面。三个场方程中的第一个被称为主要度量条件，也是迄今为止最复杂的一个。本研究考虑了 2+1 维的 NSF，并提出了基于以下策略的解决方案：通过要求度量张量的 uu 分量为零来简化主度量条件，然后寻找一个由独立项之和组成的可加可分的解，每个项都与某个微分算子 ∂ 中的一个项相关联，以便于抵消。采用这种方法的主要动机是，它可以提出如何在更高维度中找到解，在更高维度中，∂的作用由纽曼和彭罗斯的乙算子扮演。
{"title":"Solution for the null-surface formulation in 2+1 dimensions with radiation source","authors":"T. Harriott, J. G. Williams","doi":"10.1139/cjp-2023-0256","DOIUrl":"https://doi.org/10.1139/cjp-2023-0256","url":null,"abstract":"The null-surface formulation (NSF) of general relativity has three coupled and highly nonlinear eld equations whose solution determines (a family of) null surfaces indicated by the variable u. This variable is one of a set of intrinsic coordinates that are defined in terms of the surfaces. The first of the three field equations is called the main metricity condition, and it is by far the most complicated. This work considers the NSF in 2+1 dimensions and presents a solution that is founded on the following strategy: Simplify the main metricity condition by requiring the uu-component of the metric tensor to be zero and then search for an additively separable solution formed from a sum of separate terms, each term being linked with a term in a certain differential operator ∂ so as to cause a convenient cancellation. The main motivation for this approach is that it may suggest how to find a solution in higher dimensions, where the role of ∂ is played by the eth operator of Newman and Penrose.","PeriodicalId":9413,"journal":{"name":"Canadian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140477061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we study the dynamic properties of spin–orbit coupling (SOC) hyperfine f =1 spinor antiferromagnetic Bose–Einstein condensates with the external magnetic field. The condensate is confined in a toroidal trap and the numerical results are obtained based on the multicomponent Gross–Pitaevskii equation. Our results show that, in the presence of SOC, the spin dynamics for zero magnetic field slows with an increase of radius of the torus. However, this process accelerates when the magnetic field is considered. In addition, in this case, the oscillation behavior is almost consistent with the considered maximum radius. In the absence of SOC, the periodicity of spin dynamics vanishes. We also compare the thermalization time for different magnetic fields and radii, which decreases considerably for nonzero magnetic fields with the increase of radius. Furthermore, our analysis suggests that for stronger magnetic field strength the density structure can be regulated. As a consequence, the condensate recovers from the necklace to an annular-shaped state.
本文研究了自旋轨道耦合（SOC）超精细 f =1 自旋反铁磁性玻色-爱因斯坦凝聚体在外部磁场作用下的动态特性。冷凝物被限制在一个环形陷阱中，数值结果是基于多分量格罗斯-皮塔耶夫斯基方程得出的。我们的结果表明，在存在 SOC 的情况下，零磁场下的自旋动力学会随着环形半径的增大而减慢。然而，当考虑磁场时，这一过程会加速。此外，在这种情况下，振荡行为与所考虑的最大半径几乎一致。在没有 SOC 的情况下，自旋动力学的周期性消失了。我们还比较了不同磁场和半径下的热化时间，在非零磁场下，随着半径的增加，热化时间大大缩短。此外，我们的分析表明，对于较强的磁场强度，密度结构是可以调节的。因此，冷凝物会从项链状恢复到环状。
{"title":"Effects of magnetic field on spin–orbit-coupled f = 1 spinor condensate in a toroidal trap","authors":"Qiang Zhao","doi":"10.1139/cjp-2023-0282","DOIUrl":"https://doi.org/10.1139/cjp-2023-0282","url":null,"abstract":"In this paper, we study the dynamic properties of spin–orbit coupling (SOC) hyperfine f =1 spinor antiferromagnetic Bose–Einstein condensates with the external magnetic field. The condensate is confined in a toroidal trap and the numerical results are obtained based on the multicomponent Gross–Pitaevskii equation. Our results show that, in the presence of SOC, the spin dynamics for zero magnetic field slows with an increase of radius of the torus. However, this process accelerates when the magnetic field is considered. In addition, in this case, the oscillation behavior is almost consistent with the considered maximum radius. In the absence of SOC, the periodicity of spin dynamics vanishes. We also compare the thermalization time for different magnetic fields and radii, which decreases considerably for nonzero magnetic fields with the increase of radius. Furthermore, our analysis suggests that for stronger magnetic field strength the density structure can be regulated. As a consequence, the condensate recovers from the necklace to an annular-shaped state.","PeriodicalId":9413,"journal":{"name":"Canadian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140487203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Ismayilova, S. Asadullayeva, M. Musayev, D.J. Askerov
In the presented work, we propose a systematic investigation of the electronic and optical properties of MnGa2Se4 by combining the spectroscopic ellipsometry carried out at room temperature in the spectral range of 1–4 eV and density functional theory (DFT) calculations. Ellipsometric measurements were collected at an incidence angle between 60° and 75° with a 5° step. The optical direct gap energies of MnGa2Se4 were estimated from the linear extrapolation of the absorption coefficients that were verified by band structure calculation. DFT calculation of the imaginary part ɛ shows that first critical point occurs at 2.46 eV and represents the direct optical transition at Γ point. The total magnetic moment of compound is 3.38 mB. The major contribution in total magnetic moment is due to 3 d state of Mn atoms.
