This study explores asymptotically flat wormhole solutions within the framework of f(R,T)gravity.We analyze f(R,T)expressed as f(R,T)=R+λT+λ_(1)T^(2).A linear equation of state(EoS)is employed for both radial and la...This study explores asymptotically flat wormhole solutions within the framework of f(R,T)gravity.We analyze f(R,T)expressed as f(R,T)=R+λT+λ_(1)T^(2).A linear equation of state(EoS)is employed for both radial and lateral pressures,resulting in a power-law shape function.The investigation encompasses solutions characterized by both negative and positive energy densities.It has been determined that solutions with positive energy density comply with all energy conditions,specifically the null,weak,strong,and dominant energy conditions.Additionally,we identify constraints on the parametersλ,λ_(1),and the parameters associated with the EoS and shape function.展开更多
We perform the manifestly covariant quantization of f(R)gravity in the de Donder gauge condition(or harmonic gauge condition)for general coordinate invariance.We explicitly calculate various equal-time commutation rel...We perform the manifestly covariant quantization of f(R)gravity in the de Donder gauge condition(or harmonic gauge condition)for general coordinate invariance.We explicitly calculate various equal-time commutation relations(ETCRs),in particular the ETCR between the metric and its time derivative,and show that it has a nonvanishing and nontrivial expression,whose situation should be contrasted to the previous result in higher-derivative or quadratic gravity where the ETCR was found to be identically vanishing.We also clarify global symmetries,the physical content of f(R)gravity,and clearly show that this theory is manifestly unitary and has a massive scalar and massless graviton as physical modes.展开更多
Aiming at the problem of dynamic instability of hard-brittle jointed rock surrounding in deep tunnel/roadway engineering,combining with the support concepts of"coupling rigidity with flexibility"and"ove...Aiming at the problem of dynamic instability of hard-brittle jointed rock surrounding in deep tunnel/roadway engineering,combining with the support concepts of"coupling rigidity with flexibility"and"overcoming rigidity by flexibility",the prevention and control method with"rigid-flexible coupling(R-F-C)"was put forward.Through numerical simulation calculation,the impact damage process,acoustic emission(AE)evolution characteristics,and element stress/displacement evolution characteristics of unsupported surrounding rock structure model,rigid supporting surrounding rock structure model,and"R-F-C"supporting surrounding rock structure model under horizontal bidirectional impact loading were compared and analyzed.Based on the theory of stress wave propagation,the dynamic instability catastrophe mechanism of three kinds of supporting structure models induced by horizontal bidirectional impact loading was revealed.Based on the Mohr-Coulomb strength theory,the stress discrimination methods of dynamic catastrophe of surrounding rock induced by horizontal bidirectional impact loading under three kinds of supporting structures were proposed.Combined with the above numerical simulation study,the explosion impact physical and mechanical test of"R-F-C"surrounding rock supporting plate structure was further designed and carried out.Finally,combined with the"conceptual model of ball-cliff potential energy instability",the energy driving theory and energy transformation mechanism of impact-induced rockburst under three kinds of supporting structures were discussed deeply.The research results provided a scientific basis for further promoting the effective application of"R-F-C"supporting structure in the prevention and control of dynamic instability of deep tunnel/roadway surrounding rock.展开更多
We have examined an isotropic and homogeneous cosmological model in f(R,T^(φ))gravity,where R represents the Ricci scalar and T^(φ)exhibits the energy momentum tensor's trace.We examine the stability criteria by...We have examined an isotropic and homogeneous cosmological model in f(R,T^(φ))gravity,where R represents the Ricci scalar and T^(φ)exhibits the energy momentum tensor's trace.We examine the stability criteria by performing the dynamical system analysis for our model f(R,T^(φ))=R+2(a T^(φ)+b),where a and b are the constants.We derive a set of autonomous equations and find their solutions by assuming a flat potential V0.We assess the equilibrium points from these equations and find the eigenvalues.We analyze the physical interpretation of the phase space for this system.We obtain three stable equilibrium points.We also examine the interaction between the scalar field and dark energy,represented by Q=ψH_(ρde)and determine the equilibrium points for this interaction.We identify four stable equilibrium points for this interaction.We calculate the values of the physical parameters for both scenarios at each equilibrium point,indicating the Universe's accelerated expansion.展开更多
文摘This study explores asymptotically flat wormhole solutions within the framework of f(R,T)gravity.We analyze f(R,T)expressed as f(R,T)=R+λT+λ_(1)T^(2).A linear equation of state(EoS)is employed for both radial and lateral pressures,resulting in a power-law shape function.The investigation encompasses solutions characterized by both negative and positive energy densities.It has been determined that solutions with positive energy density comply with all energy conditions,specifically the null,weak,strong,and dominant energy conditions.Additionally,we identify constraints on the parametersλ,λ_(1),and the parameters associated with the EoS and shape function.
