The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Carlo Rovelli - One of the best experts on this subject based on the ideXlab platform.
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the Physical Boundary hilbert space and volume operator in the lorentzian new spin foam theory
Classical and Quantum Gravity, 2010Co-Authors: You Ding, Carlo RovelliAbstract:A covariant spin-foam formulation of quantum gravity has been recently developed, characterized by a kinematics which appears to match well the one of canonical loop quantum gravity. In this paper we reconsider the implementation of the constraints that defines the model. We define in a simple way the Boundary Hilbert space of the theory, introducing a slight modification of the embedding of the SU(2) representations into the ones. We then show directly that all constraints vanish on this space in a weak sense. The vanishing is exact (and not just in the large quantum number limit). We also generalize the definition of the volume operator in the spin-foam model to the Lorentzian signature and show that it matches the one of loop quantum gravity, as in the Euclidean case.
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The Physical Boundary Hilbert space and volume operator in the Lorentzian new spin-foam theory
Classical and Quantum Gravity, 2010Co-Authors: You Ding, Carlo RovelliAbstract:A covariant spin-foam formulation of quantum gravity has been recently developed, characterized by a kinematics which appears to match well the one of canonical loop quantum gravity. In this paper we reconsider the implementation of the constraints that defines the model. We define in a simple way the Boundary Hilbert space of the theory, introducing a slight modification of the embedding of the SU (2) representations into the SL(2, C) ones. We then show directly that all constraints vanish on this space in a weak sense. The vanishing is exact (and not just in the large quantum number limit.) We also generalize the definition of the volume operator in the spinfoam model to the Lorentzian signature, and show that it matches the one of loop quantum gravity, as does in the Euclidean case.
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Physical Boundary Hilbert space and volume operator in the Lorentzian new spin-foam theory
Classical and Quantum Gravity, 2010Co-Authors: You Ding, Carlo RovelliAbstract:A covariant spin-foam formulation of quantum gravity has been recently developed, characterized by a kinematics which appears to match well the one of canonical loop quantum gravity. In this paper we reconsider the implementation of the constraints that defines the model. We define in a simple way the Boundary Hilbert space of the theory, introducing a slight modification of the embedding of the SU(2) representations into the SL(2,C) ones. We then show directly that all constraints vanish on this space in a weak sense. The vanishing is exact (and not just in the large quantum number limit.) We also generalize the definition of the volume operator in the spinfoam model to the Lorentzian signature, and show that it matches the one of loop quantum gravity, as does in the Euclidean case.
Sharidan Shafie - One of the best experts on this subject based on the ideXlab platform.
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energy transfer in mixed convection mhd flow of nanofluid containing different shapes of nanoparticles in a channel filled with saturated porous medium
Nanoscale Research Letters, 2015Co-Authors: Gul Aaiza, Ilyas Khan, Sharidan ShafieAbstract:Energy transfer in mixed convection unsteady magnetohydrodynamic (MHD) flow of an incompressible nanofluid inside a channel filled with saturated porous medium is investigated. The channel with non-uniform walls temperature is taken in a vertical direction under the influence of a transverse magnetic field. Based on the Physical Boundary conditions, three different flow situations are discussed. The problem is modelled in terms of partial differential equations with Physical Boundary conditions. Four different shapes of nanoparticles of equal volume fraction are used in conventional base fluids, ethylene glycol (EG) (C2H6O2) and water (H2O). Solutions for velocity and temperature are obtained discussed graphically in various plots. It is found that viscosity and thermal conductivity are the most prominent parameters responsible for different results of velocity and temperature. Due to higher viscosity and thermal conductivity, C2H6O2 is regarded as better convectional base fluid compared to H2O.
