We explore the possibility of attributing the recent discovery of the variable hard X-ray source ... more We explore the possibility of attributing the recent discovery of the variable hard X-ray source CXOM82 J095550.2+694047 in M82 to the gravitational magnification by an intervening stellar object along the line of sight acting as a mi-crolens. The duration of the event (> 84 days) allows us to set robust constraints on the mass and location of the microlensing object when combined with the dynam-ical properties of the Galactic halo, M82 and typical globular clusters. Except for the extremely low probability, the microlensing magnification by MACHO in either the Galactic halo or M82 halo is able to explain the X-ray variability of CXOM82 J095550.2+694047. It is hoped that the lensing hypothesis can be tested soon by measurement of the light curve.
The combination of the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data with other fin... more The combination of the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data with other finer scale cosmic microwave background (CMB) experiments (CBI and ACBAR) and two structure formation measurements (2dF-GRS and Lyman α forest) suggest a ΛCDM cosmological model with a running spectral power index of primordial density fluctuations. Motivated by this new result on the index of primordial power spectrum, we present the first study on the predicted lensing probabilities of image separation in a spatially flat ΛCDM model with a running spectral index (RSI-ΛCDM model). It is shown that the RSI-ΛCDM model suppress the predicted lensing probabilities on small splitting angles of less than about 4 ′′ compared with that of standard power-law ΛCDM (PL-ΛCDM) model. Subject headings: cosmology:theory—dark matter—galaxies:halos—gravitational lensing—early universe—large-scale structure PACS numbers:98.80.Es,98.62.Sb,95.35.+d,98.80.Cq – 2 – 1.
The tension between luminous matter and dynamical matter has long been an interesting and controv... more The tension between luminous matter and dynamical matter has long been an interesting and controversial topic in the investigation of galaxies. This is particularly true when we study spiral galaxies for which we have high quality observations of rotation curves. The solutions to the tension are proposed in two different approaches, one is the dark matter hypothesis and the other is MOdified Newtonian Dynamics (MOND) theory. When we test the solutions by using observational data of rotation curves, the controversy arises when we apply them to both low surface brightness (LSB) galaxies and high surface brightness (HSB) galaxies. Usually one likes to use the rotation curves of LSB galaxies, since dark matter is needed or the Newtonian acceleration falls below the characteristic acceleration a 0 in most regions of such galaxies, even near their centers. But for HSB galaxies, dark matter is needed or Newtonian acceleration falls below the characteristic acceleration a 0 only in their ou...
We consider the effects on the Cosmic Background Radiation (CBR) of a single, spherically symmetr... more We consider the effects on the Cosmic Background Radiation (CBR) of a single, spherically symmetric structure using the Tolman-Bondi solutions in a closed universe. The exact frequency shift of a photon passing through the center of a lump which is located between the last scattering surface and an observer is calculated. An approximate expression of the frequency shift ∆ν0 ν0 to the first order of δ(x) (the density contrast) is given. We find that there are several redshifts of the perturbing lump where the net frequency shift is zero. With increasing Ω, the first positions of zero frequency shift move toward lower redshift; the larger the value of Ω, the further they move. At the vicinity of the last scattering surface, where the universe is close to flat, the frequency shift will always be the same as that for a flat universe.
We explore the possibility of attributing the recent discovery of the hard X-ray variable source ... more We explore the possibility of attributing the recent discovery of the hard X-ray variable source CXOM82 J095550.2+694047 in M82 to the gravitational magnification by an intervening stellar obeject along the line of sight as microlens. The duration of the event ($>84$ days) allows us to set robust constraints on the mass and location of the mircolensing object when combined with the dynamical properties of the Galactic halo, the M82 and typical globular clusters. Except for the extremely low probablity, the microlensing magnification by MACHO in either the Galactic halo or the M82 halo is able to explain the X-ray variability of CXOM82 J095550.2+694047. It is hoped that the lensing hypothesis can be soon tested by the light curve measurement.
We study the statistics of large-separation multiply-imag ed quasars lensed by clusters of galaxi... more We study the statistics of large-separation multiply-imag ed quasars lensed by clusters of galaxies. In particular, we examine how the observed brightest cluster galaxies (BCGs) affect the predicted numbers of wide-separation lenses. We model the lens as an NFW-profiled dark matter halo with a truncated sing ular isothermal sphere to represent the BCG in its center. We mainly make predictions for the Sloan Digital Sky Survey Quasar Lens Search (SQLS) sample from the Data Release 5 (DR5) in two standardCDM cosmological models: a model with matter density M = 0.3 and �8 = 0.9, as is usually adopted in the literature (�CDM1), and a model suggested by the WMAP seven-year (WMAP7) data withM = 0.266 and�8 = 0.801. We also study the lensing properties for the WMAP3 cosmology in order to compare with the previous work. We find that BCGs in the centers of clusters sig nificantly enhance the lensing efficiency by a factor of 2 ∼ 3 compared with that of NFW-profiled pure dark matter halos. In addition, the dependence of mass ratios of BCGs to their host halos on the host halo masses reduces the lensing rate by ∼ 20% from assuming a constant ratio as in previous studies, but considering the evolution of this ratio with redshift out to z ∼ 1 would reduce it by ∼ 3%. Moreover, we predict that the numbers of lensed quasars with image separations larger than 10 '' in the statistical sample of SQLS from DR5 are 1.22 and 0.47, respectively forCDM1 and WMAP7 and0.73 and 0.33 for separations between 10 '' and 20 '' , which are consistent with the only observed cluster lens with such a large separation in the complete SQLS sample.
