1,555 research outputs found
Using remote vision: The effects of video image frame rate on visual object recognition performance
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.The process of using remote vision was simulated in order to determine the effects of video image frame rate on the performance in visual recognition of stationary environmental hazards in the dynamic video footage of the pedestrian travel environment. The recognition performance was assessed against two different video image frame rate variations: 25 and 2 fps. The assessment included a range of objective and subjective criteria. The obtained results show that the effects of the frame rate variations on the performance are statistically insignificant. This paper belongs to the process of development of a novel system for navigation of visually impaired pedestrians. The navigation system includes a remote vision facility, and the visual recognition of the environmental hazards by the sighted human guide is a basic activity in aiding the visually impaired user of the system in mobility
Quantum Geons and Noncommutative Spacetimes
Physical considerations strongly indicate that spacetime at Planck scales is
noncommutative. A popular model for such a spacetime is the Moyal plane. The
Poincar\`e group algebra acts on it with a Drinfel'd-twisted coproduct. But the
latter is not appropriate for more complicated spacetimes such as those
containing the Friedman-Sorkin (topological) geons. They have rich
diffeomorphism groups and in particular mapping class groups, so that the
statistics groups for N identical geons is strikingly different from the
permutation group . We generalise the Drinfel'd twist to (essentially)
generic groups including to finite and discrete ones and use it to modify the
commutative spacetime algebras of geons as well to noncommutative algebras. The
latter support twisted actions of diffeos of geon spacetimes and associated
twisted statistics. The notion of covariant fields for geons is formulated and
their twisted versions are constructed from their untwisted versions.
Non-associative spacetime algebras arise naturally in our analysis. Physical
consequences, such as the violation of Pauli principle, seem to be the outcomes
of such nonassociativity.
The richness of the statistics groups of identical geons comes from the
nontrivial fundamental groups of their spatial slices. As discussed long ago,
extended objects like rings and D-branes also have similar rich fundamental
groups. This work is recalled and its relevance to the present quantum geon
context is pointed out.Comment: 41 page
Dirac operator on the q-deformed Fuzzy sphere and Its spectrum
The q-deformed fuzzy sphere is the algebra of
dim. matrices, covariant with respect to the adjoint action
of \uq and in the limit , it reduces to the fuzzy sphere
. We construct the Dirac operator on the q-deformed fuzzy
sphere- using the spinor modules of \uq. We explicitly obtain
the zero modes and also calculate the spectrum for this Dirac operator. Using
this Dirac operator, we construct the \uq invariant action for the spinor
fields on which are regularised and have only finite modes. We
analyse the spectrum for both being root of unity and real, showing
interesting features like its novel degeneracy. We also study various limits of
the parameter space (q, N) and recover the known spectrum in both fuzzy and
commutative sphere.Comment: 19 pages, 6 figures, more references adde
Aspects of Boundary Conditions for Nonabelian Gauge Theories
The boundary values of the time-component of the gauge potential form
externally specifiable data characterizing a gauge theory. We point out some
consequences such as reduced symmetries, bulk currents for manifolds with
disjoint boundaries and some nuances of how the charge algebra is realized.Comment: 15 page
Lehmann-Symanzik-Zimmermann S-Matrix elements on the Moyal Plane
Field theories on the Groenewold-Moyal(GM) plane are studied using the
Lehmann-Symanzik-Zimmermann(LSZ) formalism. The example of real scalar fields
is treated in detail. The S-matrix elements in this non-perturbative approach
are shown to be equal to the interaction representation S-matrix elements. This
is a new non-trivial result: in both cases, the S-operator is independent of
the noncommutative deformation parameter and the change in
scattering amplitudes due to noncommutativity is just a time delay. This result
is verified in two different ways. But the off-shell Green's functions do
depend on . In the course of this analysis, unitarity of the
non-perturbative S-matrix is proved as well.Comment: 18 pages, minor corrections, To appear in Phys. Rev. D, 201
Twisted Gauge and Gravity Theories on the Groenewold-Moyal Plane
Recent work [hep-th/0504183,hep-th/0508002] indicates an approach to the
formulation of diffeomorphism invariant quantum field theories (qft's) on the
Groenewold-Moyal (GM) plane. In this approach to the qft's, statistics gets
twisted and the S-matrix in the non-gauge qft's becomes independent of the
noncommutativity parameter theta^{\mu\nu}. Here we show that the noncommutative
algebra has a commutative spacetime algebra as a substructure: the Poincare,
diffeomorphism and gauge groups are based on this algebra in the twisted
approach as is known already from the earlier work of [hep-th/0510059]. It is
natural to base covariant derivatives for gauge and gravity fields as well on
this algebra. Such an approach will in particular introduce no additional gauge
fields as compared to the commutative case and also enable us to treat any
gauge group (and not just U(N)). Then classical gravity and gauge sectors are
the same as those for \theta^{\mu \nu}=0, but their interactions with matter
fields are sensitive to theta^{\mu \nu}. We construct quantum noncommutative
gauge theories (for arbitrary gauge groups) by requiring consistency of twisted
statistics and gauge invariance. In a subsequent paper (whose results are
summarized here), the locality and Lorentz invariance properties of the
S-matrices of these theories will be analyzed, and new non-trivial effects
coming from noncommutativity will be elaborated.
This paper contains further developments of [hep-th/0608138] and a new
formulation based on its approach.Comment: 17 pages, LaTeX, 1 figur
Abelian BF-Theory and Spherically Symmetric Electromagnetism
Three different methods to quantize the spherically symmetric sector of
electromagnetism are presented: First, it is shown that this sector is
equivalent to Abelian BF-theory in four spacetime dimensions with suitable
boundary conditions. This theory, in turn, is quantized by both a reduced phase
space quantization and a spin network quantization. Finally, the outcome is
compared with the results obtained in the recently proposed general quantum
symmetry reduction scheme. In the magnetically uncharged sector, where all
three approaches apply, they all lead to the same quantum theory.Comment: 21 pages, LaTeX2e, v2: minor corrections in some formulas and a new
referenc
Bosonic Description of Spinning Strings in Dimensions
We write down a general action principle for spinning strings in 2+1
dimensional space-time without introducing Grassmann variables. The action is
written solely in terms of coordinates taking values in the 2+1 Poincare group,
and it has the usual string symmetries, i.e. it is invariant under a)
diffeomorphisms of the world sheet and b) Poincare transformations. The system
can be generalized to an arbitrary number of space-time dimensions, and also to
spinning membranes and p-branes.Comment: Latex, 12 page
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