21,941 research outputs found
On the Approximation of the Quantum Gates using Lattices
A central question in Quantum Computing is how matrices in can be
approximated by products over a small set of "generators". A topology will be
defined on so as to introduce the notion of a covering exponent
\cite{letter}, which compares the length of products required to covering
with balls against the Haar measure of
balls. An efficient universal set over will be constructed using the
Pauli matrices, using the metric of the covering exponent. Then, the
relationship between and will be manipulated to correlate angles
between points on and give a conjecture on the maximum of angles between
points on a lattice. It will be shown how this conjecture can be used to
compute the covering exponent, and how it can be generalized to universal sets
in .Comment: This is an updated version of arxiv.org:1506.0578
Integrated controls/structures study of advanced space systems
A cost tradeoff is postulated for a stiff structure utilizing minimal controls (and control expense) to point and stabilize the vehicle. Extra costs for a stiff structure are caused by weight, packaging size, etc. Likewise, a more flexible vehicle should result in reduced structural costs but increased costs associated with additional control hardware and data processing required for vibration control of the structure. This tradeoff occurs as the ratio of the control bandwidth required for the mission to the lowest (significant) bending mode of the vehicle. The cost of controlling a spacecraft for a specific mission and the same basic configuration but varying the flexibility is established
An investigation of the use of Faraday rotation for the measurement of magnetic fields
Potential use of Faraday rotation and Kerr magnetooptical effect for magnetic field measurement
Investigation of the use of the Kerr magneto-optic effect for the measurement of magnetic fields, phase 2 Final report
Use of Kerr magnetooptical for measuring magnetic field
Families of Quintic Calabi-Yau 3-Folds with Discrete Symmetries
At special loci in their moduli spaces, Calabi-Yau manifolds are endowed with
discrete symmetries. Over the years, such spaces have been intensely studied
and have found a variety of important applications. As string compactifications
they are phenomenologically favored, and considerably simplify many important
calculations. Mathematically, they provided the framework for the first
construction of mirror manifolds, and the resulting rational curve counts.
Thus, it is of significant interest to investigate such manifolds further. In
this paper, we consider several unexplored loci within familiar families of
Calabi-Yau hypersurfaces that have large but unexpected discrete symmetry
groups. By deriving, correcting, and generalizing a technique similar to that
of Candelas, de la Ossa and Rodriguez-Villegas, we find a calculationally
tractable means of finding the Picard-Fuchs equations satisfied by the periods
of all 3-forms in these families. To provide a modest point of comparison, we
then briefly investigate the relation between the size of the symmetry group
along these loci and the number of nonzero Yukawa couplings. We include an
introductory exposition of the mathematics involved, intended to be accessible
to physicists, in order to make the discussion self-contained.Comment: 54 pages, 3 figure
Raising the unification scale in supersymmetry
In the minimal supersymmetric standard model, the three gauge couplings
appear to unify at a mass scale near GeV. We investigate the
possibility that intermediate scale particle thresholds modify the running
couplings so as to increase the unification scale. By requiring consistency of
this scenario, we derive some constraints on the particle content and locations
of the intermediate thresholds. There are remarkably few acceptable solutions
with a single cleanly defined intermediate scale far below the unification
scale.Comment: 22 pages, macros included. One figure, available at
ftp://ftp.phys.ufl.edu/incoming/rais.ep
Role of oxygen in the electron-doped superconducting cuprates
We report on resistivity and Hall measurements in thin films of the
electron-doped superconducting cuprate PrCeCuO.
Comparisons between x = 0.17 samples subjected to either ion-irradiation or
oxygenation demonstrate that changing the oxygen content has two separable
effects: 1) a doping effect similar to that of cerium, and 2) a disorder
effect. These results are consistent with prior speculations that apical oxygen
removal is necessary to achieve superconductivity in this compound.Comment: 5 pages, 5 figure
On the Nature of the Cosmological Constant Problem
General relativity postulates the Minkowski space-time to be the standard
flat geometry against which we compare all curved space-times and the
gravitational ground state where particles, quantum fields and their vacuum
states are primarily conceived. On the other hand, experimental evidences show
that there exists a non-zero cosmological constant, which implies in a deSitter
space-time, not compatible with the assumed Minkowski structure. Such
inconsistency is shown to be a consequence of the lack of a application
independent curvature standard in Riemann's geometry, leading eventually to the
cosmological constant problem in general relativity.
We show how the curvature standard in Riemann's geometry can be fixed by
Nash's theorem on locally embedded Riemannian geometries, which imply in the
existence of extra dimensions. The resulting gravitational theory is more
general than general relativity, similar to brane-world gravity, but where the
propagation of the gravitational field along the extra dimensions is a
mathematical necessity, rather than being a a postulate. After a brief
introduction to Nash's theorem, we show that the vacuum energy density must
remain confined to four-dimensional space-times, but the cosmological constant
resulting from the contracted Bianchi identity is a gravitational contribution
which propagates in the extra dimensions. Therefore, the comparison between the
vacuum energy and the cosmological constant in general relativity ceases to be.
Instead, the geometrical fix provided by Nash's theorem suggests that the
vacuum energy density contributes to the perturbations of the gravitational
field.Comment: LaTex, 5 pages no figutres. Correction on author lis
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