The fermionic free energy and entropy are calculated in Garfinkle–Horowitz–Strominger dilatonic b... more The fermionic free energy and entropy are calculated in Garfinkle–Horowitz–Strominger dilatonic black hole background spacetime, by using 't Hfoot's brick wall model. It turns out that the fermionic entropy in Garfinkle–Horowitz–Strominger dilatonic black hole back ground spacetime is 7/2 times the Bosonic entropy.
International Journal of Theoretical Physics, 1998
The Klein–Gordon equation and Diracequation are solved in the backgrounds of a (1 +1)-dimensional... more The Klein–Gordon equation and Diracequation are solved in the backgrounds of a (1 +1)-dimensional black hole with 'tHooft and“quasiperiodic” boundary conditions,respectively. The corresponding entropies of bosons and fermions arecalculated; the divergence in the fermionic entropy hasthe same form as that in the bosonic one, except thatthe coefficient is different.
We calculate the strong lensing probability as a function of the image-separation �θ in TeVeS (te... more We calculate the strong lensing probability as a function of the image-separation �θ in TeVeS (tensor-vector- scalar) cosmology, which is a relativistic version of MOND (MOdified Newtonian Dynamics). The lens, often an elliptical galaxy, is modeled by the Hernquist profile. We assume a flat cosmology with b = 1−� = 0.04 and the simplest interpolating function� (x) = min(1, x). For comparison, we recalculated the probabilities for lenses by Singular Isothermal Sphere (SIS) galaxy halos in LCDM with Schechter-fit velocity function. The amplification bias is calculated based on the magnification o f the second bright image rather than the total of the two brighter images. Our calculations show that the Hernquist model predicts insuffi cient but acceptable probabilities in flat TeVeS cosmology compared with the resu lts of the well defined combined sample of Cosmic Lens All-Sky Survey (CLASS) and Jodrell Bank/Very Large Array Astrometric Survey (JVAS); at the same time, it predicts high...
We explore the possibility of attributing the recent discovery of the variable hard X-ray source ... more We explore the possibility of attributing the recent discovery of the variable hard X-ray source CXOM82 J095550.2+694047 in M82 to the gravitational magnification by an intervening stellar object along the line of sight acting as a mi-crolens. The duration of the event (> 84 days) allows us to set robust constraints on the mass and location of the microlensing object when combined with the dynam-ical properties of the Galactic halo, M82 and typical globular clusters. Except for the extremely low probability, the microlensing magnification by MACHO in either the Galactic halo or M82 halo is able to explain the X-ray variability of CXOM82 J095550.2+694047. It is hoped that the lensing hypothesis can be tested soon by measurement of the light curve.
The combination of the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data with other fin... more The combination of the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data with other finer scale cosmic microwave background (CMB) experiments (CBI and ACBAR) and two structure formation measurements (2dF-GRS and Lyman α forest) suggest a ΛCDM cosmological model with a running spectral power index of primordial density fluctuations. Motivated by this new result on the index of primordial power spectrum, we present the first study on the predicted lensing probabilities of image separation in a spatially flat ΛCDM model with a running spectral index (RSI-ΛCDM model). It is shown that the RSI-ΛCDM model suppress the predicted lensing probabilities on small splitting angles of less than about 4 ′′ compared with that of standard power-law ΛCDM (PL-ΛCDM) model. Subject headings: cosmology:theory—dark matter—galaxies:halos—gravitational lensing—early universe—large-scale structure PACS numbers:98.80.Es,98.62.Sb,95.35.+d,98.80.Cq – 2 – 1.
The tension between luminous matter and dynamical matter has long been an interesting and controv... more The tension between luminous matter and dynamical matter has long been an interesting and controversial topic in the investigation of galaxies. This is particularly true when we study spiral galaxies for which we have high quality observations of rotation curves. The solutions to the tension are proposed in two different approaches, one is the dark matter hypothesis and the other is MOdified Newtonian Dynamics (MOND) theory. When we test the solutions by using observational data of rotation curves, the controversy arises when we apply them to both low surface brightness (LSB) galaxies and high surface brightness (HSB) galaxies. Usually one likes to use the rotation curves of LSB galaxies, since dark matter is needed or the Newtonian acceleration falls below the characteristic acceleration a 0 in most regions of such galaxies, even near their centers. But for HSB galaxies, dark matter is needed or Newtonian acceleration falls below the characteristic acceleration a 0 only in their ou...
