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On The Correspondence Between Noncommuative Field Theory And Gravity  [PDF]
Hyun Seok Yang
Physics , 2006, DOI: 10.1142/S0217732307023675
Abstract: In this brief review, I summarize the new development on the correspondence between noncommuative (NC) field theory and gravity, shortly referred to as the NCFT/Gravity correspondence. I elucidate why a gauge theory in NC spacetime should be a theory of gravity. A basic reason for the NCFT/Gravity correspondence is that the $\Lambda$-symmetry (or B-field transformations) in NC spacetime can be considered as a par with diffeomorphisms, which results from the Darboux theorem. This fact leads to a striking picture about gravity: Gravity can emerge from a gauge theory in NC spacetime. Gravity is then a collective phenomenon emerging from gauge fields living in fuzzy spacetime.
The new basic theory on Quaternary environmental research

ZHAO Jingbo,

地理学报 , 2004,
Abstract: On the basis of extensive survey to the Quaternary paleosols, soils and weathering layers in the vast northern China and the Loess Plateau, we found some unusually special phenomena of chemical components such as unsuccessive illuvium, twin illuviums, unusually thick illuvium and multi-illuviums etc. According to the analysis on the content of CaCO3 and the data of penetrating experiment, a new theory of illuvial depth or removal depth of CaCO3 in weathering and leaching belt was constructed, which indicates that the time of CaCO3 removing to the illuvial depth is very short, and the effect of time factor on illuvial depth can be ignored. The theory can be taken as a credible foundation for studying many geological and geographical problems in weathering and leaching belt. When the illuvial depth of CaCO3 is bigger than the thickness of developing belt of soil or paleosol, it can be determined that the paleosol has turned into weathering crust. When the illuvial depth of CaCO3 is bigger than the thickness of paleosol, paleosol is leaching moderately acid soil. When two, three layers or unusually thick CaCO3 illuviums exist in the same weathering section or at the bottom of the same paleosol, there were two or more periods forming paleosol and corresponding climatic stages at that time. On the basis of the equation of relationship between mean annual rainfall (y) and illuvial depth of CaCO3 (x) (y = 305.5x + 168.5) determined in the paper, mean annual precipitation during the development of paleosol can be calculated.
New results at 3PN via an effective field theory of gravity
Porto, Rafael A.
High Energy Physics - Phenomenology , 2007,
Abstract: NRGR, an Effective Field Theory approach to gravity, has emerged as a powerful tool to systematically compute higher order corrections in the Post-Newtonian expansion. Here we discuss in somehow more detail the recently reported new results for the spin-spin gravitational potential at third Post-Newtonian order.
New results at 3PN via an effective field theory of gravity  [PDF]
Rafael A. Porto
Physics , 2007,
Abstract: NRGR, an Effective Field Theory approach to gravity, has emerged as a powerful tool to systematically compute higher order corrections in the Post-Newtonian expansion. Here we discuss in somehow more detail the recently reported new results for the spin-spin gravitational potential at third Post-Newtonian order.
Is nonsymmetric gravity related to string theory?  [PDF]
J. A. Nieto,J. Socorro
Physics , 1996,
Abstract: In this work we raise the question whether nonsymmetric gravity and string theory are related. We start making the observation, that the gravitational field $ g_{\mu\nu}$ and the nonsymmetric gauge field $ A_{\mu\nu}$ arising in the low energy limit in the string theory are exactly the same two basic fields used in four dimensions in nonsymmetric gravity. We argue, that this connection between nonsymmetric gravity and string theory at the level of the gauge fields $ g_{\mu\nu}$ and $ A_{\mu\nu}$ is not, however, reflected at the level of the corresponding associated actions. In an effort to find a connection between such an actions we discover a new gravitational action, which suggests an alternative version of the bosonic string in which the target and the world-volume metrics are unified.