{"title":"Computational and experimental approach for investigation of optical properties of single-crystal MnGa2Se4","authors":"N. Ismayilova, S. Asadullayeva, M. Musayev, D.J. Askerov","doi":"10.1139/cjp-2023-0255","DOIUrl":"https://doi.org/10.1139/cjp-2023-0255","url":null,"abstract":"In the presented work, we propose a systematic investigation of the electronic and optical properties of MnGa2Se4 by combining the spectroscopic ellipsometry carried out at room temperature in the spectral range of 1–4 eV and density functional theory (DFT) calculations. Ellipsometric measurements were collected at an incidence angle between 60° and 75° with a 5° step. The optical direct gap energies of MnGa2Se4 were estimated from the linear extrapolation of the absorption coefficients that were verified by band structure calculation. DFT calculation of the imaginary part ɛ shows that first critical point occurs at 2.46 eV and represents the direct optical transition at Γ point. The total magnetic moment of compound is 3.38 mB. The major contribution in total magnetic moment is due to 3 d state of Mn atoms.","PeriodicalId":9413,"journal":{"name":"Canadian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139600506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zainab N. Jaf, H. Miran, M. M. Rahman, A. Amri, Zhong-Tao Jiang
This contribution demonstrates density functional theory (DFT) calculations on the optoelectronic properties of monoclinic CuO under high pressures up to 15 GPa. In this account, the experimentally measured indirect band gap energy value of 1.41 eV has theoretically been predicted by tuning the Hubbard parameter (U) values for the partial electronic states. The values of Hubbard parameter correspond to UCu-3d = 8 eV and UO-2p = 4.5 eV. The electronic and optical characteristics were examined under applied pressure and the results reveal development in the band gap values with increasing pressure from (1.41 – 2.01) eV. Total and projected density of states (TDOS and PDOS) for the adopted pressures have been provided and displayed that the major contribution in the valance and conduction bands comes from O-2p and Cu-3d electronic states, correspondingly. The plotted reflectivity data suggests high optical reflectivity magnitudes relatively in the ultraviolet area. The investigated systems under variant pressures manifest rather an excellent absorption coefficient in the ultraviolet area pushing them to be employed in solar cell technologies. Our analyzed results of the wavelength dependent electrical conductivity of the investigated materials confirm the absorptivity behavior in the ultraviolet and small part of visible region of electromagnetic waves (EMW). Finally and most importantly, our obtained results of loss functions for the entire surveyed systems reveal and slight energy loss in a range of EMW including ultraviolet and visible regions.
