7,604 research outputs found
Building Blocks of Physical States in a Non-Critical 3-Brane on R*S^3
The physical states in a world-volume model of a non-critical 3-brane are
systematically constructed using techniques of four-dimensional conformal field
theories on R*S^3 developed recently. Invariant combinations of creation modes
under a special conformal transformation provide building blocks of physical
states. Any state can be created by acting with such building blocks on a
conformally invariant vacuum in an invariant way under the other conformal
charges: the Hamiltonian and rotation generators on S^3. We explicitly
construct building blocks for scalar, vector and gravitational fields, and
classify them as finite types.Comment: 56 page
CMB Anisotropies Reveal Quantized Gravity
A novel primordial spectrum with a dynamical scale of quantum gravity origin
is proposed to explain the sharp fall off of the angular power spectra at low
multipoles in the COBE and WMAP observations. The spectrum is derived from
quantum fluctuations of the scalar curvature in a renormalizable model of
induced gravity. This model describes the very early universe by the conformal
field fluctuating about an inflationary background with the expansion time
constant of order of the Planck mass.Comment: 12 pages, 2 figure
Vertex Operators in 4D Quantum Gravity Formulated as CFT
We study vertex operators in 4D conformal field theory derived from quantized
gravity, whose dynamics is governed by the Wess-Zumino action by Riegert and
the Weyl action. Conformal symmetry is equal to diffeomorphism symmetry in the
ultraviolet limit, which mixes positive-metric and negative-metric modes of the
gravitational field and thus these modes cannot be treated separately in
physical operators. In this paper, we construct gravitational vertex operators
such as the Ricci scalar, defined as space-time volume integrals of them are
invariant under conformal transformations. Short distance singularities of
these operator products are computed and it is shown that their coefficients
have physically correct sign. Furthermore, we show that conformal algebra holds
even in the system perturbed by the cosmological constant vertex operator as in
the case of the Liouville theory shown by Curtright and Thorn.Comment: 26 pages, rewrote review part concisely, added explanation
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Injectable and Spatially Patterned Microporous Annealed Particle (MAP) Hydrogels for Tissue Repair Applications.
Spatially patterned hydrogels are becoming increasingly popular in the field of regenerative medicine and tissue repair because of their ability to guide cell infiltration and migration. However, postfabrication technologies are usually required to spatially pattern a hydrogel, making these hydrogels difficult to translate into the clinic. Here, an injectable spatially patterned hydrogel is reported using hyaluronic acid (HA)-based particle hydrogels. These particle hydrogels are sequentially loaded into a syringe to form a pattern and, once injected, they maintain the pattern. The applicability of this hydrogel in a wound healing skin model, a subcutaneous implant model, as well as a stroke brain model is examined and distinct patterning in all models tested is shown. This injectable and spatially patterned hydrogel can be used to create physical or biochemical gradients. Further, this design can better match the scaffold properties within the physical location of the tissue (e.g., wound border vs wound center). This allows for better design features within the material that promote repair and regeneration
Antennas for 20/30 GHz and beyond
Antennas of 20/30 GHz and higher frequency, due to the small wavelength, offer capabilities for many space applications. With the government-sponsored space programs (such as ACTS) in recent years, the industry has gone through the learning curve of designing and developing high-performance, multi-function antennas in this frequency range. Design and analysis tools (such as the computer modelling used in feedhorn design and reflector surface and thermal distortion analysis) are available. The components/devices (such as BFN's, weight modules, feedhorns and etc.) are space-qualified. The manufacturing procedures (such as reflector surface control) are refined to meet the stringent tolerance accompanying high frequencies. The integration and testing facilities (such as Near-Field range) also advance to facilitate precision assembling and performance verification. These capabilities, essential to the successful design and development of high-frequency spaceborne antennas, shall find more space applications (such as ESGP) than just communications
Making a Universe
For understanding the origin of anisotropies in the cosmic microwave
background, rules to construct a quantized universe is proposed based on the
dynamical triangulation method of the simplicial quantum gravity. A
-dimensional universe having the topology is created numerically in
terms of a simplicial manifold with -simplices as the building blocks. The
space coordinates of a universe are identified on the boundary surface , and the time coordinate is defined along the direction perpendicular
to . Numerical simulations are made mainly for 2-dimensional
universes, and analyzed to examine appropriateness of the construction rules by
comparing to analytic results of the matrix model and the Liouville theory.
Furthermore, a simulation in 4-dimension is made, and the result suggests an
ability to analyze the observations on anisotropies by comparing to the scalar
curvature correlation of a -surface formed as the last scattering
surface in the universe.Comment: 27pages,18figures,using jpsj.st
Angle-resolved photoemission spectra in the cuprates from the d-density wave theory
Angle-resolved photoemission spectra present two challenges for the d-density
wave (DDW) theory of the pseudogap state of the cuprates: (1) hole pockets near
are not observed, in apparent contradiction with the assumption
of translational symmetry breaking, and (2) there are no well-defined
quasiparticles at the {\it antinodal} points, in contradiction with the
predictions of mean-field theory of this broken symmetry state. Here, we show
how these puzzles can be resolved.Comment: 4 pages, 3 eps figures, RevTex
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