In this paper, we use the metric coefficients and the equation of motion obtained in the second post- Newtonian approximation of scalar-tensor theory to derive the second-order light propagation equation and the light...In this paper, we use the metric coefficients and the equation of motion obtained in the second post- Newtonian approximation of scalar-tensor theory to derive the second-order light propagation equation and the light deflection angle and compare it with previous works. These results are useful for precision astrometry missions like ASTROD, GALA, Darwin and SIM which aim at astrometry with micro-arcsecond and nano-aresecond accuracies, and need for the second post-Newtonian framework and ephemeris for observations to determine the stellar and spacecraft positions.展开更多
As a continuing investigation of an earlier work that establishes the cofiinear solutions to the three-body problem with general masses under a scalar-tensor theory, we study these solutions and prove their uniqueness...As a continuing investigation of an earlier work that establishes the cofiinear solutions to the three-body problem with general masses under a scalar-tensor theory, we study these solutions and prove their uniqueness up to the first order post-Newtonian approximation. With the help of observed bounds on the scalar field in the Solar System, we show that the seventh-order polynomial equation determining the distance ratio among the three masses has either one or three positive roots. However, in the case with three positive roots, it is found that two positive roots break down the slow-motion condition for the post-Newtonian approximation so that only one positive root is physically valid. The resulting uniqueness suggests that the locations of the three masses are very close to their Newtonian positions with post-Newtonian corrections of general relativity and the scalar field. We also prove that, in the framework of the scalar-tensor theory, the angular velocity of the collinear configuration is always less than the Newtonian one when all other parameters are fixed. These results are valid only for three-body systems where upper-bounds on the scalar field are compatible with those of the Solar System.展开更多
We present the model of an anisotropic universe with string fluid as the source of matter within the framework of the scalar-tensor theory of gravitation. An exact solution of field equations is obtained by applying B...We present the model of an anisotropic universe with string fluid as the source of matter within the framework of the scalar-tensor theory of gravitation. An exact solution of field equations is obtained by applying Berman＇s law of variation to Hubble＇s parameter which yields a constant value of the deceleration parameter. The nature of classical potential is examined for the model under consideration. It has also been found that the massive strings dominate in the early universe and finally disap-pear from the universe. This is in agreement with current astronomical observations. The physical and dynamical properties of the model are also discussed.展开更多
We investigate the main features of a disformal Kerr black hole merger in quadratic degenerate higher-order scalar-tensor theories.In the ringdown stage of the black hole merger,for the prograde orbit,the real part of...We investigate the main features of a disformal Kerr black hole merger in quadratic degenerate higher-order scalar-tensor theories.In the ringdown stage of the black hole merger,for the prograde orbit,the real part of the quasinormal modes decreases with an increase in the disformal parameter,and the imaginary part also decreases,except in the Kerr case for a large spin parameter.However,for the retrograde orbit,the real part increases with an increase in the disformal parameter,and the imaginary part always decreases with it.For the approximate final spin,regardless of an equal spin,unequal spin,or generic spin configuration merger,the final black hole spin always increases with an increase in the disformal parameter.Our results show that the disformal parameter in the disformal Kerr solution and the MOG parameter in the Kerr-MOG case have obviously different effects on the black hole merger,which suggests the differences between these two spacetime structures.展开更多
We make a full classification of scalar monomials built of the Riemann curvature tensor up to the quadratic order and of the covariant derivatives of the scalar field up to the third order.From the point of view of th...We make a full classification of scalar monomials built of the Riemann curvature tensor up to the quadratic order and of the covariant derivatives of the scalar field up to the third order.From the point of view of the effective field theory,the third or even higher order covariant derivatives of the scalar field are of the same importance as the higher curvature terms,and thus should be taken into account.Moreover,the higher curvature terms and the higher order derivatives of the scalar field are complementary to each other,of which novel ghostfree combinations may exist.We make a systematic classification of all the possible monomials,according to the numbers of the Riemann tensor and the higher derivatives of the scalar field in each monomial.A complete basis of monomials at each order is derived,of which the linear combinations may yield novel ghostfree Lagrangians.We also develop diagrammatic representations for the monomials,which may help to simplify the analysis.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No. 10875171
