New unification theories predict large extra dimensions （LEDs）. If that is the case, gravity would be stronger at short ranges than what Newtonian gravity predicts. LEDs could also have effects at atomic level. In t...New unification theories predict large extra dimensions （LEDs）. If that is the case, gravity would be stronger at short ranges than what Newtonian gravity predicts. LEDs could also have effects at atomic level. In this paper we propose a new method to constrain the size of ‘gravity-only’ LEDs by analysing how these LEDs modify the energy of the atomic transitions 1s-2s and 2s-2p （Lamb shift）, in the particular case of the hydrogen and muonium atoms. We estimate these effects by using Bethe＇s non-relativistic treatment of Lamb shift. In the particular case of three LEDs, which may be a candidate to explain the interaction mechanism of dark matter particles, we have found that current knowledge in atomic spectroscopy could constrain their sizes to less than 10 μm. Although our contributions do not reach the sensitivity given by SN1987a, they are still slightly better than recent constraints given by Inverse Square Law tests of the Eoet-Wash group at Washington University, which gave R3 〈 36.6 μm.展开更多
Within the context of Newton’s theory of gravitation, restricted to point-like test particles and central bodies, stable circular orbits in ordinary space are related to stable circular paths on a massless, unmovable...Within the context of Newton’s theory of gravitation, restricted to point-like test particles and central bodies, stable circular orbits in ordinary space are related to stable circular paths on a massless, unmovable, undeformable vortex-like surface, under the action of a tidal gravitational field along the symmetry axis. An interpretation is made in the light of a holographic principle, in the sense that motions in ordinary space are connected with motions on a selected surface and vice versa. Then ordinary space is conceived as a 3-hypersurface bounding a n-hypervolume where gravitation takes origin, within a n-hyperspace. The extension of the holographic principle to extra dimensions implies the existence of a minimum distance where test particles may still be considered as distinct from the central body. Below that threshold, it is inferred test particles lose theirs individuality and “glue” to the central body via unification of the four known interactions and, in addition, 1) particles can no longer be conceived as point-like but e.g., strings or membranes, and 2) quantum effects are dominant and matter turns back to a pre-big bang state. A more detailed formulation including noncircular motions within the context of general relativity, together with further knowledge on neutron stars, quark stars and black holes, would provide further insight on the formulation of quantum gravity.展开更多
The main goal of this paper is to determine the effect of an extra dimension on a traversable wormhole. Here an earlier study by the author [Phys. Rev. D 98, 064041 (2018)] is extended in several significant ways. To ...The main goal of this paper is to determine the effect of an extra dimension on a traversable wormhole. Here an earlier study by the author [Phys. Rev. D 98, 064041 (2018)] is extended in several significant ways. To begin with, the extra spatial dimension is assumed to be time dependent, while the redshift and shape functions, as well as the extra dimension, are functions of both r and l, the respective radial and extra coordinates;the last of these is therefore a function of r, l, and t. The main objective is to determine the conditions that allow the throat of the wormhole to be threaded with ordinary matter (by respecting the null energy condition) and that the same conditions lead to a violation of the null energy condition in the fifth dimension, which is therefore responsible for sustaining the wormhole. The dependence of the extra dimension on l and t is subject to additional conditions that are subsequently analyzed in this paper. Finally, the extra dimension may be extremely small or even curled up.展开更多
Magnetic Monopole SearchesIsolated supermassive monopole candidate events have not been confirmed. The most sensitive experiments obtain negative results.
We investigate an(n+1)-dimensional generalized Randall-Sundrum model with an anisotropic metric which has three different scale factors.One obtains a positive effective cosmological constant Ωeff∼10^−124(in Planck u...We investigate an(n+1)-dimensional generalized Randall-Sundrum model with an anisotropic metric which has three different scale factors.One obtains a positive effective cosmological constant Ωeff∼10^−124(in Planck units),which only needs a solution kr≃50−80 without fine tuning.Both the visible and hidden brane tensions are positive,which renders the two branes stable.Then,we find that the Hubble parameter is close to a constant in a large region near its minimum,thus causing the acceleration of the universe.Meanwhile,the scale of extra dimensions is smaller than the observed scale but greater than the Planck length.This may suggest that the observed present acceleration of the universe is caused by the extra-dimensional evolution.展开更多
特高压交流输变电工程输送距离长,建设规模大,施工安全风险大,文明施工和环保水保要求高,建设管理难度增大。本文以淮南-南京-上海1 000 k V交流特高压工程为例,集成应用地理信息系统、三维可视化和IT等技术,对施工现场实施无人机航摄,...特高压交流输变电工程输送距离长,建设规模大,施工安全风险大,文明施工和环保水保要求高,建设管理难度增大。本文以淮南-南京-上海1 000 k V交流特高压工程为例,集成应用地理信息系统、三维可视化和IT等技术,对施工现场实施无人机航摄,开展特高压工程施工安全管控系统研究[1-6],实现施工现场的安全、质量、环保水保和通道清理信息的管控,使建设管理人员全面地掌握施工现场信息,进一步提高基建管理水平。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No 10475114)the Foundation of Minor Planets of Purple Mountain Observatory, China
文摘New unification theories predict large extra dimensions （LEDs）. If that is the case, gravity would be stronger at short ranges than what Newtonian gravity predicts. LEDs could also have effects at atomic level. In this paper we propose a new method to constrain the size of ‘gravity-only’ LEDs by analysing how these LEDs modify the energy of the atomic transitions 1s-2s and 2s-2p （Lamb shift）, in the particular case of the hydrogen and muonium atoms. We estimate these effects by using Bethe＇s non-relativistic treatment of Lamb shift. In the particular case of three LEDs, which may be a candidate to explain the interaction mechanism of dark matter particles, we have found that current knowledge in atomic spectroscopy could constrain their sizes to less than 10 μm. Although our contributions do not reach the sensitivity given by SN1987a, they are still slightly better than recent constraints given by Inverse Square Law tests of the Eoet-Wash group at Washington University, which gave R3 〈 36.6 μm.
