On a Phenomenological Approach to Gravity

Applying the theory of sources I consider the consequences of using field theoretical 3- graviton vertex instead of the vertex of general relativity. As an example I look for the lowest nonlinear terms in the exteriormetric of a spherically symmetric body. Themethod suggests that the algorithm of obtaining the metric cannot be reduced to solving the Einstein equation. It also seems that in nonlinear approximation the concept of a test particle moving in external gravitational field can be sustained only for a nonrelativistic particle.     

A New Exponential Gravity

We propose a new exponential f（R） gravity model with f（R） = （R - λc） e^λ（c/R）n and n 〉 3, λ ≥ 1, c 〉 0 to explain late-time acceleration of the universe. At the high curvature region, the model behaves like the A CDM model. In the asymptotic future, it reaches a stable de-Sitter spaeetime. It is a cosmologically viable model and can evade the local gravity constraints easily. This model shares many features with other f（R） dark energy models like Hu-Sawicki model and ExponentiM gravity model. In it the dark energy equation of state is of an oscillating form and can cross phantom divide line ωde = -1. In particular, in the parameter range 3 〈 n ≤ 4, λ ～ 1, the model is most distinguishable from other models. For instance, when n = 4, λ = 1, the dark energy equation of state will cross -1 in the earlier future and has a stronger oscillating form than the other models, the dark energy density in asymptotical future is smaller than the one in the high curvature region. This new model can evade the local gravity tests easily when n 〉 3 and λ 〉 1.     

On a Three-Dimensional Gravity Model with Higher Derivatives

The purpose of this work is to present a model for 3D massive gravity with topological and higher-derivative terms. Causality and unitarity are discussed at tree-level. Power-counting renormalizability is also contemplated.     

Non-Geometric Conditional Phase Gate by Quantum Zeno Dynamics in Laser-Excited Nitrogen-Vacancy Centers

Based on the quantum Zeno dynamics,we propose a two-qubit non-geometric conditional phase gate between two nitrogen-vacancy centers coupled to a whispering-gallery mode cavity.The varying phases design of periodic laser can be used for realizing non-geometric conditional phase gate,and the cavity mode is virtually excited during the gate operation.Thus,the fidelity of the gate operation is insensitive to cavity decay and the fluctuation of the preset laser intensity.The numerical simulation with a realistic set of experimental parameters shows that the gate fidelity 0.987 can be within reached in the near future.     

A New Parametrization for Tetrad Gravity

A new version of tetrad gravity in globally hyperbolic, asymptotically flat at spatial infinity spacetimes with Cauchy surfaces diffeomorphic to R ³ is obtained by using a new parametrization of arbitrary cotetrads to define a set of configurational variables to be used in the ADM metric action. Seven of the fourteen first class constraints have the form of the vanishing of canonical momenta. A comparison is made with other models of tetrad gravity and with the ADM canonical formalism for metric gravity.     

Inertia and Gravity: a New Approach to Dynamical Theory in General Relativity

A new approach to gravitational field dynamics is proposed, as an alternative to the standard formulation of General Relativity. The spacetime metric tensor is split, into an externally fixed background geometry (inertia) and a local dynamical field (gravity); and a dynamical theory of matter and gravity in the inertial background is developed. The physical origin of inertia (Mach's Principle), and its observable properties, are discussed. The coordinate representations of inertia and gravity are found to have an internal gauge degree of freedom, due to the Equivalence Principle; the transformation properties of these fields, and the notion of covariant gauge conditions, are discussed. The dynamics of matter and gravitic fields is then investigated, using: (i) The group of motion of the inertial background, appearing as an externally fixed Lie symmetry in the matter and gravity action principles, which yields weakly conserved energy-momentum-like objects; and (ii) an internal symmetry gauge group, yielding strongly conserved “internal currents”. A fully covariant field-theoretical formalism is used, in which all quantities and operations are tensorial; the well-known difficulties of “coordinate effects” in the standard nontensorial formulation are thus avoided. The physical significance of various types of conservation laws is discussed; and a complete family of energy-momentum tensors of gravity, covariantly conserved together with the matter energy-momentum, is deduced from a tensorial action principle. Treating gravity as an independent dynamical interaction, on an equal footing with other (matter) interactions, we are then finally led to the conclusion that the gravitic energy-momentum of a system is fully determined by the matter energy-momentum; various physical implications of this are discussed in some detail.     

一种新型衍射超分辨光学器件

提出了一种提高通过光学系统的部分光线的空间频率,来提高系统分辨率的新型衍射超分辨光学器件。该器件通过把部分低频光线移到高频带,使得艾里斑的主斑变小,同时焦深也得到了延长,模拟计算结果表明,在中心峰值强度相等的条件下,用该器件所获得的超分辨效果比目前最好的纯相位型超分辨光阑要好。     

New Electrically Charged Black Hole in Higher Derivative Gravity

In this paper, new electrically charged asymptotically flat black hole solutions are numerically derived in the context of higher derivative gravity. These solutions can be interpreted as generalizations of two different classes of non-charged asymptotically flat spacetimes: Schwarzschild and non-Schwarzschild solutions. Extreme black hole solutions and black holes with negative mass were found.     