We consider the effects on the Cosmic Background Radiation (CBR) of a single, spherically symmetr... more We consider the effects on the Cosmic Background Radiation (CBR) of a single, spherically symmetric structure using the Tolman-Bondi solutions in a closed universe. The exact frequency shift of a photon passing through the center of a lump which is located between the last scattering surface and an observer is calculated. An approximate expression of the frequency shift ∆ν0 ν0 to the first order of δ(x) (the density contrast) is given. We find that there are several redshifts of the perturbing lump where the net frequency shift is zero. With increasing Ω, the first positions of zero frequency shift move toward lower redshift; the larger the value of Ω, the further they move. At the vicinity of the last scattering surface, where the universe is close to flat, the frequency shift will always be the same as that for a flat universe.
We explore the possibility of attributing the recent discovery of the hard X-ray variable source ... more We explore the possibility of attributing the recent discovery of the hard X-ray variable source CXOM82 J095550.2+694047 in M82 to the gravitational magnification by an intervening stellar obeject along the line of sight as microlens. The duration of the event ($>84$ days) allows us to set robust constraints on the mass and location of the mircolensing object when combined with the dynamical properties of the Galactic halo, the M82 and typical globular clusters. Except for the extremely low probablity, the microlensing magnification by MACHO in either the Galactic halo or the M82 halo is able to explain the X-ray variability of CXOM82 J095550.2+694047. It is hoped that the lensing hypothesis can be soon tested by the light curve measurement.
We study the statistics of large-separation multiply-imag ed quasars lensed by clusters of galaxi... more We study the statistics of large-separation multiply-imag ed quasars lensed by clusters of galaxies. In particular, we examine how the observed brightest cluster galaxies (BCGs) affect the predicted numbers of wide-separation lenses. We model the lens as an NFW-profiled dark matter halo with a truncated sing ular isothermal sphere to represent the BCG in its center. We mainly make predictions for the Sloan Digital Sky Survey Quasar Lens Search (SQLS) sample from the Data Release 5 (DR5) in two standardCDM cosmological models: a model with matter density M = 0.3 and �8 = 0.9, as is usually adopted in the literature (�CDM1), and a model suggested by the WMAP seven-year (WMAP7) data withM = 0.266 and�8 = 0.801. We also study the lensing properties for the WMAP3 cosmology in order to compare with the previous work. We find that BCGs in the centers of clusters sig nificantly enhance the lensing efficiency by a factor of 2 ∼ 3 compared with that of NFW-profiled pure dark matter halos. In addition, the dependence of mass ratios of BCGs to their host halos on the host halo masses reduces the lensing rate by ∼ 20% from assuming a constant ratio as in previous studies, but considering the evolution of this ratio with redshift out to z ∼ 1 would reduce it by ∼ 3%. Moreover, we predict that the numbers of lensed quasars with image separations larger than 10 '' in the statistical sample of SQLS from DR5 are 1.22 and 0.47, respectively forCDM1 and WMAP7 and0.73 and 0.33 for separations between 10 '' and 20 '' , which are consistent with the only observed cluster lens with such a large separation in the complete SQLS sample.
The fermionic free energy and entropy are calculated in Garfinkle–Horowitz–Strominger dilatonic b... more The fermionic free energy and entropy are calculated in Garfinkle–Horowitz–Strominger dilatonic black hole background spacetime, by using 't Hfoot's brick wall model. It turns out that the fermionic entropy in Garfinkle–Horowitz–Strominger dilatonic black hole back ground spacetime is 7/2 times the Bosonic entropy.
International Journal of Theoretical Physics, 1998
The Klein–Gordon equation and Diracequation are solved in the backgrounds of a (1 +1)-dimensional... more The Klein–Gordon equation and Diracequation are solved in the backgrounds of a (1 +1)-dimensional black hole with 'tHooft and“quasiperiodic” boundary conditions,respectively. The corresponding entropies of bosons and fermions arecalculated; the divergence in the fermionic entropy hasthe same form as that in the bosonic one, except thatthe coefficient is different.
We calculate the strong lensing probability as a function of the image-separation �θ in TeVeS (te... more We calculate the strong lensing probability as a function of the image-separation �θ in TeVeS (tensor-vector- scalar) cosmology, which is a relativistic version of MOND (MOdified Newtonian Dynamics). The lens, often an elliptical galaxy, is modeled by the Hernquist profile. We assume a flat cosmology with b = 1−� = 0.04 and the simplest interpolating function� (x) = min(1, x). For comparison, we recalculated the probabilities for lenses by Singular Isothermal Sphere (SIS) galaxy halos in LCDM with Schechter-fit velocity function. The amplification bias is calculated based on the magnification o f the second bright image rather than the total of the two brighter images. Our calculations show that the Hernquist model predicts insuffi cient but acceptable probabilities in flat TeVeS cosmology compared with the resu lts of the well defined combined sample of Cosmic Lens All-Sky Survey (CLASS) and Jodrell Bank/Very Large Array Astrometric Survey (JVAS); at the same time, it predicts high...
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