New Black Hole Solutions in Brans-Dicke Theory of Gravity  [PDF]
Hongsu Kim
Physics , 1998, DOI: 10.1103/PhysRevD.60.024001
Abstract: Existence check of non-trivial, stationary axisymmetric black hole solutions in Brans-Dicke theory of gravity in different direction from those of Penrose, Thorne and Dykla, and Hawking is performed. Namely, working directly with the known explicit spacetime solutions in Brans-Dicke theory, it is found that non-trivial Kerr-Newman-type black hole solutions different from general relativistic solutions could occur for the generic Brans-Dicke parameter values -5/2\leq \omega <-3/2. Finally, issues like whether these new black holes carry scalar hair and can really arise in nature and if they can, what the associated physical implications would be are discussed carefully.
Toward a Background Independent Quantum Theory of Gravity  [PDF]
Vishnu Jejjala,Djordje Minic,Chia-Hsiung Tze
Physics , 2004, DOI: 10.1142/S0218271804006371
Abstract: Any canonical quantum theory can be understood to arise from the compatibility of the statistical geometry of distinguishable observations with the canonical Poisson structure of Hamiltonian dynamics. This geometric perspective offers a novel, background independent non-perturbative formulation of quantum gravity. We invoke a quantum version of the equivalence principle, which requires both the statistical and symplectic geometries of canonical quantum theory to be fully dynamical quantities. Our approach sheds new light on such basic issues of quantum gravity as the nature of observables, the problem of time, and the physics of the vacuum. In particular, the observed numerical smallness of the cosmological constant can be rationalized in this approach.
A new quantum theory of gravity in the framework of general relativity  [PDF]
Chang-Yu Zhu,Heng Fan
Physics , 2009,
Abstract: Observed physical phenomena can be described well by quantum mechanics or general relativity. People may try to find an unified fundamental theory which mainly aims to merge gravity with quantum theory. However, difficulty in merging those theories self-consistently still exists, and no such theory is generally accepted. Here we try to propose a quantum theory with space and time in symmetrical positions in the framework of general relativity. In this theory, Dirac matter fields, gauge fields and gravity field are formulated in an unified way which satisf Dirac equation, Yang-Mills equation and Einstein equation in operator form. This combines the quantum mechanics and general relativity .
The quantum vacuum, fractal geometry, and the quest for a new theory of gravity  [PDF]
E. F. Halerewicz Jr
Physics , 2000,
Abstract: In this letter recent developments are shown in experimental and theoretical physics which brings into question the validity of General Relativity. This letter emphasizes the construction of a fractal 3+\phi^3 spacetime, in N-dimensions in order to formalize a physical and consistent theory of `quantum gravity.' It is then shown that a `quantum gravity' effect could arise by means of the Strong Equivalence Principle. Which is made possible through a pressure of the form -kappa(R^{ca}_{b}-{1\over 2}g^{c sigma}_{ab}R^c)=kappa T^{c sigma}_{ab}. Where it is seen that nuclear pressures can be added to rethe gravitational field equations by means of twistor spaces.
EvoL: The new Padova T-SPH parallel code for cosmological simulations - I. Basic code: gravity and hydrodynamics  [PDF]
Emiliano Merlin,Umberto Buonomo,Tommaso Grassi,Lorenzo Piovan,Cesare Chiosi
Physics , 2009, DOI: 10.1051/0004-6361/200913514
Abstract: We present EvoL, the new release of the Padova N-body code for cosmological simulations of galaxy formation and evolution. In this paper, the basic Tree + SPH code is presented and analysed, together with an overview on the software architectures. EvoL is a flexible parallel Fortran95 code, specifically designed for simulations of cosmological structure formation on cluster, galactic and sub-galactic scales. EvoL is a fully Lagrangian self-adaptive code, based on the classical Oct-tree and on the Smoothed Particle Hydrodynamics algorithm. It includes special features such as adaptive softening lengths with correcting extra-terms, and modern formulations of SPH and artificial viscosity. It is designed to be run in parallel on multiple CPUs to optimize the performance and save computational time. We describe the code in detail, and present the results of a number of standard hydrodynamical tests.
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