这篇论文展示了单斜氧化铜在高达 15 GPa 的高压下的光电特性的密度泛函理论（DFT）计算。在这篇论文中，通过调整部分电子态的哈伯德参数 (U) 值，从理论上预测了实验测量的 1.41 eV 间接带隙能值。哈伯德参数值分别为 UCu-3d = 8 eV 和 UO-2p = 4.5 eV。在施加压力的情况下，对电子和光学特性进行了检测，结果表明，随着压力的增加，带隙值在 (1.41 - 2.01) eV 之间发生了变化。提供了所采用压力下的总态密度和投影态密度（TDOS 和 PDOS），显示价带和导带的主要贡献分别来自 O-2p 和 Cu-3d 电子态。绘制的反射率数据表明，紫外线区域的光学反射率相对较高。在不同的压力下，所研究的系统在紫外线区域表现出极好的吸收系数，这促使它们被用于太阳能电池技术中。我们分析了所研究材料随波长变化的电导率，结果证实了它们在紫外线和一小部分可见光电磁波（EMW）区域的吸收特性。最后，也是最重要的一点是，我们获得的整个调查系统的损耗函数结果显示，在包括紫外线和可见光区域在内的电磁波范围内存在轻微的能量损耗。
{"title":"DFT+U investigation on high pressure properties of monoclinic CuO","authors":"Zainab N. Jaf, H. Miran, M. M. Rahman, A. Amri, Zhong-Tao Jiang","doi":"10.1139/cjp-2023-0241","DOIUrl":"https://doi.org/10.1139/cjp-2023-0241","url":null,"abstract":"This contribution demonstrates density functional theory (DFT) calculations on the optoelectronic properties of monoclinic CuO under high pressures up to 15 GPa. In this account, the experimentally measured indirect band gap energy value of 1.41 eV has theoretically been predicted by tuning the Hubbard parameter (U) values for the partial electronic states. The values of Hubbard parameter correspond to UCu-3d = 8 eV and UO-2p = 4.5 eV. The electronic and optical characteristics were examined under applied pressure and the results reveal development in the band gap values with increasing pressure from (1.41 – 2.01) eV. Total and projected density of states (TDOS and PDOS) for the adopted pressures have been provided and displayed that the major contribution in the valance and conduction bands comes from O-2p and Cu-3d electronic states, correspondingly. The plotted reflectivity data suggests high optical reflectivity magnitudes relatively in the ultraviolet area. The investigated systems under variant pressures manifest rather an excellent absorption coefficient in the ultraviolet area pushing them to be employed in solar cell technologies. Our analyzed results of the wavelength dependent electrical conductivity of the investigated materials confirm the absorptivity behavior in the ultraviolet and small part of visible region of electromagnetic waves (EMW). Finally and most importantly, our obtained results of loss functions for the entire surveyed systems reveal and slight energy loss in a range of EMW including ultraviolet and visible regions.","PeriodicalId":9413,"journal":{"name":"Canadian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139619476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we have considered the flat Friedmann-Lemaître-Robertson-Walker (FRW) model in the framework of f( R, ∇ R) gravity. We have analyzed the significance of bulk viscosity in the f( R, ∇ R) gravity model to study the expansion of the universe. We have considered two bulk viscosity parameterizations and the use of power-law cosmology to constrain the model parameters H0 and q. Using the Bayesian analysis and likelihood function in conjunction with the Markov Chain Monte Carlo method, we obtained the model parameters [Formula: see text] and [Formula: see text]. The behaviors of energy density, bulk viscous pressure, and the effective equation of the state parameter with redshift are investigated in detail. These features demonstrate that the bulk viscosity is a valid candidate for acquiring the negative pressure needed to effectively drive the expansion of the universe. To check the validity of the f( R, ∇ R) model, we also analyze the behavior of energy conditions. The adiabatic squared speed of the sound is used to test the model’s stability. The Om( z) diagnostic is used in the model to identify the quintessence and phantom regions.
{"title":"Observational constraint in f(R, ∇R) gravity model in power-law cosmology","authors":"A. Dixit","doi":"10.1139/cjp-2023-0122","DOIUrl":"https://doi.org/10.1139/cjp-2023-0122","url":null,"abstract":"In this paper, we have considered the flat Friedmann-Lemaître-Robertson-Walker (FRW) model in the framework of f( R, ∇ R) gravity. We have analyzed the significance of bulk viscosity in the f( R, ∇ R) gravity model to study the expansion of the universe. We have considered two bulk viscosity parameterizations and the use of power-law cosmology to constrain the model parameters H0 and q. Using the Bayesian analysis and likelihood function in conjunction with the Markov Chain Monte Carlo method, we obtained the model parameters [Formula: see text] and [Formula: see text]. The behaviors of energy density, bulk viscous pressure, and the effective equation of the state parameter with redshift are investigated in detail. These features demonstrate that the bulk viscosity is a valid candidate for acquiring the negative pressure needed to effectively drive the expansion of the universe. To check the validity of the f( R, ∇ R) model, we also analyze the behavior of energy conditions. The adiabatic squared speed of the sound is used to test the model’s stability. The Om( z) diagnostic is used in the model to identify the quintessence and phantom regions.","PeriodicalId":9413,"journal":{"name":"Canadian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139529874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We construct a new cosmological model based on relativistic theory of gravity characterized by massive gravitons. The new Friedmann–Robertson–Walker model is characterized by the presence of a static traversable wormhole, massive gravitons, and a variable gravitational coupling constant. To recover the Bianchi identity, a second cosmic fluid is introduced in the theory. Motivated from cosmic dark radiation phenomenological arguments, which suggest that the dynamical component of dark energy could be dominated by a bath of dark radiation, we assume that the original cosmic fluid is radiative, whereas the new cosmic fluid is phantom. The total equation of state of our model is equal to −1. The new model is characterized by an effective Hubble parameter. The solutions of the dynamical equations reveal an accelerated universe with a scale factor of hyperbolic type which allows the deceleration parameter to change sign from a decelerating phase to an accelerating phase. We have evaluated the deceleration parameter, the jerk and the present day variations of the gravitational constant which agree with astronomical observations.