New Holographic Dark Energy in Chern-Simons Gravity and Cosmography

We have considered a five-dimensional action, which is composed of a gravitational sector and a sector of matter, where the gravitational sector is given by a Chern-Simons gravity action instead of the Einstein-Hilbert action and where the matter sector is given by the so-called perfect fluid with barotropic EoS and new holographic dark energy. We will study the dynamic formulation of Chern-Simons gravity, where the coupling constant is promoted to a scalar field with potential. We have studied the implications of replacing the Einstein-Hilbert action by the Chern-Simons action on the cosmological evolution for a 5D FRW metric. The deceleration parameter shows that our considered model cannot cross the phantom divide. Also the natures of the cosmography parameters are examined in Chern-Simons gravity.     

On the Dimension of Tetrads in the Effective Gravity

JETP Letters - Two different sources of emergent gravity lead to the inverse square of length dimension of metric field, [gμν] = 1/[l]2, as distinct from the conventional dimensionless...     

On Matter and Metric in Affine Theory of Gravity

The affine theory was conceived as a geometric model, wherein the connection field is the primary structure of the space-time. According to the program lying on the basis of this theory, metric and some sort of matter are somehow to be deduced from the connection field. In the present paper, we point out classical ways to a realization of this program. It is shown that, even in that case where the introduction of the metric seems to exclude the coupling of gravity to matter, the situation is not so hopeless as one may assume. In particular, for a symmetric Einstein tensor, it is answered the old question as to a self-consistent introduction of a metric and a metrical energy-momentum tensor controversially debated by Einstein, Eddington, and Weyl.     

On the True Nature of Renormalizability in Horava-Lifshitz Gravity

We argue that the true nature of the renormalizability of Horava-Lifshitz gravity lies in the presence of higher order spatial derivatives and not in the anisotropic Lifshitz scaling of space and time. We discuss the possibility of constructing a higher order spatial derivatives model that has the same renormalization properties of Horava-Lifshitz gravity but that does not make use of the Lifshitz scaling. In addition, the state-of-the-art of the Lorentz symmetry restoration in Horava-Lifshitz-type theories of gravitation is reviewed.     

测量重力加速度的新方法

提出利用液体粘滞系数测定仪来设计测量当地的重力加速度的方法,减小了时间误差,并用计算机软件来处理数据,提高了测量精度。提供了一种新的实验室测量重力加速度的方法,扩充了大学物理实验内容。     

A New Approach to Modifying Theories of Gravity

We propose a new point of view for interpreting Newton’s and Einstein’s theories of gravity. By taking inspiration from Continuum Mechanics and its treatment of anisotropies, we formulate new gravitational actions for modified theories of gravity. These models are simple and natural generalisations with many interesting properties. Above all, their precise form can, in principle, be determined experimentally.     

On Nonlinear σ-Models Arising in (Super-)Gravity

In a previous paper with Gibbons [1] we derived a list of three dimensional symmetric space σ-models obtained by dimensional reduction of a class of four dimensional gravity theories with abelian gauge fields and scalars. Here we give a detailed analysis of their group theoretical structure leading to an abstract parametrization in terms of “triangular” group elements. This allows for a uniform treatment of all these models. As an interesting application we give a simple derivation of a “Quadratic Mass Formula” for strictly stationary black holes. Received: 3 August 1998 / Accepted: 1 December 1999     

On the Origin of Entropic Gravity and Inertia

It was recently suggested that quantum field theory is not fundamental but emerges from the loss of phase space information about matter crossing causal horizons. Possible connections between this formalism and Verlinde’s entropic gravity and Jacobson’s thermodynamic gravity are proposed. The holographic screen in Verlinde’s formalism can be identified as local Rindler horizons and its entropy as that of the bulk fields beyond the horizons. This naturally resolves some issues on entropic gravity. The quantum fluctuation of the fields is the origin of the thermodynamic nature of entropic gravity. It is also suggested that inertia is related to dragging Rindler horizons.     

Gravity wave turbulence in a laboratory flume

We present an experimental study of the statistics of surface gravity wave turbulence in a flume of a horizontal size 12 x 6 m. For a wide range of amplitudes the wave energy spectrum was found to scale as Eomega approximately omega(-nu) in a frequency range of up to one decade. However, nu appears to be nonuniversal: it depends on the wave intensity and ranges from about 6 to 4. We discuss our results in the context of existing theories and argue that at low wave amplitudes the wave statistics is affected by the flume finite size, and at high amplitudes the wave breaking effect dominates.     

测量重力加速度的一种新方法

提出了一种测量重力加速度的新方法,结合CCD杨氏模量实验仪给出了重力加速度和杨氏模量的物理关系式,从测量结果可知,所测重力加速度与标准值相比其相对误差甚小,说明该实验方案确实可行,具有一定的应用价值。