文摘In this paper, we use the metric coefficients and the equation of motion obtained in the second post- Newtonian approximation of scalar-tensor theory to derive the second-order light propagation equation and the light deflection angle and compare it with previous works. These results are useful for precision astrometry missions like ASTROD, GALA, Darwin and SIM which aim at astrometry with micro-arcsecond and nano-aresecond accuracies, and need for the second post-Newtonian framework and ephemeris for observations to determine the stellar and spacecraft positions.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11573015 and J1210039the Innovation Training Project for Undergraduates of Nanjing University,China
文摘As a continuing investigation of an earlier work that establishes the cofiinear solutions to the three-body problem with general masses under a scalar-tensor theory, we study these solutions and prove their uniqueness up to the first order post-Newtonian approximation. With the help of observed bounds on the scalar field in the Solar System, we show that the seventh-order polynomial equation determining the distance ratio among the three masses has either one or three positive roots. However, in the case with three positive roots, it is found that two positive roots break down the slow-motion condition for the post-Newtonian approximation so that only one positive root is physically valid. The resulting uniqueness suggests that the locations of the three masses are very close to their Newtonian positions with post-Newtonian corrections of general relativity and the scalar field. We also prove that, in the framework of the scalar-tensor theory, the angular velocity of the collinear configuration is always less than the Newtonian one when all other parameters are fixed. These results are valid only for three-body systems where upper-bounds on the scalar field are compatible with those of the Solar System.
文摘We present the model of an anisotropic universe with string fluid as the source of matter within the framework of the scalar-tensor theory of gravitation. An exact solution of field equations is obtained by applying Berman＇s law of variation to Hubble＇s parameter which yields a constant value of the deceleration parameter. The nature of classical potential is examined for the model under consideration. It has also been found that the massive strings dominate in the early universe and finally disap-pear from the universe. This is in agreement with current astronomical observations. The physical and dynamical properties of the model are also discussed.
基金Supported by the National Key Research and Development Program of China(2020YFC2201400)the National Natural Science Foundation of China(12275079,12035005,12275078)。
文摘We investigate the main features of a disformal Kerr black hole merger in quadratic degenerate higher-order scalar-tensor theories.In the ringdown stage of the black hole merger,for the prograde orbit,the real part of the quasinormal modes decreases with an increase in the disformal parameter,and the imaginary part also decreases,except in the Kerr case for a large spin parameter.However,for the retrograde orbit,the real part increases with an increase in the disformal parameter,and the imaginary part always decreases with it.For the approximate final spin,regardless of an equal spin,unequal spin,or generic spin configuration merger,the final black hole spin always increases with an increase in the disformal parameter.Our results show that the disformal parameter in the disformal Kerr solution and the MOG parameter in the Kerr-MOG case have obviously different effects on the black hole merger,which suggests the differences between these two spacetime structures.
基金supported by the National Natural Science Foundation of China(Grant No.11975020)。
文摘We make a full classification of scalar monomials built of the Riemann curvature tensor up to the quadratic order and of the covariant derivatives of the scalar field up to the third order.From the point of view of the effective field theory,the third or even higher order covariant derivatives of the scalar field are of the same importance as the higher curvature terms,and thus should be taken into account.Moreover,the higher curvature terms and the higher order derivatives of the scalar field are complementary to each other,of which novel ghostfree combinations may exist.We make a systematic classification of all the possible monomials,according to the numbers of the Riemann tensor and the higher derivatives of the scalar field in each monomial.A complete basis of monomials at each order is derived,of which the linear combinations may yield novel ghostfree Lagrangians.We also develop diagrammatic representations for the monomials,which may help to simplify the analysis.