{"title":"Traversable wormhole model with massive gravitons, two fluids, and a variable gravity","authors":"R. El-Nabulsi, Waranont Anukool","doi":"10.1139/cjp-2023-0033","DOIUrl":"https://doi.org/10.1139/cjp-2023-0033","url":null,"abstract":"We construct a new cosmological model based on relativistic theory of gravity characterized by massive gravitons. The new Friedmann–Robertson–Walker model is characterized by the presence of a static traversable wormhole, massive gravitons, and a variable gravitational coupling constant. To recover the Bianchi identity, a second cosmic fluid is introduced in the theory. Motivated from cosmic dark radiation phenomenological arguments, which suggest that the dynamical component of dark energy could be dominated by a bath of dark radiation, we assume that the original cosmic fluid is radiative, whereas the new cosmic fluid is phantom. The total equation of state of our model is equal to −1. The new model is characterized by an effective Hubble parameter. The solutions of the dynamical equations reveal an accelerated universe with a scale factor of hyperbolic type which allows the deceleration parameter to change sign from a decelerating phase to an accelerating phase. We have evaluated the deceleration parameter, the jerk and the present day variations of the gravitational constant which agree with astronomical observations.","PeriodicalId":9413,"journal":{"name":"Canadian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139626706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An accurate inter-atomic potential energy surface for ground state of SH2-is reported at the multi-reference configuration interaction level of theory using aug-cc-pVQZ basis set. The calculated ab initio energy points are utilized, after semiempirically correcting the dynamical correlation by the many-body expansion-scaled external correlation method. In order to verify the accuracy of the potential energy surface, molecular reaction dynamics including the relationship between reaction probability and collision energy, thermal rate constant and integral scattering cross section are calculated by using the quantum time-dependent wave packet method. The final results show that our potential energy surface is accurate and the molecular reaction dynamics results are satisfactory, and the accurate potential energy surface and its dynamics results can also lay a foundation for the future experimental research of SH- containing molecules.
利用 aug-cc-pVQZ 基集，在多参考构型相互作用理论水平上报告了 SH2- 基态的精确原子间势能面。利用多体膨胀缩放外部相关方法对动力学相关性进行半经验校正后，利用计算出的 ab initio 能量点。为了验证势能面的准确性，使用量子时变波包法计算了分子反应动力学，包括反应概率与碰撞能量、热速率常数和积分散射截面之间的关系。最终结果表明，我们的势能面是准确的，分子反应动力学结果也是令人满意的，准确的势能面及其动力学结果也可以为今后含 SH 分子的实验研究奠定基础。
{"title":"Potential energy surface and quantum dynamics calculation of SH2-(2A′) based on ab initio scaled external correlation correction","authors":"Hongyu Ma, Ning Gu","doi":"10.1139/cjp-2023-0176","DOIUrl":"https://doi.org/10.1139/cjp-2023-0176","url":null,"abstract":"An accurate inter-atomic potential energy surface for ground state of SH2-is reported at the multi-reference configuration interaction level of theory using aug-cc-pVQZ basis set. The calculated ab initio energy points are utilized, after semiempirically correcting the dynamical correlation by the many-body expansion-scaled external correlation method. In order to verify the accuracy of the potential energy surface, molecular reaction dynamics including the relationship between reaction probability and collision energy, thermal rate constant and integral scattering cross section are calculated by using the quantum time-dependent wave packet method. The final results show that our potential energy surface is accurate and the molecular reaction dynamics results are satisfactory, and the accurate potential energy surface and its dynamics results can also lay a foundation for the future experimental research of SH- containing molecules.","PeriodicalId":9413,"journal":{"name":"Canadian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138999841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we consider the formation of vortices in multilayer stacks of Bose–Einstein condensates with tilted dipoles