文摘Within the context of Newton’s theory of gravitation, restricted to point-like test particles and central bodies, stable circular orbits in ordinary space are related to stable circular paths on a massless, unmovable, undeformable vortex-like surface, under the action of a tidal gravitational field along the symmetry axis. An interpretation is made in the light of a holographic principle, in the sense that motions in ordinary space are connected with motions on a selected surface and vice versa. Then ordinary space is conceived as a 3-hypersurface bounding a n-hypervolume where gravitation takes origin, within a n-hyperspace. The extension of the holographic principle to extra dimensions implies the existence of a minimum distance where test particles may still be considered as distinct from the central body. Below that threshold, it is inferred test particles lose theirs individuality and “glue” to the central body via unification of the four known interactions and, in addition, 1) particles can no longer be conceived as point-like but e.g., strings or membranes, and 2) quantum effects are dominant and matter turns back to a pre-big bang state. A more detailed formulation including noncircular motions within the context of general relativity, together with further knowledge on neutron stars, quark stars and black holes, would provide further insight on the formulation of quantum gravity.
文摘The main goal of this paper is to determine the effect of an extra dimension on a traversable wormhole. Here an earlier study by the author [Phys. Rev. D 98, 064041 (2018)] is extended in several significant ways. To begin with, the extra spatial dimension is assumed to be time dependent, while the redshift and shape functions, as well as the extra dimension, are functions of both r and l, the respective radial and extra coordinates;the last of these is therefore a function of r, l, and t. The main objective is to determine the conditions that allow the throat of the wormhole to be threaded with ordinary matter (by respecting the null energy condition) and that the same conditions lead to a violation of the null energy condition in the fifth dimension, which is therefore responsible for sustaining the wormhole. The dependence of the extra dimension on l and t is subject to additional conditions that are subsequently analyzed in this paper. Finally, the extra dimension may be extremely small or even curled up.
文摘Magnetic Monopole SearchesIsolated supermassive monopole candidate events have not been confirmed. The most sensitive experiments obtain negative results.
基金Supported by the Key Program of National Natural Science Foundation of China(11535005)the National Natural Science Foundation of China(11647087)+5 种基金Foundation for Young and Yiddle-Aged Teachers Basic Ability Improvement in Guangxi Universities(2018KY0326)Special Foundation for Science and Technology Base and Talents in Guangxi(2018AD19310)China Postdoctoral Science Foundation funded project(2019M651750)Open project of state key laboratory of solid state microstructure physics(M31037)the Natural Science Foundation of Yangzhou Polytechnic Institute(201917)the Natural Science Foundation of Changzhou Institute of Technology(YN1509)。
文摘We investigate an(n+1)-dimensional generalized Randall-Sundrum model with an anisotropic metric which has three different scale factors.One obtains a positive effective cosmological constant Ωeff∼10^−124(in Planck units),which only needs a solution kr≃50−80 without fine tuning.Both the visible and hidden brane tensions are positive,which renders the two branes stable.Then,we find that the Hubble parameter is close to a constant in a large region near its minimum,thus causing the acceleration of the universe.Meanwhile,the scale of extra dimensions is smaller than the observed scale but greater than the Planck length.This may suggest that the observed present acceleration of the universe is caused by the extra-dimensional evolution.
文摘特高压交流输变电工程输送距离长,建设规模大,施工安全风险大,文明施工和环保水保要求高,建设管理难度增大。本文以淮南-南京-上海1 000 k V交流特高压工程为例,集成应用地理信息系统、三维可视化和IT等技术,对施工现场实施无人机航摄,开展特高压工程施工安全管控系统研究[1-6],实现施工现场的安全、质量、环保水保和通道清理信息的管控,使建设管理人员全面地掌握施工现场信息,进一步提高基建管理水平。