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energy transfer in mixed convection mhd flow of nanofluid containing different shapes of nanoparticles in a channel filled with saturated porous medium
Nanoscale Research Letters, 2015Co-Authors: Gul Aaiza, Ilyas Khan, Sharidan ShafieAbstract:Energy transfer in mixed convection unsteady magnetohydrodynamic (MHD) flow of an incompressible nanofluid inside a channel filled with saturated porous medium is investigated. The channel with non-uniform walls temperature is taken in a vertical direction under the influence of a transverse magnetic field. Based on the Physical Boundary conditions, three different flow situations are discussed. The problem is modelled in terms of partial differential equations with Physical Boundary conditions. Four different shapes of nanoparticles of equal volume fraction are used in conventional base fluids, ethylene glycol (EG) (C2H6O2) and water (H2O). Solutions for velocity and temperature are obtained discussed graphically in various plots. It is found that viscosity and thermal conductivity are the most prominent parameters responsible for different results of velocity and temperature. Due to higher viscosity and thermal conductivity, C2H6O2 is regarded as better convectional base fluid compared to H2O.
John R. Hipp - One of the best experts on this subject based on the ideXlab platform.
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Both Sides of the Street: Introducing Measures of Physical and Social Boundaries Based on Differences Across Sides of the Street, and Consequences for Crime
Journal of Quantitative Criminology, 2021Co-Authors: Young-an Kim, John R. HippAbstract:Objectives Although previous studies have theorized the importance of Physical and social boundaries (edges) in understanding crime in place, the relationship between edges and the level of crime has been less studied empirically. The current study examines the effects of Physical and social boundaries on crime in street segments. Methods To empirically measure boundaries, we introduce an approach of looking at the differences of land use (Physical Boundary), socioeconomic status, or racial composition (social boundaries) on both sides of a street segment. We estimated a series of negative binomial regression models in which measures of the Physical and social boundaries are included while controlling for the effects of structural characteristic and the conventional Physical Boundary measures of highways, parks, and rivers. Results We observed that there are positive relationships between all three of these Boundary measures and violent and property crimes. The results indicated that Physical and social boundaries are important to consider in understanding the spatial patterns of crime. Moreover, the current study confirmed the moderating effects between social and Physical boundaries. Conclusions Our results indicate that although much empirical research focuses solely on Physical boundaries, our measures of social and Physical boundaries have important consequences for the spatial location of crime, and therefore are worthy of further research.
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Both Sides of the Street: Introducing Measures of Physical and Social Boundaries Based on Differences Across Sides of the Street, and Consequences for Crime
Journal of Quantitative Criminology, 2021Co-Authors: Young-an Kim, John R. HippAbstract:Although previous studies have theorized the importance of Physical and social boundaries (edges) in understanding crime in place, the relationship between edges and the level of crime has been less studied empirically. The current study examines the effects of Physical and social boundaries on crime in street segments. To empirically measure boundaries, we introduce an approach of looking at the differences of land use (Physical Boundary), socioeconomic status, or racial composition (social boundaries) on both sides of a street segment. We estimated a series of negative binomial regression models in which measures of the Physical and social boundaries are included while controlling for the effects of structural characteristic and the conventional Physical Boundary measures of highways, parks, and rivers. We observed that there are positive relationships between all three of these Boundary measures and violent and property crimes. The results indicated that Physical and social boundaries are important to consider in understanding the spatial patterns of crime. Moreover, the current study confirmed the moderating effects between social and Physical boundaries. Our results indicate that although much empirical research focuses solely on Physical boundaries, our measures of social and Physical boundaries have important consequences for the spatial location of crime, and therefore are worthy of further research.
You Ding - One of the best experts on this subject based on the ideXlab platform.
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the Physical Boundary hilbert space and volume operator in the lorentzian new spin foam theory
Classical and Quantum Gravity, 2010Co-Authors: You Ding, Carlo RovelliAbstract:A covariant spin-foam formulation of quantum gravity has been recently developed, characterized by a kinematics which appears to match well the one of canonical loop quantum gravity. In this paper we reconsider the implementation of the constraints that defines the model. We define in a simple way the Boundary Hilbert space of the theory, introducing a slight modification of the embedding of the SU(2) representations into the ones. We then show directly that all constraints vanish on this space in a weak sense. The vanishing is exact (and not just in the large quantum number limit). We also generalize the definition of the volume operator in the spin-foam model to the Lorentzian signature and show that it matches the one of loop quantum gravity, as in the Euclidean case.