by numerical simulations of the Gross–Pitaevskii equation. Different dependencies of critical rotation frequency (CRF) and optical lattice height, vortex number, and rotation frequency are studied, depending on the direction of the dipole axis and dipole strength. Our results show that the CRF in z = 0 is minimum. When the optical lattice height is gradually increased, the CRF decreases gradually. Reducing of dipole strength in anisotropic dipole–dipole interaction (DDI) favours the formation of vortices, and such decline in isotropic DDI hinders the creation of vortices. The reason for this difference is that the repulsive interaction is favorable and the attractive interaction is disadvantageous for the vortex formation. In addition, we study the first-order correlation function and focus on variation of coherence. For small rotation frequency, the break of coherence occurs earlier in the case of purely repulsive interaction. With an increase in rotation frequency, the coherence concurrently disappears in layer z = 2. Moreover, we also investigate the quenched dynamics, showing that the increase of angular momentum is induced by changing the direction of dipoles and in this process the vortex number remains unchanged.
在本文中，我们通过对格罗斯-皮塔耶夫斯基方程的数值模拟，考虑了具有倾斜偶极子的玻色-爱因斯坦凝聚体多层堆栈中涡旋的形成。研究了临界旋转频率（CRF）与光晶格高度、涡旋数和旋转频率的不同依赖关系，这取决于偶极子轴的方向和偶极子强度。结果表明，z = 0 时的临界旋转频率最小。当光晶格高度逐渐增加时，CRF 逐渐减小。各向异性偶极子-偶极子相互作用（DDI）中偶极子强度的降低有利于涡旋的形成，而各向同性偶极子-偶极子相互作用（DDI）中偶极子强度的降低则阻碍了涡旋的形成。造成这种差异的原因是，斥力相互作用对涡旋的形成有利，而吸引力相互作用对涡旋的形成不利。此外，我们还研究了一阶相关函数，并关注相干性的变化。对于较小的旋转频率，在纯粹斥力相互作用的情况下，相干性的断裂发生得更早。随着旋转频率的增加，相干性在 z = 2 层同时消失。此外，我们还研究了淬火动力学，结果表明角动量的增加是由偶极子方向的改变引起的，在此过程中涡旋数保持不变。
{"title":"Vortices in multilayer stacks of Bose–Einstein condensates with tilted dipoles","authors":"Qiang Zhao","doi":"10.1139/cjp-2023-0095","DOIUrl":"https://doi.org/10.1139/cjp-2023-0095","url":null,"abstract":"In this paper, we consider the formation of vortices in multilayer stacks of Bose–Einstein condensates with tilted dipoles by numerical simulations of the Gross–Pitaevskii equation. Different dependencies of critical rotation frequency (CRF) and optical lattice height, vortex number, and rotation frequency are studied, depending on the direction of the dipole axis and dipole strength. Our results show that the CRF in z = 0 is minimum. When the optical lattice height is gradually increased, the CRF decreases gradually. Reducing of dipole strength in anisotropic dipole–dipole interaction (DDI) favours the formation of vortices, and such decline in isotropic DDI hinders the creation of vortices. The reason for this difference is that the repulsive interaction is favorable and the attractive interaction is disadvantageous for the vortex formation. In addition, we study the first-order correlation function and focus on variation of coherence. For small rotation frequency, the break of coherence occurs earlier in the case of purely repulsive interaction. With an increase in rotation frequency, the coherence concurrently disappears in layer z = 2. Moreover, we also investigate the quenched dynamics, showing that the increase of angular momentum is induced by changing the direction of dipoles and in this process the vortex number remains unchanged.","PeriodicalId":9413,"journal":{"name":"Canadian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139009887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Z. Yousaf, M.Z. Bhatti, Timothy Ganesan Andrew, H. Aman
A coupled formulation of the Gauss-Bonnet invariant term G and the
energy momentum trace T term provide a modified f(G,T) gravity,
has been analyzed in this study. The functional form for the
f(G,T) gravity has been taken as f(G,T)=αT+ βGn,
α and β are free parameters. The field equations are
produced in general, which then used a dust case to extract a novel
Hubble parameter. The stability of the assumed model and explanation
for the late time acceleration have been studied by the energy
bound. Furthermore, the dynamical variables are used to analyze the
behavior of the equation of state parameter by restricting different
parameters with respect to the recent observational data. A
quintessence-like evolution has been achieved as a result of this
study.
