8,320 research outputs found
New Operators for Spin Net Gravity: Definitions and Consequences
Two operators for quantum gravity, angle and quasilocal energy, are briefly
reviewed. The requirements to model semi-classical angles are discussed. To
model semi-classical angles it is shown that the internal spins of the vertex
must be very large, ~10^20.Comment: 7 pages, 2 figures, a talk at the MG9 Meeting, Rome, July 2-8, 200
Quantum Geometry Phenomenology: Angle and Semiclassical States
The phenomenology for the deep spatial geometry of loop quantum gravity is
discussed. In the context of a simple model of an atom of space, it is shown
how purely combinatorial structures can affect observations. The angle operator
is used to develop a model of angular corrections to local, continuum
flat-space 3-geometries. The physical effects involve neither breaking of local
Lorentz invariance nor Planck scale suppression, but rather reply on only the
combinatorics of SU(2) recouping theory. Bhabha scattering is discussed as an
example of how the effects might be observationally accessible.Comment: 5 pages, slightly extended version of the contribution to the
Loops'11 conference proceeding
Does listening to a personal music player or reading a book during the uptake period of a PET-CT oncology scan cause extra 18F-fluorodeoxyglucose (18FDG) activity in the skeletal muscles?
Peer reviewe
Analysis of standing vertical jumps using a force platform
A force platform analysis of vertical jumping provides an engaging demonstration of the kinematics and dynamics of one-dimensional motion. The height of the jump may be calculated (1) from the flight time of the jump, (2) by applying the impulse–momentum theorem to the force–time curve, and (3) by applying the work–energy theorem to the force-displacement curve
The Snowmelt-Runoff Model (SRM) user's manual
A manual to provide a means by which a user may apply the snowmelt runoff model (SRM) unaided is presented. Model structure, conditions of application, and data requirements, including remote sensing, are described. Guidance is given for determining various model variables and parameters. Possible sources of error are discussed and conversion of snowmelt runoff model (SRM) from the simulation mode to the operational forecasting mode is explained. A computer program is presented for running SRM is easily adaptable to most systems used by water resources agencies
On the Universality of the Entropy-Area Relation
We present an argument that, for a large class of possible dynamics, a
canonical quantization of gravity will satisfy the Bekenstein-Hawking
entropy-area relation. This result holds for temperatures low compared to the
Planck temperature and for boundaries with areas large compared to Planck area.
We also relate our description, in terms of a grand canonical ensemble, to
previous geometric entropy calculations using area ensembles.Comment: 6 page
Quasilocal Energy for Spin-net Gravity
The Hamiltonian of a gravitational system defined in a region with boundary is quantized. The classical Hamiltonian, and starting point for the regularization, is required by functional differentiablity of the Hamiltonian constraint. The boundary term is the quasilocal energy of the system and becomes the ADM mass in asymptopia. The quantization is carried out within the framework of canonical quantization using spin networks. The result is a gauge invariant, well-defined operator on the Hilbert space induced from the state space on the whole spatial manifold. The spectrum is computed. An alternate form of the operator, with the correct naive classical limit, but requiring a restriction on the Hilbert space, is also defined. Comparison with earlier work and several consequences are briefly explored
Continuous Dependence and Differentiating Solutions of a Second Order Boundary Value Problem with Average Value Condition
Using a few conditions, continuous dependence, and a result regarding smoothness of initial conditions, we show that derivatives, with respect to each of the boundary data, of solutions to a second order boundary value problem with an average value integral condition solve the associated variational equation with interesting boundary conditions
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