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The Physical Boundary Hilbert space and volume operator in the Lorentzian new spin-foam theory
Classical and Quantum Gravity, 2010Co-Authors: You Ding, Carlo RovelliAbstract:A covariant spin-foam formulation of quantum gravity has been recently developed, characterized by a kinematics which appears to match well the one of canonical loop quantum gravity. In this paper we reconsider the implementation of the constraints that defines the model. We define in a simple way the Boundary Hilbert space of the theory, introducing a slight modification of the embedding of the SU (2) representations into the SL(2, C) ones. We then show directly that all constraints vanish on this space in a weak sense. The vanishing is exact (and not just in the large quantum number limit.) We also generalize the definition of the volume operator in the spinfoam model to the Lorentzian signature, and show that it matches the one of loop quantum gravity, as does in the Euclidean case.
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Physical Boundary Hilbert space and volume operator in the Lorentzian new spin-foam theory
Classical and Quantum Gravity, 2010Co-Authors: You Ding, Carlo RovelliAbstract:A covariant spin-foam formulation of quantum gravity has been recently developed, characterized by a kinematics which appears to match well the one of canonical loop quantum gravity. In this paper we reconsider the implementation of the constraints that defines the model. We define in a simple way the Boundary Hilbert space of the theory, introducing a slight modification of the embedding of the SU(2) representations into the SL(2,C) ones. We then show directly that all constraints vanish on this space in a weak sense. The vanishing is exact (and not just in the large quantum number limit.) We also generalize the definition of the volume operator in the spinfoam model to the Lorentzian signature, and show that it matches the one of loop quantum gravity, as does in the Euclidean case.
Gul Aaiza - One of the best experts on this subject based on the ideXlab platform.
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energy transfer in mixed convection mhd flow of nanofluid containing different shapes of nanoparticles in a channel filled with saturated porous medium
Nanoscale Research Letters, 2015Co-Authors: Gul Aaiza, Ilyas Khan, Sharidan ShafieAbstract:Energy transfer in mixed convection unsteady magnetohydrodynamic (MHD) flow of an incompressible nanofluid inside a channel filled with saturated porous medium is investigated. The channel with non-uniform walls temperature is taken in a vertical direction under the influence of a transverse magnetic field. Based on the Physical Boundary conditions, three different flow situations are discussed. The problem is modelled in terms of partial differential equations with Physical Boundary conditions. Four different shapes of nanoparticles of equal volume fraction are used in conventional base fluids, ethylene glycol (EG) (C2H6O2) and water (H2O). Solutions for velocity and temperature are obtained discussed graphically in various plots. It is found that viscosity and thermal conductivity are the most prominent parameters responsible for different results of velocity and temperature. Due to higher viscosity and thermal conductivity, C2H6O2 is regarded as better convectional base fluid compared to H2O.
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energy transfer in mixed convection mhd flow of nanofluid containing different shapes of nanoparticles in a channel filled with saturated porous medium
Nanoscale Research Letters, 2015Co-Authors: Gul Aaiza, Ilyas Khan, Sharidan ShafieAbstract:Energy transfer in mixed convection unsteady magnetohydrodynamic (MHD) flow of an incompressible nanofluid inside a channel filled with saturated porous medium is investigated. The channel with non-uniform walls temperature is taken in a vertical direction under the influence of a transverse magnetic field. Based on the Physical Boundary conditions, three different flow situations are discussed. The problem is modelled in terms of partial differential equations with Physical Boundary conditions. Four different shapes of nanoparticles of equal volume fraction are used in conventional base fluids, ethylene glycol (EG) (C2H6O2) and water (H2O). Solutions for velocity and temperature are obtained discussed graphically in various plots. It is found that viscosity and thermal conductivity are the most prominent parameters responsible for different results of velocity and temperature. Due to higher viscosity and thermal conductivity, C2H6O2 is regarded as better convectional base fluid compared to H2O.