{"title":"f(G,T) and its Cosmological Implications","authors":"Z. Yousaf, M.Z. Bhatti, Timothy Ganesan Andrew, H. Aman","doi":"10.1139/cjp-2023-0200","DOIUrl":"https://doi.org/10.1139/cjp-2023-0200","url":null,"abstract":"A coupled formulation of the Gauss-Bonnet invariant term G and the
 energy momentum trace T term provide a modified f(G,T) gravity,
 has been analyzed in this study. The functional form for the
 f(G,T) gravity has been taken as f(G,T)=αT+ βG<sup>n</sup>,
 α and β are free parameters. The field equations are
 produced in general, which then used a dust case to extract a novel
 Hubble parameter. The stability of the assumed model and explanation
 for the late time acceleration have been studied by the energy
 bound. Furthermore, the dynamical variables are used to analyze the
 behavior of the equation of state parameter by restricting different
 parameters with respect to the recent observational data. A
 quintessence-like evolution has been achieved as a result of this
 study.","PeriodicalId":9413,"journal":{"name":"Canadian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135092252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adijgkiga BANOUGA, Abdoul Karim KAGONE, Wêpari Charles YAGUIBOU, Niéssan KOHIO, Zacharie Koalaga, François ZOUGMORE
Le succès ou l'échec de la coupure du courant électrique par le disjoncteur dépend fortement des propriétés physico-chimiques de l'arc électrique créé. Dans ce travail, nous nous intéressons aux propriétés thermodynamiques du plasma d’air contaminé par de la vapeur d’alliage d'argent et de dioxyde d'étain. Il s’agit notamment de la masse volumique, de la vitesse du son dans le plasma, de l’enthalpie massique, de la densité d’énergie et de la densité de flux thermique. Elles sont déterminées à l’équilibre thermodynamique dans une gamme de température de 500 K à 20000 K et à la pression atmosphérique. Les résultats obtenus montrent que, pour une même température donnée, la masse volumique augmente lorsque la vapeur d’alliage d’argent et de dioxyde d’étain augmente dans le mélange. La vitesse du son dans le plasma et la capacité calorifique diminuent lorsque la vapeur d’alliage AgSnO2 augmente dans le mélange. Pour une même température donnée, l’enthalpie massique diminue entre 3000 K et 20000 K, avec l’augmentation de vapeur d’alliage AgSnO2. La densité d’énergie et la densité de flux thermique diminuent entre 10000 K et 20000 K, lorsque la vapeur d’alliage AgSnO2 augmente dans le mélange. L’augmentation du pourcentage de la vapeur de contact électrique en AgSnO2, ralentit l’extinction de l’arc électrique créé à l’intérieur du disjoncteur, surtout au-delà de 0,1% de vapeur. Ce ralentissement de l’extinction de l’arc électrique peut entraîner un échec de coupure de courant électrique par le disjoncteur et donc détériorer les performances du disjoncteur à air.
断路器切断电流的成功或失败在很大程度上取决于所产生的电弧的物理化学性质。在这项工作中，我们感兴趣的是银合金蒸汽和二氧化锡污染空气等离子体的热力学性质。其中包括密度、等离子体中的声速、质量焓、能量密度和热流密度。它们是在500k到20000 K的温度范围内的热力学平衡和大气压下确定的。结果表明，在给定温度下，合金银和二氧化锡在混合物中的蒸气增加，密度增加。随着混合物中AgSnO2合金蒸汽的增加，等离子体中的声速和热容降低。在相同温度下，随着AgSnO2合金蒸气的增加，质量焓在3000 K ~ 20000 K之间降低。当混合物中AgSnO2合金蒸气增加时，能量密度和热流密度在10000 K ~ 20000 K之间降低。在AgSnO2中电接触蒸汽百分比的增加减缓了断路器内部产生的电弧的熄灭，特别是超过0.1%的蒸汽。这种缓慢的电弧熄灭可能导致断路器断电失败，从而降低空气断路器的性能。
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