文摘We perform the manifestly covariant quantization of f(R)gravity in the de Donder gauge condition(or harmonic gauge condition)for general coordinate invariance.We explicitly calculate various equal-time commutation relations(ETCRs),in particular the ETCR between the metric and its time derivative,and show that it has a nonvanishing and nontrivial expression,whose situation should be contrasted to the previous result in higher-derivative or quadratic gravity where the ETCR was found to be identically vanishing.We also clarify global symmetries,the physical content of f(R)gravity,and clearly show that this theory is manifestly unitary and has a massive scalar and massless graviton as physical modes.
基金Project(2023AH051167)supported by the Natural Science Research Project of Anhui Educational Committee,ChinaProject(AHBP2024B-04)supported by the Foundation of Anhui Engineering Research Center of New Explosive Materials and Blasting Technology,China+1 种基金Project(GXZDSYS2023103)supported by the Open Fund for Anhui Key Laboratory of Mining Construction Engineering,ChinaProjects(52274071,52404155)supported by the National Natural Science Foundation of China。
文摘Aiming at the problem of dynamic instability of hard-brittle jointed rock surrounding in deep tunnel/roadway engineering,combining with the support concepts of"coupling rigidity with flexibility"and"overcoming rigidity by flexibility",the prevention and control method with"rigid-flexible coupling(R-F-C)"was put forward.Through numerical simulation calculation,the impact damage process,acoustic emission(AE)evolution characteristics,and element stress/displacement evolution characteristics of unsupported surrounding rock structure model,rigid supporting surrounding rock structure model,and"R-F-C"supporting surrounding rock structure model under horizontal bidirectional impact loading were compared and analyzed.Based on the theory of stress wave propagation,the dynamic instability catastrophe mechanism of three kinds of supporting structure models induced by horizontal bidirectional impact loading was revealed.Based on the Mohr-Coulomb strength theory,the stress discrimination methods of dynamic catastrophe of surrounding rock induced by horizontal bidirectional impact loading under three kinds of supporting structures were proposed.Combined with the above numerical simulation study,the explosion impact physical and mechanical test of"R-F-C"surrounding rock supporting plate structure was further designed and carried out.Finally,combined with the"conceptual model of ball-cliff potential energy instability",the energy driving theory and energy transformation mechanism of impact-induced rockburst under three kinds of supporting structures were discussed deeply.The research results provided a scientific basis for further promoting the effective application of"R-F-C"supporting structure in the prevention and control of dynamic instability of deep tunnel/roadway surrounding rock.
基金funded by Researchers Supporting Project No.RSPD2025R733,King Saud University,Riyadh,Saudi Arabia。
文摘We have examined an isotropic and homogeneous cosmological model in f(R,T^(φ))gravity,where R represents the Ricci scalar and T^(φ)exhibits the energy momentum tensor's trace.We examine the stability criteria by performing the dynamical system analysis for our model f(R,T^(φ))=R+2(a T^(φ)+b),where a and b are the constants.We derive a set of autonomous equations and find their solutions by assuming a flat potential V0.We assess the equilibrium points from these equations and find the eigenvalues.We analyze the physical interpretation of the phase space for this system.We obtain three stable equilibrium points.We also examine the interaction between the scalar field and dark energy,represented by Q=ψH_(ρde)and determine the equilibrium points for this interaction.We identify four stable equilibrium points for this interaction.We calculate the values of the physical parameters for both scenarios at each equilibrium point,indicating the Universe's accelerated expansion.
